A new study published in the journal Nature Communications Earth & Environment suggests that the conditions necessary for photosynthesis on Mars may exist beneath the dusty ice surface in the Red Planet’s mid-latitudes. Photosynthesis is the process by which living things such as plants, algae and cyanobacteria produce chemical energy using water and light. Water and light are needed for this to happen and make up most of the oxygen in Earth’s atmosphere.

Researchers believe that a fairly thick layer of ice on Mars could filter out the sun’s harsh radiation, while also allowing in enough sunlight for photosynthesis, creating “radiation zones.” These zones can be anywhere from 5 to 38 cm below the ice surface, depending on the amount of dust on the ice.

The team, led by NASA Jet Propulsion Laboratory scientist Aditya Khullar, used computer simulations to find that dusty Martian ice can melt from the inside, and that the ice covering it protects this shallow liquid water from evaporation of dry Mars.

“We don’t claim to have found life on Mars, but we think the dusty Martian ice outcrops in the mid-latitudes are the most accessible places to look for life on Mars so far,” Khüller said.

The researchers also found that the polar regions of Mars, where most of the ice is located, would be too cold for these habitable zones due to the lack of underground melting. Such melting would most likely occur in the mid-latitude regions of the Red Planet.

The team’s theory has some support from both non-Martian sources and our own observational data. “I was surprised to learn that analogues of life could potentially be found in ice containing dust and sediment on Earth. These are called ‘cryoconite holes’ and because they are darker than the ice, they form when dust and sediment on the surface of the ice melt into ice.” added Khüller.

Once inside the ice every summer, even though the top of the ice is frozen, sunlight warms liquid water around the dark powder in the ice. This is because ice is semi-permeable, allowing sunlight to penetrate below the surface.

Of course, none of this means that photosynthetic life exists or ever existed on Mars. But this is intriguing and could lead to further research into the possible existence of subsurface radiation zones on the Red Planet.

“Today, I am working with a team of scientists to develop advanced simulations of where and when dust ice might melt on Mars. We are also reproducing some of these scenarios in the laboratory to study them in more detail with dusty ice,” said Khüller.