Life on Mars could be preserved in ice

Was there life on Mars? So far, Mars missions have searched for it in vain. If there ever was any, clues to it could be hidden in the ice beneath the surface, suspects a team from NASA's Goddard Space Flight Center and Pennsylvania State University (Penn State).

The researchers investigated whether and for how long traces of life can be preserved on the neighboring planet. These could still be detected after millions of years, writes the team led by Alexander Pavlov in the journal Astrobiology.

For the study, the team froze E. coli bacteria. Some samples were frozen in pure water ice, while to another part, the researchers added components of Martian soil, such as silicate rocks and clay, to the water ice.

Radiation on Mars simulated

They then cooled the samples down to minus 51 degrees Celsius and exposed them in a radiation chamber at Penn State to radiation equivalent to 20 million years on the Martian surface. Some samples were exposed to further radiation at NASA's Goddard Space Flight Center as if they had spent another 30 million years on the Martian surface.

The evaluation showed that in the samples frozen in pure water ice, about 10 percent of the bacteria's amino acids survived the radiation equivalent of 50 million years. The samples frozen with ice and Martian soil, on the other hand, decomposed significantly faster and did not withstand the radiation.

In 2022, the team conducted a similar study. In it, amino acids decomposed faster in a mixture of 10 percent water ice and 90 percent Martian soil than those found only in sediment. According to the results of this study, it was expected that organic material would decompose even faster in ice or water alone.

Bacteria in ice?

“We were therefore surprised that the organic materials placed only in water ice were destroyed much more slowly than in samples containing water and soil,” Pavlov said. “Harmful particles generated by radiation are frozen in place in solid ice and may not be able to reach organic compounds.” Pure ice or regions with a lot of ice are therefore suitable places to search for biological material on Mars.

“Fifty million years is far more than the expected age of some surface occurrences on Mars, which are often less than two million years old,” said Christopher House, a geoscientist at Penn State and co-author of the study. “This means that organic life would have been preserved in the ice.” So if there were bacteria on Mars, they should be found beneath the surface.

For the study, the team examined not only the conditions on Mars but also on Europa and Enceladus, the ice moons of Jupiter and Saturn. They found that decomposition proceeds more slowly at the even lower temperatures prevailing there. Europa is the destination of NASA's Europa Clipper mission, which launched in October 2024 and is scheduled to arrive at the Jovian moon in 2030. There, it will search for traces of life, among other things.

(wpl)