The conditions necessary for photosynthesis on Mars may exist beneath the dusty ice surface in the Red Planet’s mid-latitudes, according to new research.

Photosynthesis It is the process by which living things such as plants, algae and cyanobacteria create chemical energy. It requires water and light and makes up most of the oxygen in Earth’s atmosphere. A new study shows that an extremely thick ice sheet on Mars can filter out harsh solar radiation but also allow in enough sunlight for photosynthesis, creating “radiative habitat zones.”

Just as photosynthesis requires the right light, these results need to be seen in the right light. Although they do not suggest that life exists on Mars now or at any time in the Red Planet’s history, the results do give scientists involved in this ongoing research an idea of ​​where to look.

“We do not claim to have found life on Mars, but rather believe that the dusty Martian ice in the mid-latitudes are by far the most accessible places to search for life on Mars,” said study leader Aditya Khullar, a NASA Jet scientist. This was reported to Space.com by Motion Lab.

Both Earth and Mars are in the Sun’s so-called “habitable zone,” a region where the temperature around the star is sufficient for liquid water to exist on the planet’s surface. However, although 71% of Earth’s surface is covered by oceans of liquid water, Mars appears to be a mostly dry landscape.

Observations made by Mars missions such as the Curiosity and Perseverance rovers have shown that this is not always the case. Geological features such as dry lake beds and river tributaries examined by these studies indicate that liquid water flowed on the surface of the Red Planet billions of years ago. Additionally, missions flying over Mars, such as NASA’s Mars Reconnaissance Orbiter (MRO), have discovered water ice on Mars, often in unexpected regions.

Scientists believe Mars lost its liquid water billions of years ago when its magnetic field dissipated (Earth’s magnetosphere is still strong) and its atmosphere was largely cleared. This meant there was little to prevent the loss of evaporated water into space. The lack of a thick atmosphere also means modern-day Mars has been bombarded
Ultraviolet radiation from the Sun that is fatal to living things and destroys the complex molecules necessary for life.

“Unlike Earth, Mars does not have a protective ozone shield, so the surface has 30% more harmful ultraviolet radiation than our planet,” Huller said. “So on Mars, regions where photosynthesis can occur are most likely in dust ice, because surface dust ice blocks harmful UV radiation on the Martian surface, and liquid water is very unstable on the Martian surface due to the dryness of the atmosphere”.

Using computer simulations, the team found that dusty Martian ice can melt from the inside, and that the ice covering the surface prevents this shallow subsurface liquid water from evaporating into the dry Martian atmosphere.

“Therefore, two essential components for photosynthesis may be present in dusty Martian ice in mid-latitudes,” added Hüller. “Photosynthesis requires liquid water as well as sufficient sunlight. Two previous independent simulations of dense Martian snow had shown that subsurface melting could occur in the mid-latitudes of Mars today if small amounts of dust (less than 1%) were present in the snow.”

“The discovery several years ago of powder ice exposed within buried powder snow layers associated with Martian craters revealed a mechanism by which it melts beneath the surface to form shallow subsurface liquid water.”

Hüller explained that the team found that in exposed dust ice, the overlying ice could block harmful ultraviolet radiation on the Martian surface. This ice also allows sufficient sunlight for photosynthesis to penetrate below the ice surface.

The depths where the radiation concentrates are located depend on the amount of dust in the ice. The team’s simulations showed that very dusty blocks of ice received too much sunlight. However, ice with a dust content of 0.01% to 0.1% will allow a radiation zone 2 to 15 inches (5 to 38 centimeters) deep to exist. Less “contaminated” ice would allow a deeper and wider radiation zone to exist at a depth of 7 to 10 feet (2.2 to 3.1 meters).

The team believes that the polar regions of Mars, where most of the ice is located, would be too cold for these radiative habitable zones to exist due to the lack of subsurface melting. Such melting is most likely to occur in the mid-latitude regions of the Red Planet.

The team’s theory is supported by observational data from our planet, not Mars.

“I was surprised to learn that potentially similar analogues of life exist in ice containing dust and sediment on Earth,” Huller added. “These are called ‘cryoconite holes’ and are formed as a result of the melting of dust and sediment on the surface of the ice because it is darker than the ice.”

The researcher continued: Every summer, liquid water forms around the dark powder in the ice due to heating from sunlight, even though the ice above it is frozen like a cap. This is because ice is translucent and allows sunlight to penetrate below the surface.

“People have found microorganisms living in these shallow underground habitats on Earth,” Huller said. “Microorganisms are often dormant during the winter months when there is not enough sunlight to form liquid water in powder ice.”

Of course, none of this means that photosynthetic life exists or ever existed on Mars. However, this is intriguing and may stimulate further research into the possible existence of regions of concentrated subsurface radiation on the Red Planet.

“I am working with a team of scientists to develop advanced simulations of whether, where and when dust ice will melt on Mars today,” Huller concluded. “We are also reproducing some of these powder ice scenarios in the laboratory to study them in more detail.”

The team’s research was published today (October 17) in the journal Nature Communications Earth & Environment.