Biocolonizer species are putting the conservation of the granite at Machu Picchu at risk

There is a wide variety of biocolonizer species that are putting the conservation of the granite at Machu Picchu at risk.

The Sacred Rock is one of the most important monuments at the Inca sanctuary Machu Picchu, located in the Cusco region in Peru. It is a granitic rock that the Inca culture used for religious worship as it was regarded as the gateway between earth and heaven. Owing to the location and climate conditions of the site, many rocks in the archaeological city are affected by biocolonization. And at the Sacred Rock in particular "it is possible to see various exfoliation processes; in other words, there are small losses of material that are causing small areas of the rock to flake," explained the UPV/EHU PhD holder and lecturer Héctor Morillas. He is conducting various pieces of research work relating to Machu Picchu in collaboration with the IBeA research group of the Department of Analytical Chemistry and with the Department of Plant Biology and Ecology at the UPV/EHU's Faculty of Science and Technology.

By applying a non-destructive, multi-analytical methodology, the researchers have determined the role played by the species of lichens, algae, mosses, cyanobacteria, etc. colonizing the Sacred Rock with respect to the conservation problems it is displaying. As Morillas explained, "once these species penetrate the material through some kind of minor deterioration that has been forming, they attach themselves to the material itself so that they can feed off the minerals belonging to the rock, gradually degrading it. As time passes, these micro-organisms can cause minor delamination that could result in the progressive loss of this rock."

Monitoring biogenic pigments to determine depth

After determining the family to which each of the species of micro-organisms found in numerous micro samples of the rock belongs, as well as which biogenic pigments are excreted by each of them, "we carried out in-depth profiling to predict how far these micro-organisms may have penetrated." That way, the researchers have concluded that "there is a wide variety of biocolonizer species in the Sacred Rock, most of which have penetrated through the porous substrate, and which could be one of the factors responsible for the stress being enduring by this rock," said Doctor Morillas, who currently lectures in the UPV/EHU's Department of Mathematics and Experimental Sciences Didactics.

This piece of research is just one of the studies being conducted by the UPV/EHU's group of researchers at this location. In fact, the diagnosis of the conservation state of various buildings, such as temples, houses or meditation areas in the archaeological city, has also begun; at the same time, the building material used throughout Machu Picchu has been analysed and "we are also studying possible alterations in the granitic material owing to possible incorrect restoration carried out in the past in certain places at Machu Picchu." The researcher has also conducted "an ecotoxicity study of the city itself and all the surrounding area of the Archaeological Park where we have analysed the soil, air and rainwater for potential contaminants." What is more, Morillas has analysed rock paintings located in the park and has been able to specify the materials used to produce them; "these paintings are believed to date back much earlier than the pre-Hispanic era." Finally, the researcher added that "thanks to all this we are drawing up the bases of a project with various universities and institutions in other countries to study the conservation of emblematic UNESCO locations."

From Science Daily

Dog burial as common ritual in Neolithic populations of north-eastern Iberian Peninsula

Top: remains of adult dog in partial anatomical connection in La Serreta. Bottom: dog in anatomical connection between human skeletons, in the necropolis Bòbila Madurell.

Coinciding with the Pit Grave culture (4200-3600 years before our era), coming from Southern Europe, the Neolithic communities of the north-eastern Iberian Peninsula started a ceremonial activity related to the sacrifice and burial of dogs. The high amount of cases that are recorded in Catalonia suggests it was a general practice and it proves the tight relationship between humans and these animals, which, apart from being buried next to them, were fed a similar diet to humans'.

This is the conclusion of a research study led by Universitat Autònoma de Barcelona (UAB) and the University of Barcelona (UB), which provides new data to describe and understand the presence of dogs in sacred and funerary spaces of the middle Neolithic in the Iberian Peninsula, and gets an insight on the relation between humans and these animals. The study has been published in the Journal of Archaeological Science: Reports.

The study analyses the remains of twenty-six dogs found in funerary structures from four sites and necropolises of the Barcelona region, and has conducted an isotopic analysis for eighteen of them, to determine whether the relation with their owners included other aspects, such as a control of their diet.

Dogs were aged between one month and six years old, predominating hose between twelve and eighteen years old, and had homogeneous sizes, between forty and fifty centimetres high. These were mainly buried in circular graves, together or near the humans, although some have been found separately in nearby graves and one was found at the entrance of the mortuary chamber. The skeletons were semi-complete in anatomical connection -only one was found as full, near a kid- without bone fractures or marks due manipulation by evisceration, or any signs of predators.

"Choosing young animals aged up to one year old suggests there was an intention in the sacrifice. Although we can think it was for human consumption, the fact that these were buried near humans suggests there was an intention and a direct relation with death and the funerary ritual," says Silvia Albizuri, researcher from the Prehistoric Studies and Research Seminar (SERP) of the UB and first author of the article. "This hypothesis is consistent, in addition, with the fact that they are found in an area of cultural influence that gives a symbolic value to the dog during that period, such as Southern France or Northern Italy."

A diet rich in cereal and vegetables, controlled by humans

The isotopic study of the remains and its comparison with humans' and other herbivorous animals' diet in the site shows the diet of most of these animals was similar to the diet of humans, with a high presence of cereal, such as corn, and vegetables. In two puppies and two adult dogs, nutrition was mainly vegetarian and only a few cases had a diet rich in animal protein.

"These data show a close coexistence between dogs and humans, and probably, a specific preparation of their nutrition, which is clear in the cases of a diet based on vegetables. They would probably do so to obtain a better control of their tasks on security and to save the time they would have to spend looking for food. This management would explain the homogeneity of the size of the animals," says Eulàlia Subirà, researcher in the Research Group on Biological Anthropology (GREAB) of UAB.

Little-studied animals

The presence of dogs in prehistoric disposal structures is not common, which makes it a little-studied group among domestic animals. Their presence in graves is even lower. This is why the presence of these skeletons in anatomical connection like the ones in this study is considered exceptional.

There have been older cases of individual isolated burials in the Iberian Peninsula, but only later documented as a general practice related to the funerary ritual. This ritual spread and lasted during a hundred years, until the Iron Age.

Regarding food, there are only a few studies, with some cases of mixed diets in France, Anatolia and China. "Recently, we saw dogs have ten genes with a key function for starch and fat digestion, which would make the carbohydrates assimilation more efficient than its ancestor's, the wolf. Our study helps reaching the conclusion that during the Neolithic, several vegetables were introduced to their nutrition," notes Eulàlia Subirà.

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New molecular blueprint advances our understanding of photosynthesis

The cryo-EM structure of the NAD(P)H dehydrogenase-like complex (NDH). The atomic coordinate model shown as spheres, colored according to the different subunits, in front of an electron micrograph of frozen NDH particles in the background.

Researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have used one of the most advanced microscopes in the world to reveal the structure of a large protein complex crucial to photosynthesis, the process by which plants convert sunlight into cellular energy.

The finding, published in the journal Nature, will allow scientists to explore for the first time how the complex functions and could have implications for the production of a variety of bioproducts, including plastic alternatives and biofuels.

"This work will lead to a better understanding of how photosynthesis occurs, which could allow us to improve the efficiency of photosynthesis in plants and other green organisms -- potentially boosting the amount of food, and thus biomass, they produce," said lead researcher Karen Davies, a biophysicist at Berkeley Lab. "This is particularly important if you want to produce renewable bioproducts that are cost-effective alternatives to current petroleum-based products."

Discovered decades ago, the protein complex targeted by the researchers, called NADH dehydrogenase-like complex (NDH), is known to help regulate the phase of photosynthesis where the energy of sunlight is captured and stored in two types of cellular energy molecules, which are later utilized to power the conversion of carbon dioxide into sugar. Past investigations revealed that NDH reshuffles the energized electrons moving among other protein complexes in the chloroplast in a way that ensures the correct ratio of each energy molecule is produced. Furthermore, NDH of cyanobacteria performs several additional roles including increasing the amount of carbon dioxide (CO2) available for sugar production by linking CO2 uptake with electron transfer.

In order for scientists to truly comprehend how NDH executes these important functions, they needed a molecular blueprint indicating the location and connectivity of all the atoms in the complex. This is something that even highly powerful transmission electron microscopy (TEM) technology simply could not provide until very recently.

"Research on this enzyme has been difficult and experimental results confounding for the last 20 years or so because we have lacked complete information about the enzyme's structure," said Davies. "Knowing the structure is important for generating and testing out hypotheses of how the enzyme functions. The resolution we obtained for our structure of NDH has only really been achievable since the commercialization of the direct electron counting camera, developed in collaboration with Berkeley Lab."

Prior to this invention, explained Davies, a staff scientist in Berkeley Lab's Molecular Biophysics and Integrative Bioimaging Division (MBIB), determining the structure of a single molecule could take several years because cryo-TEM imaging relied on film, meaning that each exposure had to be developed and scanned before it could be analyzed. The main limitation, however, was that most images turned out blurry. When you directed a beam of electrons at a molecule, the charged, high-energy particles excited the atoms in the molecule, often making them move at the moment of exposure. This meant that researchers needed to take and process hundreds, if not thousands, of film images in order to get an accurate glimpse of an entire molecule.

The new electron counting camera solves this problem by taking digital movies with an extremely high frame rate, so individual frames can be aligned to eliminate blurring caused by beam-induced particle motion.

In the current study, first author Thomas Laughlin, a UC Berkeley graduate student with a joint appointment at MBIB, isolated NDH complexes from membranes of a photosynthetic cyanobacterium provided by the Junko Yano and Vittal Yachandra Lab in MBIB and imaged them using a state-of-the-art cryo-TEM instrument fitted with the latest direct electron detector. Located on the UC Berkeley campus, the cryo-TEM facility is managed by the Bay Area CryoEM consortium, which is partly funded by Berkeley Lab.

The resulting atom density map was then used to build a model of NDH that shows the arrangement of all the protein subunits of NDH and the most likely position of all the atoms in the complex. By examining this model, Davies' team will be able to formulate and then test hypotheses of how NDH facilitates sugar production by balancing the ratio of the two cellular energy molecules.

"While the structure of NDH alone certainly addresses many questions, I think it has raised several more that we had not even thought to consider before," said Laughlin.

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Tidal tails: The beginning of the end of an open star cluster

Image of the Hyades, the star cluster closest to the Sun.

In the course of their life, open star clusters continuously lose stars to their surroundings. The resulting swath of tidal tails provides a glimpse into the evolution and dissolution of a star cluster. Thus far only tidal tails of massive globular clusters and dwarf galaxies have been discovered in the Milky Way system. In open clusters, this phenomenon existed only in theory. Researchers at Heidelberg University have now finally verified the existence of such a tidal tail in the star cluster closest to the Sun, the Hyades. An analysis of measurements from the Gaia satellite led to the discovery.

Open star clusters are collections of approximately 100 to a few thousand stars that emerge almost simultaneously from a collapsing gas cloud and move through space at about the same speed. Owing to a number of influences, however, they do begin to disperse after a few hundred million years. Among the factors working against the gravitationally bound stars is the tidal force of a galaxy, which pulls the stars out of the cluster. Tidal tails then form during the movement of the star cluster through the Milky Way. It is the beginning of the end of an open star cluster.

Together with researchers from the Max Planck Institute for Astronomy in Heidelberg, scientists from the Centre for Astronomy of Heidelberg University (ZAH) have detected this phenomenon for the first time in the Hyades, one of the older and best-studied open star clusters in the Milky Way system. They studied the data published in April 2018 from the Gaia satellite, which has been systematically mapping the heavens for five years. Rather than taking direct photographs, Gaia measures the stars' motion and position.

From this data, the Heidelberg astronomers identified two tidal tails of the Hyades with a total of approximately 500 stars extending up to 650 light-years from the cluster. Dr Siegfried Röser of the Königstuhl State Observatory of the ZAH explains that one of the tails precedes the open star cluster and the other follows it. "Our discovery shows that it is possible to trace the trajectories of individual stars of the Milky Way back to their point of origin in a star cluster," states Dr Röser. The astronomer believes that this marks the beginning of many significant discoveries in galactic astronomy. Apart from the Heidelberg astronomers, a team of researchers from Vienna also discovered the tidal tails of the Hyades.

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A nearby river of stars

Night sky centered on the south Galactic pole in a so-called stereographic projection. In this special projection, the Milky Way curves around the entire image in an arc. The stars in the stream are displayed in red and cover almost the entire southern Galactic hemisphere, thereby crossing many well-known constellations.

Astronomy & Astrophysics publishes the work of researchers from the University of Vienna, who have found a river of stars, a stellar stream in astronomical parlance, covering most of the southern sky. The stream is relatively nearby and contains at least 4000 stars that have been moving together in space since they formed, about 1 billion years ago. Due to its proximity to Earth, this stream is a perfect workbench on which to test the disruption of clusters, measure the gravitational field of the Milky Way, and learn about coeval extrasolar planet populations with upcoming planet-finding missions. For their search, the authors used data from the ESA Gaia satellite.

Our own host galaxy, the Milky Way, is home to star clusters of variable sizes and ages. We find many baby clusters within molecular clouds, fewer middle-age and old age clusters in the Galactic disk, and even fewer massive, old globular clusters in the halo. These clusters, regardless of their origin and age, are all subject to tidal forces along their orbits in the Galaxy. Given enough time, the Milky Way gravitational forces relentlessly pull them apart, dispersing their stars into the collection of stars we know as the Milky Way.

"Most star clusters in the Galactic disk disperse rapidly after their birth as they do not contain enough stars to create a deep gravitational potential well, or in other words, they do not have enough glue to keep them together. Even in the immediate solar neighborhood, there are, however, a few clusters with sufficient stellar mass to remain bound for several hundred million years. So, in principle, similar, large, stream-like remnants of clusters or associations should also be part of the Milky Way disk." says Stefan Meingast, lead author of the paper published in Astronomy & Astrophysics.

Thanks to the precision of the Gaia measurements, the authors could measure the 3D motion of stars in space. When carefully looking at the distribution of nearby stars moving together, one particular group of stars, as yet unknown and unstudied, immediately caught the eye of the researchers. It was a group of stars that showed precisely the expected characteristics of a cluster of stars born together but being pulled apart by the gravitational field of the Milky Way.

"Identifying nearby disk streams is like looking for the proverbial needle in a haystack. Astronomers have been looking at, and through, this new stream for a long time, as it covers most of the night sky, but only now realize it is there, and it is huge, and shockingly close to the Sun" says João Alves, second author of the paper. "Finding things close to home is very useful, it means they are not too faint nor too blurred for further detailed exploration, as astronomers dream."

Due to sensitivity limitations of the Gaia observations, their selection only contained about 200 sources. An extrapolation beyond these limits suggests the stream should have at least 4000 stars, thereby making the structure more massive than most know clusters in the immediate solar neighborhood. The authors also determined the stream's age to be around one billion years. As such, it already has completed four full orbits around the Galaxy, enough time to develop the stream-like structure as a consequence of gravitational interaction with the Milky Way disk.

"As soon as we investigated this particular group of stars in more detail, we knew that we had found what we were looking for: A coeval, stream-like structure, stretching for hundreds of parsecs across a third of the entire sky." Says Verena Fürnkranz, co-author and Masters student at the University of Vienna. "It was so thrilling to be part of a new discovery" she adds.

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Massive Bolivian earthquake reveals mountains 660 kilometers below our feet

Graphic showing the Transition Zone inside the Earth Princeton seismologist Jessica Irving worked with then-graduate student Wenbo Wu and another collaborator to determine the roughness at the top and bottom of the transition zone, a layer within the mantle, using scattered earthquake waves. They found that the top of the transition zone, a layer located 410 kilometers down, is mostly smooth, but the base of the transition zone, 660 km down, in some places is much rougher than the global surface average. “In other words, stronger topography than the Rocky Mountains or the Appalachians is present at the 660-km boundary,” said Wu. NOTE: This graphic is not to scale.

Most schoolchildren learn that the Earth has three (or four) layers: a crust, mantle and core, which is sometimes subdivided into an inner and outer core. That's not wrong, but it does leave out several other layers that scientists have identified within the Earth.

In a study published this week in Science, Princeton geophysicists Jessica Irving and Wenbo Wu, in collaboration with Sidao Ni from the Institute of Geodesy and Geophysics in China, used data from an enormous earthquake in Bolivia to find mountains and other topography on a layer located 660 kilometers (410 miles) straight down, which separates the upper and lower mantle. (Lacking a formal name for this layer, the researchers simply call it "the 660-km boundary.")

To peer deep into the Earth, scientists use the most powerful waves on the planet, which are generated by massive earthquakes. "You want a big, deep earthquake to get the whole planet to shake," said Irving, an assistant professor of geosciences.

Big earthquakes are vastly more powerful than small ones -- energy increases 30-fold with every step up the Richter scale -- and deep earthquakes, "instead of frittering away their energy in the crust, can get the whole mantle going," Irving said. She gets her best data from earthquakes that are magnitude 7.0 or higher, she said, as the shockwaves they send out in all directions can travel through the core to the other side of the planet -- and back again. For this study, the key data came from waves picked up after a magnitude 8.2 earthquake -- the second-largest deep earthquake ever recorded -- that shook Bolivia in 1994.

"Earthquakes this big don't come along very often," she said. "We're lucky now that we have so many more seismometers than we did even 20 years ago. Seismology is a different field than it was 20 years ago, between instruments and computational resources."

Seismologists and data scientists use powerful computers, including Princeton's Tiger supercomputer cluster, to simulate the complicated behavior of scattering waves in the deep Earth.

The technology depends on a fundamental property of waves: their ability to bend and bounce. Just as light waves can bounce (reflect) off a mirror or bend (refract) when passing through a prism, earthquake waves travel straight through homogenous rocks but reflect or refract when they encounter any boundary or roughness.

"We know that almost all objects have surface roughness and therefore scatter light," said Wu, the lead author on the new paper, who just completed his geosciences Ph.D. and is now a postdoctoral researcher at the California Institute of Technology. "That's why we can see these objects -- the scattering waves carry the information about the surface's roughness. In this study, we investigated scattered seismic waves traveling inside the Earth to constrain the roughness of the Earth's 660-km boundary."

The researchers were surprised by just how rough that boundary is -- rougher than the surface layer that we all live on. "In other words, stronger topography than the Rocky Mountains or the Appalachians is present at the 660-km boundary," said Wu. Their statistical model didn't allow for precise height determinations, but there's a chance that these mountains are bigger than anything on the surface of the Earth. The roughness wasn't equally distributed, either; just as the crust's surface has smooth ocean floors and massive mountains, the 660-km boundary has rough areas and smooth patches. The researchers also examined a layer 410 kilometers (255 miles) down, at the top of the mid-mantle "transition zone," and they did not find similar roughness.

"They find that Earth's deep layers are just as complicated as what we observe at the surface," said seismologist Christine Houser, an assistant professor at the Tokyo Institute of Technology who was not involved in this research. "To find 2-mile (1-3 km) elevation changes on a boundary that is over 400 miles (660 km) deep using waves that travel through the entire Earth and back is an inspiring feat. ... Their findings suggest that as earthquakes occur and seismic instruments become more sophisticated and expand into new areas, we will continue to detect new small-scale signals which reveal new properties of Earth's layers."

What it means

The presence of roughness on the 660-km boundary has significant implications for understanding how our planet formed and continues to function. That layer divides the mantle, which makes up about 84 percent of the Earth's volume, into its upper and lower sections. For years, geoscientists have debated just how important that boundary is. In particular, they have investigated how heat travels through the mantle -- whether hot rocks are carried smoothly from the core-mantle boundary (almost 2,000 miles down) all the way up to the top of the mantle, or whether that transfer is interrupted at this layer. Some geochemical and mineralogical evidence suggests that the upper and lower mantle are chemically different, which supports the idea that the two sections don't mix thermally or physically. Other observations suggest no chemical difference between the upper and lower mantle, leading some to argue for what's called a "well-mixed mantle," with both the upper and lower mantle participating in the same heat-transfer cycle.

"Our findings provide insight into this question," said Wu. Their data suggests that both groups might be partially right. The smoother areas of the 660-km boundary could result from more thorough vertical mixing, while the rougher, mountainous areas may have formed where the upper and lower mantle don't mix as well.

In addition, the roughness the researchers found, which existed at large, moderate and small scales, could theoretically be caused by heat anomalies or chemical heterogeneities. But because of how heat in transported within the mantle, Wu explained, any small-scale thermal anomaly would be smoothed out within a million years. That leaves only chemical differences to explain the small-scale roughness they found.

What could cause significant chemical differences? The introduction of rocks that used to belong to the crust, now resting quietly in the mantle. Scientists have long debated the fate of the slabs of sea floor that get pushed into the mantle at subduction zones, the collisions happening found all around the Pacific Ocean and elsewhere around the world. Wu and Irving suggest that remnants of these slabs may now be just above or just below the 660-km boundary.

Read more at Science Daily

What's age got to do with it?

It's often said: It's not how old you are, it's how old you feel. New research shows that physiological age is a better predictor of survival than chronological age. The study is published today in the European Journal of Preventive Cardiology, a journal of the European Society of Cardiology (ESC).

"Age is one of the most reliable risk factors for death: the older you are, the greater your risk of dying," said study author Dr Serge Harb, cardiologist at the Cleveland Clinic in the United States. "But we found that physiological health is an even better predictor. If you want to live longer then exercise more. It should improve your health and your length of life."

Based on exercise stress testing performance, the researchers developed a formula to calculate how well people exercise -- their "physiological age" -- which they call A-BEST (Age Based on Exercise Stress Testing). The equation uses exercise capacity, how the heart responds to exercise (chronotropic competence), and how the heart rate recovers after exercise.

"Knowing your physiological age is good motivation to increase your exercise performance, which could translate into improved survival," said Dr Harb. "Telling a 45-year-old that their physiological age is 55 should be a wake-up call that they are losing years of life by being unfit. On the other hand, a 65-year-old with an A-BEST of 50 is likely to live longer than their peers."

The study included 126,356 patients referred to the Cleveland Clinic between 1991 and 2015 for their first exercise stress test, a common examination for diagnosing heart problems. It involves walking on a treadmill, which gets progressively more difficult. During the test, exercise capacity, heart rate response to exercise, and heart rate recovery are all routinely measured. The data were used to calculate A-BEST, taking into account gender and use of medications that affect heart rate.

The average age of study participants was 53.5 years and 59% were men. More than half of patients aged 50-60 years -- 55% of men and 57% of women -- were physiologically younger according to A-BEST. After an average follow-up of 8.7 years, 9,929 (8%) participants had died. As expected, the individual components of A-BEST were each associated with mortality.

Patients who died were ten years older than those who survived. But A-BEST was a significantly better predictor of survival than chronological age, even after adjusting for sex, smoking, body mass index, statin use, diabetes, hypertension, coronary artery disease, and end-stage kidney disease. This was true for the overall cohort and for both men and women when they were analysed separately.

Dr Harb said doctors could use A-BEST to report results of exercise testing to patients "Telling patients their estimated age based on exercise performance is a powerful estimate of longevity and easier to understand than providing results for the individual components of the examination."

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NASA's Opportunity rover mission on Mars comes to end

This infographic highlights NASA's twin robot geologists, the Mars Exploration Rovers (MER) Spirit and Opportunity.

One of the most successful and enduring feats of interplanetary exploration, NASA's Opportunity rover mission is at an end after almost 15 years exploring the surface of Mars and helping lay the groundwork for NASA's return to the Red Planet.

The Opportunity rover stopped communicating with Earth when a severe Mars-wide dust storm blanketed its location in June 2018. After more than a thousand commands to restore contact, engineers in the Space Flight Operations Facility at NASA's Jet Propulsion Laboratory (JPL) made their last attempt to revive Opportunity Tuesday, to no avail. The solar-powered rover's final communication was received June 10.

"It is because of trailblazing missions such as Opportunity that there will come a day when our brave astronauts walk on the surface of Mars," said NASA Administrator Jim Bridenstine. "And when that day arrives, some portion of that first footprint will be owned by the men and women of Opportunity, and a little rover that defied the odds and did so much in the name of exploration."

Designed to last just 90 Martian days and travel 1,100 yards (1,000 meters), Opportunity vastly surpassed all expectations in its endurance, scientific value and longevity. In addition to exceeding its life expectancy by 60 times, the rover traveled more than 28 miles (45 kilometers) by the time it reached its most appropriate final resting spot on Mars -- Perseverance Valley.

"For more than a decade, Opportunity has been an icon in the field of planetary exploration, teaching us about Mars' ancient past as a wet, potentially habitable planet, and revealing uncharted Martian landscapes," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate. "Whatever loss we feel now must be tempered with the knowledge that the legacy of Opportunity continues -- both on the surface of Mars with the Curiosity rover and InSight lander -- and in the clean rooms of JPL, where the upcoming Mars 2020 rover is taking shape."

The final transmission, sent via the 70-meter Mars Station antenna at NASA's Goldstone Deep Space Complex in California, ended a multifaceted, eight-month recovery strategy in an attempt to compel the rover to communicate.

"We have made every reasonable engineering effort to try to recover Opportunity and have determined that the likelihood of receiving a signal is far too low to continue recovery efforts," said John Callas, manager of the Mars Exploration Rover (MER) project at JPL.

Opportunity landed in the Meridiani Planum region of Mars on Jan. 24, 2004, seven months after its launch from Cape Canaveral Air Force Station in Florida. Its twin rover, Spirit, landed 20 days earlier in the 103-mile-wide (166-kilometer-wide) Gusev Crater on the other side of Mars. Spirit logged almost 5 miles (8 kilometers) before its mission wrapped up in May 2011.

From the day Opportunity landed, a team of mission engineers, rover drivers and scientists on Earth collaborated to overcome challenges and get the rover from one geologic site on Mars to the next. They plotted workable avenues over rugged terrain so that the 384-pound (174-kilogram) Martian explorer could maneuver around and, at times, over rocks and boulders, climb gravel-strewn slopes as steep as 32-degrees (an off-Earth record), probe crater floors, summit hills and traverse possible dry riverbeds. Its final venture brought it to the western limb of Perseverance Valley.

"I cannot think of a more appropriate place for Opportunity to endure on the surface of Mars than one called Perseverance Valley," said Michael Watkins, director of JPL. "The records, discoveries and sheer tenacity of this intrepid little rover is testament to the ingenuity, dedication, and perseverance of the people who built and guided her."

More Opportunity Achievements

• Set a one-day Mars driving record March 20, 2005, when it traveled 721 feet (220 meters).
• Returned more than 217,000 images, including 15 360-degree color panoramas.
• Exposed the surfaces of 52 rocks to reveal fresh mineral surfaces for analysis and cleared 72 additional targets with a brush to prepare them for inspection with spectrometers and a microscopic imager.
• Found hematite, a mineral that forms in water, at its landing site.
• Discovered strong indications at Endeavour Crater of the action of ancient water similar to the drinkable water of a pond or lake on Earth.

All of the off-roading and on-location scientific analyses were in service of the Mars Exploration Rovers' primary objective: To seek out historical evidence of the Red Planet's climate and water at sites where conditions may once have been favorable for life. Because liquid water is required for life, as we know it, Opportunity's discoveries implied that conditions at Meridiani Planum may have been habitable for some period of time in Martian history.

"From the get-go, Opportunity delivered on our search for evidence regarding water," said Steve Squyres, principal investigator of the rovers' science payload at Cornell University. "And when you combine the discoveries of Opportunity and Spirit, they showed us that ancient Mars was a very different place from Mars today, which is a cold, dry, desolate world. But if you look to its ancient past, you find compelling evidence for liquid water below the surface and liquid water at the surface."

All those accomplishments were not without the occasional extraterrestrial impediment. In 2005 alone, Opportunity lost steering to one of its front wheels, a stuck heater threatened to severely limit the rover's available power, and a Martian sand ripple almost trapped it for good. Two years later, a two-month dust storm imperiled the rover before relenting. In 2015, Opportunity lost use of its 256-megabyte flash memory and, in 2017, it lost steering to its other front wheel.

Each time the rover faced an obstacle, Opportunity's team on Earth found and implemented a solution that enabled the rover to bounce back. However, the massive dust storm that took shape in the summer of 2018 proved too much for history's most senior Mars explorer.

"When I think of Opportunity, I will recall that place on Mars where our intrepid rover far exceeded everyone's expectations," Callas said. "But what I suppose I'll cherish most is the impact Opportunity had on us here on Earth. It's the accomplished exploration and phenomenal discoveries. It's the generation of young scientists and engineers who became space explorers with this mission. It's the public that followed along with our every step. And it's the technical legacy of the Mars Exploration Rovers, which is carried aboard Curiosity and the upcoming Mars 2020 mission. Farewell, Opportunity, and well done."

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Orangutans make complex economic decisions about tool use

An adult male uses a stick tool.

Flexible tool use is closely associated to higher mental processes such as the ability to plan actions. Now a group of cognitive biologists and comparative psychologists from the University of Vienna, the University of St Andrews and the University of Veterinary Medicine Vienna that included Isabelle Laumer and Josep Call, has studied tool related decision-making in a non-human primate species -- the orangutan. They found that the apes carefully weighed their options: eat an immediately available food reward or wait and use a tool to obtain a better reward instead? To do so the apes considered the details such as differences in quality between the two food rewards and the functionality of the available tools in order to obtain a high quality food reward, even when multidimensional task components had to be assessed simultaneously.

Tool-use in animals is a rare and often quickly rated as intelligent due to its striking nature. For instance, antlions throw small pebbles at potential prey, archer fish down prey by spitting water at them, and sea otters use stones to crack open shells. Nevertheless, most types of tool use are quite inflexible, typically applied to one situation and tightly controlled by processes that are a part of the respective animal's inborn behavioural repertoire. In contrast, intelligent tool use requires the integration of multiple sources of information to flexibly adapt to quickly changing environmental conditions.

Orangutans share 97 percent of their DNA with us and are among the most intelligent and most endangered primates. They have human-like long-term memory, routinely use a variety of sophisticated tools in the wild and construct elaborate sleeping nests each night from foliage and branches. In their natural habitat, the evergreen rainforests of Borneo and Sumatra, orangutans have to consider several factors simultaneously, such as the predictability to find ripe fruits, the distance and reachability of food as well as the available tools to open extractable food sources. So far it was unknown how orangutans adapt their decisions when the use of a tool is involved and how many factors they can process at the same time in order to make profitable decisions.

Researchers from the University of Vienna, the University of Veterinary Medicine Vienna and the University of St Andrews investigated for the first time how orangutans adapt their decisions when the use of a tool is involved and how many factors they can process at the same time in order to make profitable decisions at the Wolfgang Koehler Primate Research Center in Leipzig.

The researchers used two different types of food items: Banana-pellets, which are the orangutans' most favourite food type, and apple pieces which they like but disregard if banana-pellets are available. They could extract these items from two different apparatuses: an apparatus required probing with a stick tool to obtain the food item while the other required dropping a ball inside it. Each apparatus could only be operated with the respective tool. During testing, orang-utans were confronted with either one or two baited apparatus/es and a choice between two items (usually a food item and a tool). Once the apes had picked one item the other was immediately removed.

Orangutans flexibly adapted their decisions to different conditions: "If the apple piece (likeable food) or the banana-pellet (favourite food) was out of immediate reach inside the apparatus and the choice was between an immediate banana-pellet and a tool, they chose the food over the tool, even when the tool was functional for the respective apparatus," explains Isabelle Laumer who conducted the experiment. "However, when the orangutans could choose between the apple-piece and a tool they chose the tool but only if it worked for the available apparatus: For example when the stick and the likeable food was available but the apes faced the ball-apparatus baited with the favourite banana-pellet, they chose the apple-piece over the non-functional tool. However when the stick-apparatus with the banana-pellet inside was available they chose the stick-tool over the immediate apple-piece," she further explains. "In a final task, that required the orangutans to simultaneously focus on the two apparatuses, one baited with the banana-pellet and the other with the apple and the orangutans had to choose between the two tools they were still able to make profitable decisions by choosing the tool that enabled them to operate the apparatus with the favorite food."

These results are similar to findings in Gofffin cockatoos that have been previously tested in the same task. "Similar to the apes, the cockatoos could overcome immediate impulses in favor of future gains even if this implied tool use. "The birds were confronted with the choice between a tool to retrieve an out-of-reach food item and an immediate reward. We found that they, similar to the apes, were highly sensible to the quality of the immediate relative to the out-of-reach reward at the same time as to whether the available tool would actually work with the task at hand," explains Alice Auersperg, the head of the Goffin Lab in Austria. She continues: "Again, this suggests that similar cognitive abilities can evolve independently in distantly related species."Nevertheless, the cockatoos did reach their limit at the very last task in which both apparatuses baited with both possible food qualities and both tools were available at the same time."

"Optimality models suggest that orangutans should flexibly adapt their foraging decisions depending on the availability of high nutritional food sources, such as fruits," says Josep Call from the University of St Andrews. "Our study shows that orangutans can simultaneously consider multi-dimensional task components in order to maximize their gains and it is very likely that we haven´t even reached the full extent of their information processing capabilities."

Read more at Science Daily

New dinosaur with heart-shaped tail provides evolutionary clues for African continent

Quarry.

A new dinosaur that wears its "heart" on its tail provides new clues to how ecosystems evolved on the African continent during the Cretaceous period according to researchers at Ohio University.

The OHIO team identified and named the new species of dinosaur in an article published this week in PLOS ONE. The new dinosaur, the third now described from southwestern Tanzania by the NSF-funded team, is yet another member of the large, long-necked titanosaur sauropods. The partial skeleton was recovered from Cretaceous-age (~100 million years ago) rocks exposed in a cliff surface in the western branch of the great East African Rift System.

The new dinosaur is named Mnyamawamtuka moyowamkia (Mm-nya-ma-wah-mm-too-ka mm-oh-yo-wa-mm-key-ah), a name derived from Swahili for "animal of the Mtuka (with) a heart-shaped tail" in reference to the name of the riverbed (Mtuka) in which it was discovered and due to the unique shape of its tail bones.

The initial discovery of Mnyamawamtuka took place in 2004, when part of the skeleton was discovered high in a cliff wall overlooking the seasonally dry Mtuka riverbed, with annual excavations continuing through 2008. "Although titanosaurs became one of the most successful dinosaur groups before the infamous mass extinction capping the Age of Dinosaurs, their early evolutionary history remains obscure, and Mnyamawamtuka helps tell those beginnings, especially for their African-side of the story," said lead author Dr. Eric Gorscak, a recent Ph.D. graduate of Ohio University, current research associate at the Field Museum of Natural History (Chicago) and new assistant professor at the Midwestern University in Downers Grove, just outside of Chicago. "The wealth of information from the skeleton indicates it was distantly related to other known African titanosaurs, except for some interesting similarities with another dinosaur, Malawisaurus, from just across the Tanzania-Malawi border," noted Dr. Gorscak.

Titanosaurs are best known from Cretaceous-age rocks in South America, but other efforts by the team include new species discovered in Tanzania, Egypt, and other parts of the African continent that reveal a more complex picture of dinosaurian evolution on the planet. "The discovery of dinosaurs like Mnyamawamtuka and others we have recently discovered is like doing a four-dimensional connect the dots," said Dr. Patrick O'Connor, professor of anatomy at Ohio University and Gorscak's advisor during his Ph.D. research. "Each new discovery adds a bit more detail to the picture of what ecosystems on continental Africa were like during the Cretaceous, allowing us to assemble a more holistic view of biotic change in the past."

The excavation process spanned multiple years, and included field teams suspended by ropes and large-scale mechanical excavators to recover one of the more complete specimens from this part of the sauropod dinosaur family tree. "Without the dedication of several field teams, including some whose members donned climbing gear for the early excavations, the skeleton would have eroded away into the river during quite intense wet seasons in this part of the East African Rift System," added O'Connor.

"This latest discovery is yet another fine example of how Ohio University researchers work the world over in their pursuit of scientific research," Ohio University President M. Duane Nellis said. "This team has turned out a number of notable discoveries which collectively contribute significantly to our understanding of the natural world."

Mnyamawamtuka and the other Tanzanian titanosaurs are not the only animals discovered by the research team. Remains of bizarre relatives of early crocodiles, the oldest evidence for "insect farming," and tantalizing clues about the early evolution of monkeys and apes have been discovered in recent years. Such findings from the East African Rift provide a crucial glimpse into ancient ecosystems of Africa and provide the impetus for future work elsewhere on the continent.

"This new dinosaur gives us important information about African fauna during a time of evolutionary change," said Judy Skog, a program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "The discovery offers insights into paleogeography during the Cretaceous. It's also timely information about an animal with heart-shaped tail bones during this week of Valentine's Day."

Read more at Science Daily

Moving artificial leaves out of the lab and into the air

An artificial, bio-inspired leaf. Carbon dioxide (red and black balls) enter the leaf as water (white and red balls) evaporates from the bottom of the leaf. An artificial photosystem (purple circle at the center of the leaf) made of a light absorber coated with catalysts converts carbon dioxide to carbon monoxide and converts water to oxygen (shown as double red balls) using sunlight.

Artificial leaves mimic photosynthesis -- the process whereby plants use water and carbon dioxide from the air to produce carbohydrates using energy from the sun. But even state-of-the-art artificial leaves, which hold promise in reducing carbon dioxide from the atmosphere, only work in the laboratory because they use pure, pressurized carbon dioxide from tanks.

But now, researchers from the University of Illinois at Chicago have proposed a design solution that could bring artificial leaves out of the lab and into the environment. Their improved leaf, which would use carbon dioxide -- a potent greenhouse gas -- from the air, would be at least 10 times more efficient than natural leaves at converting carbon dioxide to fuel. Their findings are reported in the journal ACS Sustainable Chemistry & Engineering.

"So far, all designs for artificial leaves that have been tested in the lab use carbon dioxide from pressurized tanks. In order to implement successfully in the real world, these devices need to be able to draw carbon dioxide from much more dilute sources, such as air and flue gas, which is the gas given off by coal-burning power plants," said Meenesh Singh, assistant professor of chemical engineering in the UIC College of Engineering and corresponding author on the paper.

Unhooking the pressurized carbon dioxide supply from these leaves means that they must have a way to collect and concentrate carbon dioxide from the air to drive their artificial photosynthetic reactions.

Singh and his colleague Aditya Prajapati, a graduate student in his lab, proposed solving this problem by encapsulating a traditional artificial leaf inside a transparent capsule made of a semi-permeable membrane of quaternary ammonium resin and filled with water. The membrane allows water from inside to evaporate out when warmed by sunlight. As water passes out through the membrane, it selectively pulls in carbon dioxide from the air. The artificial photosynthetic unit inside the capsule is made up of a light absorber coated with catalysts that convert the carbon dioxide to carbon monoxide, which can be siphoned off and used as a basis for the creation of various synthetic fuels. Oxygen is also produced and can either be collected or released into the surrounding environment.

"By enveloping traditional artificial leaf technology inside this specialized membrane, the whole unit is able to function outside, like a natural leaf," Singh said.

According to their calculations, 360 leaves, each 1.7 meters long and 0.2 meters wide, would produce close to a half-ton of carbon monoxide per day that could be used as the basis for synthetic fuels. Three hundred and sixty of these artificial leaves covering a 500-meter square area would be able to reduce carbon dioxide levels by 10 percent in the surrounding air within 100 meters of the array in one day.

Read more at Science Daily

Giant 'megalodon' shark extinct earlier than previously thought

Megalodon extinction graphical abstract.

Megalodon -- a giant predatory shark that has inspired numerous documentaries, books and blockbuster movies -- likely went extinct at least one million years earlier than previously thought, according to new research published Feb. 13 in PeerJ -- the Journal of Life and Environmental Sciences.

Earlier research, which used a worldwide sample of fossils, suggested that the 50-foot-long, giant shark Otodus megalodon went extinct 2.6 million years ago. Another recent study attempted to link this extinction (and that of other marine species) with a supernova known to have occurred at about this time.

However, a team of researchers led by vertebrate paleontologist Robert Boessenecker with the College of Charleston, Charleston, South Carolina, noted that in many places there were problems with the data regarding individual fossils in the study estimating the extinction date.

In the new study, the researchers reported every fossil occurrence of O. megalodon from the densely sampled rock record of California and Baja California (Mexico) in order to estimate the extinction.

Besides Boessenecker, the research team included Dana Ehret, of New Jersey State Museum; Douglas Long, of the California Academy of Sciences; Morgan Churchill, of the University of Wisconsin Oshkosh; Evan Martin, of the San Diego Natural History Museum; and Sarah Boessenecker, of the University of Leicester, United Kingdom.

They found that genuine fossil occurrences were present until the end of the early Pliocene epoch, 3.6 million years ago. All later fossils either had poor data provenance and likely came from other fossil sites or showed evidence of being eroded from older deposits. Until 3.6 million years ago, O. megalodon had a continuous fossil record on the West Coast.

"We used the same worldwide dataset as earlier researchers but thoroughly vetted every fossil occurrence, and found that most of the dates had several problems-fossils with dates too young or imprecise, fossils that have been misidentified, or old dates that have since been refined by improvements in geology; and we now know the specimens are much younger," Boessenecker said.

"After making extensive adjustments to this worldwide sample and statistically re-analyzing the data, we found that the extinction of O. megalodon must have happened at least one million years earlier than previously determined."

This is a substantial adjustment as it means that O. megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.

"The extinction of O. megalodon was previously thought to be related to this marine mass extinction-but in reality, we now know the two are not immediately related," Boessenecker said.

It also is further unclear if this proposed mass extinction is actually an extinction, as marine mammal fossils between 1 and 2 million years old are extraordinarily rare-giving a two-million- year-long period of "wiggle room."

"Rather, it is possible that there was a period of faunal turnover (many species becoming extinct and many new species appearing) rather than a true immediate and catastrophic extinction caused by an astronomical cataclysm like a supernova," Boessenecker said.

The researchers speculate that competition with the newly evolved modern great white shark (Carcharodon carcharias) is a more likely reason for megalodon's extinction.

Great whites first show up with serrated teeth about 6 million years ago and only in the Pacific; by 4 million years ago, they are finally found worldwide.

Read more at Science Daily

Ecosystem changes following loss of great white sharks

Great white shark.

A new study has documented unexpected consequences following the decline of great white sharks from an area off South Africa. The study found that the disappearance of great whites has led to the emergence of sevengill sharks, a top predator from a different habitat. A living fossil, sevengill sharks closely resemble relatives from the Jurassic period, unique for having seven gills instead of the typical five in most other sharks.

These findings are part of a long-term collaborative study between shark researcher Neil Hammerschlag from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, and wildlife naturalist Chris Fallows from Apex Shark Expeditions.

The research focused on the waters surrounding Seal Island in False Bay, South Africa, a site well known for its "flying" great white sharks that breach out of the water when attacking Cape fur seals. Since the year 2000, the research team has spent over 8,000 hours observing great whites from boats, during which they recorded 6,333 shark sightings, and 8,076 attacks on seals. These data revealed that for more than a decade, great white numbers were relatively stable, but in 2015 sightings began to drop off steeply.

"In 2017 and 2018, their numbers reached an all-time low, with great whites completely disappearing from our surveys for weeks and months at a time," said study lead author Neil Hammerschlag, a research associate professor at the UM Rosenstiel School and Abess Center for Ecosystem Science & Policy. "While the reasons for their decline and disappearance remains unknown, it provided a truly unique opportunity for us to see what happens to an ocean ecosystem following the loss of an apex predator."

"In 18+ years of working at Seal Island, we had never seen sevengill sharks in our surveys," said co-author Chris Fallows. "Following the disappearance of white sharks in 2017, sevengill began to show up for the first time and have been increasing in number ever since."

During periods of great white absence in 2017 and 2018, the researchers documented 120 sevengill shark sightings and even witnessed an individual attacking a live seal. In South African waters, sevengill sharks have no equal in the food web with the exception of the great white and orca whale. Historically, the only well-known aggregation site for sevengills in False Bay was located 18 km away from Seal Island within inshore kelp beds. The study suggested that the appearance of sevengill sharks at Seal Island was due to the disappearance of great whites, thereby allowing sevengills to exploit the area without risk of predation from great white sharks or competition with them for shared prey.

Read more at Science Daily

Antarctic ice shelves buckle under weight of meltwater lakes

Meltwater lakes in Antarctica.

The filling and draining of meltwater lakes has been found to cause a floating Antarctic ice shelf to flex, potentially threatening its stability.

A team of British and American researchers, co-led by the University of Cambridge, has measured how much the McMurdo ice shelf in Antarctica flexes in response to the filling and draining of meltwater lakes on its surface. This type of flexing had been hypothesised before and simulated by computer models, but this is the first time the phenomenon has been measured in the field. The results are reported in the journal Nature Communications.

The results demonstrate a link between surface melting and the weakening of Antarctic ice shelves and support the idea that recent ice shelf breakup around the Antarctic Peninsula may have been triggered, at least in part, by large amounts of surface meltwater produced in response to atmospheric warming.

As the climate continues to warm, more and more ice shelves may become susceptible to flex, fracture and break up over the coming century.

Most of the Antarctic continent is covered by the Antarctic Ice Sheet, which is up to four kilometres thick and contains enough ice to raise global sea levels by about 58 metres. Over most of the continent and for most of the year, air temperatures are well below zero and the ice surface remains frozen. But around 75% of the ice sheet is fringed by floating ice shelves, which are up to a kilometre thick, mostly below sea level, but with tens of metres of their total height protruding above the water. In the summer months, when air temperatures rise above freezing, the surfaces of these ice shelves are susceptible to melting.

"Surface water on ice shelves has been known about for a long time," said co-author Dr Ian Willis from Cambridge's Scott Polar Research Institute. "Over 100 years ago, members of both Shackleton's Nimrod team and the Northern Party team of Scott's British Antarctic Expedition mapped and recorded water on the Nansen Ice Shelf, around 300 kilometres from where we did our study on the McMurdo Ice Shelf. For the last few decades, it has also been possible to see widespread surface meltwater forming on many ice shelves each summer from satellite imagery."

What is not fully known is the extent to which surface water might destabilise an ice shelf, especially in warmer summers when more meltwater is produced. If the slope of the ice shelf is sufficiently steep, the water may flow off the ice shelf to the ocean in large surface rivers, mitigating against any potential instability.

The danger comes if water pools up in surface depressions on the ice shelf to form large lakes. The extra weight of the water will push down on the floating ice, causing it to sink a bit further into the sea. Around the edge of the lake, the ice will flex upwards to compensate. "If the lake then drains, the ice shelf will now flex back, rising up where the lake used to be, sinking down around the edge," said lead author Dr Alison Banwell, also from SPRI. "It is this filling and draining of lakes that causes the ice shelf to flex, and if the stresses are large enough, fractures might also develop."

Banwell and co-author Professor Doug MacAyeal from the University of Chicago had previously suggested that the filling and draining of hundreds of lakes might have led to the catastrophic breakup of the Larsen B Ice Shelf 2002 when 3,250 square kilometres of ice was lost in just a few days.

"We had been able to model the rapid disintegration of that ice shelf via our meltwater loading-induced fracture mechanism," said Banwell. "However, the problem was that no one had actually measured ice shelf flex and fracture in the field, and so we were unable to fully constrain the parameters in our model. That's partly why we set out to try to measure the process on the McMurdo ice shelf."

Using helicopters, snow machines and their own two feet, the researchers set up a series of pressure sensors to monitor the rise and fall of water levels in depressions which filled to become lakes, and GPS receivers to measure small vertical movements of the ice shelf.

"It was a lot of work to obtain the data, but they reveal a fascinating story," said MacAyeal. "Most of the GPS signal is due to the ocean tides, which move the floating ice shelf up and down by several metres twice a day. But when we removed this tidal signal we found some GPS receivers moved down, then up by around one metre over a few weeks whereas others, just a few hundred metres away, hardly moved at all. The ones that moved down then up the most were situated where lakes were filling and draining, and there was relatively little movement away from the lakes. It is this differential vertical motion that shows the ice shelf is flexing. We'd anticipated this result, but it was very nice when we found it."

Read more at Science Daily

Neanderthal footprints found in Gibraltar

The place where the footprint was found.

The  international journal Quaternary Science Reviews has just published a paper which has involved the participation of Gibraltarian scientists from The Gibraltar National Museum alongside colleagues from Spain, Portugal and Japan. The results which have been published come from an area of the Catalan Bay Sand Dune.

This work started ten years ago, when the first dates using the OSL method were obtained. It is then that the first traces of footprints left by vertebrates were found. In subsequent years the successive natural collapse of sand has revealed further material and has permitted a detailed study including new dates.

The sand sheets in the rampant dunes above Catalan Bay are a relic of the last glaciation, when sea level was up to 120 metres below present levels and a great field of dunes extended eastwards from the base of the Rock. The identified footprints correspond to species which are known, from fossil material, to have inhabited Gibraltar. The identified footprints correspond to Red Deer, Ibex, Aurochs, Leopard and Straight-tusked Elephant. In addition the scientists have found the footprint of a young human (106-126 cm in height), possibly Neanderthal, which dates to around 29 thousand years ago. It would coincide with late Neanderthal dates from Gorham's Cave.

If confirmed to be Neanderthal, these dunes would become only the second site in the world with footprints attributed to these humans, the other being Vartop Cave in Romania. These findings add further international importance to the Gibraltar Pleistocene heritage, declared of World Heritage Value in 2016.

The research was supported by HM Government of Gibraltar under the Gibraltar Caves Project and the annual excavations in the Gibraltar Caves, with additional support to the external scientists from the Spanish EU project MICINN-FEDER: CGL2010-15810/BTE.

Minister for Heritage John Cortes MP commented, "This is extraordinary research and gives us an incredible insight into the wildlife community of Gibraltar's past. We should all take a moment to imagine the scene when these animals walked across our landscape. It helps us understand the importance of looking after our heritage. I congratulate the research team on uncovering this fascinating, hidden evidence of our Rock's past."

From Science Daily

NASA finds possible second impact crater under Greenland ice

Just 114 miles from the newly-found Hiawatha impact crater under the ice of northwest Greenland, lies a possible second impact crater. The 22-mile wide feature would be the second crater found under an ice sheet, and if confirmed, would be the 22nd-largest crater on Earth. A NASA-led team discovered the feature using satellite data of the surface of the Greenland Ice Sheet as well as radar measurements from NASA’s airborne campaign Operation IceBridge.

A NASA glaciologist has discovered a possible second impact crater buried under more than a mile of ice in northwest Greenland.

his follows the finding, announced in November 2018, of a 19-mile-wide crater beneath Hiawatha Glacier -- the first meteorite impact crater ever discovered under Earth's ice sheets. Though the newly found impact sites in northwest Greenland are only 114 miles apart, at present they do not appear to have formed at the same time.

If the second crater, which has a width of over 22 miles, is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.

"We've surveyed the Earth in many different ways, from land, air and space -- it's exciting that discoveries like these are still possible," said Joe MacGregor, a glaciologist with NASA's Goddard Space Flight Center in Greenbelt, Maryland, who participated in both findings.

Before the discovery of the Hiawatha impact crater, scientists generally assumed that most evidence of past impacts in Greenland and Antarctica would have been wiped away by unrelenting erosion by the overlying ice. Following the finding of that first crater, MacGregor checked topographic maps of the rock beneath Greenland's ice for signs of other craters. Using imagery of the ice surface from the Moderate Resolution Imaging Spectroradiometer instruments aboard NASA's Terra and Aqua satellites, he soon noticed a circular pattern some 114 miles to the southeast of Hiawatha Glacier. The same circular pattern also showed up in ArcticDEM, a high-resolution digital elevation model of the entire Arctic derived from commercial satellite imagery.

"I began asking myself 'Is this another impact crater? Do the underlying data support that idea?'," MacGregor said. "Helping identify one large impact crater beneath the ice was already very exciting, but now it looked like there could be two of them."

MacGregor reported the discovery of this second possible crater in Geophysical Research Letters on Feb.11.

To confirm his suspicion about the possible presence of a second impact crater, MacGregor studied the raw radar images that are used to map the topography of the bedrock beneath the ice, including those collected by NASA's Operation IceBridge. What he saw under the ice were several distinctive features of a complex impact crater: a flat, bowl-shaped depression in the bedrock that was surrounded by an elevated rim and centrally located peaks, which form when the crater floor equilibrates post-impact. Though the structure isn't as clearly circular as the Hiawatha crater, MacGregor estimated the second crater's diameter at 22.7 miles. Measurements from Operation IceBridge also revealed a negative gravity anomaly over the area, which is characteristic of impact craters.

"The only other circular structure that might approach this size would be a collapsed volcanic caldera," MacGregor said. "But the areas of known volcanic activity in Greenland are several hundred miles away. Also, a volcano should have a clear positive magnetic anomaly, and we don't see that at all."

Although the newly found impact craters in northwest Greenland are only 114 miles apart, they do not appear to have been formed at the same time. From the same radar data and ice cores that had been collected nearby, MacGregor and his colleagues determined that the ice in the area was at least 79,000 years old. The layers of ice were smooth, suggesting the ice hadn't been strongly disturbed during that time. This meant that either the impact happened more than 79,000 years ago or -- if it took place more recently -- any impact-disturbed ice had long ago flowed out of the area and been replaced by ice from farther inland.

The researchers then looked at rates of erosion: they calculated that a crater of that size would have initially been more half a mile deep between its rim and floor, which is an order of magnitude greater than its present depth. Taking into account a range of plausible erosion rates, they calculated that it would have taken anywhere between roughly a hundred thousand years and a hundred million years for the ice to erode the crater to its current shape -- the faster the erosion rate, the younger the crater would be within the plausible range, and vice versa.

"The ice layers above this second crater are unambiguously older than those above Hiawatha, and the second crater is about twice as eroded," MacGregor said. "If the two did form at the same time, then likely thicker ice above the second crater would have equilibrated with the crater much faster than for Hiawatha."

To calculate the statistical likelihood that the two craters were created by unrelated impact events, MacGregor's team used recently published estimates that leverage lunar impact rates to better understand Earth's harder-to-detect impact record. By employing computer models that can track the production of large craters on Earth, they found that the abundance of said craters that should naturally form close to one another, without the need for a twin impact, was consistent with Earth's cratering record.

"This does not rule out the possibility that the two new Greenland craters were made in a single event, such as the impact of a well separated binary asteroid, but we cannot make a case for it either," said William Bottke, a planetary scientist with the Southwest Research Institute in Boulder, Colorado, and co-author of both MacGregor's paper and the new lunar impact record study.

Indeed, two pairs of unrelated but geographically close craters have already been found in Ukraine and Canada, but the ages of the craters in the pairs are different from one another.

Read more at Science Daily

Discovery of the oldest evidence of mobility on Earth

Previously, the oldest traces of this kind found dated to approximately 600 million years ago: the Ediacaran period, also characterized by a peak in dioxygen and a proliferation in biodiversity. Scale bar: 1 cm.

An international and multi-disciplinary team coordinated by Abderrazak El Albani at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) has uncovered the oldest fossilised traces of motility. Whereas previous remnants were dated to 570 million years ago, this new evidence is 2.1 billion years old. They were discovered in a fossil deposit in Gabon, where the oldest multicellular organisms have already been found. These results appear in the 11 February 2019 edition of PNAS.

A few years ago, geologist Abderrazak El Albani and his team at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) discovered the oldest existing fossils of multicellular organisms in a deposit in Gabon. Located in the Franceville Basin, the deposit allowed scientists to re-date the appearance of multicellular life on Earth to 2.1 billion years -- approximately 1.5 billion years earlier than previously thought (600 million). At the time, researchers showed that this rich biodiversity co-occurred with a peak in dioxygenation of the atmosphere, and developed in a calm and shallow marine environment.

In this same geological deposit, the team has now uncovered the existence of fossilised traces of motility. This shows that certain multicellular organisms in this primitive marine ecosystem were sophisticated enough to move through its mud, rich in organic matter.

The traces were analysed and reconstructed in 3D using X-ray computed micro-tomography, a non-destructive imaging technique. The more or less sinuous structures are tubular, of a generally consistent diameter of a few millimetres, and run through fine layers of sedimentary rock. Geometrical and chemical analysis reveals that they are biological in origin and appeared at the same time the sediment was deposited.

The traces are located next to fossilised microbial biofilms, which formed carpets between the superficial sedimentary layers. It is plausible that the organisms behind this phenomenon moved in search of nutritive elements and the dioxygen, both produced by cyanobacteria.

What did these living elements look like? Though difficult to know for certain, they may have been similar to colonial amoebae, which cluster together when resources become scarce, forming a type of slug, which moves in search of a more favourable environment.

Read more at Science Daily

Possibility of recent underground volcanism on Mars

This is the Martian South Pole. A new study in Geophysical Research Letters argues there needs to be an underground source of heat for liquid water to exist underneath the polar ice cap.

A study published last year in the journal Science suggested liquid water is present beneath the south polar ice cap of Mars. Now, a new study in the AGU journal Geophysical Research Letters argues there needs to be an underground source of heat for liquid water to exist underneath the polar ice cap.

The new research does not take sides as to whether the liquid water exists. Instead, the authors suggest recent magmatic activity -- the formation of a magma chamber within the past few hundred thousand years -- must have occurred underneath the surface of Mars for there to be enough heat to produce liquid water underneath the kilometer-and-a-half thick ice cap. On the flip side, the study's authors argue that if there was not recent magmatic activity underneath the surface of Mars, then there is not likely liquid water underneath the ice cap.

"Different people may go different ways with this, and we're really interested to see how the community reacts to it," said Michael Sori, an associate staff scientist in the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper.

The potential presence of recent underground magmatic activity on Mars lends weight to the idea that Mars is an active planet, geologically speaking. That fact could give scientists a better understanding of how planets evolve over time.

The new study is intended to further the debate around the possibility of liquid water on Mars. The presence of liquid water on the Red Planet has implications for potentially finding life outside of Earth and could also serve as a resource for future human exploration of our neighboring planet.

"We think that if there is any life, it likely has to be protected in the subsurface from the radiation," said Ali Bramson, a postdoctoral research associate at the Lunar and Planetary Laboratory at the University of Arizona and a co-lead author of the new paper. "If there are still magmatic processes active today, maybe they were more common in the recent past, and could supply more widespread basal melting. This could provide a more favorable environment for liquid water and thus, perhaps, life."

Examining the environment

Mars has two giant ice sheets at its poles, both a couple of kilometers thick. On Earth, it is common for liquid water to be present underneath thick ice sheets, with the planet's heat causing the ice to melt where it meets the Earth's crust.

In a paper published last year in Science, scientists said they detected a similar phenomenon on Mars. They claimed radar observations detected evidence of liquid water at the base of Mars's south polar ice cap. However, the Science study did not address how the liquid water could have gotten there.

Mars is much cooler than Earth so it was unclear what type of environment would be needed to melt the ice at the base of the ice cap. Although previous research has examined if liquid water could exist at the base of Mars's ice caps, no one had yet looked at the specific location where the Science study claimed to have detected water.

"We thought there was a lot of room to figure out if [the liquid water] is real, what sort of environment would you need to melt the ice in the first place, what sort of temperatures would you need, what sort of geological process would you need? Because under normal conditions, it should be too cold," Sori said.

Looking for the heat

The new study's authors first assumed the detection of liquid water underneath the ice cap was correct and then worked to figure out what parameters were needed for the water to exist. They performed physical modeling of Mars to understand how much heat is coming out of the interior of the planet and if there could be enough salt at the base of the ice cap to melt the ice. Salt lowers the melting point of ice significantly so it was thought that salt could have led to melting at the base of the ice cap.

The model showed salt alone would not raise the temperature high enough to melt the ice. Instead, the authors propose there needs to be additional heat coming from Mars's interior.

One plausible heat source would be volcanic activity in the planet's subsurface. The study's authors argue that magma from the deep interior of Mars rose towards the planet's surface about 300,000 years ago. It did not break the surface, like a volcanic eruption, but pooled in a magma chamber below the surface. As the magma chamber cooled, it released heat that melted the ice at the base of the ice sheet. The magma chamber is still providing heat to the ice sheet to generate liquid water today.

The idea of volcanic activity on Mars is not new -- there is a lot of evidence of volcanism on the planet's surface. But most of the volcanic features on Mars are from millions of years ago, leading scientists to believe volcanic activity below and above the planet's surface stopped long ago.

The new study, however, proposes that there could have been more recent underground volcanic activity. And, if there was volcanic activity happening hundreds of thousands of years ago, there's a possibility it could be happening today, according to the study's authors.

"This would imply that there is still active magma chamber formation going on in the interior of Mars today and it is not just a cold, sort of dead place, internally," Bramson said.

Jack Holt, a professor at the at the Lunar and Planetary Laboratory at the University of Arizona, said the question of how water could exist underneath the south polar ice cap immediately came to his mind after the Science paper was published, and the new paper adds an important constraint on the possibility of water being there. He said it will likely add to the debate in the planetary science community about the finding and point out that more research needs to be done to evaluate it.

Read more at Science Daily

Climate of North American cities will shift hundreds of miles in one generation

Under current high emissions the average urban dweller is going to have to drive more than 500 miles to the south to find a climate similar to their home city by 2080.

In one generation, the climate experienced in many North American cities is projected to change to that of locations hundreds of miles away -- or to a new climate unlike any found in North America today.

A new study and interactive web application aim to help the public understand how climate change will impact the lives of people who live in urban areas of the United States and Canada. These new climate analyses match the expected future climate in each city with the current climate of another location, providing a relatable picture of what is likely in store.

"Under current high emissions the average urban dweller is going to have to drive more than 500 miles to the south to find a climate like that expected in their home city by 2080," said study author Matt Fitzpatrick of the University of Maryland Center for Environmental Science. "Not only is climate changing, but climates that don't presently exist in North America will be prevalent in a lot of urban areas."

The study found that by the 2080s, even if limits are placed on emissions, the climate of North American urban areas will feel substantially different, and in many cases completely unlike contemporary climates found anywhere in the western hemisphere north of the equator.

If emissions continue unabated throughout the 21st century, the climate of North American urban areas will become, on average, most like the contemporary climate of locations about 500 miles away and mainly to the south. In the eastern U.S., nearly all urban areas, including Boston, New York, and Philadelphia, will become most similar to contemporary climates to the south and southwest. Climates of most urban areas in the central and western U.S. will become most similar to contemporary climates found to the south or southeast.

"Within the lifetime of children living today, the climate of many regions is projected to change from the familiar to conditions unlike those experienced in the same place by their parents, grandparents, or perhaps any generation in millennia," said Fitzpatrick. "Many cities could experience climates with no modern equivalent in North America."

The climate of cities in the northeast will tend to feel more like the humid subtropical climates typical of parts of the Midwest or southeastern U.S. today -- warmer and wetter in all seasons. For instance, unless we take action to mitigate emissions, Washington, D.C. will feel more like northern Mississippi. The climates of western cities are expected to become more like those of the desert Southwest or southern California -- warmer in all seasons, with changes in the amount and seasonal distribution of precipitation. San Francisco's climate will resemble that of Los Angeles. New York will feel more like northern Arkansas.

Scientists analyzed 540 urban areas that encompassed approximately 250 million inhabitants in the United States and Canada. For each urban area, they mapped the similarity between that city's future climate expected by the 2080s and contemporary climate in the western hemisphere north of the equator using 12 measures of climate, including minimum and maximum temperature and precipitation during the four seasons.

The study also mapped climate differences under two emission trajectories: unmitigated emissions (RCP8.5), the scenario most in line with what might be expected given current policies and the speed of global action, and mitigated emissions (RCP4.5), which assumes policies are put in place to limit emissions, such as the Paris Agreement.

Climate-analog mapping is a statistical technique that matches the expected future climate at one location -- your city of residence, for instance -- with the current climate of another familiar location to provide a place-based understanding of climate change. Combining climate mapping with the interactive web application provides a powerful tool to communicate how climate change may impact the lives of a large portion of the population of the United States and Canada.

"We can use this technique to translate a future forecast into something we can better conceptualize and link to our own experiences," said Fitzpatrick. "It's my hope that people have that 'wow' moment, and it sinks in for the first time the scale of the changes we're expecting in a single generation."

Read more at Science Daily

Climate change may destroy tiger's home

A James Cook University scientist says the last coastal stronghold of an iconic predator, the endangered Bengal tiger, could be destroyed by climate change and rising sea levels over the next 50 years.

"Fewer than 4,000 Bengal tigers are alive today," said JCU's Professor Bill Laurance, a co-author of the study.

"That's a really low number for the world's biggest cat, which used to be far more abundant but today is mainly confined to small areas of India and Bangladesh," he said.

"Spanning more than 10,000 square kilometres, the Sundarbans region of Bangladesh and India is the biggest mangrove forest on Earth, and also the most critical area for Bengal tiger survival," said lead-author Dr Sharif Mukul, an assistant professor at Independent University Bangladesh.

"What is most terrifying is that our analyses suggest tiger habitats in the Sundarbans will vanish entirely by 2070," said Dr Mukul.

The researchers used computer simulations to assess the future suitability of the low-lying Sundarban region for tigers and their prey species, using mainstream estimates of climatic trends from the Intergovernmental Panel on Climate Change. Their analyses included factors such as extreme weather events and sea-level rise.

"Beyond climate change, the Sundarbans are under growing pressure from industrial developments, new roads, and greater poaching," said Professor Laurance.

"So, tigers are getting a double whammy -- greater human encroachment on the one hand and a worsening climate and associated sea-level rises on the other," he said.

But the researchers emphasise there is still hope.

"The more of the Sundarbans that can be conserved -- via new protected areas and reducing illegal poaching -- the more resilient it will be to future climatic extremes and rising sea levels," said Professor Laurance.

"Our analyses are a preliminary picture of what could happen if we don't start to look after Bengal tigers and their critical habitats," said Dr Mukul.

"There is no other place like the Sundarbans left on Earth," said Professor Laurance. "We have to look after this iconic ecosystem if we want amazing animals like the Bengal tiger to have a chance of survival."

From Science Daily