Dusty ice exposed on the surface of Mars may provide the conditions necessary for the presence of photosynthetic life, according to a modeling study.
The results, published in the journal Communications Earth & Environment, suggest that ice deposits located at the planet’s mid-latitudes should be a key site in the search for life on Mars.
The high, harmful ultraviolet radiation levels from the Sun make current life on the surface of Mars almost certainly impossible.
However, a sufficiently thick layer of ice can absorb this radiation and protect the cells living beneath its surface. Any life under these conditions would have to be in the so-called radiative habitable zone – shallow enough to receive enough visible light for photosynthesis, but deep enough to be protected from ultraviolet radiation.
Aditya Khuller and colleagues calculated whether this radiative habitable zone could exist in ice with the level of dust and the ice structure observed on Mars.
They found that very dusty ice would block too much sunlight, but that in ice with 0.01-0.1% dust, a habitable region could exist at depths between 5 and 38 centimeters (depending on the size and purity of the ice crystals). In cleaner ice, a larger habitable zone could exist between 2.15 and 3.10 meters in depth.
The authors explain that dust particles inside the ice could cause occasional localized melting at depths of up to about 1.5 meters, providing the liquid water needed for the survival of any photosynthetic life.
They suggest that Mars’ polar regions would be too cold for this process, but subsurface melting could occur in mid-latitude areas (roughly between 30 and 50 degrees latitude).
The authors warn that the potential existence of theoretically habitable zones does not mean that photosynthetic life is, or ever has been, present on Mars.
However, they suggest that the few cases of ice exposed at Mars’ mid-latitudes could be key areas for future searches for life.
