Photosynthesis may occur in the dusty ice of Mars.

The discovery that Martian reserves of both dry and water ice extend beyond the polar caps was, among other things, due to an unexpected finding in 2008: at that time, the Phoenix spacecraft used its robotic arm to dig a small trench, or more accurately, to slightly scrape the Martian surface in the Green Valley, which is located in the mid-latitudes of Mars' Northern Hemisphere.

In a photograph taken immediately after this, something white was clearly visible under the regolith at a depth of five to six centimeters. When that something disappeared a few days later, it became apparent that it was not salt but ice, which sublimated quickly in the thin atmosphere of the Red Planet.

Subsequently, data from satellite instruments allowed scientists to create a map of the distribution of water ice on Mars. It turned out that a significant portion of the planet's surface contains ice at depths of 10 to 20 centimeters, meaning it can be accessed without the need for an excavator.

However, it became even more intriguing after a detailed examination of images from certain Martian canyons. For instance, in Dao Vallis—a winding, empty channel of an ancient river. Planetologists suspect that the white streaks visible in it are ice that does not even need to be excavated. According to scientists, it formed from snow that fell over the last millions of years during Martian glacial periods, accumulated, compacted, hardened, and was covered by layers of Martian dust.

Regarding this dust blanket, researchers have put forth an interesting idea: it is mostly impermeable and quite dark, meaning it absorbs a considerable amount of solar energy. This leads scientists to suspect that somewhere beneath this cover, accumulated ice may thaw in places, and it will not sublimate because it is shielded from the atmosphere, with the layers above creating pressure that theoretically allows water to exist in a liquid state.

Where asteroid impacts or winds on steep hillsides expose the ice, enough sunlight can penetrate through it to facilitate photosynthesis, which means there could be microscopic life in these hypothetical reservoirs of melted water. A bold hypothesis was shared in Nature by a team of American scientists led by Aditya Huller from the California Institute of Technology.

NASA notes that such subglacial bodies of water on Earth are rich in microbes, algae, and fungi, all of which successfully perform photosynthesis, making the examination of Martian ice for potential thawing locations one of the most intriguing tasks in the search for extraterrestrial life.

In any case, it seems that life on Mars should be sought somewhere beneath the surface, as the planet has an extremely weak magnetic field and, as previously mentioned, a thin atmosphere, meaning the exposed surface is very poorly protected from solar and galactic radiation.