Is There Life Beneath Mars’ Icy Surface?

While evidence of life on Mars has not yet been found, a team of NASA scientists believe they have a clear idea of ​​where to explore.

In a study published in Nature Communications Earth & Environmentthey explain how, using computer modeling, they demonstrated that sunlight could penetrate Martian water ice, enabling photosynthesis in shallow pools of meltwater below the surface.

The tropical regions of Mars are favored

The paper points out that tropical regions of Mars, between 30 and 60 degrees latitude, are promising locations for searching for these meltwater pools. But how is this possible?

As NASA explains, there are two types of ice on Mars: frozen water and frozen carbon dioxide. The study focused on frozen water ice that formed from snow mixed with dust that fell to the surface during a series of ice ages over the last million years.

photo credit: © Kimberly Casey CC BY-NC-SA 4.0These cryoconite holes were photographed on the Matanuska Glacier in Alaska. Cryoconite is formed from mineral particles that accumulate on the surface of snow and ice. © Kimberly Casey CC BY-NC-SA 4.0

Being darker, the dust in the ice absorbs heat from the sun's rays more than the surrounding pristine ice. This can lead to ice melting up to a few meters below the surface.

This phenomenon exists on Earth, notably on certain glaciers in Alaska (see front page image). When wind-borne dust particles settle on the ice, they absorb sunlight and trigger melting. So-called cryoconite holes then form. These cavities gradually deepen each under the effect of new melting.

At a certain depth, the radiation is no longer sufficient for the holes to continue to grow. On the other hand, the heat which penetrates inside will create a pocket of melt water at the bottom of these cavities. This is where a simple microbial life form can thrive.

“ This is a common phenomenon on Earth says Phil Christensen of Arizona State University in Tempe of cryoconite holes. “ Dense snow and ice can melt from the inside out, letting in sunlight that warms them like in a greenhouse, rather than melting from the top down. »

The study suggests that dusty ice allows enough light to pass through for photosynthesis to occur up to 3 meters below the surface. “ In this scenario, upper layers of ice prevent evaporation from shallow pools of water below the surface, while providing protection from harmful radiation », Underlines NASA.

Thanks to this work, future robotic and human missions could target mid-latitude exploration areas and the type of analysis: remote sensing to identify places where ice is exposed, drilling or excavation at shallow depths, analysis of samples of ice to search for biosignatures or organic molecules. So many valuable indications for the search for life on Mars.