The surface of the Mars is extremely cold, irradiated and dried. But at one time the planet was much warmer and moist, with running water, lakes and even an ocean that covered most of its northern hemisphere. For this reason, scientists speculate that life occurred on Mars billions of years ago and could still be there today. Since the landing of 1 and 2 Viking ended up on the surface in 1976, the search for evidence of life in the past (and maybe possibly present) has not been completed.
Since missions such as curiosity and perseverance continue to research promising regions that were once Lakebee (The Gale and Jezero Craters), there are still questions about where to search next. In a recently published work, the researchers proposed to look for photosynthetic bacteria that were embedded in the snow and the ice around the middle of Mars. With “stradiative zones” on earth as a template, they argue that photosynthetically active bacteria could survive in exposed ice stains.
Research was made by Dr. Aditya Khuller, a postdoctoral researcher at the Jet Propulsion Laboratory (JPL) of the NASA and the Polar Science Center at the University of Washington (UW-PSC). For him, colleagues from the UW Applied Physics Laboratory, the School of Earth & Space Exploration at Arizona State University (Sees-Asu) and the Institute for Arctic and Alpine (Instaar) at the University of Colorado Boulder (UC Boulder). The paper in which its results were detailed was presented on the 56th Mondplanetary Science Conference (2025 LPSC).
On earth, bacteria can survive and thrive even at depths of several meters. The protective ozone layer of the earth protects these organisms from harmful ultraviolet radiation (UV) and enables them to safely absorb the radiation (par) as photosynthetically active. On Mars, which has a thin atmosphere (less than 1% of the earth) and no ozone layer, about 30% more harmful UV radiation reaches the surface. However, the numerical modeling predicts that ice and snow can melt around the equator under the surface.
The presence of this liquid water in these depths could make these underground environments the easiest accessible places for future astrobiology missions. In order to examine this possibility, the team developed a radiation transmission model (RTM) based on earlier examinations that the Delta Eddington method uses (a simplified means of calculating the radiation flows). This model made it possible for you to simulate vertically stacked layers of snow, ice and Mars dust.
Since the sun river on Mars has not yet been measured, the Glacier ice cream in Greenland used the team as an analogue. Their results showed that in all cases most of the solar radiation is absorbed within the upper meter of the ice cream, but increases due to the grain size. Overall, they found that solar radiation can reach a maximum depth of around 6.5 meters in clean ice. At the same time, biologically harmful UV in a clean granular, packed ice (Firn) penetrated about 3 m (~ 10 ft). Their results also showed that the par penetration varied considerably due to the amount of dust in the ice.
For ice cream with 0.01% dust, the par reached only 25 cm below the surface, while the top penalty depth from UV was reduced to about 7 cm (2.75 inches). For ice cream with 0.1% dust concentrations, this was reduced to only 5 cm (~ 2 inches) with a peak -UV penetration of 1.5 cm (0.6 inches). Overall, they found that the Mars may have radiantly habitually habitable zones in exposed spots of ice with medium width in depths of a few centimeters for dusty ice cream up to several meters for cleaner ice cream.
On earth, microbes require temperatures of more than -18 °C (-0.67 °F) for the cell division. Favorable solar radiation conditions and the presence of liquid water are now required for photosynthesis. And while the conditions within the Marsian polar ice are too cold to melt in these depths, numerical models indicate that small amounts of melting and drainage can occur in exposed spots of the snow cover with medium width directly below the surface. As the team states, this could have a significant impact on the search for life on Mars:
“Under similar short-lived almost frozen conditions there are widespread microbial habitats that contain cyanobacteria, chlorophytes, fungi, diatoms and heterotrophic bacteria, in the flat surface (top a few centimeters to measuring devices) of ice sheets, glaciers and lake ice cream, which contain dust and sediment on earth.
“In summer, ice melts in the flat surface due to the solar heating at these areas. The photosynthesis then occurs in the underground surface, under a translucent ice lid, with nutrients that are from the dust and the sediment in the underground, liquid water until next summer.”
When ice and snow experience seasonal melts in equatorial regions, microbes like cyanobacteria could combine this water with nutrients from Mars dust in the ice to carry out photosynthesis. If such habitats exist, they would be the simplest accessible places to find evidence of life on Mars.
Further reading: USA
