Survival of ancient microbial life in Martian ice

 Ancient microbial life could survive 50 million years in Martian ice, NASA study says

Is there life on Mars? If life ever existed on Mars, its best hiding place may be frozen deep within the planet’s ice. This means, Mars’ frozen ice caps may be time capsules for ancient life. This is at least according to science studies. Laboratory experiments show that key building blocks of proteins can survive tens of millions of years in pure ice, even under relentless cosmic radiation. Ice mixed with Martian-like soil, however, destroys organic material far more quickly. The findings point future missions toward drilling into clean, buried ice rather than studying rocks or dirt. NASA's Phoenix mission in 2008 was the first to excavate down and capture photos of ice in the Mars equivalent of the Arctic Circle. Future missions to Mars may want to dig into ice rather than rock. Scientists say ancient microbes, or traces of them, could be locked inside Martian ice deposits, preserved for tens of millions of years.

Scientists from NASA Goddard Space Flight Center and Penn State successfully recreated Mars like conditions in the laboratory to test this idea. The scientists found that pieces of amino acids from Escherichia coli bacteria, if trapped in Martian permafrost or ice caps, could survive more than 50 million years even under constant cosmic radiation. The findings suggest that missions searching for life on Mars should prioritise pure ice or ice rich permafrost instead of focusing mainly on rocks, clay, or soil. Fifty million years is too much for some current surface ice deposits on Mars. The work was funded by NASA's Planetary Science Division Internal Scientist Funding Program through the Fundamental Laboratory Research work package at Goddard Space Flight Center. "Fifty million years is far greater than the expected age for some current surface ice deposits on Mars, which are often less than two million years old, meaning any organic life present within the ice would be preserved," said co author Christopher House, professor of geosciences, affiliate of the Huck Institutes of the Life Sciences and the Earth and Environment Systems Institute, and director of the Penn State Consortium for Planetary and Exoplanetary Science and Technology. "That means if there are bacteria near the surface of Mars, future missions can find it."

The study was led by Alexander Pavlov, a space scientist at NASA Goddard who completed a doctorate in geosciences at Penn State in 2001. In pure water ice, more than 10 % of the amino acids, which are the building blocks of proteins, survived the full 50 million year simulation. By contrast, samples mixed with Mars like sediment broke down 10 times faster and did not survive. A 2022 study by the same team had shown that amino acids preserved in a mixture of 10% water ice and 90% Martian soil were destroyed more quickly than samples containing only sediment. The researchers think the faster breakdown in mixed samples may happen because a thin film forms where ice touches minerals. The layer could allow radiation to move more freely and damage amino acids. The results were striking. "Based on the 2022 study findings, it was thought that organic material in ice or water alone would be destroyed even more rapidly than the 10% water mixture," Pavlov said. "So, it was surprising to find that the organic materials placed in water ice alone are destroyed at a much slower rate than the samples containing water and soil."

The team sealed E. coli bacteria inside test tubes filled with pure water ice. Other samples were combined with water and materials commonly found in Martian sediment, including silicate based rocks and clay. "While in solid ice, harmful particles created by radiation get frozen in place and may not be able to reach organic compounds," Pavlov said. "These results suggest that pure ice or ice-dominated regions are an ideal place to look for recent biological material on Mars." The frozen samples were placed in a gamma radiation chamber at Penn State’s Radiation Science and Engineering Center. The chamber was cooled to minus 60 degrees Fahrenheit to match temperatures in icy regions of Mars. The bacteria were then exposed to radiation equivalent to 20 million years of cosmic ray bombardment on the Martian surface. Afterward, the samples were vacuum sealed and shipped back to NASA Goddard under cold conditions for amino acid testing. Researchers then modelled an additional 30 years of radiation exposure, bringing the total to 50 million years.

NASA’s Europa Clipper mission will study Europa’s ice shell and subsurface ocean. Europa is the fourth largest of Jupiter’s 95 moons. Europa Clipper launched in 2024 and is traveling 1.8 billion miles to reach Jupiter in 2030. The spacecraft will perform 49 close flybys to determine whether environments beneath the surface could support life. The team also tested organic material at temperatures similar to those on Europa, an icy moon of Jupiter, and Enceladus, an icy moon of Saturn. At those even colder temperatures, deterioration slowed down further. Pavlov said the findings are encouraging for NASA's Europa Clipper mission, which will study Europa's ice shell and subsurface ocean. When it comes to Mars, accessing buried ice will require the right tools. The 2008 NASA Mars Phoenix mission was the first to dig down and photograph ice in the Martian equivalent of the Arctic Circle. "There is a lot of ice on Mars, but most of it is just below the surface," House said. "Future missions need a large enough drill or a powerful scoop to access it, similar to the design and capabilities of Phoenix."

In addition to House and Pavlov, the research team included Zhidan Zhang, a retired lab technologist in the Penn State Department of Geosciences, along with Hannah McLain, Kendra Farnsworth, Daniel Glavin, Jamie Elsila, and Jason Dworkin of NASA Goddard. The team also tested organic material at temperatures similar to those on Europa, an icy moon of Jupiter, and Enceladus, an icy moon of Saturn. At those even colder temperatures, deterioration slowed down further. The research features in the journal Astrobiology, titled “Slow Radiolysis of Amino Acids in Mars-Like Permafrost Conditions: Applications to the Search for Extant Life on Mars.”