Apr 27, 2017

Using math to investigate possibility of time travel

Ben Tippett, a mathematics and physics instructor at UBC, recently published a study about the feasibility of time travel.
After some serious number crunching, a UBC researcher has come up with a mathematical model for a viable time machine.

Ben Tippett, a mathematics and physics instructor at UBC's Okanagan campus, recently published a study about the feasibility of time travel. Tippett, whose field of expertise is Einstein's theory of general relativity, studies black holes and science fiction when he's not teaching. Using math and physics, he has created a formula that describes a method for time travel.

"People think of time travel as something as fiction," says Tippett. "And we tend to think it's not possible because we don't actually do it. But, mathematically, it is possible."

Ever since HG Wells published his book Time Machine in 1885, people have been curious about time travel--and scientists have worked to solve or disprove the theory, he says. In 1915 Albert Einstein announced his theory of general relativity, stating that gravitational fields are caused by distortions in the fabric of space and time. More than 100 years later, the LIGO Scientific Collaboration--an international team of physics institutes and research groups--announced the detection of gravitational waves generated by colliding black holes billions of lightyears away, confirming Einstein's theory.

The division of space into three dimensions, with time in a separate dimension by itself, is incorrect, says Tippett. The four dimensions should be imagined simultaneously, where different directions are connected, as a space-time continuum. Using Einstein's theory, Tippett says that the curvature of space-time accounts for the curved orbits of the planets.

In "flat" -- or uncurved -- space-time, planets and stars would move in straight lines. In the vicinity of a massive star, space-time geometry becomes curved and the straight trajectories of nearby planets will follow the curvature and bend around star.

"The time direction of the space-time surface also shows curvature. There is evidence showing the closer to a black hole we get, time moves slower," says Tippett. "My model of a time machine uses the curved space-time -- to bend time into a circle for the passengers, not in a straight line. That circle takes us back in time."

While it is possible to describe this type of time travel using a mathematical equation, Tippett doubts that anyone will ever build a machine to make it work.

"HG Wells popularized the term 'time machine' and he left people with the thought that an explorer would need a 'machine or special box' to actually accomplish time travel," Tippett says. "While is it mathematically feasible, it is not yet possible to build a space-time machine because we need materials--which we call exotic matter--to bend space-time in these impossible ways, but they have yet to be discovered."

For his research, Tippett created a mathematical model of a Traversable Acausal Retrograde Domain in Space-time (TARDIS). He describes it as a bubble of space-time geometry which carries its contents backward and forwards through space and time as it tours a large circular path. The bubble moves through space-time at speeds greater than the speed of light at times, allowing it to move backward in time.

Read more at Science Daily

DNA from extinct humans discovered in cave sediments

This is an entrance to the archaeological site of Vindija Cave, Croatia.
While there are numerous prehistoric sites in Europe and Asia that contain tools and other human-made artefacts, skeletal remains of ancient humans are scarce. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have therefore looked into new ways to get hold of ancient human DNA. From sediment samples collected at seven archaeological sites, the researchers "fished out" tiny DNA fragments that had once belonged to a variety of mammals, including our extinct human relatives. They retrieved DNA from Neandertals in cave sediments of four archaeological sites, also in layers where no hominin skeletal remains have been discovered. In addition, they found Denisovan DNA in sediments from Denisova Cave in Russia. These new developments now enable researchers to uncover the genetic affiliations of the former inhabitants of many archaeological sites which do not yield human remains.

By looking into the genetic composition of our extinct relatives, the Neandertals, and their cousins from Asia, the Denisovans, researchers can shed light on our own evolutionary history. However, fossils of ancient humans are rare, and they are not always available or suitable for genetic analyses. "We know that several components of sediments can bind DNA," says Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology. "We therefore decided to investigate whether hominin DNA may survive in sediments at archaeological sites known to have been occupied by ancient hominins."

To this aim Meyer and his team collaborated with a large network of researchers excavating at seven archaeological sites in Belgium, Croatia, France, Russia and Spain. Overall, they collected sediment samples covering a time span from 14,000 to over 550,000 years ago. Using tiny amounts of material the researchers recovered and analyzed fragments of mitochondrial DNA -- genetic material from the mitochondria, the "energy factories" of the cell -- and identified them as belonging to twelve different mammalian families that include extinct species such as the woolly mammoth, the woolly rhinoceros, the cave bear and the cave hyena.

The researchers then looked specifically for ancient hominin DNA in the samples. "From the preliminary results, we suspected that in most of our samples, DNA from other mammals was too abundant to detect small traces of human DNA," says Viviane Slon, Ph.D. student at the Max Planck Institute in Leipzig and first author of the study. "We then switched strategies and started targeting specifically DNA fragments of human origin." Nine samples from four archaeological sites contained enough ancient hominin DNA for further analyses: Eight sediment samples contained Neandertal mitochondrial DNA from either one or multiple individuals, while one sample contained Denisovan DNA. Most of these samples originated from archaeological layers or sites where no Neandertal bones or teeth were previously found.

Read more at Discovery News

Scythian horse breeding unveiled: Lessons for animal domestication

These are Kazakh horses in North Central Kazakhstan.
Nomad Scythian herders roamed vast areas spanning the Central Asian steppes during the Iron Age, approximately from the 9th to the 1st century BCE (Before Common Era). These livestock pastoralists, who lived on wagons covered by tents, left their mark in the history of warfare for their exceptional equestrian skills. They were among the first to master mounted riding and to make use of composite bows while riding. A new study published in Science led by Professor Ludovic Orlando and involving 33 international researchers from 16 universities, now reveals the suite of traits that Scythian breeders selected to engineer the type of horse that best fit their purpose.

The study took advantage of exceptionally preserved horse remains in royal Scythian burials, such as the site of Arzhan, Tuva Republic, where over 200 horses have been excavated but also at Berel', Kazakhstan, where no less than 13 horses were preserved in a single, permafrozen funerary chamber. Applying the latest methods in ancient DNA research, the researchers could sequence the genome of 13 Scythian stallions. These were 2,300-2,700 years old and included 11 specimens from Berel' and two from Arzhan. The researchers also sequenced the genome of one 4,100 year-old mare from Chelyabinsk, Russia, belonging to the earlier Sintashta culture, which developed the first two-wheeled chariots drawn by horses.

The DNA variation observed at key genes revealed a large diversity of coat coloration patterns within Scythian horses, including bay, black, chestnut, cream and spotted animals. Scythian horses did not carry the mutation responsible for alternate gaits, and as a consequence, were not natural amblers. However, some but not all individuals carried variants associated with short-distance sprint performance in present-day racing horses. This indicates that Scythian breeders valued animals showing diverse endurance and speed potential.

"With the exception of two horses, none of the animals were related. It fits with Herodotus' depiction of Scythian funerary rituals, whereby sacrificed horses represented gifts from allied tribes spread across the steppes," says Dr. Pablo Librado, post-doctoral researcher at the Centre for GeoGenetics, University of Copenhagen, Denmark, and co-leading author of the study.

Importantly, none of the ancient horses analyzed in the study were inbred, which suggests that Scythian breeders succeeded in maintaining natural herd structures and did not perform selection through a limited number of valuable lineages. This contrasts with modern management practice where single stallions can be used to father hundreds of offspring. Patterns of genetic variation along the genome also revealed a total of 121 genes selected by Scythian breeders, most of which are involved in the development of forelimbs. This is reminiscent of the morphological indices measured on bones, and indicates that Scythian breeders selected horses showing more robust morphologies.

"In this study we wanted to go beyond the myth of Scythians being aggressive warriors, drinking the blood of their enemies in skull mugs. We wanted to reveal the many facets of the exceptional relationship that these people developed with their horses," says Ludovic Orlando, Professor of Molecular Archaeology at the Centre for GeoGenetics, University of Copenhagen and CNRS Research Director at the AMIS laboratory, University of Toulouse.

The genome data set generated in the study also reveals important lessons for the history of horse management, which started some 5,500 years ago, and animal domestication as a whole. By contrasting patterns of genetic variation in ancient and present-day horses, the authors found support for a significant demographic collapse during the last 2,300 years, which resulted in an important reduction of genetic diversity within horse domesticates. During the same time period, reproductive management has involved an increasingly reduced number of stallions, up to the point that, today, almost all domesticates virtually carry the same, or highly similar, Y-chromosome haplotype(s).

"Many Y-chromosome haplotypes co-existed within Scythian horse populations. The first three millennia of horse domestication thus preserved a large diversity of male lineages. It only vanished within the last 2,000 years," adds Dr. Cristina Gamba, post-doctoral researcher at the Centre for GeoGenetics at the time of the study, and co-leading author of the study.

The authors also found that the demographic collapse and loss of Y-chromosomal diversity observed within the last 2,300 years was mirrored by a significant accumulation of deleterious mutations in the genome of the horse. As these mutations reduce the fitness of their carriers, it shows that the last two millennia of horse management have negatively impacted the horse. However, early domestication stages, as represented by the Sintashta and Scythian genomes, did not have such an impact. This contrasts with the Cost-of-domestication hypothesis, which posits a negative impact starting from early domestication stages. In the case of horse domestication, it is likely that the demographic collapse within the last 2,000 years reduced the efficacy of negative selection to purge out deleterious mutations, which could then accumulate in the horse genome.

Finally, the researchers developed a novel statistical method to investigate the genome data for signatures of positive selection in early domestication stages. They found that the genomic regions showing the most extreme signatures were involved in the development of the neural crest, and expressed within tissues derived from the neural crest.

Read more at Science Daily

Cassini Probe Survives First ‘Grand Finale’ Ring Dive Around Saturn

NASA's Cassini spacecraft has survived its first plunge through the narrow gap between Saturn's cloud tops and the giant planet's innermost rings, a region that no probe had ever explored before.

The space agency's Deep Space Network Goldstone Complex in California picked up Cassini's signal at 11:56pm PDT yesterday (April 26; 2:56 am EDT and 0656 GMT today, April 27) — nearly a full day after the historic dive took place. Data began coming in from the probe 5 minutes after contact was established, NASA officials said.

"In the grandest tradition of exploration, NASA's Cassini spacecraft has once again blazed a trail, showing us new wonders and demonstrating where our curiosity can take us if we dare," Jim Green, director of NASA's Planetary Science Division, in Washington, DC, said in a statement.

Cassini zipped through the gap at 2:00 am PDT (5:00 am EDT and 0900 GMT) yesterday, coming within about 1,900 miles (3,000 kilometers) of Saturn's upper atmosphere and 190 miles (300 km) of the visible edge of the innermost rings, NASA officials said.

The probe crossed the ring plane at about 77,000 mph (124,000 km/h) relative to Saturn, they added — fast enough that a collision with even a small particle could have seriously damaged Cassini. To minimize that possibility, the spacecraft used its dish-shaped, 13-foot-wide (4 meters) high-gain antenna as a shield during the dive.

 Because the antenna was oriented toward incoming particles, Cassini couldn't communicate with Earth as it dove. The probe was programmed to gather science data during the plunge and then re-establish contact with mission controllers 20 hours later, NASA officials said. (It currently takes 78 minutes for signals to travel from Cassini to its handlers here on Earth.)

"No spacecraft has ever been this close to Saturn before. We could only rely on predictions, based on our experience with Saturn's other rings, of what we thought this gap between the rings and Saturn would be like," Cassini project manager Earl Maize, of NASA's Jet Propulsion Laboratory in Pasadena, California, said in the same statement.

"I am delighted to report that Cassini shot through the gap just as we planned and has come out the other side in excellent shape," Maize added.

Cassini is scheduled to perform 21 more of these dives during the current "Grand Finale" phase of its mission, with the events occurring about once every week. The next plunge will come on May 2.

The $3.2 billion Cassini-Huygens mission — a joint effort involving NASA, the European Space Agency, and the Italian Space Agency — launched in October 1997 and reached the Saturn system in July 2004. (Huygens was a piggyback lander that touched down on Saturn's largest moon, Titan, in January 2005.)

Read more at Discovery News

Recordings Show Baby Humpback Whales ‘Whispering’ to Avoid Killer Whales

A humpback whale mother-calf pair in Western Australia's Exmouth Gulf.
Newborn humpback whales, like human infants, are extremely vocal, yet new recordings reveal that baby whales often “whisper” to their mother in order to avoid being overheard by orcas, otherwise known as killer whales.

The sweet sounds, described in a study published in the journal Functional Ecology, were music to the ears of ecologists who were hoping to learn more about the first months of a humpback whale’s life.

“It is amazing to hear whales produce sounds underwater in an environment that is hard to access and is foreign to us,” lead author Simone Videsen of Aarhus University told Seeker. “It can only make you happy to hear these sounds produced by calves. The calls produced by the calves are very varied, and some of them sound like grunts while others are very squeaky.”

She added that the calves also produce rubbing sounds, “like two balloons being rubbed together,” which she and her colleagues suspect occurs when calves nudge their mother, signaling that they want to nurse.

Videsen and her team weren’t sure what they would record when they affixed lightweight tags to the backs of eight humpback whale calves and two mothers. The sensitive, high-tech data tags, or “DTAGS,” were attached with suction cups and recorded sounds for up to 48 hours before they detached and floated to the surface.

Humpback whales are often on the move. They spend their summers in the food-rich waters of the Antarctic or Arctic before migrating 5,000 miles in the winter to the tropics in order to breed and mate. The moms and calves included in the study were located at Exmouth Gulf in the northwestern region of the state of Western Australia.

Humpback whale calf wearing a data tag.
The researchers noted that humpback whales are slow to reproduce. Pregnancies last for a year, and calves — measuring 16.4 feet at birth, but growing by up to 3.3 feet per month — stay with their mothers until they are one year old. This includes the lengthy migration, which is a perilous one involving rough sea conditions and strong winds. As mothers and their calves approach the polar regions, the humpback whales must also contend with freezing temperatures.

Perhaps the whales’ greatest challenge, however, is to stay in communication with each other without being overheard.

“Potential eavesdroppers could be killer whales that are known to prey upon humpback whale calves in the area,” Videsen explained. “These [predators] could use the communication between mother and calf as a homing cue.”

“Other potential listeners could be male humpback whales that want to mate with the mother, which would disrupt potential nursing time for the calf,” she added.

As the newborns whisper, the mothers appear to emit very quiet calls from time to time in response. The mothers have the ability to vocalize much louder, so the finding suggests that they are intentionally controlling the sound of their calls.

The whale newborns might be incapable of making louder sounds, due to their smaller body size and inexperience in vocalizing, but many infants throughout the animal kingdom can make a noisy racket.

If the mothers and calves are intentionally lowering the strength of their vocalizations, that would suggest an extraordinary level of not only self-awareness, but also awareness of what others in the region could be capable of hearing. These skills could indicate a very high level of intelligence.

It has long been documented that loud man-made sounds, such as those produced by ships and military exercises, impact whales and other marine life. The determination that humpback whales whisper suggests that human-produced machinery sounds could be particularly harmful to calves and their mothers.

Read more at Discovery News

Apr 26, 2017

'Iceball' planet discovered through microlensing

This artist's concept shows OGLE-2016-BLG-1195Lb, a planet discovered through a technique called microlensing.
Scientists have discovered a new planet with the mass of Earth, orbiting its star at the same distance that we orbit our sun. The planet is likely far too cold to be habitable for life as we know it, however, because its star is so faint. But the discovery adds to scientists' understanding of the types of planetary systems that exist beyond our own.

"This 'iceball' planet is the lowest-mass planet ever found through microlensing," said Yossi Shvartzvald, a NASA postdoctoral fellow based at NASA's Jet Propulsion Laboratory, Pasadena, California, and lead author of a study published in the Astrophysical Journal Letters.

Microlensing is a technique that facilitates the discovery of distant objects by using background stars as flashlights. When a star crosses precisely in front of a bright star in the background, the gravity of the foreground star focuses the light of the background star, making it appear brighter. A planet orbiting the foreground object may cause an additional blip in the star's brightness. In this case, the blip only lasted a few hours. This technique has found the most distant known exoplanets from Earth, and can detect low-mass planets that are substantially farther from their stars than Earth is from our sun.

The newly discovered planet, called OGLE-2016-BLG-1195Lb, aids scientists in their quest to figure out the distribution of planets in our galaxy. An open question is whether there is a difference in the frequency of planets in the Milky Way's central bulge compared to its disk, the pancake-like region surrounding the bulge. OGLE-2016-BLG-1195Lb is located in the disk, as are two planets previously detected through microlensing by NASA's Spitzer Space Telescope.

"Although we only have a handful of planetary systems with well-determined distances that are this far outside our solar system, the lack of Spitzer detections in the bulge suggests that planets may be less common toward the center of our galaxy than in the disk," said Geoff Bryden, astronomer at JPL and co-author of the study.

For the new study, researchers were alerted to the initial microlensing event by the ground-based Optical Gravitational Lensing Experiment (OGLE) survey, managed by the University of Warsaw in Poland. Study authors used the Korea Microlensing Telescope Network (KMTNet), operated by the Korea Astronomy and Space Science Institute, and Spitzer, to track the event from Earth and space.

KMTNet consists of three wide-field telescopes: one in Chile, one in Australia, and one in South Africa. When scientists from the Spitzer team received the OGLE alert, they realized the potential for a planetary discovery. The microlensing event alert was only a couple of hours before Spitzer's targets for the week were to be finalized, but it made the cut.

With both KMTNet and Spitzer observing the event, scientists had two vantage points from which to study the objects involved, as though two eyes separated by a great distance were viewing it. Having data from these two perspectives allowed them to detect the planet with KMTNet and calculate the mass of the star and the planet using Spitzer data.

"We are able to know details about this planet because of the synergy between KMTNet and Spitzer," said Andrew Gould, professor emeritus of astronomy at Ohio State University, Columbus, and study co-author.

Although OGLE-2016-BLG-1195Lb is about the same mass as Earth, and the same distance from its host star as our planet is from our sun, the similarities may end there.

OGLE-2016-BLG-1195Lb is nearly 13,000 light-years away and orbits a star so small, scientists aren't sure if it's a star at all. It could be a brown dwarf, a star-like object whose core is not hot enough to generate energy through nuclear fusion. This particular star is only 7.8 percent the mass of our sun, right on the border between being a star and not.

Alternatively, it could be an ultra-cool dwarf star much like TRAPPIST-1, which Spitzer and ground-based telescopes recently revealed to host seven Earth-size planets. Those seven planets all huddle closely around TRAPPIST-1, even closer than Mercury orbits our sun, and they all have potential for liquid water. But OGLE-2016-BLG-1195Lb, at the sun-Earth distance from a very faint star, would be extremely cold -- likely even colder than Pluto is in our own solar system, such that any surface water would be frozen. A planet would need to orbit much closer to the tiny, faint star to receive enough light to maintain liquid water on its surface.

Ground-based telescopes available today are not able to find smaller planets than this one using the microlensing method. A highly sensitive space telescope would be needed to spot smaller bodies in microlensing events. NASA's upcoming Wide Field Infrared Survey Telescope (WFIRST), planned for launch in the mid-2020s, will have this capability.

"One of the problems with estimating how many planets like this are out there is that we have reached the lower limit of planet masses that we can currently detect with microlensing," Shvartzvald said. "WFIRST will be able to change that."

Read more at Science Daily

Early evidence of Middle Stone Age projectiles found in South Africa's Sibudu Cave

Analyzed serrated pieces.
Innovations in stone knapping technology during the South African Middle Stone Age enabled the creation of early projectile weapons, according to a study published April 26, 2017 in the open-access journal PLOS ONE by Veerle Rots from University of Liège, Belgium, and colleagues.

The South African Middle Stone Age (MSA) is considered a period of major technological advancement, with hunter-gatherers introducing new manipulative techniques using heat and pressure to create stone projectile weapons. However, the timing and location of these developments is a topic of much debate.

The authors of the present study examined 25 weapon point fragments excavated from the Sibudu Cave site, analyzing their technological and functional differences and comparing them with reference samples produced for the purpose by an experienced knapper. Some of the points had two faces, a likely result of applying pressure to both sides. Some had serrations, or jagged edges, that were likely produced by a technique known as pressure flaking.

The researchers found that 14 of the 25 point fragments bore evidence of impact-related damage, animal residues, and wear features that strongly indicated that these points may have been were used for hunting. Examination of the impact-related fractures and the distribution of the points indicated that these points may have been attached to handles to form projectile weapons and that these weapons were projected from a distance, most likely with a flexible spear-thrower or a bow.

While further research would help to confirm the timeline and development of stone knapping techniques, the new Sibudu Cave site data may push back the evidence for the use of pressure flaking during the MSA to 77,000 years ago. The authors note that these findings highlight the diversity of technical innovations adopted by southern African MSA humans.

From Science Daily

Paleontologists identify new 507-million-year-old sea creature with can opener-like pincers

This specimen of Tokummia katalepsis shows a number of strong legs on the left partially protruding from the body, the shape of the bivalved carapace and dozens of small paddle-like limbs below the trunk at the lower right. This nearly complete fossil was chosen as the main reference for the new genus Tokummia and new species katalep.
Paleontologists at the University of Toronto (U of T) and the Royal Ontario Museum (ROM) have uncovered a new fossil species that sheds light on the origin of mandibulates, the most abundant and diverse group of organisms on Earth, to which belong familiar animals such as flies, ants, crayfish and centipedes. The finding was announced in a study published today in Nature.

The creature, named Tokummia katalepsis by the researchers, is a new and exceptionally well-preserved fossilized arthropod -- a ubiquitous group of invertebrate animals with segmented limbs and hardened exoskeletons. Tokummia documents for the first time in detail the anatomy of early "mandibulates," a hyperdiverse sub-group of arthropods which possess a pair of specialized appendages known as mandibles, used to grasp, crush and cut their food. Mandibulates include millions of species and represent one of the greatest evolutionary and ecological success stories of life on Earth.

"In spite of their colossal diversity today, the origin of mandibulates had largely remained a mystery," said Cédric Aria, lead author of the study and recent graduate of the PhD program in the Department of Ecology & Evolutionary Biology at U of T, now working as a post-doctoral researcher at the Nanjing Institute for Geology and Palaeontology, in China. "Before now we've had only sparse hints at what the first arthropods with mandibles could have looked like, and no idea of what could have been the other key characteristics that triggered the unrivaled diversification of that group."

Tokummia lived in a tropical sea teeming with life and was among the largest Cambrian predators, exceeding 10 cm in length fully extended. An occasional swimmer, the researchers conclude its robust anterior legs made it a preferred bottom-dweller, as lobsters or mantis shrimps today. Specimens come from 507 million-year-old sedimentary rocks near Marble Canyon in Kootenay national park, British Columbia. Most specimens at the basis of this study were collected during extensive ROM-led fieldwork activities in 2014.

"This spectacular new predator, one of the largest and best preserved soft-bodied arthropods from Marble Canyon, joins the ranks of many unusual marine creatures that lived during the Cambrian Explosion, a period of rapid evolutionary change starting about half a billion years ago when most major animal groups first emerged in the fossil record," said co-author Jean-Bernard Caron, senior curator of invertebrate paleontology at the ROM and an associate professor in the Departments of Ecology & Evolutionary Biology and Earth Sciences at U of T.

Analysis of several fossil specimens, following careful mechanical preparation and photographic work at the ROM, showed that Tokummia sported broad serrated mandibles as well as large but specialized anterior claws, called maxillipeds, which are typical features of modern mandibulates.

"The pincers of Tokummia are large, yet also delicate and complex, reminding us of the shape of a can opener, with their couple of terminal teeth on one claw, and the other claw being curved towards them," said Aria. "But we think they might have been too fragile to be handling shelly animals, and might have been better adapted to the capture of sizable soft prey items, perhaps hiding away in mud. Once torn apart by the spiny limb bases under the trunk, the mandibles would have served as a revolutionary tool to cut the flesh into small, easily digestible pieces."

The body of Tokummia is made of more than 50 small segments covered by a broad two-piece shell-like structure called a bivalved carapace. Importantly, the animal bears subdivided limb bases with tiny projections called endites, which can be found in the larvae of certain crustaceans and are now thought to have been critical innovations for the evolution of the various legs of mandibulates, and even for the mandibles themselves.

The many-segmented body is otherwise reminiscent of myriapods, a group that includes centipedes, millipedes, and their relatives. "Tokummia also lacks the typical second antenna found in crustaceans, which illustrates a very surprising convergence with such terrestrial mandibulates," said Aria.

The study also resolves the affinities of other emblematic fossils from Canada's Burgess Shale more than a hundred years after their discovery. "Our study suggests that a number of other Burgess Shale fossils such as Branchiocaris, Canadaspis and Odaraia form with Tokummia a group of crustacean-like arthropods that we can now place at the base of all mandibulates," said Aria.

The animal was named after Tokumm Creek, which flows through Marble Canyon in northern Kootenay National Park, and the Greek for "seizing." The Marble Canyon fossil deposit was first discovered in 2012 during prospection work led by the Royal Ontario Museum and is part of the Burgess Shale fossil deposit, which extends to the north into Yoho National Park in the Canadian Rockies. All specimens are held in the collections of the Royal Ontario Museum on behalf of Parks Canada.

Read more at Science Daily

Earliest Evidence of Humans in the Americas Could ‘Change Everything’ If True

A mastodon skeleton on display in a diorama with a model of a Native American.
When archaeologist Steven Holen and his team recently completed an extensive analysis of mastodon fossils excavated in California, they were shocked by what they discovered.

“The findings went against nearly everything that we have been taught about early human history in North America,” Holen, co-director of the Center for American Paleolithic Research, told Seeker. “Shock and disbelief initially set in, because we knew that our conclusions would be so controversial.”

He was right. A very heated scientific debate is now raging over the team's study, published in the journal Nature. The paper holds that early humans modified the now-extinct large mammal’s bones around 130,000 years ago. That’s 128,508 years before Christopher Columbus began to explore the Central and South American coasts, and some 115,400 years before humans were thought to have entered North America.

The mastodon's remains were initially spotted in late 1992 during routine paleontological mitigation work at a freeway expansion project site managed by the California Department of Transportation. The location, off State Route 54 in San Diego, has since been named the Cerutti Mastodon site in honor of field paleontologist Richard Cerutti, who led the excavation.

Mastodon bones, tusks, and molars were found buried deeply alongside large stone tools, according to co-author Cerutti, Holen, and their colleagues.

“The tools include stone hammers and stone anvils to break bones to enable marrow extraction and/or to acquire raw material for bone and tooth tools,” explained co-author Richard Fullager, a researcher at the University of Wollongong’s Center for Archaeological Science.

Co-author Daniel Fisher, director of the University of Michigan’s Museum of Paleontology, added that the stone tool wielders “very strategically set up a process” to harvest the marrow from the mammoth’s long bones and to recover “dense fragments of bone” for tool production.

Mastodon remains and stones found at the Cerutti Mastodon site.
In 2014, research geologist and co-author James Paces of the US Geological Survey conducted rigorous uranium-series dating of the mastodon fossils and yielded an estimated burial age of approximately 130,000–130,700 years ago.

More recently, he and the rest of the research team — including senior author and archaeologist Kathleen Holen, Steven Holen’s wife — evaluated microscopic damage present on the mastodon fossils and stones. They compared those patterns with marks produced during experimental studies where they used stone cobbles for percussion of large elephant bones. (Modern elephants are distantly related to mastodons, which became extinct 10,000–11,000 years ago.)

The Holens and their international team of nine other scientists say that they ruled out natural or geological reasons for the mastodon bone breakages, stone shapes, and arrangement of the objects at the San Diego site. They even studied other areas where flood events left bone materials redistributed, and could find nothing like what was discovered at Cerutti Mastodon.

When Erella Hovers, head of the Institute of Archaeology at the Hebrew University of Jerusalem, learned about the new findings, her initial reaction mirrored that of Steven Holen.

She told Seeker that she felt “surprised” and that there was “some brow raising.” Nevertheless, she said, she believes that “the conclusions are well supported.”

“The Eurasian archaeological record of the period shows a lot of movement of various hominins [early humans] across continents,” Hovers continued. “It is not too inconceivable that the Americas were also reached, even if not fully colonized, at that time.”

If true, the scenario begs the question: What species of human was in what is now San Diego around 130,000 years ago?

Possible candidates include Homo erectus (aka Upright Man), Neanderthals, Denisovans, and anatomically modern humans from that time.

Recreation of a Neanderthal.
“Anatomically modern humans have not been found so early in northeastern Asia, but it is not totally impossible that they were around and even made it to North America, if the earliest dates for modern humans further south in China prove to be right,” Fullager said. “It seems unlikely — but again, not impossible — that any human species other than ‘cognitively modern humans’ could make the journey by boat.”

“Neanderthals, Denisovans, or some mix of these genetic populations were in southern Siberia, and feasibly in northeastern Siberia, at this time,” he added. “They could have made the journey by land to North America at the right window of opportunity — after temperatures had risen, ice had melted and the sea levels had not yet drowned Beringia [the Bering Land Bridge].”

Regarding the possibility that early humans arrived in the Americas via watercraft, Holen pointed out that there is evidence for early human travels over water. Mariners are thought to have arrived on the island of Crete 130,000 years ago, and human activity on the island of Sulawesi is believed to have occurred 118,000 years ago. It is therefore possible, he said, that early humans “crossed larger bodies of water like the Bering Strait as well.”

Mastodon remains at the Cerutti Mastodon site.
Numerous scientists question these theories and Holen and his team's conclusions concerning the mastodon remains.

“The presence of a Homo population in North America 130,000 years ago is a huge claim, and I can only remain extremely skeptical for the moment,” Bastien Llamas of the Australian Center for Ancient DNA (ACAD) told Seeker.

Alan Cooper conducted a genetic study with Llamas of the early peopling of the Americas and is the director of ACAD.

“Extraordinary claims such as this require extraordinary evidence,” he said, noting that he does not see such evidence in the new paper.

Anthropologist David Meltzer of Southern Methodist University, a leading expert on the colonization of North America, echoed Cooper’s concerns.

“If you are going to push human antiquity in the New World back more than 100,000 years in one fell swoop, you’ll have to do so with a far better archaeological case than this one,” Meltzer said. “Extraordinary claims require extraordinary proof. We have none of the detailed taphonomic [fossil] evidence necessary to support such a grandiose and extraordinary claim.”

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Cassini Begins Its Grand Finale With a Dive Between Saturn’s Rings

This artist's rendering shows NASA's Cassini spacecraft above Saturn's northern hemisphere, heading toward its first dive between Saturn and its rings on April 26, 2017.
Running low on fuel, NASA's Cassini spacecraft has begun the final — and most daring — phase of its epic mission to Saturn.

After using a final flyby of the moon Titan on Friday to boost its speed, Cassini was flung by the moon's gravity to a trajectory that sent it diving through the 1,200-mile (1,930 kilometers) gap between the planet's upper atmosphere and innermost rings, NASA officials said.

Cassini completed the first crossing of the ring plane at about 2 a.m. PDT (5 a.m. EDT, or 0900 GMT) Wednesday, the space agency said in a statement.

This final journey will end Sept. 15 when the spacecraft burns up in Saturn's crushing atmosphere. There is no turning back now; Cassini is on a "ballistic trajectory," and its fate is sealed, NASA scientists have said. The Grand Finale has been designed to prevent the spacecraft from contaminating the potentially habitable Saturnian moons.

"We're guaranteed to end up in Saturn's atmosphere in September," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "If we get hit by a particle [during the first dive] that disables the spacecraft, we are still guaranteed to end up in Saturn," he told Space.com.

Cassini is expected to be out of contact for about a day after this first dive while it takes detailed observations of Saturn and the ring gap, NASA officials said in a statement. The earliest the spacecraft is expected to check in is 12:05 a.m. PDT (3:05 a.m. EDT, or 0705 GMT) on Thursday (April 27), and it should return data and images soon after.

Saturn mysteries remain

Assuming a successful first dive, Cassini will loop around Saturn's southern hemisphere on a wide orbit, setting itself up for another 21 weekly dives that will take it to within 1,840 miles (2,960 km) of the planet's atmosphere, where it will continue its unprecedented investigations into Saturn's mysteries. NASA tracks the spacecraft's path in its Grand Finale Orbit Guide.

Cassini launched in October 1997 through a collaboration among NASA, the European Space Agency and the Italian Space Agency, and it has been in orbit around the ringed gas giant since 2004. In that time, it has gathered numerous observations of the planet, its rings and its moons. Long-duration missions such as Cassini are essential for studying the massive planet; indeed, 13 years is a very short time to explore a world with a 29-year orbit around the sun, mission scientists said.

"We've only been at Saturn for what is, effectively, half a Saturn year," Edgington said. "But [in that time], we're seeing all these detailed changes going on within that system."

Over the course of Cassini's stay at the gas giant, ferocious storms have come and gone in Saturn's turbulent atmosphere. Planetary scientists have also been able to study the dynamics of the moon Titan's thick atmosphere, even forecasting weather systems as its seasons slowly change, Edgington noted.

But many questions remain, and hopes are high that Cassini's Grand Finale will yield some of the biggest discoveries yet to come in the 20 years since the mission's launch, Cassini researchers have said.

"The Grand Finale is a brand-new mission," Linda Spilker, Cassini project scientist at JPL, said during a news conference on April 4. "We're going to a place that we've never been before … and I think some of the biggest discoveries may come from these final orbits."

For instance, the length of a day on Saturn is still unknown, Edgington noted. The planet's axis of rotation and axis of its magnetic field are parallel, which makes it very difficult to measure how long it takes for the planet's core to complete one rotation. By making very close passes to Saturn, however, Cassini's Grand Finale will be able to measure the small-scale fluctuations in magnetism to not only pin down how long a Saturnian day is but also reveal its internal structure, he said.

"We're also going to be measuring the tiny particles that will be inside that gap [between Saturn and its rings]," Edgington said. "These are particles that come from the rings. They're charged particles; they become trapped along the magnetic-field lines that intersect the rings. And we'll be able to measure them as they travel along the magnetic field. We're talking tiny ice grains, or maybe even products of water being broken up by sunlight in that region."

These intimate studies of Saturn's rings could reveal how much material they contain and how old they are, Edgington said. Using this information, scientists could test planetary formation models that may ultimately reveal how planets evolve and how their moons accrete material, he added.

Protecting Enceladus and Titan

For Cassini's Grand Finale, scientists took significant measures to ensure Saturn's moons would not be contaminated with microbes from Earth, Edgington said.

"NASA has certain rules to follow about not contaminating any place that we think might be habitable," he said.

Although engineers put great effort into sterilizing the spacecraft before they launched, researchers have found that a few hardy bacteria can survive for long periods in extreme environments, and some of these Earth microbes may be lurking inside Cassini's components. NASA decided to incinerate Cassini at the mission's end to reduce the risk that these tough microbes would contaminate the Saturn moons Enceladus or Titan, which scientists regard as two of the best places in the solar system to search for life.

In 2005, Europe's Huygens probe landed on Titan's surface and, at the time, met all planetary protection requirements. Since Cassini has been studying Titan over the years after Huygen's landing, however, the atmospheric moon's habitable potential has become clear. The potential habitability and planetary protection standards for Enceladus are higher than for Titan, but making sure Cassini avoids both moons is a bonus, said Cassini mission scientists.

Enceladus is a small, icy moon that could easily fit inside the state of New Mexico, but its implication in the search for life elsewhere in the solar system is huge. Thanks to Cassini, we now know that Enceladus has a subsurface ocean of liquid water that erupts through the moon's ice as plumes. The spacecraft has been able to "taste" the particles being released to space, revealing that the moon contains organic molecules (carbon-containing compounds).

Read more at Discovery News