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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Records of cometary dust hitting the asteroid Ryugu

Ryugu is a near-Earth asteroid that gained significant attention when the Japanese Hayabusa2 mission collected samples and returned them to Earth. These samples have proven to offer a treasure trove of insights into the solar systems, including the possible role of asteroids in delivering organic molecules to earth.

Now, a team of scientists have performed an intensive investigation of Ryugu samples, discovering evidence that points to cometary organic matter being transported from space to the near-Earth region.

The team included Megumi Matsumoto, an assistant professor from the Earth Science Department at Tohoku University Graduate School of Science.

Details of their findings were published in the journal Science Advances on January 19, 2024.

Asteroid Ryugu has no protective atmospheres, and its surface layer is directly exposed to space.

Small interplanetary dust in space can hit the asteroid surface, causing changes to the composition of the asteroid surface materials.

Matsumoto and her colleagues revealed that the sample surfaces contain small 'melt splashes,' ranging in size from 5 to 20 micrometers.

These melt splashes were created when micrometeoroids of cometary dust bombarded Ryugu.

"Our 3D CT imaging and chemical analyses showed that the melt splashes consist mainly of silicate glasses with voids and small inclusions of spherical iron sulfides," says Matsumoto.

"The chemical compositions of the melt splashes suggest that Ryugu's hydrous silicates mixed with cometary dust."

The mixing and melting of Ryugu's surface materials and cometary dust during impact induced heating and rapid cooling formed the melt splashes.

The voids correspond to the water vapor released from the Ryugu's hydrous silicates and subsequently captured in the melt splashes.

Analysis also revealed small carbonaceous materials with abundant nano-pores and iron sulfide inclusions in the melt splashes.

The carbonaceous materials are texturally similar to primitive organic matter in cometary dust, though they lack nitrogen and oxygen, making them chemically different from organic matter.

"We propose that the carbonaceous materials formed from cometary organic matter via the evaporation of volatiles, such as nitrogen and oxygen, during the impact-induced heating. This suggests that cometary matter was transported to the near-Earth region from the outer solar system," adds Matsumoto.

"This organic matter might be the small seeds of life once delivered from space to Earth."

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NASA's Perseverance rover investigates geologically rich Mars terrain

NASA's Perseverance rover is well into its second science campaign, collecting rock-core samples from features within an area long considered by scientists to be a top prospect for finding signs of ancient microbial life on Mars. The rover has collected four samples from an ancient river delta in the Red Planet's Jezero Crater since July 7, bringing the total count of scientifically compelling rock samples to 12.

"We picked the Jezero Crater for Perseverance to explore because we thought it had the best chance of providing scientifically excellent samples -- and now we know we sent the rover to the right location," said Thomas Zurbuchen, NASA's associate administrator for science in Washington. "These first two science campaigns have yielded an amazing diversity of samples to bring back to Earth by the Mars Sample Return campaign."

Twenty-eight miles (45 kilometers) wide, Jezero Crater hosts a delta -- an ancient fan-shaped feature that formed about 3.5 billion years ago at the convergence of a Martian river and a lake. Perseverance is currently investigating the delta's sedimentary rocks, formed when particles of various sizes settled in the once-watery environment. During its first science campaign, the rover explored the crater's floor, finding igneous rock, which forms deep underground from magma or during volcanic activity at the surface.

"The delta, with its diverse sedimentary rocks, contrasts beautifully with the igneous rocks -- formed from crystallization of magma -- discovered on the crater floor," said Perseverance project scientist Ken Farley of Caltech in Pasadena, California. "This juxtaposition provides us with a rich understanding of the geologic history after the crater formed and a diverse sample suite. For example, we found a sandstone that carries grains and rock fragments created far from Jezero Crater -- and a mudstone that includes intriguing organic compounds."

"Wildcat Ridge" is the name given to a rock about 3 feet (1 meter) wide that likely formed billions of years ago as mud and fine sand settled in an evaporating saltwater lake. On July 20, the rover abraded some of the surface of Wildcat Ridge so it could analyze the area with the instrument called Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, or SHERLOC.

SHERLOC's analysis indicates the samples feature a class of organic molecules that are spatially correlated with those of sulfate minerals. Sulfate minerals found in layers of sedimentary rock can yield significant information about the aqueous environments in which they formed.

What Is Organic Matter?

Organic molecules consist of a wide variety of compounds made primarily of carbon and usually include hydrogen and oxygen atoms. They can also contain other elements, such as nitrogen, phosphorus, and sulfur. While there are chemical processes that produce these molecules that don't require life, some of these compounds are the chemical building blocks of life. The presence of these specific molecules is considered to be a potential biosignature -- a substance or structure that could be evidence of past life but may also have been produced without the presence of life.

In 2013, NASA's Curiosity Mars rover found evidence of organic matter in rock-powder samples, and Perseverance has detected organics in Jezero Crater before. But unlike that previous discovery, this latest detection was made in an area where, in the distant past, sediment and salts were deposited into a lake under conditions in which life could potentially have existed. In its analysis of Wildcat Ridge, the SHERLOC instrument registered the most abundant organic detections on the mission to date.

"In the distant past, the sand, mud, and salts that now make up the Wildcat Ridge sample were deposited under conditions where life could potentially have thrived," said Farley. "The fact the organic matter was found in such a sedimentary rock -- known for preserving fossils of ancient life here on Earth -- is important. However, as capable as our instruments aboard Perseverance are, further conclusions regarding what is contained in the Wildcat Ridge sample will have to wait until it's returned to Earth for in-depth study as part of the agency's Mars Sample Return campaign."

The first step in the NASA-ESA (European Space Agency) Mars Sample Return campaign began when Perseverance cored its first rock sample in September 2021. Along with its rock-core samples, the rover has collected one atmospheric sample and two witness tubes, all of which are stored in the rover's belly.

The geologic diversity of the samples already carried in the rover is so good that the rover team is looking into depositing select tubes near the base of the delta in about two months. After depositing the cache, the rover will continue its delta explorations.

"I've studied Martian habitability and geology for much of my career and know first-hand the incredible scientific value of returning a carefully collected set of Mars rocks to Earth," said Laurie Leshin, director of NASA's Jet Propulsion Laboratory in Southern California. "That we are weeks from deploying Perseverance's fascinating samples and mere years from bringing them to Earth so scientists can study them in exquisite detail is truly phenomenal. We will learn so much."

More About the Mission

A key objective for Perseverance's mission on Mars is astrobiology, including caching samples that may contain signs of ancient microbial life. The rover will characterize the planet's geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith.

Subsequent NASA missions, in cooperation with ESA, would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.

The Mars 2020 Perseverance mission is part of NASA's Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.

Read more at Science Daily

New insight into the origin of water on Earth

Scientists have found the interstellar organic matter could produce an abundant supply of water by heating, suggesting that organic matter could be the source of terrestrial water.

There remains a number of mysteries on our planet including the elusive origin of water on the earth. Active studies suggested that terrestrial water had been delivered by icy comets or meteorites containing hydrous silicates that came from outside the "snow line" -- the boundary beyond which ice can condense due the low temperatures. More recent studies, however, have provided observations opposing to cometary origin theory, yet still failing to suggest plausible substitutions for the source of terrestrial water. "Until now, much less attention has been paid to organic matter, comparing to ices and silicates, even though there is an abundance inside the snow line" says planetary scientist Akira Kouchi at Hokkaido University.

In the recent study published in Scientific Reports, a group of scientists led by Akira Kouchi demonstrates that heating of the interstellar organic matter at high temperature could yield abundant water and oil. This suggests that water could be produced inside the snow line, without any contribution of comets or meteorites delivered from outside the snow line.

As a first step, the researchers made an analog of organic matter in interstellar molecular clouds using chemical reagents. To make the analog, they referred to analytical data of interstellar organics made by irradiating UV on a mixture containing H2O, CO, and NH3, which mimicked its natural synthetic process. Then, they gradually heated the organic matter analog from 24 to 400 ? under a pressured condition in a diamond anvil cell. The sample was uniform until 100 ?, but was separated into two phases at 200 ?. At approximately 350 ?, the formation of water droplets became evident and the sizes of the droplets increased as the temperature rose. At 400 ?, in addition to water droplets, black oil was produced.

The group conducted similar experiments with larger amounts of organic matter, which also yielded water and oil. Their analysis of absorption spectra revealed that the main component of the aqueous product was pure water. Additionally, chemical analysis of produced oil showed similar characteristics to the typical crude oil found beneath the earth.

"Our results show that the interstellar organic matter inside the snow line is a potential source of water on the earth. Moreover, the abiotic oil formation we observed suggests more extensive sources of petroleum for the ancient Earth than previously thought," says Akira Kouchi. "Future analyses of organic matter in samples from the asteroid Ryugu, which the Japan's asteroid explorer Hayabusa2 will bring back later this year, should advance our understanding of the origin of terrestrial water."

From Science Daily

Tracking records of the oldest life forms on Earth

Rocks with banded iron formations and biosignatures - 1,900 million years old, Michigan, US (top left), 2,700 million years old, Ontario, Canada (bottom left) and 2,500 million years old, Karijini National Park, Western Australia (right).

The discovery provides a new characteristic 'biosignature' to track the remains of ancient life preserved in rocks which are significantly altered over billions of years and could help identify life elsewhere in the Solar System.

The research, published in two papers -- one in the Journal of the Geological Society and another in Earth and Planetary Science Letters -- solves the longstanding problem of how scientists can track records of life on Earth in highly metamorphosed rocks more than 3,700 million years old, with organic material often turning into the carbon-based mineral graphite.

In the first study, published in Earth and Planetary Science Letters, the team analysed ten rock samples of banded iron formations (BIF) from Canada, India, China, Finland, USA and Greenland spanning over 2,000 million years of history.

They argue that carbon preserved in graphite-like crystals -'graphitic carbon'- located alongside minerals such as apatite, which our teeth and bones are made of, and carbonate, are the biosignatures of the oldest life forms on Earth.

"Life on Earth is all carbon-based and over time, it decomposes into different substances, such as carbonate, apatite and oil. These become trapped in layers of sedimentary rock and eventually the oil becomes graphite during subsequent metamorphism in the crust," explained Dr Dominic Papineau (UCL Earth Sciences, Center for Planetary Sciences and the London Centre for Nanotechnology).

"Our discovery is important as it is hotly debated whether the association of graphite with apatite is indicative of a biological origin of the carbon found in ancient rocks. We now have multiple strands of evidence that these mineral associations are biological in banded iron formations. This has huge implications for how we determine the origin of carbon in samples of extra-terrestrial rocks returned from elsewhere in the Solar System."

The team investigated the composition of BIF rocks as they are almost always of Precambrian age (4,600 million years old to 541 million years old) and record information about the oldest environments on Earth.

For this, they analysed the composition of rocks ranging from 1,800 million years old to more than 3,800 million years old using a range of methods involving photons, electrons, and ions to characterise the composition of graphite and other minerals of potential biogenic origin.

"Previously, it was assumed that finding apatite and graphite together in ancient rocks was a rare occurrence but this study shows that it is commonplace in BIF across a range of rock metamorphic grades," said team member Dr Matthew Dodd (UCL Earth Sciences and the London Centre for Nanotechnology).

The apatite and graphite minerals are thought to have two possible origins: mineralised products of decayed biological organic matter, which includes the breakdown of molecules in oil at high temperatures, or formation through non-biological reactions which are relevant to the chemistry of how life arose from non-living matter.

By showing evidence for the widespread occurrence of graphitic carbon in apatite and carbonate in BIF along with its carbon-isotope composition, the researchers conclude that the minerals are most consistent with a biological origin from the remains of Earth's oldest life forms.

To investigate the extent to which high-temperature metamorphism causes a loss in molecular, elemental and isotope signatures from biological matter in rocks, they analysed the same minerals from a 1,850 million year old BIF rock in Michigan which had metamorphosed in 550 degree Celsius heat.

In this second study, published today in Journal of the Geological Society, the team show that several biosignatures are found in the graphitic carbon and the associated apatite, carbonate and clays.

They used a variety of high-tech instruments to detect traces of key molecules, elements, and carbon isotopes of graphite and combined this with several microscopy techniques to study tiny objects trapped in rocks which are invisible to the naked eye.

Together, all of their observations of the composition are consistent with an origin from decayed biomass, such as that of ancient animal fossils in museums, but which has been strongly altered by high temperatures.

"Our new data provide additional lines of evidence that graphite associated with apatite in BIF is most likely biological in origin. Moreover, by taking a range of observations from throughout the geological record, we resolve a long-standing controversy regarding the origin of isotopically light graphitic carbon with apatite in the oldest BIF," said Dr Papineau.

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