Climate change threatens Antarctic meteorites

Using artificial intelligence, satellite observations, and climate model projections, a team of researchers from Switzerland and Belgium calculate that for every tenth of a degree of increase in global air temperature, an average of nearly 9,000 meteorites disappear from the surface of the ice sheet. This loss has major implications, as meteorites are unique samples of extraterrestrial bodies that provide insights into the origin of life on Earth and the formation of the Moon.

Disappearing at an alarming rate

By 2050, about a quarter of the estimated of 300,000 -- 800,000 meteorites in Antarctica will be lost due to glacial melt.

By end of the century, researchers anticipate that number could rise approaching a loss of meteorites closer to three-quarters of the meteorites on the continent under a high-warming scenario.

Published in the journal Nature Climate Change, Harry Zekollari co-led the study while working under Professor Daniel Farinotti in the Laboratory of Hydraulics, Hydrology and Glaciology at the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich.

Zekollari and co-lead Veronica Tollenaar, Université Libre de Bruxelles, reveal in the study that ongoing warming results in the loss of about 5,000 meteorites a year, outpacing the collection efforts of Antarctic meteorites by a factor five.

Meteorites -- time capsules of the universe

Zekollari, now an Associate Professor of Glaciology at Vrije Universiteit Brussel, calls for a major international effort to preserve the scientific value of meteorites, "We need to accelerate and intensify efforts to recover Antarctic meteorites. The loss of Antarctic meteorites is much like the loss of data that scientists glean from ice cores collected from vanishing glaciers -- once they disappear, so do some of the secrets of the universe."

Meteorites are fragments from space that provide unique information about our solar system.

Antarctica is the most prolific place to find meteorites, and to date, about 60 percent of all meteorites ever found on Earth have been collected from the surface of the Antarctic ice sheet.

The flow of the ice sheet concentrates meteorites in so-called "meteorite stranding zones," where their dark crust allows them to be easily detected.

In addition to intensifying recovery operations, there is potential to increase the efficiency of meteorite recovery missions in the short term.

This potential relies mainly on data-driven analysis to identify unexplored meteorite stranding zones and mapping areas exposing blue ice where meteorites are often found.

Extraterrestrial heritage slipping away

Due to their dark colour, meteorites preferentially heat up with respect to the surrounding ice.

As this heat transfers from the meteorites to the ice, it can warm up the ice, and eventually cause the ice to locally melt, leading to a sinking of meteorites underneath the surface of the ice sheet.

Once the meteorites enter the ice sheet, even at shallow depths, they cannot be detected anymore, and they are thus lost for science.

As atmospheric temperatures increase, so does the surface temperature of the ice, intensifying the loss.

"Even when temperatures of the ice are well below zero, the dark meteorites warm-up so much in the sun that they can melt the ice directly beneath the meteorite. Through this process, the warm meteorite creates a local depression in the ice and over time fully disappears under the surface," says Tollenaar.

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Meteorite analysis shows Earth's building blocks contained water

When our Sun was a young star, 4.56 billion years ago, what is now our solar system was just a disk of rocky dust and gas. Over tens of millions of years, tiny pebbles of dust coalesced, like a snowball rolling larger and larger, to become kilometer-sized "planetesimals" -- the building blocks of Earth and the other inner planets.

Researchers have long tried to understand the ancient environments in which these planetesimals formed.

For example, water is now abundant on Earth, but has it always been?

In other words, did the planetesimals that accreted into our planet contain water?

Now, a new study combines meteorite data with thermodynamic modeling and determines that the earliest inner solar system planetesimals must have formed in the presence of water, challenging current astrophysical models of the early solar system.

The research was conducted in the laboratory of Paul Asimow (MS '93, PhD '97), Eleanor and John R. McMillan Professor of Geology and Geochemistry and appears in the journal Nature Astronomy on January 9.

Researchers have samples of the earliest years of the solar system in the form of iron meteorites.

These meteorites are the remnants of the metallic cores of the earliest planetesimals in our solar system that avoided accretion into a forming planet and instead orbited around the solar system before ultimately falling onto our planet.

The chemical compositions of meteorites such as these can reveal information about the environments in which they formed and answer questions such as whether the building blocks of Earth formed far from our Sun, where cooler temperatures allowed the existence of water ice, or if they instead formed closer to the Sun, where the heat would have evaporated any water and resulted in dry planetesimals.

If the latter is correct, then Earth would have formed dry and gained its water through some other method later in its evolution.

Though the meteorites themselves do not contain any water, scientists can infer its long-lost presence by examining its impact on other chemical elements.

Water is composed of two hydrogen atoms and one oxygen atom.

In the presence of other elements, water will often transfer its oxygen atom away in a process called oxidation.

For example, iron metal (Fe) reacts with water (H2O) to form iron oxide (FeO). A sufficient excess of water can drive the process further, producing Fe2O3 and FeO(OH), the ingredients of rust.

Mars, for example, is covered in rusty iron oxide, providing strong evidence that the Red Planet once had water.

Damanveer Grewal, a former Caltech postdoctoral scholar and first author of the new study, specializes in using chemical signatures from iron meteorites to gather information about the early solar system.

Though any iron oxide from the earliest planetesimals is now long gone, the team could determine how much iron would have been oxidized by examining the metallic nickel, cobalt, and iron contents of these meteorites.

These three elements should be present in roughly equal ratios relative to other primitive materials, so if any iron was "missing," this would imply that the iron had been oxidized.

"Iron meteorites have been somewhat neglected by the planet-formation community, but they constitute rich stores of information about the earliest period of solar system history, once you work out how to read the signals," says Asimow.

"The difference between what we measured in the inner solar system meteorites and what we expected implies an oxygen activity about 10,000 times higher."

The researchers found that those iron meteorites thought to be derived from the inner solar system had about the same amount of missing iron metal as meteorites derived from the outer solar system.

For this to be the case, the planetesimals from both groups of meteorites must have formed in a part of the solar system where water was present, implying that the building blocks of planets accreted water right from the beginning.

The signatures of water in these planetesimals challenge many of the current astrophysical models of the solar system.

If planetesimals formed at Earth's current orbital position, water would have existed only if the inner solar system was much cooler than models currently predict.

Alternatively, they may have formed further out, where it was cooler, and migrated in.

"If water was present in the early building blocks of our planet, other important elements like carbon and nitrogen were likely present as well," says Grewal.

"The ingredients for life may have been present in the seeds of rocky planets right from the start."

"However, the method only detects water that was used up in oxidizing iron," adds Asimow.

"It is not sensitive to excess water that might go on to form the ocean. So, the conclusions of this study are consistent with Earth accretion models that call for late addition of even more water-rich material."

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Ryugu samples illuminate terrestrial weathering effects on primitive meteorites

A groundbreaking study conducted by a team of international scientists has unveiled unprecedented insights into the nature of the asteroid Ryugu and shed light on the composition of water- and carbon-rich small bodies in the solar system.

Asteroids like Ryugu are remnants of planetary embryos that never reached larger sizes, making them invaluable windows into materials that formed in the early solar system.

The study centered on laboratory measurements of the samples brought back to the Earth by the Hayabusa2 spacecraft in 2020.

Led by the Japan Aerospace Exploration Agency (JAXA), Hayabusa2 aimed to uncover the true nature of Ryugu and explore how astrologists can use knowledge from meteorites to interpret telescopic observations of other hydrous asteroids.

Unlike meteorites derived from similar hydrous asteroids, the Ryugu samples avoided terrestrial alteration -- the interaction with oxygen and water in the Earth's atmosphere.

Reflectance spectroscopy, a primary technique linking laboratory analyses of meteorites to asteroid observations, was employed to compare fresh Ryugu samples with meteorites altered in terrestrial environments.

The team successfully developed analytical procedures that avoided exposing the samples to Earth's atmosphere, ensuring the preservation of their original conditions.

Previous studies suggested that Ryugu's sample mineralogy resembled CI chondrites, the most primitive meteorites chemically.

However, other studies have contradicted this by revealing a significant difference in reflectance spectra between Ryugu samples and CI chondrites.

Further investigations in the new study indicated that heating CI samples under reducing conditions at 300 °C reproduced Ryugu's sample mineralogy well, resulting in spectra closely matching those of Ryugu samples.

The findings challenge previous assumptions about the parent bodies of CI chondrites and underscore the susceptibility of primitive meteorite spectra to terrestrial weathering.

The study suggests that actual CI chondrite parent bodies likely exhibit darker and flatter reflectance spectra than previously thought.

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More than a meteorite: New clues about the demise of dinosaurs

What wiped out the dinosaurs? A meteorite plummeting to Earth is only part of the story, a new study suggests. Climate change triggered by massive volcanic eruptions may have ultimately set the stage for the dinosaur extinction, challenging the traditional narrative that a meteorite alone delivered the final blow to the ancient giants.

That's according to a study published in Science Advances, co-authored by Don Baker, a professor in McGill University's Department of Earth and Planetary Sciences.

The research team delved into volcanic eruptions of the Deccan Traps -- a vast and rugged plateau in Western India formed by molten lava.

Erupting a staggering one million cubic kilometres of rock, it may have played a key role in cooling the global climate around 65 million years ago.

The work took researchers around the world, from hammering out rocks in the Deccan Traps to analyzing the samples in England and Sweden.

A new season?: 'Volcanic winters'

In the lab, the scientists estimated how much sulfur and fluorine was injected into the atmosphere by massive volcanic eruptions in the 200,000 years before the dinosaur extinction.

Remarkably, they found the sulfur release could have triggered a global drop in temperature around the world -- a phenomenon known as a volcanic winter.

"Our research demonstrates that climatic conditions were almost certainly unstable, with repeated volcanic winters that could have lasted decades, prior to the extinction of the dinosaurs. This instability would have made life difficult for all plants and animals and set the stage for the dinosaur extinction event. Thus our work helps explain this significant extinction event that led to the rise of mammals and the evolution of our species," said Prof.

Don Baker.

New technique

Uncovering clues within ancient rock samples was no small feat.

In fact, a new technique developed at McGill helped decode the volcanic history.

The technique for estimating sulfur and fluorine releases-a complex combination of chemistry and experiments-is a bit like cooking pasta.

"Imagine making pasta at home. You boil the water, add salt, and then the pasta. Some of the salt from the water goes into the pasta, but not much of it," explains Baker.

Similarly, some elements become trapped in minerals as they cool following a volcanic eruption.

Just as you could calculate salt concentrations in the water that cooked the pasta from analyzing salt in the pasta itself, the new technique allowed scientists to measure sulfur and fluorine in rock samples.

With this information, the scientists could calculate the amount of these gases released during the eruptions.

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Meteorites likely source of nitrogen for early Earth

Micrometeorites originating from icy celestial bodies in the outer Solar System may be responsible for transporting nitrogen to the near-Earth region in the early days of our solar system. That discovery was published today in Nature Astronomy by an international team of researchers, including University of Hawai'i at Manoa scientists, led by Kyoto University.

Nitrogen compounds, such as ammonium salts, are abundant in material born in regions far from the sun, but evidence of their transport to Earth's orbital region had been poorly understood.

"Our recent findings suggests the possibility that a greater amount of nitrogen compounds than previously recognized was transported near Earth, potentially serving as building blocks for life on our planet," says Hope Ishii, study co-author and affiliate faculty at the Hawai'i Institute of Geophysics and Planetology in the UH Manoa School of Ocean and Earth Science and Technology (SOEST).

Like all asteroids, Ryugu is a small, rocky object that orbits the sun.

The Japan Aerospace Exploration Agency's Hayabusa2 spacecraft explored Ryugu and brought material from its surface back to Earth in 2020.

This intriguing asteroid is rich in carbon and has undergone significant space weathering caused by micrometeorite collisions and exposure to charged ions streaming from the sun.

In this study, the scientists aimed to discover clues about the materials arriving near Earth's orbit, where Ryugu is currently located, by examining the evidence of space weathering in Ryugu samples.

Using an electron microscope, they found that the surface of the Ryugu samples are covered with tiny minerals composed of iron and nitrogen (iron nitride: Fe4N).

"We proposed that tiny meteorites, called micrometeorites, containing ammonia compounds were delivered from icy celestial bodies and collided with Ryugu," said Toru Matsumoto, lead author of the study and assistant professor at Kyoto University.

"The micrometeorite collisions trigger chemical reactions on magnetite and lead to the formation of the iron nitride."

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New study provides novel insights into the cosmic evolution of amino acids

Scientists perform computational simulations for biological molecules detected in meteorites to clarify the origin of life on Earth.

All biological amino acids on Earth appear exclusively in their left-handed form, but the reason underlying this observation is elusive. Recently, scientists from Japan uncovered new clues about the cosmic origin of this asymmetry. Based on the optical properties of amino acids found on the Murchison meteorite, they conducted physics-based simulations, revealing that the precursors to the biological amino acids may have determined the amino acid chirality during the early phase of galactic evolution.

If you look at your hands, you will notice that they are mirror images of each other. However, no matter how hard you try to flip and rotate one hand, you will never be able to superimpose it perfectly over the other. Many molecules have a similar property called "chirality," which means that the "left-handed" (L) version of a molecule cannot be superimposed onto its "right-handed" (D) mirror image version. Even though both versions of a chiral molecule, called "enantiomers," have the same chemical formula, the way they interact with other molecules, especially with other chiral molecules, can vary immensely.

Interestingly, one of the many mysteries surrounding the origin of life as we know it has to do with chirality. It turns out that biological amino acids (AAs) -- the building blocks of proteins -- on Earth appear only in one of their two possible enantiomeric forms, namely the L-form. However, if you synthesize AAs artificially, both L and D forms are produced in equal amounts. This suggests that, at some early point in the past, L-AAs must have come to dominate a hetero-chiral world. This phenomenon is known as "chiral symmetry breaking."

Against this backdrop, a research team led by Assistant Professor Mitsuo Shoji from University of Tsukuba, Japan, conducted a study aimed at solving this mystery. As explained in their paper published in The Journal of Physical Chemistry Letters, the team sought to find evidence supporting the cosmic origin of the homochirality of AAs on Earth, as well as iron out some inconsistencies and contradictions in our previous understanding.

"The idea that homochirality may have originated in space was suggested after AAs were found in the Murchison meteorite that fell in Australia in 1969," explains Dr. Shoji. Curiously enough, in the samples obtained from this meteorite, each of the L-enantiomers was more prevalent than its D-enantiomer counterpart. One popular explanation for this suggests that the asymmetry was induced by ultraviolet circularly polarized light (CPL) in the star-forming regions of our galaxy. Scientists verified that this type of radiation can, indeed, induce asymmetric photochemical reactions that, given enough time, would favor the production of L-AAs over D-AAs. However, the absorption properties of the AA isovaline are opposite to those of the other AAs, meaning that the UV-based explanation alone is either insufficient or incorrect.

Against this backdrop, Dr. Shoji's team pursued an alternate hypothesis. Instead of far-UV radiation, they hypothesized that the chiral asymmetry was, in fact, induced specifically by the CP Lyman-α (Lyα) emission line, a spectral line of hydrogen atom that permeated the early Milky Way. Moreover, instead of focusing only on photoreactions in AAs, the researchers investigated the possibility of the chiral asymmetry starting in the precursors to the AAs, namely amino propanals (APs) and amino nitriles (ANs).

Through quantum mechanical calculations, the team analyzed Lyα-induced reactions for producing AAs along the chemical pathway adopted in Strecker synthesis. They then noted the ratios of L- to D-enantiomers of AAs, APs, and ANs at each step of the process.

The results showed that L-enantiomers of ANs are preferentially formed under right-handed CP (R-CP) Lyα irradiation, with their enantiomeric ratios matching those for the corresponding AAs. "Taken together, our findings suggest that ANs underlie the origin of the homochirality," remarks Dr. Shoji. "More specifically, irradiating AN precursors with R-CP Lyα radiation lead to a higher ratio of L-enantiomers. The subsequent predominance of L-AAs is possible via reactions induced by water molecules and heat."

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Two meteorites are providing a detailed look into outer space

If you've ever seen a shooting star, you might have actually seen a meteor on its way to Earth. Those that land here are called meteorites and can be used to peek back in time, into the far corners of outer space or at the earliest building blocks of life. Today, scientists report some of the most detailed analyses yet of the organic material of two meteorites. They've identified tens of thousands of molecular "puzzle pieces," including a larger amount of oxygen atoms than they had expected.

The researchers will present their results at the spring meeting of the American Chemical Society (ACS).

Previously, the team led by Alan Marshall, Ph.D., investigated complex mixtures of organic materials found on Earth, including petroleum. But now, they are turning their attention toward the skies -- or the things that have fallen from them. Their ultra-high resolution mass spectrometry (MS) technique is starting to reveal new information about the universe and could ultimately provide a window into the origin of life itself.

"This analysis gives us an idea of what's out there, what we're going to run into as we move forward as a 'spacefaring' species," says Joseph Frye-Jones, a graduate student who is presenting the work at the meeting. Both Marshall and Frye-Jones are at Florida State University and the National High Magnetic Field Laboratory.

Thousands of meteorites fall to Earth every year, but only a rare few are "carbonaceous chondrites," the category of space rock that contains the most organic, or carbon-containing, material. One of the most famous is the "Murchison" meteorite, which fell in Australia in 1969 and has been studied extensively since. A newer entry is the relatively unexplored "Aguas Zarcas," which fell in Costa Rica in 2019, bursting through back porches and even a doghouse as its pieces fell to the ground. By understanding the organic makeup of these meteorites, researchers can obtain information about where and when the rocks formed, and what they ran into on their journey through space.

To make sense of the complicated jumble of molecules on the meteorites, the scientists turned to MS. This technique blasts a sample apart into tiny particles, then basically reports the mass of each one, represented as a peak. By analyzing the collection of peaks, or the spectrum, scientists can learn what was in the original sample. But in many cases, the resolution of the spectrum is only good enough to confirm the presence of a compound that was already presumed to be there, rather than providing information about unknown components.

This is where Fourier-transform ion cyclotron resonance (FT-ICR) MS comes in, which is also known as "ultra-high resolution" MS. It can analyze incredibly complex mixtures with very high levels of resolution and accuracy. It's especially well suited for analyzing mixtures, like petroleum, or the complex organic material extracted from a meteorite. "With this instrument, we really have the resolution to look at everything in many kinds of samples," says Frye-Jones.

The researchers extracted the organic material from samples of both the Murchison and Aguas Zarcas meteorites, then analyzed it with ultra-high resolution MS. Rather than analyzing only one specific class of molecules at a time, such as amino acids, they chose to look at all soluble organic material at once. This provided the team with more than 30,000 peaks for each meteorite to analyze, and over 60% of them could be given a unique molecular formula. Frye-Jones says these results represent the first analysis of this type on the Aguas Zarcas meteorite, and the highest-resolution analysis on the Murchison one. In fact, this team identified nearly twice as many molecular formulas as previously reported for the older meteorite.

Once determined, the data were sorted into unique groups based on various characteristics, such as whether they included oxygen or sulfur, or whether they potentially contained a ring structure or double bonds. They were surprised to find a large amount of oxygen content among the compounds. "You don't think of oxygen-containing organics as being a big part of meteorites," explained Marshall.

The researchers will next turn their attention to two far more precious samples: a few grams of lunar dust from the Apollo 12 and 14 missions of 1969 and 1971, respectively. These samples predate Marshall's invention of FT-ICR MS in the early 1970s. Instrumentation has come a long way in the decades since and is now perfectly poised to analyze these powders. The team will soon compare their results from the meteorite analyses to the data they obtain from the lunar samples, hoping to learn more information about where the moon's surface came from. "Was it from meteorites? Solar radiation? We should be able to soon shed some light on that," says Marshall.

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Where did Earth's water come from? Not melted meteorites, according to scientists

Water makes up 71% of Earth's surface, but no one knows how or when such massive quantities of water arrived on Earth.

A new study published in the journal Nature brings scientists one step closer to answering that question. Led by University of Maryland Assistant Professor of Geology Megan Newcombe, researchers analyzed melted meteorites that had been floating around in space since the solar system's formation 4 1/2 billion years ago. They found that these meteorites had extremely low water content -- in fact, they were among the driest extraterrestrial materials ever measured.

These results, which let researchers rule them out as the primary source of Earth's water, could have important implications for the search for water -- and life -- on other planets. It also helps researchers understand the unlikely conditions that aligned to make Earth a habitable planet.

"We wanted to understand how our planet managed to get water because it's not completely obvious," Newcombe said. "Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge."

The team of researchers analyzed seven melted, or achondrite, meteorites that crashed into Earth billions of years after splintering from at least five planetesimals -- objects that collided to form the planets in our solar system. In a process known as melting, many of these planetesimals were heated up by the decay of radioactive elements in the early solar system's history, causing them to separate into layers with a crust, mantle and core.

Because these meteorites fell to Earth only recently, this experiment was the first time anyone had ever measured their volatiles. UMD geology graduate student Liam Peterson used an electron microprobe to measure their levels of magnesium, iron, calcium and silicon, then joined Newcombe at the Carnegie Institution for Science's Earth and Planets Laboratory to measure their water contents with a secondary ion mass spectrometry instrument.

"The challenge of analyzing water in extremely dry materials is that any terrestrial water on the sample's surface or inside the measuring instrument can easily be detected, tainting the results," said study co-author Conel Alexander, a scientist at the Carnegie Institution for Science.

To reduce contamination, researchers first baked their samples in a low-temperature vacuum oven to remove any surface water. Before the samples could be analyzed in the secondary ion mass spectrometer, the samples had to be dried out once again.

"I had to leave the samples under a turbo pump -- a really high-quality vacuum -- for more than a month to draw down the terrestrial water enough," Newcombe said.

Some of their meteorite samples came from the inner solar system, where Earth is located and where conditions are generally assumed to have been warm and dry. Other rarer samples came from the colder, icier outer reaches of our planetary system. While it was generally thought that water came to Earth from the outer solar system, it has yet to be determined what types of objects could have carried that water across the solar system.

"We knew that plenty of outer solar system objects were differentiated, but it was sort of implicitly assumed that because they were from the outer solar system, they must also contain a lot of water," said Sune Nielsen, a study co-author and geologist at the Woods Hole Oceanographic Institution. "Our paper shows this is definitely not the case. As soon as meteorites melt, there is no remaining water."

After analyzing the achondrite meteorite samples, researchers discovered that water comprised less than two millionths of their mass. For comparison, the wettest meteorites -- a group called carbonaceous chondrites -- contain up to about 20% of water by weight, or 100,000 times more than the meteorite samples studied by Newcombe and her co-authors.

This means that the heating and melting of planetesimals leads to near-total water loss, regardless of where these planetesimals originated in the solar system and how much water they started out with. Newcombe and her co-authors discovered that, contrary to popular belief, not all outer solar system objects are rich in water. This led them to conclude that water was likely delivered to Earth via unmelted, or chondritic, meteorites.

Newcombe said their findings have applications beyond geology. Scientists of many disciplines -- and especially exoplanet researchers -- are interested in the origin of Earth's water because of its deep connections with life.

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Meteorites reveal likely origin of Earth's volatile chemicals

By analysing meteorites, Imperial researchers have uncovered the likely far-flung origin of Earth's volatile chemicals, some of which form the building blocks of life.

They found that around half the Earth's inventory of the volatile element zinc came from asteroids originating in the outer Solar System -- the part beyond the asteroid belt that includes the planets Jupiter, Saturn, and Uranus. This material is also expected to have supplied other important volatiles such as water.

Volatiles are elements or compounds that change from solid or liquid state into vapour at relatively low temperatures. They include the six most common elements found in living organisms, as well as water. As such, the addition of this material will have been important for the emergence of life on Earth.

Prior to this, researchers thought that most of Earth's volatiles came from asteroids that formed closer to the Earth. The findings reveal important clues about how Earth came to harbour the special conditions needed to sustain life.

Senior author Professor Mark Rehka?mper, of Imperial College London's Department of Earth Science and Engineering, said: "Our data show that about half of Earth's zinc inventory was delivered by material from the outer Solar System, beyond the orbit of Jupiter. Based on current models of early Solar System development, this was completely unexpected."

Previous research suggested that the Earth formed almost exclusively from inner Solar System material, which researchers inferred was the predominant source of Earth's volatile chemicals. In contrast, the new findings suggest the outer Solar System played a bigger role than previously thought.

Professor Rehka?mper added: "This contribution of outer Solar System material played a vital role in establishing the Earth's inventory of volatile chemicals. It looks as though without the contribution of outer Solar System material, the Earth would have a much lower amount of volatiles than we know it today -- making it drier and potentially unable to nourish and sustain life."

The findings are published today in Science.

To carry out the study, the researchers examined 18 meteorites of varying origins -- eleven from the inner Solar System, known as non-carbonaceous meteorites, and seven from the outer Solar System, known as carbonaceous meteorites.

For each meteorite they measured the relative abundances of the five different forms -- or isotopes -- of zinc. They then compared each isotopic fingerprint with Earth samples to estimate how much each of these materials contributed to the Earth's zinc inventory. The results suggest that while the Earth only incorporated about ten per cent of its mass from carbonaceous bodies, this material supplied about half of Earth's zinc.

The researchers say that material with a high concentration of zinc and other volatile constituents is also likely to be relatively abundant in water, giving clues about the origin of Earth's water.

First author on the paper Rayssa Martins, PhD candidate at the Department of Earth Science and Engineering, said: "We've long known that some carbonaceous material was added to the Earth, but our findings suggest that this material played a key role in establishing our budget of volatile elements, some of which are essential for life to flourish."

Next the researchers will analyse rocks from Mars, which harboured water 4.1 to 3 billion years ago before drying up, and the Moon. Professor Rehka?mper said: "The widely held theory is that the Moon formed when a huge asteroid smashed into an embryonic Earth about 4.5 billion years ago. Analysing zinc isotopes in moon rocks will help us to test this hypothesis and determine whether the colliding asteroid played an important part in delivering volatiles, including water, to the Earth."

Read more at Science Daily

17-pound meteorite discovered in Antarctica

Antarctica is a tough place to work, for obvious reasons -- it's bitterly cold, remote, and wild. However, it's one of the best places in the world to hunt for meteorites. That's partly because Antarctica is a desert, and its dry climate limits the degree of weathering the meteorites experience. On top of the dry conditions, the landscape is ideal for meteorite hunting: the black space rocks stand out clearly against snowy fields. Even when meteorites sink into the ice, the glaciers' churning motion against the rock below helps re-expose the meteorites near the surface of the continent's blue ice fields.

An international team of researchers who just got back from Antarctica can attest to the continent's meteorite-hunter-friendliness: they returned with five new meteorites, including one that weighs 16.7 pounds (7.6 kg).

Maria Valdes, a research scientist at the Field Museum and the University of Chicago, estimates that of the roughly 45,000 meteorites retrieved from Antarctica over the past century, only about a hundred or so are this size or larger. "Size doesn't necessarily matter when it comes to meteorites, and even tiny micrometeorites can be incredibly scientifically valuable," says Valdes, "but of course, finding a big meteorite like this one is rare, and really exciting."

Valdes was one of four scientists on the mission, led by Vinciane Debaille of the Université Libre de Bruxelles (FNRS-ULB); the research team was rounded out by Maria Schönbächler (ETH-Zurich) and Ryoga Maeda (VUB-ULB). The researchers were the first to explore potential new meteorite sites mapped using satellite imagery by Veronica Tollenaar, a thesis student in glaciology at the ULB.

"Going on an adventure exploring unknown areas is exciting," says Debaille, "but we also had to deal with the fact that the reality on the ground is much more difficult than the beauty of satellite images." Despite timing their trip for Antarctica's summertime in late December, temperatures hovered around 14° F (-10° C). Valdes notes that some days during their trip, it was actually colder in Chicago than it was in Antarctica, but spending days riding snowmobiles and trekking through ice fields and then sleeping in a tent made the Antarctic weather feel more extreme.

The five meteorites recovered by the team will be analyzed at the Royal Belgian Institute of Natural Sciences; meanwhile, sediment potentially containing tiny micrometeorites was divided among the researchers for study at their institutions.

Valdes says she's eager to see what the analyses of the meteorites reveal, because "studying meteorites helps us better understand our place in the universe. The bigger a sample size we have of meteorites, the better we can understand our Solar System, and the better we can understand ourselves."

Read more at Science Daily

Martian meteorite contains large diversity of organic compounds

The Martian meteorite Tissint contains a huge diversity of organic compounds, found an international team of researchers led by Technical University of Munich and Helmholtz Munich's Philippe Schmitt-Kopplin and including Carnegie's Andrew Steele. Their work is published in Science Advances.

Tissint, which crash landed in Morocco more than 11 years ago, is one of only five Martian meteorites that have been observed as they fell to Earth. Pieces of it were found scattered around the desert about 30 miles from the town after which it is named.

This sample of Martian rock was formed hundreds of millions of years ago on our next-door planetary neighbor and was launched into space by a violent event. Unraveling the origin stories of the Tissint meteorite's organic compounds can help scientists understand whether the Red Planet ever hosted life, as well as Earth's geologic history.

"Mars and Earth share many aspects of their evolution," said lead author Schmitt-Kopplin. "And while life arose and thrived on our home planet, the question of whether it ever existed on Mars is a very hot research topic that requires deeper knowledge of our neighboring planet's water, organic molecules, and reactive surfaces."

Organic molecules contain carbon, hydrogen, oxygen, nitrogen, sulfur, and sometimes other elements. Organic compounds are commonly associated with life, although previous Martian meteorite research demonstrated that they can be created by non-biological processes, referred to as abiotic organic chemistry.

"Understanding the processes and sequence of events that shaped this rich organic bounty will reveal new details about Mars' habitability and potentially about the reactions that could lead to the formation of life," added Steele, who has done extensive research on organic material in Martian meteorites, including Tissint, and is a member of both the Perseverance and Curiosity rovers' science teams.

The researchers were able to thoroughly analyze the meteorite's organic inventory, revealing a link between the type and diversity of organic molecules and specific mineralogy. Their efforts resulted in the most comprehensive catalog ever made of the diversity of organic compounds found in a Martian meteorite or in a sample collected and analyzed by a rover. This work uncovered details about how the processes occurring in Mars' mantle and crust evolved, especially with regard to abiotic organics that formed from water-rock interactions.

Of particular interest was the abundance of organic magnesium compounds, a suite of organic molecules not previously seen on Mars, which offer new insights about the high-pressure, high-temperature geochemistry that shaped the Red Planet's deep interior and indicate a connection between its carbon cycle and its mineral evolution.

The researchers say that samples returned from Mars by future missions should provide an unprecedented amount of information about the formation, stability and dynamics of organic compounds in real Martian environments.

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Meteorites plus gamma rays could have given Earth the building blocks for life

Even as detailed images of distant galaxies from the James Webb Space Telescope show us more of the greater universe, scientists still disagree about how life began here on Earth. One hypothesis is that meteorites delivered amino acids -- life's building blocks -- to our planet. Now, researchers reporting in ACS Central Science have experimentally shown that amino acids could have formed in these early meteorites from reactions driven by gamma rays produced inside the space rocks.

Ever since Earth was a newly formed, sterile planet, meteorites have been hurtling through the atmosphere at high speeds toward its surface. If the initial space debris had included carbonaceous chondrites -- a class of meteorite whose members contain significant amounts of water and small molecules, such as amino acids -- then it could have contributed to the evolution of life on Earth. However, the source of amino acids in meteorites has been hard to pinpoint. In previous lab experiments, Yoko Kebukawa and colleagues showed that reactions between simple molecules, such as ammonia and formaldehyde, can synthesize amino acids and other macromolecules, but liquid water and heat are required. Radioactive elements, such as aluminum-26 (26Al) -- which is known to have existed in early carbonaceous chondrites -- release gamma rays, a form of high-energy radiation, when they decay. This process could have provided the heat needed to make biomolecules. So, Kebukawa and a new team wanted to see whether radiation could have contributed to the formation of amino acids in early meteorites.

The researchers dissolved formaldehyde and ammonia in water, sealed the solution in glass tubes and then irradiated the tubes with high-energy gamma rays produced from the decay of cobalt-60. They found that the production of α-amino acids, such as alanine, glycine, α-aminobutyric acid and glutamic acid, and β-amino acids, such as β-alanine and β-aminoisobutyric acid, rose in the irradiated solutions as the total gamma-ray dose increased. Based on these results and the expected gamma ray dose from the decay of 26Al in meteorites, the researchers estimated that it would have taken between 1,000 and 100,000 years to produce the amount of alanine and β-alanine found in the Murchison meteorite, which landed in Australia in 1969. This study provides evidence that gamma ray-catalyzed reactions can produce amino acids, possibly contributing to the origin of life on Earth, the researchers say.

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Scientists identify potential source of 'shock-darkened' meteorites, with implications for hazardous asteroid deflection

When the Chelyabinsk fireball exploded across Russian skies in 2013, it littered Earth with a relatively uncommon type of meteorite. What makes the Chelyabinsk meteorites and others like them special is their dark veins, created by a process called shock darkening. Yet, planetary scientists have been unable to pinpoint a nearby asteroid source of these kinds of meteorites -- until now.

In a new paper published in the Planetary Science Journal, University of Arizona scientists identified an asteroid named 1998 OR2 as one potential source of shock-darkened meteorites. The near-Earth asteroid is about 1 1/2 miles wide and made a close approach to Earth in April 2020. When pieces of asteroids break off into space and then land on Earth, they are considered meteorites.

"Shock darkening is an alteration process caused when something impacts a planetary body hard enough that the temperatures partially or fully melt those rocks and alter their appearance both to the human eye and in our data," said lead study author Adam Battle, a UArizona graduate student studying planetary science. "This process has been seen in meteorites many times but has only been seen on asteroids in one or two cases way out in the main asteroid belt, which is found between Mars and Jupiter."

Battle's adviser and study co-author Vishnu Reddy,a planetary sciences professor, discovered shock darkening on main belt asteroids in 2013 and 2014. Reddy co-leads the Space Domain Awareness lab at the Lunar and Planetary Laboratory with engineering professor Roberto Furfaro. Battle has worked in the lab since 2019.

"Impacts are very common in asteroids and any solid body in the solar system because we see impact craters on these objects from spacecraft images. But impact melt and shock-darkening effects on meteorites derived from these bodies are rare. Finding a near-Earth asteroid dominated by this process has implications for impact hazard assessment," Reddy said. "Adam's work has shown that ordinary chondrite asteroids can appear as carbonaceous in our classification tools if they are affected by shock darkening. These two materials have different physical strengths, which is important when trying to deflect a hazardous asteroid."

For this study, Battle, Reddy and their team used the RAPTORS system, a telescope atop the Kuiper Space Sciences building on campus, to collect data on 1998 OR2's surface composition and determined that it looked like an ordinary chondrite asteroid. Chondrite asteroids contain the minerals olivine and pyroxene and are lighter in appearance.

But when the team ran the data through a classification tool, it suggested the asteroid was instead a carbonaceous asteroid, a type of asteroid that is characteristically dark and relatively featureless.

"The mismatch was one of the early things that got the project going to investigate potential causes for the discrepancy," Battle said. "The asteroid is not a mixture of ordinary chondrite and carbonaceous asteroids, but rather it is definitely an ordinary chondrite, based on its minerology, which has been altered -- likely through the shock darkening process -- to look like a carbonaceous asteroid to the classification tool."

Shock darkening was hypothesized in the late 1980s but didn't gain traction and went unstudied until 2013 when the fireball over Russia produced meteorites with shock-darkened characteristics.

Scientists, including Reddy, started getting more interested in shock darkening, and Reddy soon discovered shock-darkened asteroids in the main asteroid belt. On Earth, 2%, or roughly 1,400 of about 60,000 ordinary chondrite meteorites have undergone some degree of shock or impact process, Battle said.

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Meteorite provides record of asteroids 'spitting out' pebbles

In 2019, NASA's OSIRIS-REx spacecraft sent back images of a geological phenomenon no one had ever seen before: pebbles were flying off the surface of the asteroid Bennu. The asteroid appeared to be shooting off swarms of marble-sized rocks. Scientists had never seen this behavior from an asteroid before, and it's a mystery exactly why it happens. But in a new paper in Nature Astronomy, researchers show the first evidence of this process in a meteorite.

"It's fascinating to see something that was just discovered by a space mission on an asteroid millions of miles away from Earth, and find a record from the same geological process in the museum's meteorite collection," says Philipp Heck, the Robert A. Pritzker Curator of Meteoritics at Chicago's Field Museum and the senior author of the Nature Astronomy study.

Meteorites are pieces of rock that fall to Earth from outer space; they can be made of pieces of moons and planets, but most often, they're broken-off bits of asteroids. The Aguas Zarcas meteorite is named after the Costa Rican town where it fell in 2019; it came to the Field Museum as a donation from Terry and Gail Boudreaux. Heck and his student, Xin Yang, were preparing the meteorite for another study when they noticed something strange.

"We were trying to isolate very tiny minerals from the meteorite by freezing it with liquid nitrogen and thawing it with warm water, to break it up," says Yang, a graduate student at the Field Museum and the University of Chicago and the paper's first author. "That works for most meteorites, but this one was kind of weird -- we found some compact fragments that wouldn't break apart."

Heck says that finding bits of meteorite that won't disintegrate isn't unheard of, but scientists usually just shrug and break out the mortar and pestle. "Xin had a very open mind, he said, 'I'm not going to crush these pebbles to sand, this is interesting,'" says Heck. Instead, the researchers devised a plan to figure out what these pebbles were and why they were so resistant to breaking apart.

"We did CT scans to see how the pebbles compared to the other rocks making up the meteorite," says Heck. "What was striking is that these components were all squished -- normally, they'd be spherical -- and they all had the same orientation. They were all deformed in the same direction, by one process." Something had happened to the pebbles that didn't happen to the rest of the rock around them.

"This was exciting, we were very curious about what it meant," says Yang.

The scientists had a clue, though, from the 2019 OSIRIS-REx findings. From there, they put together a hypothesis, which they supported with physical models. The asteroid underwent a high-speed collision, and the area of impact got deformed. That deformed rock eventually broke apart due to the huge temperature differences the asteroid experiences when it rotates, since the side facing the sun is more than 300° F warmer than the side facing away. "This constant thermal cycling makes the rock brittle, and it breaks apart into gravel," says Heck.

These pebbles are then ejected from the asteroid's surface. "We don't yet know what the process is that ejects the pebbles," says Heck -- they might be dislodged by smaller impacts other space collisions, or they might just get released by the thermal stress the asteroid undergoes. But once the pebbles are disturbed, Heck says, "you don't need much to eject something -- the escape velocity is very low." A recent study of Bennu revealed that its surface is loosely bound and behaves like popcorn in a bucket.

The pebbles then entered a very slow orbit around the asteroid, and eventually, they fell back down to its surface further away where there was no deformation. Then, Heck and Yang say, the asteroid underwent another collision, the loose mixed pebbles on the surface got transformed into a solid rock. "It basically packed everything together, and this loose gravel became a cohesive rock," says Heck. The same impact may have dislodged the new rock, sending it careening into space. Eventually, that chunk fell to Earth as the Aguas Zarcas meteorite, carrying evidence of the pebble mixing.

This could explain the pebbles present in Aguas Zarcas, making the meteorite the first physical evidence of the geological process observed by OSIRIS-REx on Bennu. "It provides a new way of explaining the way that minerals on the surfaces of asteroids get mixed," says Yang.

That's a big deal, Heck says, because for a long time, scientists assumed that the main way that the minerals on the surfaces of asteroids get rearranged is through big crashes, which don't happen very often. "From OSIRIS-REx we know that these particle ejection events are much more frequent than these high-velocity impacts," says Heck, "so they probably play a more important role in determining the makeup of asteroids and meteorites."

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What a Martian meteorite can teach us about Earth's origins

What do Mars and Iceland have in common?

These days, not so much. But more than 4.5 billion years ago, it's possible the Red Planet had a crust comparable to Iceland today. This discovery, hidden in the oldest martian fragments found on Earth, could provide information about our planet that was lost over billions of years of geological movement and could help explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.

These insights into Earth's past came out of a new study, published today in Nature Communications, by an international team that includes an NAU researcher. The study details how they found the likely martian origin of the 4.48-billion-year-old meteorite, informally named Black Beauty. Its origin is one of the oldest regions of Mars.

"This meteorite recorded the first stage of the evolution of Mars and, by extension, of all terrestrial planets, including the Earth," said Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science. "As the Earth lost its old surface mainly due to plate tectonics, observing such settings in extremely ancient terrains on Mars is a rare window into the ancient Earth surface that we lost a long time ago."

What Mars can tell us about Earth

The team, led by Anthony Lagain from Curtin University in Australia, searched for the location of origin of a martian meteorite (officially named NWA -- Northwest Africa -- 7034 for where it was found on Earth). This meteorite, the chemistry of which indicates that Mars had volcanic activity to that found on Earth, recorded the first stage of Mars' evolution. Although it was ejected from the surface of Mars five to 10 million years ago after an asteroid impact, its source region and geological context has remained a mystery.

This team studied chemical and physical properties of Black Beauty to pinpoint where it came from; they determined it was from Terra Cimmeria-Sirenum, one of the most ancient regions of Mars. It may have a surface similar to Earth's continents. Planetary bodies like Mars have impacts craters all over their surface, so finding the right one is challenging. In a previous study, Lagain's team developed a crater detection algorithm that uses high-resolution images of the surface of Mars to identify small impact craters, finding about 90 million as small as 50 meters in diameter. In this study, they were able to isolate the most plausible ejection site -- the Karratha crater that excavated ejecta of an older crater named Khujirt.

"For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before the NASA's Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater," said Lagain, a research fellow in the School of Earth and Planetary Sciences at Curtin. "This research paved the way to locate the ejection site of other Martian meteorites, in order to create the most exhaustive view of the Red Planet's geological history."

Payré studies the nature and formation of Mars' crust to determine if Earth and Mars share a common past that include both a continent-like and ocean-like crust. She uses orbital observations captured in this region to investigate whether traces of volcanism similar to Iceland exist on Mars.

"As of today, Mars' crust complexity is not understood, and knowing about the origin of these amazing ancient fragments could lead future rover and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of Mars' evolution, and perhaps the Earth's," she said. "This work paves the road to locate the ejection site of other martian meteorites that will provide the most exhaustive view of the geological history of Mars and will answer one of the most intriguing questions: why Mars, now dry and cold, evolved so differently from Earth, a flourishing planet for life?"

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Martian meteorite upsets planet formation theory

A new study of an old meteorite contradicts current thinking about how rocky planets like the Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen and noble gases as they form. The work is published June 16 in Science.

A basic assumption about planet formation is that planets first collect these volatiles from the nebula around a young star, said Sandrine Péron, a postdoctoral scholar working with Professor Sujoy Mukhopadhyay in the Department of Earth and Planetary Sciences, University of California, Davis.

Because the planet is a ball of molten rock at this point, these elements initially dissolve into the magma ocean and then degass back into the atmosphere. Later on, chondritic meteorites crashing into the young planet deliver more volatile materials.

So scientists expect that the volatile elements in the interior of the planet should reflect the composition of the solar nebula, or a mixture of solar and meteoritic volatiles, while the volatiles in the atmosphere would come mostly from meteorites. These two sources -- solar vs. chondritic -- can be distinguished by the ratios of isotopes of noble gases, in particular krypton.

Mars is of special interest because it formed relatively quickly -- solidifying in about 4 million years after the birth of the Solar System, while the Earth took 50 to 100 million years to form.

"We can reconstruct the history of volatile delivery in the first few million years of the Solar System," Péron said.

Meteorite from Mars' interior

Some meteorites that fall to Earth come from Mars. Most come from surface rocks that have been exposed to Mars' atmosphere. The Chassigny meteorite, which fell to Earth in north-eastern France in 1815, is rare and unusual because it is thought to represent the interior of the planet.

By making extremely careful measurements of minute quantities of krypton isotopes in samples of the meteorite using a new method set up at the UC Davis Noble Gas Laboratory, the researchers could deduce the origin of elements in the rock.

"Because of their low abundance, krypton isotopes are challenging to measure," Péron said.

Surprisingly, the krypton isotopes in the meteorite correspond to those from chondritic meteorites, not the solar nebula. That means that meteorites were delivering volatile elements to the forming planet much earlier than previously thought, and in the presence of the nebula, reversing conventional thinking.

"The Martian interior composition for krypton is nearly purely chondritic, but the atmosphere is solar," Péron said. "It's very distinct."

The results show that Mars' atmosphere cannot have formed purely by outgassing from the mantle, as that would have given it a chondritic composition. The planet must have acquired atmosphere from the solar nebula, after the magma ocean cooled, to prevent substantial mixing between interior chondritic gases and atmospheric solar gases.

The new results suggest that Mars' growth was completed before the solar nebula was dissipated by radiation from the Sun. But the irradiation should also have blown off the nebular atmosphere on Mars, suggesting that atmospheric krypton must have somehow been preserved, possibly trapped underground or in polar ice caps.

"However, that would require Mars to have been cold in the immediate aftermath of its accretion," Mukhopadhyay said. "While our study clearly points to the chondritic gases in the Martian interior, it also raises some interesting questions about the origin and composition of Mars' early atmosphere."

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When worlds collide: Studying impact craters to uncover the secrets of the solar system

While for humans the constants might be death and taxes, for planets the constants are gravity and collisions.

Brandon Johnson studies the latter, using information about impacts to understand the history and the composition of planets, moons, asteroids and meteorites throughout the solar system.

"Impact cratering is the most ubiquitous surface process shaping planetary bodies," Johnson said. "Craters are found on almost every solid body we've ever seen. They are a major driver of change in planetary bodies. They drive the evolution of planetary crusts. All the planets and asteroids were built from a series of impacts. Studying impacts can help us determine the composition and structure of planets."

As an associate professor in the Department of Earth, Atmospheric, and Planetary Sciences in Purdue University's College of Science, Johnson has studied almost every major planetary body in the solar system. And the time scale of his research ranges from relatively recent impacts to nearly the beginning of the solar system itself.

Collecting clues about collisions helps Johnson reconstruct the environment in which the collisions took place, offering deep insights into how and when bodies formed. His research is helping humans explore the planetary bodies in the solar system with only physics, math and a computer. Space missions and laboratory analyses provide a constant supply of new data and questions to work on.

"Most meteorites contain chondrules -- small, previously molten, particles," Johnson said. "Essentially, by studying the formation of chondrules by impacts, we can better understand what was going on in the nascent solar system. For example, based on one impact, we were able to determine that Jupiter had already formed right around 5 million years after the first solar system solids, changing the timeline of our understanding of the solar system."

Johnson and his lab staff incorporate known factors about the composition and physics of planetary bodies into complex computer models, running the models through a range of conditions and comparing the results with observed phenomena. Analyzing movements and collisions can offer insights into the composition of asteroids and meteorites, helping scientists understand how elements like water and metal are distributed through a solar system. By studying impact craters and basins on places like Pluto, Venus and icy moons, and the mechanics of other processes occurring on Europa and asteroids like Psyche, his team can understand more about their interiors; whether they have molten cores and plate tectonics, for example, or whether they have liquid oceans.

His work doesn't just span the solar system. He studies impacts closer to home, too, including on Earth's own moon and terrestrial impacts that may have affected the way Earth's crust, atmosphere and biosphere evolved.

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Giant impact crater in Greenland occurred a few million years after dinosaurs went extinct

Danish and Swedish researchers have dated the enormous Hiawatha impact crater, a 31 km-wide meteorite crater buried under a kilometer of Greenlandic ice. The dating ends speculation that the meteorite impacted after the appearance of humans and opens up a new understanding of Earth's evolution in the post-dinosaur era.

Ever since 2015, when researchers at the University of Copenhagen's GLOBE Institute discovered the Hiawatha impact crater in northwestern Greenland, uncertainty about the crater's age has been the subject of considerable speculation. Could the asteroid have slammed into Earth as recently as 13,000 years ago, when humans had long populated the planet? Could its impact have catalyzed a nearly 1,000-year period of global cooling known as the Younger Dryas?

New analyses performed on grains of sand and rocks from the Hiawatha impact crater by the Natural History Museum of Denmark and the GLOBE Institute at the University of Copenhagen, as well as the Swedish Museum of Natural History in Stockholm, demonstrate that the answer is no. The Hiawatha impact crater is far older. In fact, a new study published in the journal Science Advances today reports its age to be 58 million years old.

"Dating the crater has been a particularly tough nut to crack, so it's very satisfying that two laboratories in Denmark and Sweden, using different dating methods arrived at the same conclusion. As such, I'm convinced that we've determined the crater's actual age, which is much older than many people once thought," says Michael Storey of the Natural History Museum of Denmark.

"Determining the new age of the crater surprised us all. In the future, it will help us investigate the impact's possible effect on climate during an important epoch of Earth's history" says Dr. Gavin Kenny of the Swedish Museum of Natural History.

As one of those who helped discover the Hiawatha impact crater in 2015, Professor Nicolaj Krog Larsen of the GLOBE Institute at the University of Copenhagen is pleased that the crater's exact age is now confirmed.

"It is fantastic to now know its age. We've been working hard to find a way to date the crater since we discovered it seven years ago. Since then, we have been on several field trips to the area to collect samples associated with the Hiawatha impact," says Professor Larsen

Age revealed by laser beams and grains of sand

No kilometer-thick ice sheet draped Northwest Greenland when the Hiawatha asteroid rammed into Earth surface releasing several million times more energy than an atomic bomb. At the time, the Arctic was covered with a temperate rainforest and wildlife abounded -- and temperatures of 20 degrees Celsius were the norm. Eight million years earlier, an even larger asteroid struck present-day Mexico, causing the extinction of Earth's dinosaurs.

The asteroid smashed into Earth, leaving a thirty-one-kilometer-wide, one-kilometer-deep crater. The crater is big enough to contain the entire city of Washington D.C. Today, the crater lies beneath the Hiawatha Glacier in Northwest Greenland. Rivers flowing from the glacier supplied the researchers with sand and rocks that were superheated by the impact 58 million years ago.

The sand was analyzed at the Natural History Museum of Denmark by heating the grains with a laser until they released argon gas, whereas the rock samples were analyzed at the Swedish Museum of Natural History using uranium-lead dating of the mineral zircon.

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Fate of the dinosaurs sealed in spring

The asteroid that killed nearly all dinosaurs struck Earth during springtime. An international team of scientists from the Vrije Universiteit (VU) Amsterdam (The Netherlands), Uppsala University (Sweden), Vrije Universiteit Brussel (Belgium) and the ESRF, the European Synchrotron (France), have determined when the meteorite crashed onto the Earth, after analysing the remains of fishes that died just after the impact. Their results are published in the journal Nature today.

Around 66 million years ago, the so-called Chicxulub meteorite crashed into the Earth, in what today is the Yucatán peninsula in Mexico, marking the demise of dinosaurs and end of the Cretaceous period. This mass extinction still puzzles scientists today, as it was one of the most selective in the history of life: all non-avian dinosaurs, pterosaurs, ammonites, and most marine reptiles disappeared, whilst mammals, birds, crocodiles, and turtles survived.

A team of scientists from the Vrije Universiteit, Uppsala University, and the ESRF have now shed light on the circumstances surrounding the diverse extinction across the different groups. The answers came from the bones of fishes that died moments after the meteorite struck.

When the meteorite impacted Earth, it rocked the continental plate and caused huge waves in water bodies, such as rivers and lakes. These moved enormous volumes of sediment that engulfed fish and buried them alive, while impact spherules (glass beads of Earth rock) rained down from the sky, less than an hour after impact. Today, the event deposit of Tanis in North Dakota (United States) preserves a fossilised ecosystem that includes paddlefishes and sturgeons, which were direct casualties of the event.

The fossil fishes were exceptionally preserved, with their bones showing almost no signs of geochemical alteration. Melanie During, researcher from Uppsala University and the VU Amsterdam and lead author of the publication, went onsite to excavate the precious specimens: "It was obvious to us that we needed to analyse these bones to get valuable information about the moment of the impact," she explains.

The team came to the ESRF, a particle accelerator that produces the world's brightest x-rays, with a partial fish specimen and representative sections of the bones and carried out high-resolution synchrotron X-ray tomography.

The ESRF is the perfect tool to research this kind of samples and the facility has developed unique expertise in palaeontology over the last two decades. "Thanks to the ESRF's data, we found that the bones registered seasonal growth, very much like trees do, growing a new layer every year on the outside of the bone," explains Sophie Sanchez of Uppsala University, and visiting scientist at the ESRF.

"The retrieved growth rings not only captured the life histories of the fishes but also recorded the latest Cretaceous seasonality and thus the season in which the catastrophic extinction occurred," states senior author Jeroen van der Lubbe of the VU in Amsterdam.

The X-ray scans also showed the distribution, shapes, and sizes of the bone cells, which are known to fluctuate with the seasons as well. "In all studied fishes, bone cell density and volumes can be traced over multiple years and they indicate whether it was spring, summer, autumn, or winter. We saw that both cell density and volumes were on the rise but had not yet peaked during the year of death, which implies that growth abruptly stopped spring" says Dennis Voeten, researcher at Uppsala University.

In parallel to synchrotron radiation studies, the team carried out carbon isotope analysis to reveal the annual feeding pattern of a fish. The availability of zooplankton, its prey of choice, oscillated seasonally and peaked in summer. This temporary increase of ingested zooplankton enriched the skeleton of the fish with the heavier 13C carbon isotope relative to the lighter 12C carbon isotope. "The carbon isotope signal across the growth record of this unfortunate paddlefish confirms that the feeding season had not yet climaxed -- death came in spring," asserts During.

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Tracking down the forces that shaped our Solar System’s evolution

Meteorites are remnants of the building blocks that formed Earth and the other planets orbiting our Sun. Recent analysis of their isotopic makeup led by Carnegie's Nicole Nie and published in Science Advances settles a longstanding debate about the geochemical evolution of our Solar System and our home planet.

In their youth, stars are surrounded by a rotating disk of gas and dust. Over time, these materials aggregate to form larger bodies, including planets. Some of these objects are broken up due to collisions in space, the remnants of which sometimes hurtle through Earth's atmosphere as meteorites.

By studying a meteorite's chemistry and mineralogy, researchers like Nie and Carnegie's Anat Shahar can reveal details about the conditions these materials were exposed to during the Solar System's tumultuous early years. Of particular interest is why so-called moderately volatile elements are more depleted on Earth and in meteoritic samples than the average Solar System, represented by the Sun's composition. They are named because their relatively low boiling points mean they evaporate easily.

It's long been theorized that periods of heating and cooling resulted in the evaporation of volatiles from meteorites. Nie and her team showed that an entirely different phenomenon is the culprit in the case of the missing volatiles.

Solving the mystery involved studying a particularly primitive class of meteorites called carbonaceous chondrites that contain crystalline droplets, called chondrules, which were part of the original disk of materials surrounding the young Sun. Because of their ancient origins, these beads are an excellent laboratory for uncovering the Solar System's geochemical history.

"Understanding the conditions under which these volatile elements are stripped from the chondrules can help us work backward to learn the conditions they were exposed to in the Solar System's youth and all the years since," Nie explained.

She and her co-authors set out to probe the isotopic variability of potassium and rubidium, two moderately volatile elements. The research team included Shahar and colleagues from The University of Chicago, where Nie was a graduate student prior to joining Carnegie -- Timo Hopp, Justin Y. Hu, Zhe J. Zhang, and Nicolas Dauphas -- as well as Xin-Yang Chen and Fang-Zhen Teng from University of Washington Seattle.

Each element contains a unique number of protons, but its isotopes have varying numbers of neutrons. This means that each isotope has a slightly different mass than the others. As a result, chemical reactions discriminate between the isotopes, which, in turn, affects the proportion of that isotope in the reaction's end products.

"This means that the different kinds of chemical processing that the chondrules experienced will be evident in their isotopic composition, which is something we can probe using precision instruments," Nie added.

Their work enabled the researchers to settle the debate about how and when in their lifespans the chondrules lost their volatiles. The isotopic record unveiled by Nie and her team indicates that the volatiles were stripped as a result of massive shockwaves passing through the material circling the young Sun that likely drove melting of the dust to form the chondrules. These types of events can be generated by gravitational instability or by larger baby planets moving through the nebular gas.

"Our findings offer new information about our Solar System's youth and the events that shaped the geochemistry of the planets, including our own," Nie concluded.

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