Rocks from Mars' Jezero Crater, which likely predate life on Earth, contain signs of water

In a new study appearing today in the journal AGU Advances, scientists at MIT and NASA report that seven rock samples collected along the "fan front" of Mars' Jezero Crater contain minerals that are typically formed in water. The findings suggest that the rocks were originally deposited by water, or may have formed in the presence of water.

The seven samples were collected by NASA's Perseverance rover in 2022 during its exploration of the crater's western slope, where some rocks were hypothesized to have formed in what is now a dried-up ancient lake. Members of the Perseverance science team, including MIT scientists, have studied the rover's images and chemical analyses of the samples, and confirmed that the rocks indeed contain signs of water, and that the crater was likely once a watery, habitable environment.

Whether the crater was actually inhabited is yet unknown. The team found that the presence of organic matter -- the starting material for life -- cannot be confirmed, at least based on the rover's measurements. But judging from the rocks' mineral content, scientists believe the samples are their best chance of finding signs of ancient Martian life once the rocks are returned to Earth for more detailed analysis.

"These rocks confirm the presence, at least temporarily, of habitable environments on Mars," says the study's lead author, Tanja Bosak, professor of geobiology in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS). "What we've found is that indeed there was a lot of water activity. For how long, we don't know, but certainly for long enough to create these big sedimentary deposits."

What's more, some of the collected samples may have originally been deposited in the ancient lake more than 3.5 billion years ago -- before even the first signs of life on Earth.

"These are the oldest rocks that may have been deposited by water, that we've ever laid hands or rover arms on," says co-author Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. "That's exciting, because it means these are the most promising rocks that may have preserved fossils, and signatures of life."

The study's MIT co-authors include postdoc Eva Scheller, and research scientist Elias Mansbach, along with members of the Perseverance science team.

At the front

The new rock samples were collected in 2022 as part of the rover's Fan Front Campaign -- an exploratory phase during which Perseverance traversed Jezero Crater's western slope, where a fan-like region contains sedimentary, layered rocks. Scientists suspect that this "fan front" is an ancient delta that was created by sediment that flowed with a river and settled into a now bone-dry lakebed. If life existed on Mars, scientists believe that it could be preserved in the layers of sediment along the fan front.

In the end, Perseverance collected seven samples from various locations along the fan front. The rover obtained each sample by drilling into the Martian bedrock and extracting a pencil-sized core, which it then sealed in a tube to one day be retrieved and returned to Earth for detailed analysis.

Prior to extracting the cores, the rover took images of the surrounding sediments at each of the seven locations. The science team then processed the imaging data to estimate a sediment's average grain size and mineral composition. This analysis showed that all seven collected samples likely contain signs of water, suggesting that they were initially deposited by water.

Specifically, Bosak and her colleagues found evidence of certain minerals in the sediments that are known to precipitate out of water.

"We found lots of minerals like carbonates, which are what make reefs on Earth," Bosak says. "And it's really an ideal material that can preserve fossils of microbial life."

Interestingly, the researchers also identified sulfates in some samples that were collected at the base of the fan front. Sulfates are minerals that form in very salty water -- another sign that water was present in the crater at one time -- though very salty water, Bosak notes, "is not necessarily the best thing for life." If the entire crater was once filled with very salty water, then it would be difficult for any form of life to thrive. But if only the bottom of the lake were briny, that could be an advantage, at least for preserving any signs of life that may have lived further up, in less salty layers, that eventually died and drifted down to the bottom.

"However salty it was, if there were any organics present, it's like pickling something in salt," Bosak says. "If there was life that fell into the salty layer, it would be very well-preserved."

Fuzzy fingerprints

But the team emphasizes that organic matter has not been confidently detected by the rover's instruments. Organic matter can be signs of life, but can also be produced by certain geological processes that have nothing to do with living matter. Perseverance's predecessor, the Curiosity rover, had detected organic matter throughout Mars' Gale Crater, which scientists suspect may have come from asteroids that made impact with Mars in the past.

And in a previous campaign, Perseverance detected what appeared to be organic molecules at multiple locations along Jezero Crater's floor. These observations were taken by the rover's Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument, which uses ultraviolet light to scan the Martian surface. If organics are present, they can glow, similar to material under a blacklight. The wavelengths at which the material glows act as a sort of fingerprint for the kind of organic molecules that are present.

In Perseverance's previous exploration of the crater floor, SHERLOC appeared to pick up signs of organic molecules throughout the region, and later, at some locations along the fan front. But a careful analysis, led by MIT's Eva Scheller, has found that while the particular wavelengths observed could be signs of organic matter, they could just as well be signatures of substances that have nothing to do with organic matter.

"It turns out that cerium metals incorporated in minerals actually produce very similar signals as the organic matter," Scheller says. "When investigated, the potential organic signals were strongly correlated with phosphate minerals, which always contain some cerium."

Scheller's work shows that the rover's measurements cannot be interpreted definitively as organic matter.

"This is not bad news," Bosak says. "It just tells us there is not very abundant organic matter. It's still possible that it's there. It's just below the rover's detection limit."

When the collected samples are finally sent back to Earth, Bosak says laboratory instruments will have more than enough sensitivity to detect any organic matter that might lie within.

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Evolution in action? New study finds possibility of nitrogen-fixing organelles

Nitrogen is a nutrient essential for all life on Earth. Although nitrogen gas (N2) is plentiful, it is largely unavailable to most organisms without a process known as nitrogen fixation, which converts dinitrogen to ammonium -- a major inorganic nitrogen source.

While there are bacteria that are able to reduce dinitrogen to ammonium, researchers at the University of Rhode Island, Institut de Ciències del Mar in Barcelona, University of California at Santa Cruz and the Massachusetts Institute of Technology have discovered nitrogen-fixing symbiotic organisms exhibiting behaviors similar to organelles.

In fact, researchers posit these symbiotic organisms -- UCYN-A, a species of cyanobacteria -- may be evolving organelle-like characteristics.

Their study was recently published in the journal Cell.

UCYN-A live in a symbiotic relationship with a closely related group of marine algae, B. bigelowii, in areas of the open ocean that are often low in nutrients.

Most nitrogen-fixing bacteria have mechanisms to regulate dinitrogen use when fixed sources of nitrogen are available, alleviating the high energetic cost of this process.

However, UCYN-A have lost the genes allowing this and are able to fix nitrogen gas into ammonium even in nutrient-rich environments.

The host, in-turn, provides it with carbon fixed photosynthetically by its chloroplasts.

The study details how researchers found a size relationship between UCYN-A and their symbiotic partner cells -- consistent with the size relationships between other organelles and their hosts.

As organelles get larger, so do their host cells - eventually dividing and replicating.

Mathematical modeling revealed the metabolic trade-offs which regulate the relative cell size through nutrient acquisition and exchange.

"It requires lots of energy as well as electrons to fix nitrogen gas, to make it into something useful," said Keisuke Inomura, assistant professor of oceanography at URI's Graduate School of Oceanography and one of the study's lead authors.

"If UCYN-A are moving along the evolutionary path toward developing into nitrogen-fixing organelles and we find cells aside from B. bigelowii also have such organelles, or are evolving similarly, it could be a game-changer."

While organelles such as mitochondria and chloroplasts are much further along on the evolutionary spectrum, researchers contend that what they are seeing may be a snapshot of the evolutionary process of bacterial-derived organelles that are nitrogen-fixing.

"Our study focuses on a much more recent symbiotic relationship that emerged about 100 million years ago, allowing us to explore the evolution of organelle formation in its early stages," explained Francisco Cornejo, co-lead author and postdoc researcher in the department of marine biology and oceanography at the Institut de Ciències del Mar.

Researchers note, however, that more study is needed to demonstrate whether this is the case.

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Astronomers reveal a new link between water and planet formation

Researchers have found water vapour in the disc around a young star exactly where planets may be forming. Water is a key ingredient for life on Earth, and is also thought to play a significant role in planet formation. Yet, until now, we had never been able to map how water is distributed in a stable, cool disc -- the type of disc that offers the most favourable conditions for planets to form around stars. The new findings were made possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.

"I had never imagined that we could capture an image of oceans of water vapour in the same region where a planet is likely forming," says Stefano Facchini, an astronomer at the University of Milan, Italy, who led the study published today in Nature Astronomy. The observations reveal at least three times as much water as in all of Earth's oceans in the inner disc of the young Sun-like star HL Tauri, located 450 light-years away from Earth in the constellation Taurus.

"It is truly remarkable that we can not only detect but also capture detailed images and spatially resolve water vapour at a distance of 450 light-years from us ," adds co-author Leonardo Testi, an astronomer at the University of Bologna, Italy. The 'spatially resolved' observations with ALMA allow astronomers to determine the distribution of water in different regions of the disc. "Taking part in such an important discovery in the iconic HL Tauri disc was beyond what I had ever expected for my first research experience in astronomy," adds Mathieu Vander Donckt from the University of Liege, Belgium, who was a master's student when he participated in the research.

A significant amount of water was found in the region where a known gap in the HL Tauri disc exists. Ring-shaped gaps are carved out in gas- and dust-rich discs by orbiting young planet-like bodies as they gather up material and grow. "Our recent images reveal a substantial quantity of water vapour at a range of distances from the star that include a gap where a planet could potentially be forming at the present time," says Facchini. This suggests that this water vapour could affect the chemical composition of planets forming in those regions.

Observing water with a ground-based telescope is no mean feat as the abundant water vapour in Earth's atmosphere degrades the astronomical signals. ALMA, operated by ESO together with its international partners, is an array of telescopes in the Chilean Atacama Desert at about 5000 metres elevation that was built in a high and dry environment specifically to minimise this degradation, providing exceptional observing conditions. "To date, ALMA is the only facility able to spatially resolve water in a cool planet-forming disc," says co-author Wouter Vlemmings, a professor at the Chalmers University of Technology in Sweden.*

"It is truly exciting to directly witness, in a picture, water molecules being released from icy dust particles," says Elizabeth Humphreys, an astronomer at ESO who also participated in the study. The dust grains that make up a disc are the seeds of planet formation, colliding and clumping into ever larger bodies orbiting the star. Astronomers believe that where it is cold enough for water to freeze onto dust particles, things stick together more efficiently -- an ideal spot for planet formation. "Our results show how the presence of water may influence the development of a planetary system, just like it did some 4.5 billion years ago in our own Solar System," Facchini adds.

With upgrades happening at ALMA and ESO's Extremely Large Telescope (ELT) coming online within the decade, planet formation and the role water plays in it will become clearer than ever. In particular METIS, the Mid-infrared ELT Imager and Spectrograph, will give astronomers unrivalled views of the inner regions of planet-forming discs, where planets like Earth form.

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Increased temperature difference between day and night can affect all life on earth

Researchers from Chalmers University of Technology, in Sweden, have discovered a change in what scientists already knew about global warming dynamics. It had been widely accepted since the 1950s that global temperature rises were not consistent throughout the day and night, with greater nighttime warming being observed. However, the recent study reveals a shift in dynamics: with greater daytime warming taking place since the 1990s. This shift means that the temperature difference between day and night is widening, potentially affecting all life on Earth.

The rise in the global average surface temperature is one of the key characteristics of human-induced climate change.

However, the temperature increase is not uniform throughout the day and night, and nighttime temperatures have increased at a faster pace than daytime temperatures in the latter half of the twentieth century.

This warming pattern, with variations between day and night is termed "asymmetric warming" and could be due to both human activities and naturally occurring phenomena.

In a new study, published in Nature Communications, an international team of researchers reinvestigated the asymmetric warming phenomenon and found that the pattern has reversed.

Between 1961 and 2020, global daytime warming has accelerated, while the warming rate of nighttime temperature is relatively constant.

This reversed trend in asymmetric warming has led to an increasing temperature difference between day and night.

"We initially aimed to confirm the previously observed phenomenon of nighttime warming surpassing daytime warming. To our surprise, not only had the asymmetric warming trend ceased, but our analyses, based on state-of-the-art observation-based datasets, indicate a complete reversal of this original warming pattern over the past three decades," says Ziqian Zhong, post-doctoral researcher at Chalmers.

Global brightening a potential cause

"A likely explanation to this change is a phenomenon called "global brightening," which has been observed since the late 1980s. It is a result of less cloud cover, which causes more sunlight to reach the Earth's surface, leading to higher daytime temperatures and, as a result, a broader difference between daytime and nighttime temperatures over the recent decades," says Ziqian Zhong.

There is currently significant uncertainty regarding the reasons behind the changes in cloud cover.

The "global brightening" may be attributed to a complex interplay between cloud-free and cloudy atmospheres, as well as the effect of small particles in the atmosphere, known as aerosols.

These aerosols can be derived from natural processes like sea spray and wildfires, but also from human activities like fossil fuel burning, and they can have a profound effect on many aspects of the environment.

Apart from the effects from global brightening, the researchers suggest another reason for the reversed asymmetric warming.

The increase in regional drought events and heatwaves suggests a potential weakening of the cooling effect due to evaporation at the Earth's surface, which would typically result in a faster increase in daytime temperatures.

The researchers found that the majority of land, 81 per cent of the total area, experienced larger nighttime warming from 1961 to 1990.

However, in the subsequent period from 1991 to 2020, a shift occurred, with 70 per cent of the observed land areas experiencing larger daytime warming instead.

Affecting all life on Earth

The larger temperature difference between day and night could potentially affect crop yields, plant growth, animal well-being and human health.

For example, an increased temperature difference between daytime and nighttime is recognised as one of the environmental stressors that could lead to elevated heart rate and blood pressure, consequently increasing cardiac workload and the mortality and morbidity of cardiovascular and respiratory diseases.

"This indicates the need to adjust strategies in different areas affected by temperature variations between day and night, such as agriculture, public health, and forestry management, to address the challenges posed by this climate change," says Ziqian Zhong.

Certain tree species in humid areas might enhance their carbon sequestration capacity due to the increased temperature difference between daytime and nighttime.

However, the increased temperature difference between daytime and nighttime might prove disadvantageous for trees in dry regions, as higher daytime temperatures may increase evaporation, leading to deficiency of soil water and unfavorable conditions for tree growth.

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Climate report: 'Uncharted territory' imperils life on Earth

An international coalition of climate scientists says in a paper published today that the Earth's vital signs have worsened beyond anything humans have yet seen, to the point that life on the planet is imperiled.

William Ripple, a distinguished professor in the Oregon State University College of Forestry, and former OSU postdoctoral researcher Christopher Wolf are the lead authors of the report, and 10 other U.S. and global scientists are co-authors.

"Without actions that address the root problem of humanity taking more from the Earth than it can safely give, we're on our way to the potential collapse of natural and socioeconomic systems and a world with unbearable heat and shortages of food and freshwater," Wolf said.

Published in BioScience, "The 2023 State of the climate report: Entering uncharted territory" notes that 20 of 35 planetary vital signs the authors use to track climate change are at record extremes.

The authors share new data illustrating that many climate-related records were broken by "enormous margins" in 2023, particularly those relating to ocean temperatures and sea ice. They also note an extraordinary Canadian wildfire season that produced unprecedented carbon dioxide emissions.

The report follows by four years the "World Scientists' Warning of a Climate Emergency" published by Ripple and collaborators in BioScience and co-signed by more than 15,000 scientists in 161 countries.

"Life on our planet is clearly under siege," Ripple said. "The statistical trends show deeply alarming patterns of climate-related variables and disasters. We also found little progress to report as far as humanity combating climate change."

Among the key numbers in the report:
 

• Fossil fuel subsidies -- actions by governments that artificially lower the cost of energy production, raise the price received by producers or lower the price paid by consumers -- roughly doubled between 2021 and 2022, from $531 billion to just over $1 trillion.
• Already this year wildfires in Canada have pumped more than 1 gigaton of carbon dioxide into the atmosphere, greater than Canada's total 2021 greenhouse gas emissions of 0.67 gigatons.
• In 2023, there have already been 38 days with global average temperatures more than 1.5 degrees Celsius above pre-industrial levels. Until this year, such days were a rarity, the authors note.
• The highest average Earth surface temperature ever recorded came this past July, and there's reason to believe it was the highest surface temperature the planet has seen in the last 100,000 years.

"As scientists, we are hugely troubled by the sudden increases in the frequency and severity of climate-related disasters," said Wolf, now a scientist with Corvallis-based Terrestrial Ecosystems Research Associates. "The frequency and severity of those disasters might be outpacing rising temperatures. By the end of the 21st century, as many as 3 to 6 billion people may find themselves outside the Earth's livable regions, meaning they will be encountering severe heat, limited food availability and elevated mortality rates."

The authors say policies are needed that take aim at the underlying issue of "ecological overshoot." When human demand on the Earth's resources is too large, the result in an array of environmental crises, including biodiversity decline. As long as humanity continues to put extreme pressure on the planet, any strategy that focuses only on carbon or climate will simply redistribute the pressure, they note.

"Our goal is to communicate climate facts and make policy recommendations," Ripple said. "It is a moral duty of scientists and our institutions to alert humanity of any potential existential threat and to show leadership in taking action."

The authors urge transitioning to a global economy that prioritizes human well-being and curtails overconsumption and excessive emissions by the rich. Specific recommendations include phasing out fossil fuel subsidies, transitioning toward plant-based diets, scaling up forest protection efforts and adopting international coal elimination and fossil fuel non-proliferation treaties.

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New recipes for origin of life may point way to distant, inhabited planets

Life on a faraway planet -- if it's out there -- might not look anything like life on Earth. But there are only so many chemical ingredients in the universe's pantry, and only so many ways to mix them. A team led by scientists at the University of Wisconsin-Madison has exploited those limitations to write a cookbook of hundreds of chemical recipes with the potential to give rise to life.

Their ingredient list could focus the search for life elsewhere in the universe by pointing out the most likely conditions -- planetary versions of mixing techniques, oven temperatures and baking times -- for the recipes to come together.

The process of progressing from basic chemical ingredients to the complex cycles of cell metabolism and reproduction that define life, the researchers say, requires not only a simple beginning but also repetition.

"The origin of life really is a something-from-nothing process," says Betül Kaçar, a NASA-supported astrobiologist and UW-Madison professor of bacteriology. "But that something can't happen just once. Life comes down to chemistry and conditions that can generate a self-reproducing pattern of reactions."

Chemical reactions that produce molecules that encourage the same reaction to happen again and again are called autocatalytic reactions. In a new study published Sept. 18 in the Journal of the American Chemical Society, Zhen Peng, a postdoctoral researcher in the Kaçar laboratory, and collaborators compiled 270 combinations of molecules -- involving atoms from all groups and series across the periodic table -- with the potential for sustained autocatalysis.

"It was thought that these sorts of reactions are very rare," says Kaçar. "We are showing that it's actually far from rare. You just need to look in the right place."

The researchers focused their search on what are called comproportionation reactions. In these reactions, two compounds that include the same element with different numbers of electrons, or reactive states, combine to create a new compound in which the element is in the middle of the starting reactive states.

To be autocatalytic, the outcome of the reaction also needs to provide starting materials for the reaction to occur again, so the output becomes a new input says Zach Adam, a co-author of the study and a UW-Madison geoscientist studying the origins of life on Earth. Comproportionation reactions result in multiple copies of some of the molecules involved, providing materials for the next steps in autocatalysis.

"If those conditions are right, you can start with relatively few of those outputs," Adam says. "Every time you take a turn of the cycle you spit out at least one extra output which speeds up the reaction and makes it happen even faster."

Autocatalysis is like a growing population of rabbits. Pairs of rabbits come together, produce litters of new rabbits, and then the new rabbits grow up to pair off themselves and make even more rabbits. It doesn't take many rabbits to soon have many more rabbits.

Looking for floppy ears and fuzzy tails out in the universe, however, probably isn't a winning strategy. Instead, Kaçar hopes chemists will pull ideas from the new study's recipe list and test them out in pots and pans simulating extraterrestrial kitchens.

"We will never definitively know what exactly happened on this planet to generate life. We don't have a time machine," Kaçar says. "But, in a test tube, we can create multiple planetary conditions to understand how the dynamics to sustain life can evolve in the first place."

Kaçar leads a NASA-supported consortium called MUSE, for Metal Utilization & Selection Across Eons. Her lab will focus on reactions including the elements molybdenum and iron, and she is excited to see what others cook up from the most exotic and unusual parts of the new recipe book.

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Life on Earth didn't arise as described in textbooks

No, oxygen didn't catalyze the swift blossoming of Earth's first multicellular organisms. The result defies a 70-year-old assumption about what caused an explosion of oceanic fauna hundreds of millions of years ago.

Between 685 and 800 million years ago, multicellular organisms began to appear in all of Earth's oceans during what's known as the Avalon explosion, a forerunner era of the more famed Cambrian explosion. During this era, sea sponges and other bizarre multicellular organisms replaced small single-celled amoeba, algae and bacteria, which until then, had had run of the planet for more than 2 billion years.

Up until now, it was believed that increased oxygen levels triggered the evolutionary arrival of more advanced marine organisms. This is being disproved by University of Copenhagen researchers working together with colleagues from Woods Hole Oceanographic Institute, the University of Southern Denmark and Lund University, among others.

By studying the chemical composition of ancient rock samples from an Omani mountain range, the researchers have been able to "measure" oxygen concentrations in the world's oceans from when these multicellular organisms appeared. Defying expectations, the result shows that Earth's oxygen concentrations had not increased. Indeed, levels remained 5-10 times lower than today, which is roughly how much oxygen there is at twice the height of Mount Everest.

"Our measurements provide a good picture of what average oxygen concentrations were in the world's oceans at the time. And it's apparent to us that there was no major increase in the amount of oxygen when more advanced fauna began to evolve and dominate Earth. In fact, there was somewhat of a slight decrease," says Associate Professor Christian J. Bjerrum, who has been quantifying the conditions surrounding the origin of life for the past 20 years.

Revises our understanding of life's origins

The new result puts to rest a 70-year research story that advances the centrality of higher oxygen concentrations in the development of more advanced life on our planet.

"The fact that we now know, with a high degree of certainty, that oxygen didn't control the development of life on Earth provides us with an entirely new story about how life arose and what factors controlled this success," says the researcher, adding:

"Specifically, it means that we need to rethink a lot of the things that we believed to be true from our childhood learning. And textbooks need to be revised and rewritten."

There remains much that the researchers don't know, as well as and a plethora of controversy. Therefore, Bjerrum hopes that the new result can spur other researchers around the world to reconsider their previous results and data in a new light.

"There are many research sections around the world, including in the United States and China, that have done lots of research on this topic, whose earlier results may shed important new details if interpreted on the basis that oxygen didn't drive the development of life," says the researcher.

Absence of oxygen may have aided development

So, if not extra oxygen, what triggered the era's explosion of life? Perhaps the exact opposite, explains the researcher:

"It's interesting that the explosion of multicellular organisms occurs at a time with low concentrations of atmospheric and oceanic oxygen. That indicates that organisms benefited from lower levels of oxygen and were able to develop in peace, as the water chemistry protected their stem cells naturally," says Christian J. Bjerrum.

According to the researcher, the same phenomenon has been studied in cancer research, in the stem cells of humans and other animals. Here, colleagues at Lund University observed that low oxygen levels are crucial for keeping stem cells under control until an organism decides that the cell ought to develop into a specific type of cell, such as a muscle cell.

"We know that animals and humans must be able to maintain low concentrations of oxygen in order to control their stem cells, and in so doing, develop slowly and sustainably. With too much oxygen, the cells will develop, and in the worst case, mutate wildly and perish. It is far from inconceivable that this mechanism applied back then," concludes Christian J. Bjerrum.

Fossils from Oman

In the new study, the researchers analysed rock samples from, among other places, the Oman Mountains in northern Oman. While quite high and very dry today, the mountains were on the seabed during the Avalon explosion's rapid blossoming of organism diversity.

The researchers have had their findings confirmed in fossils from three different mountain ranges around the world: the Oman Mountains (Oman), Mackenzie Mountains (NW Canada) and the Yangtze Gorges area of South China.

Over time, clay and sand from land are washed into the sea, where they settle into layers on the seabed. By going down through these layers and examining their chemical composition, researchers can get a picture of ocean chemistry at a particular geologic time.

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How were amino acids, one of the key building blocks of life, formed before the origin of life on Earth?

Our solar system formed from a molecular cloud, which was composed of gas and dust that was emitted into the interstellar medium (ISM), a vast space between stars. On collapse of the molecular cloud, the early sun was formed, with a large disk of gas and dust orbiting it. The dusty material collided to produce rocky material that would eventually grow in size to give large bodies called planetesimals.

The planetesimals that formed far enough from the sun, also contained large quantities of ice. The ice consisted of water and other volatile compounds, such as carbon monoxide (CO), carbon dioxide (CO2), methanol (CH3OH) and ammonia (NH3), as well as many other organic compounds, likely including some amino acids. Eventually, the ice melted due to the presence of radioactive material that heated up the bodies. This period of liquid water (termed aqueous alteration) enabled many reactions to occur, including Strecker synthesis and Formose-like reactions, the result being the production of new organic material, including amino acids. The same process also changed the rocky materials from their original minerals to new secondary minerals, such as phyllosilicates, carbonates, Fe-oxides and Fe-sulfides.

After several millions of years, the planetesimals began to freeze, as the radioactive material was used up. Later catastrophic collisions and interaction with the solar systems planets broke up the large bodies and sent their asteroidal and cometary fragments close to Earth. Further impact events have since delivered fragments of these asteroids and comets to the Earth's surface, supplying the Earth with large quantities of organic material, including amino acids, over the course of its history.

Amino acids are within all living things on Earth, being the building blocks of proteins. Proteins are essential for many processes within living organisms, including catalysing reactions (enzymes), replicating genetic material (ribosomes), transporting molecules (transport proteins) and providing a structure to cells and organisms (e.g. collagen). Therefore, amino acids would have been needed in significant amounts within the region where life began on Earth.

Previous work has identified a number of possible settings both on the Early Earth and in extraterrestrial environments that can form amino acids. Interestingly, most amino acids come in at least two forms, whose structures represent mirror images of each other, similar to human hands. Accordingly, these are often referred to as the right-handed or left-handed optical isomers. One interesting characteristic of life on Earth is that it uses one particular type of amino acids in its proteins, the left-handed optical isomer. Currently, only a certain class of meteorites (carbonaceous chondrites) are known to contain excesses of left-handed optical isomers, which has led to the idea that the amino acids used by life may have originated from these meteorites. Despite this, the amino acids in meteorites could have formed before their incorporation into the meteorites or after the meteorites had already formed.

Here, a team of scientists analysed several fragments of the asteroid Ryugu and calculated the abundance of amino acids within them. The abundance of the mineral phases within the particles had been previously reported in another publication, which allowed for a comparison between the abundance of amino acids and minerals. It was found that one particle (A0022) contained a high abundance of an amino acid that is uncommon in extraterrestrial materials, called dimethylglycine (DMG), whereas the other particle (C0008) did not contain this amino acid above detection limit. Meanwhile, the abundance of the amino acid glycine was found to be lower in A0022 compared to C0008, while the abundance of β-Alanine showed the opposite trend. Accordingly, the ratio of β-Alanine to glycine was higher for A0022 than for C0008. This ratio was shown previously to be indicative of the extent of aqueous alteration operating on planetesimals. Accordingly, it was hypothesised that some reaction related to higher levels of aqueous alteration in A0022 may explain the high abundance of DMG in this particle, compared to C0008.

As such, the mineral phases were examined to see if any additional evidence for what reaction may be causing the different amino acids abundances between the Ryugu particles. It was found that the abundance of secondary minerals (formed after aqueous alteration), including carbonate, magnetite and Fe-sulfides, was higher in A0022 than in C0008. In particular, the high abundance of carbonate pointed towards a larger quantity of CO or CO2 within the region of the planetesimal where A0022 had been altered, compared to C0008. In conjunction with the evidence for more intense aqueous alteration from the β-Alanine to glycine ratio, this indicated that more ice in general may have been present in the precursor of A0022 than in C0008.

One way to commercially produce DMG, an important nutrient for humans, is the through the Eschweiler-Clarke reaction. This reaction requires the interaction of glycine with formic acid and formaldehyde in water and also produces CO2. Glycine, formaldehyde and formic acid are all found in comets and so it is expected that they would be present in the planetesimal precursors of asteroids. Therefore, if the Eschweiler-Clarke reaction occurred during aqueous alteration within the precursor of A0022, then it could explain the high level of DMG and lower abundance of glycine in this particle, compared to C0008. Additionally, the CO2 produced could have further contributed to the formation of carbonates in A0022.

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How cosmic winds transform galactic environments

Much like how wind plays a key role in life on Earth by sweeping seeds, pollen and more from one place to another, galactic winds -- high-powered streams of charged particles and gases -- can change the chemical make-up of the host galaxies they form in, simply by blowing in a specific direction.

Using observations made by NASA's Chandra X-ray Observatory, a new study details how these energetic winds, once released from the center of a galaxy, directly influence the temperature and metal distribution of the rest of the region.

"Galactic winds are a large part of galaxy evolution in general," said Sebastian Lopez, lead author of the study and a graduate student in astronomy at The Ohio State University. "As they blow from one end of a galaxy to another, they alter the distribution of metals across the disk and enrich the surrounding intergalactic space."

In investigating the nearby spiral galaxy NGC 253, researchers found that while the amount of these elements can vary, the abundances of oxygen, neon, magnesium, silicon, sulfur and iron peaked in the center of the galaxy and decreased with distance from it. This indicates that as hot gas cools the farther away it travels from the center, it leaves behind a lower concentration of these elements.

Learning more about how the celestial detritus that make up these vast galaxies are disseminated across the cosmos could help astronomers more deeply understand how galactic formation works in other areas of the universe. "Our research could reflect that the size of a galaxy, or even its morphology, could impact how gas leaves these systems," Lopez said. The study was published online in The Astrophysical Journal.

Between 1999 and 2018, Chandra observed NGC 253 only seven times, but by analyzing image and spectral data taken from those observations, Lopez and his team were able to use specialized computer software to identify the emission lines left by passing winds. While compiling this data, they found that the research runs counter to previous X-ray studies done on NGC 253, which posit that galactic winds expand spherically, or in a bubble-like shape.

Instead, the models Lopez's team created show how the winds move in opposite directions from the middle of the galaxy and then radiate outwards toward the upper right and lower left regions. Lopez places much of this discrepancy on the data available at the time of the previous studies and the technological strides scientists have made since.

Still, there were a few similarities to previous work that did catch researchers' interest. To determine how galactic emission differences arise and if these differences depend on the galaxy's properties, they compared NGC 253 to the results of studies done on the galaxy M82, a similar starburst system located some 12 million light-years away from Earth. After detecting the same metals and similar distributions within M82 that they did with NGC 253, Lopez said that comparing the two led the team to discern that a process called charge exchange -- the stripping of an electron from a neutral atom by an ion -- plays a large part in X-ray emission.

"In order for scientists to create a realistic galaxy in simulations, we need to know where these heavy elements are going," Lopez said. "Because if you were to model it and not include charge exchange into these models, they wouldn't match up." If such calculations were inherently wrong, he said, scientists would have a hard time using their observations to make educated guesses about what the universe looks like and how it operates.

But Lopez imagines the more accurate models created from this study will help astronomers study the winds of other galaxies, such as calculating their velocities and discovering what makes them so good at creating unique stellar environments. "Next, we want to do this analysis for a larger set of different galaxies and see how things change," Lopez said.

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Human and ocean health impacts of ocean plastics

For the first time, leading researchers from the fields of healthcare, ocean science, and social science have collaborated to quantify plastic's considerable risks to all life on Earth. The Minderoo-Monaco Commission on Plastics and Human Health report, released today, presents a comprehensive analysis showing plastics as a hazard at every stage of their life cycle.

The report was led by scientists at the Minderoo Foundation, the Centre Scientifique de Monaco, and Boston College. Researchers Mark Hahn and John Stegeman at the Woods Hole Oceanographic Institution (WHOI) were lead authors on a section focusing on the impacts of plastics on the ocean.

The Commission's key findings include:

•     Plastics cause disease, impairment, and premature mortality at every stage of their life cycle, with the health repercussions disproportionately affecting vulnerable, low-income, minority communities, particularly children.
•     Toxic chemicals that are added to plastics and routinely detected in people are, among other effects, known to increase the risk of miscarriage, obesity, cardiovascular disease, and cancers.
•     Plastic waste is ubiquitous in the global environment, with microplastics occurring throughout the ocean and the marine food chain.

"It's only been a little over 50 years since we've been aware of the presence of plastics throughout the ocean," said John Stegeman, a senior scientist the Department of Biology at WHOI. "The Minderoo-Monaco Commission's work is a significant leap forward in connecting the broad health implications of plastics -- to the ocean and to humanity."

The Commission concluded that current plastic production, use, and disposal patterns are not sustainable and are responsible for significant harm to human health, the economy, and the environment -- especially the ocean -- as well as deep societal injustices. Plastics, the report notes, account for an estimated 4 to 5% of all greenhouse gas emissions across their lifecycle, equivalent to emissions from Russia, making them a large-scale contributor to climate change.

The study also calculated the cost of the health repercussions attributed to plastic production to be $250 billion in a 12-month period, which is more than the GDP of New Zealand or Finland in 2015, the year the data were collected. In addition, health care costs associated with chemicals in plastics are estimated to be in the hundreds of billions of dollars. The research also noted that the ubiquity of fast food and discount stores in poorer communities increased exposure to plastic packaging, products, and associated chemicals and impacts.

"Plastic waste endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being," said Dr. Hervé Raps, Physician Delegate for Research at Centre Scientifique de Monaco. "Besides their intrinsic effects, plastics can also be a vector for potentially pathogenic microorganisms and other chemicals adsorbed from polluted water. And alongside the new findings of this report, linking toxic chemicals to human harms, this is not the time to slow down our understanding of impacts in the ocean."

Although plastics' potential harm to human health might be news to some, the oceanographic and marine biology communities have been acutely aware of its negative environmental impacts for decades. Despite this head start, the Commission's findings reveal a pressing need for better understanding and monitoring of the effects of plastics and plastic-associated chemicals on marine species. The authors also highlight a significant lack of knowledge concerning the concentrations of the smallest micro- and nano-plastic particles (MNPs) in the marine environment and their potential impacts on marine animals and ecosystems, from the coasts to the abyss.

As a result of its findings, the Commission urged that a cap on global plastic production be a defining feature of the Global Plastics Treaty currently being negotiated at the UN, and that the Treaty focus beyond marine litter to address the impacts of plastics across their entire life cycle, including the many thousands of chemicals incorporated into plastics and the human health impacts. The positive news is that the Commission reports that many of plastics' harms can be avoided via better production practices, alternative design, less toxic chemicals, and decreased consumption.

"Ocean health is intimately and intricately connected to human health," said Mark Hahn, a senior scientist in the Department of Biology at WHOI. "Our attention now needs to be on creating a broadly acceptable international agreement that addresses the full life cycle of plastics in order to prioritize the health of the ocean that supports us all."

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Rutgers scientists identify substance that may have sparked life on Earth

A team of Rutgers scientists dedicated to pinpointing the primordial origins of metabolism -- a set of core chemical reactions that first powered life on Earth -- has identified part of a protein that could provide scientists clues to detecting planets on the verge of producing life.

The research, published in Science Advances, has important implications in the search for extraterrestrial life because it gives researchers a new clue to look for, said Vikas Nanda, a researcher at the Center for Advanced Biotechnology and Medicine (CABM) at Rutgers.

Based on laboratory studies, Rutgers scientists say one of the most likely chemical candidates that kickstarted life was a simple peptide with two nickel atoms they are calling "Nickelback" not because it has anything to do with the Canadian rock band, but because its backbone nitrogen atoms bond two critical nickel atoms. A peptide is a constituent of a protein made up of a few elemental building blocks known as amino acids.

"Scientists believe that sometime between 3.5 and 3.8 billion years ago there was a tipping point, something that kickstarted the change from prebiotic chemistry -- molecules before life -- to living, biological systems," Nanda said. "We believe the change was sparked by a few small precursor proteins that performed key steps in an ancient metabolic reaction. And we think we've found one of these 'pioneer peptides'."

The scientists conducting the study are part of a Rutgers-led team called Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA), which is part of the Astrobiology program at NASA. The researchers are seeking to understand how proteins evolved to become the predominant catalyst of life on Earth.

When scouring the universe with telescopes and probes for signs of past, present or emerging life, NASA scientists look for specific "biosignatures" known to be harbingers of life. Peptides like nickelback could become the latest biosignature employed by NASA to detect planets on the verge of producing life, Nanda said.

An original instigating chemical, the researchers reasoned, would need to be simple enough to be able to assemble spontaneously in a prebiotic soup. But it would have to be sufficiently chemically active to possess the potential to take energy from the environment to drive a biochemical process.

To do so, the researchers adopted a "reductionist" approach: They started by examining existing contemporary proteins known to be associated with metabolic processes. Knowing the proteins were too complex to have emerged early on, they pared them down to their basic structure.

After sequences of experiments, researchers concluded the best candidate was Nickelback. The peptide is made of 13 amino acids and binds two nickel ions.

Nickel, they reasoned, was an abundant metal in early oceans. When bound to the peptide, the nickel atoms become potent catalysts, attracting additional protons and electrons and producing hydrogen gas. Hydrogen, the researchers reasoned, was also more abundant on early Earth and would have been a critical source of energy to power metabolism.

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Laying geological groundwork for life on Earth

New research analyzing pieces of the most ancient rocks on the planet adds some of the sharpest evidence yet that Earth's crust was pushing and pulling in a manner similar to modern plate tectonics at least 3.25 billion years ago. The study also provides the earliest proof of when the planet's magnetic north and south poles swapped places.

The two results offer clues into how such geological changes may have resulted in an environment more conducive to the development of life on the planet.

The work, described in PNAS and led by Harvard geologists Alec Brenner and Roger Fu, focused on a portion of the Pilbara Craton in western Australia, one of the oldest and most stable pieces of the Earth's crust. Using novel techniques and equipment, the researchers show that some of the Earth's earliest surface was moving at a rate of 6.1 centimeters per year and 0.55 degrees every million years.

That speed more than doubles the rate the ancient crust was shown to be moving in a previous study by the same researchers. Both the speed and direction of this latitudinal drift leaves plate tectonics as the most logical and strongest explanations for it.

"There's a lot of work that seems to suggest that early in Earth's history plate tectonics wasn't actually the dominant way in which the planet's internal heat gets released as it is today through the shifting of plates," said Brenner, a Ph.D. candidate in the Graduate School of Arts and Sciences and member of Harvard's Paleomagnetics Lab. "This evidence lets us much more confidently rule out explanations that don't involve plate tectonics."

For example, the researchers can now argue against phenomena called "true polar wander" and "stagnant lid tectonics," which can both cause the Earth's surface to shift but aren't part of modern-style plate tectonics. The results lean more toward plate tectonic motion because the newly discovered higher rate of speed is inconsistent with aspects of the other two processes.

In the paper, the scientists also describe what's believed to be the oldest evidence of when Earth reversed its geomagnetic fields, meaning the magnetic North and South Pole flipped locations. This type of flip-flop is a common occurrence in Earth's geologic history with the pole's reversing 183 times in the last 83 million years and perhaps several hundred times in the past 160 million years, according to NASA.

The reversal tells a great deal about the planet's magnetic field 3.2 billion years ago. Key among these implications is that the magnetic field was likely stable and strong enough to keep solar winds from eroding the atmosphere. This insight, combined with the results on plate tectonics, offers clues to the conditions under which the earliest forms of life developed.

"It paints this picture of an early earth that was already really geodynamically mature," Brenner said. "It had a lot of the same sorts of dynamic processes that result in an Earth that has essentially more stable environmental and surface conditions, making it more feasible for life to evolve and develop."

Today, the Earth's outer shell consists of about 15 shifting blocks of crust, or plates, which hold the planet's continents and oceans. Over eons the plates drifted into each other and apart, forming new continents and mountains and exposing new rocks to the atmosphere, which led to chemical reactions that stabilized Earth's surface temperature over billions of years.

Evidence of when plate tectonics started is hard to come by because the oldest pieces of crust are thrust into the interior mantle, never to resurface. Only 5 percent of all rocks on Earth are older than 2.5 billion years old, and no rock is older than about 4 billion years.

Overall, the study adds to growing research that tectonic movement occurred relatively early in Earth's 4.5-billion-year history and that early forms of life came about in a more moderate environment. Members of the project revisited the Pilbara Craton in 2018, which stretches about 300 miles across. They drilled into the primordial and thick slab of crust there to collect samples that, back in Cambridge, were analyzed for their magnetic history.

Using magnetometers, demagnetizing equipment, and the Quantum Diamond Microscope -- which images the magnetic fields of a sample and precisely identifies the nature of the magnetized particles -- the researchers created a suite of new techniques for determining the age and way the samples became magnetized. This allows the researchers to determine how, when, and which direction the crust shifted as well as the magnetic influence coming from Earth's geomagnetic poles.

The Quantum Diamond Microscope was developed in a collaboration between Harvard researchers in the Departments of Earth and Planetary Sciences (EPS) and of Physics.

For future studies, Fu and Brenner plan keep their focus on the Pilbara Craton while also looking beyond it to other ancient crusts around the world. They hope to find older evidence of modern-like plate motion and when the Earth's magnetic poles flipped.

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What killed dinosaurs and other life on Earth?

Determining what killed the dinosaurs 66 million years ago at the end of the Cretaceous Period has long been the topic of debate, as scientists set out to determine what caused the five mass extinction events that reshaped life on planet Earth in a geological instant. Some scientists argue that comets or asteroids that crashed into Earth were the most likely agents of mass destruction, while others argue that large volcanic eruptions were the cause. A new Dartmouth-led study published in the Proceedings of the National Academy of Sciences (PNAS) reports that volcanic activity appears to have been the key driver of mass extinctions.

The findings provide the most compelling quantitative evidence so far that the link between major volcanic eruptions and wholesale species turnover is not simply a matter of chance.

Four of the five mass extinctions are contemporaneous with a type of volcanic outpouring called a flood basalt, the researchers say. These eruptions flood vast areas -- even an entire continent -- with lava in the blink of a geological eye, a mere million years. They leave behind giant fingerprints as evidence -- extensive regions of step-like, igneous rock (solidified from the erupted lava) that geologists call "large igneous provinces."

To count as "large," a large igneous province must contain at least 100,000 cubic kilometers of magma. For context, the 1980 eruption of Mount St. Helens involved less than one cubic kilometer of magma. The researchers say that most of the volcanoes represented in the study erupted on the order of a million times more lava than that.

The team drew on three well-established datasets on geologic time scale, paleobiology, and large igneous provinces to examine the temporal connection between mass extinction and large igneous provinces.

"The large step-like areas of igneous rock from these big volcanic eruptions seem to line up in time with mass extinctions and other significant climactic and environmental events,"says lead author Theodore Green '21, who conducted this research as part of the Senior Fellowship program at Dartmouth and is now a graduate student at Princeton.

In fact, a series of eruptions in present-day Siberia triggered the most destructive of the mass extinctions about 252 million years ago, releasing a gigantic pulse of carbon dioxide into the atmosphere and nearly choking off all life. Bearing witness are the Siberian Traps, a large region of volcanic rock roughly the size of Australia.

Volcanic eruptions also rocked the Indian subcontinent around the time of the great dinosaur die-off, creating what is known today as the Deccan plateau. This, much like the asteroid strike, would have had far-reaching global effects, blanketing the atmosphere in dust and toxic fumes, asphyxiating dinosaurs and other life in addition to altering the climate on long time scales.

On the other hand, the researchers say, the theories in favor of annihilation by asteroid impact hinge upon the Chicxulub impactor, a space rock that crash-landed into Mexico's Yucatan Peninsula around the same time that the dinosaurs went extinct.

"All other theories that attempted to explain what killed the dinosaurs, including volcanism, got steamrolled when the Chicxulub impact crater was discovered," says co-author Brenhin Keller, an assistant professor of earth sciences at Dartmouth. But there's very little evidence of similar impact events that coincide with the other mass extinctions despite decades of exploration, he points out.

At Dartmouth, Green set out to find a way to quantify the apparent link between eruptions and extinctions and test whether the coincidence was just chance or whether there was evidence of a causal relationship between the two. Working with Keller and co-author Paul Renne, professor-in-residence of earth and planetary science at University of California, Berkeley and director of the Berkeley Geochronology Center, Green recruited the supercomputers at the Dartmouth Discovery Cluster to crunch the numbers.

The researchers compared the best available estimates of flood basalt eruptions with periods of drastic species kill-off in the geological timescale, including but not limited to the five mass extinctions. To prove that the timing was more than a random chance, they examined whether the eruptions would line up just as well with a randomly generated pattern and repeated the exercise with a 100 million such patterns. They found that the agreement with extinction periods was far greater than random chance.

"While it is difficult to determine if a particular volcanic outburst caused one particular mass extinction, our results make it hard to ignore the role of volcanism in extinction," says Keller. If a causal link were to be found between volcanic flood basalts and mass extinctions, scientists expect that larger eruptions would entail more severe extinctions, but such a correlation has not been observed.

Rather than considering the absolute magnitude of eruptions, the research team ordered the volcanic events by the rate at which they spewed lava. They found that the volcanic events with the highest eruptive rates did indeed cause the most destruction, producing more severe extinctions up to the mass extinctions.

"Our results indicate that in all likelihood there would have been a mass extinction at the Cretaceous tertiary boundary of some significant magnitude, regardless of whether there was an impact or not, which can be shown more quantitatively now," says Renne. "The fact that there was an impact undoubtedly made things worse."

The researchers ran the numbers for asteroids too. The coincidence of impacts with periods of species turnover was significantly weaker, and dramatically worsened when the Chicxulub impactor was not considered, suggesting that other smaller known impactors did not cause significant extinctions.

The eruption rate of the Deccan Traps in India suggests that the stage was set for widespread extinction even without the asteroid, says Green. The impact was the double whammy that loudly sounded the death knell for the dinosaurs, he adds.

Flood basalt eruptions aren't common in the geologic record, says Green. The last one of comparable but significantly smaller scale happened about 16 million years ago in the Pacific Northwest.

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