Mars ice could preserve signs of ancient life for 50 million years

For decades, Mars has tempted scientists with its icy surface and quiet promise of life.

Now, a new study suggests that fragments of ancient microbes might still rest frozen in Martian ice, preserved far longer than anyone imagined, and surviving conditions once thought impossible for organic material.

The research shows that even after 50 million years of cosmic radiation, traces of bacteria could survive if sealed in pure ice, offering new hope for discovering biological remnants beneath Mars’s frozen crust.

Life in Mars ice

The team recreated Martian conditions in the lab using E. coli bacteria and pure water ice. They froze the samples at minus 60 degrees Fahrenheit and exposed them to intense radiation matching what Mars faces for millions of years.

The results were striking. More than 10% of the amino acids – the molecules that form proteins – remained intact.

“Fifty million years is far greater than the expected age for some current surface ice deposits on Mars,” said Christopher House of Penn State. “That means if there are bacteria near the surface of Mars, future missions can find it.”

Samples mixed with Martian soil or rock degraded much faster. Pure ice protected molecular fragments by trapping harmful particles before they could spread.

Radiation and organic matter

Alexander Pavlov at NASA Goddard led the experiments. His team wanted to know how radiation reshapes organic matter.

When radiation hits ice mixed with minerals, it forms reactive radicals that move easily and destroy amino acids. In solid ice, those radicals freeze in place, reducing the damage.

“While in solid ice, harmful particles created by radiation get frozen in place and may not be able to reach organic compounds,” Pavlov said. This means pure ice, not rocky soil, could be the best place to look for signs of life on Mars.

The experts also found that clay minerals like montmorillonite don’t help protect molecules. Instead, they may increase damage by allowing thin liquid films to form, giving radiation an easy path.

How ice reacts on Mars

Temperature changes everything. When the researchers repeated their tests at warmer, Mars-like conditions, amino acids broke down faster than they did at Europa-like cold.

At higher temperatures, radiation creates more mobile oxidants that react quickly with organic molecules.

Interestingly, the amount of water mattered too. Earlier studies suggested that more water leads to faster destruction, but the new research revealed something subtle.

In pure ice, radicals form but cannot move easily. In minerals with small amounts of water, those radicals travel through thin liquid-like layers, breaking molecules apart faster.

This behavior helps explain why ice, though exposed, is still a better long-term protector than wet clay or rock mixtures.

Lessons for other worlds

The team also tested conditions found on Europa and Enceladus – icy moons around Jupiter and Saturn. At their extreme cold, amino acids decayed much slower, suggesting powerful preservation under harsh cosmic radiation.

That discovery strengthens the case for NASA’s Europa Clipper mission, now on its journey to study Europa’s icy shell and ocean.

Clipper will search for environments that could support or preserve traces of life, guiding future missions toward promising astrobiological targets.

Reaching deeper layers of Mars ice

Mars isn’t a dead world. Its ice still shifts and reforms, shaped by the planet’s changing tilt and climate. Some deposits have existed for only a few million years – far shorter than the time amino acids can survive.

The 2008 Phoenix lander already dug into Martian ice near the surface. Future missions will need stronger drills to reach deeper layers and recover samples untouched by radiation.

“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.”

Ancient life under Mars ice

The study suggests that if microbes once lived on Mars, their chemical fingerprints may still lie beneath the frost. Pure ice can preserve organic material for tens of millions of years – long enough for human explorers to find it.

The research, supported by NASA’s Planetary Science Division and Penn State’s scientists, points to one clear truth: to find life’s traces, look for ice, not rock.

The answers may already be there, frozen in time, waiting quietly beneath the Martian surface, preserved through cosmic ages and untouched by decay.

The study is published in the journal Astrobiology.

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