Postcards from ancient Mars: Isotopes illuminate early Martian climate - Astronomy & Space Astrobiology - Planetary Sciences - UNIVERSE

NASA's Curiosity Mars rover took this selfie at a location nicknamed Mary Anning, after a 19th-century English paleontologist. Curiosity snagged three samples of drilled rock at this site on its way out of the Glen Torridon region, which scientists believe was a site where ancient conditions would have been favorable to supporting life, if it ever was present. Credit: NASA/JPL-Caltech/MSSS

A new analysis of chemical signatures measured by NASA's Curiosity Rover gives a peek at Mars's past to a time some 3.7 billion years ago, when it was warmer and wetter.

Through measurements of isotopic ratios of oxygen, a team of collaborators, including researchers from Caltech's campus and NASA's Jet Propulsion Laboratory (JPL) have discovered that the lake which once existed in Mars's Gale Crater was undergoing significant evaporation earlier than the mineralogy and geochemistry of the lake bed sediments would suggest.

The process of evaporation, while commonplace to us on Earth, gives important clues to the ancient Martian climate. The presence of evaporation signatures in the isotopic compositions of water extracted from clay minerals in the Martian rocks indicates that the Martian atmosphere was warm but also dry, promoting evaporation of standing water.

"'Warm' is relative," says Amy Hofmann, Ph.D., a visiting associate at Caltech and research scientist with JPL, which Caltech manages for NASA. "We're talking a little above freezing, but it was warm enough to potentially support the kinds of prebiotic chemistries that astrobiologists are interested in.

"This was a dynamic time in Mars's history. The planet was in the midst of a global climate transition, but we know from the rocks at Gale that Mars's surface was still experiencing chemical weathering, and the lake waters had a roughly circumneutral pH and were not particularly salty. So, add to that mix the simple organic compounds previously discovered in these same rocks, and you've got yourself a compellingly habitable local environment."

Hofmann is the lead author on a paper describing the study, which appears in the journal Proceedings of the National Academy of Sciences.

The study focuses on oxygen isotopes rather than more commonly studied hydrogen isotopes. The project is the first to find strong enrichments of oxygen-18 in an ancient Martian water reservoir. Oxygen-18 is a relatively rare form of oxygen that is heavier than its typical counterpart, oxygen-16, due to having two more neutrons. When water evaporates, the H₂O molecules containing a lighter oxygen atom tend to be the first to go, leaving behind liquid water containing a higher concentration of heavy oxygen.

The team studied samples collected by the Curiosity rover between 2012 and 2021 from the Gale Crater region of Mars. This deep depression on Mars shows signs of once having contained a large lake. The rover sampled clay minerals, which are known to more accurately retain the oxygen and hydrogen isotopic signatures imparted from the time they were formed.

Though the oxygen isotope ratios in Mars's atmosphere look quite similar to the ratios on Earth, water extracted from the clay minerals showed strong enrichments of heavier oxygen. This discovery indicates the evaporation was indeed occurring in Gale Crater at the time when those sediments were deposited.

"This discovery of the Curiosity rover team is an important step forward in our long struggle to understand how water shaped the surface of Mars in ways that remind us of Earth yet are so different in their details and their outcomes," says co-author John Eiler, the Robert P. Sharp Professor of Geology and Geochemistry and the Ted and Ginger Jenkins Leadership Chair of the Division of Geological and Planetary Sciences.

"Most important to me is the new understanding we have gained of ways the drier atmosphere and wildly changing hydrosphere on Mars controlled the life cycles of its lakes—arguably our best targets for discovering evidence of life or its chemical precursors beyond Earth." 

Provided by California Institute of Technology 

by Lori Dajose, California Institute of Technology

edited by Stephanie Baum, reviewed by Robert Egan 

Source: Postcards from ancient Mars: Isotopes illuminate early Martian climate    

Safer lithium-ion battery design prevents thermal runaway that can cause fires - Engineering - Energy & Green Tech

Ion association promotes SEI formation while facilitating anion thermal decomposition. Credit: Nature Energy (2025). DOI: 10.1038/s41560-025-01888-5

Conventional lithium-ion batteries are known to present a fire risk, and can even cause explosions in certain cases. The widespread usage of lithium-ion batteries, in everything from electric vehicles to electric toothbrushes, makes lithium-ion battery fire risk mitigation a major priority. There is a great need for lithium-ion battery designs that balance long cycle life, high voltage, and safety.

The fire risk arises when lithium-ion batteries undergo some kind of physical damage, are overcharged or even when they have manufacturing defects. This causes thermal runaway when anions—or negatively charged ions—break their bonds with lithium and release heat. Conventional lithium-ion batteries can undergo a temperature change of over 500°C when this occurs.

However, researchers in China have now found a way to drastically reduce the heat released when lithium-ion batteries are damaged. Their study, published in Nature Energy, details the new design and the experimental results of nail penetration tests, in which the temperature rise was only around 3.5°C.

Videos showing nail penetration tests of 1.1 Ah graphite-NCM811 pouch cells using commercial electrolytes (1 M LiPF₆ in, 1:1 vol%) and GBF-D2 electrolyte. Credit: Nature Energy (2025). DOI: 10.1038/s41560-025-01888-5

The new design was made possible after the team found that ion association in electrolytes within the batteries was lowering the temperature at which thermal runaway occurred by around 94°C. They realized that replacing some of the solvent in the battery with a different material should lower the risk of thermal runaway by increasing the temperature that it begins at. This replacement would also still allow solid electrolyte interphase (SEI) formation at lower temperatures, which is a normal function of a lithium-ion battery.

And so, the researchers developed a "solvent-relay strategy" that promotes ion association at room temperature for SEI formation, but induces dissociation at high temperatures for safety. The new design involves a solvent called lithium bis(fluorosulfonyl)imide, which bonds with the lithium from the existing solvent only at higher temperatures, inhibiting the anion bonds that produce eventual thermal runaway.

The team tested out the new design in 1.1 Ah pouch cells by puncturing them with a nail—a common safety assessment test for lithium-ion batteries.

"This approach enabled 4.5 V graphite-NCM811 pouch cells (1.1 Ah) that exhibited an exceptional cycle life of 4,100 hours with approximately 81.9% capacity retention (1,000 cycles under 0.45 C). These ampere-hour-scale cells also demonstrated enhanced thermal stability, with a temperature increase of less than 3.5 °C during nail penetration tests, compared to 555.2 °C for cells with commercial electrolytes," the study authors write.

This new design is a clear leap forward for lithium-ion battery safety. Although some more testing is needed, these changes could be incorporated into lithium-ion batteries in the near future.

The study authors write, "This study elucidates the critical influence of ion association on thermal runaway and establishes an effective strategy to achieve prolonged cycle life, high cut-off voltage and enhanced safety in ampere-hour-level lithium-ion batteries."

by Krystal Kasal, Phys.org

edited by Gaby Clark, reviewed by Robert Egan 

Source: Safer lithium-ion battery design prevents thermal runaway that can cause fires