According to recent research, dusty ice in the Red Planet’s mid-latitudes may be covering the conditions necessary for photosynthesis to take place on Mars.
The process of photosynthesis is how cyanobacteria, algae, and plants produce chemical energy. In order to continue, it needs light and water, and it produces most of the oxygen in the atmosphere. According to the latest research, Mars may be able to create “radiative habitable zones”—zones where a thick enough covering of ice would block off the sun’s harmful radiation while still allowing enough light to support photosynthesis.
These findings need to be interpreted in the correct context, much as photosynthesis requires the ideal amount of light to occur. The findings do not imply that life has ever existed on Mars or exists now, but they do provide scientists conducting the ongoing search with a direction to search.
The “habitable zone” is the area surrounding a star where conditions are favorable for liquid water to exist on a planet’s surface, and this includes both Earth and Mars. Mars seems to be a largely dry landscape, despite the fact that 71% of Earth’s surface is covered in oceans with liquid water.
It has been revealed by observations made by Mars missions like the Curiosity and Perseverance rovers that this was not always the case. These robots’ explorations of geological features like dried lake basins and river tributaries suggest that liquid water once flowed across the Red Planet’s landscapes billions of years ago. Furthermore, water ice has been discovered on Mars by orbiting missions like NASA’s Mars Reconnaissance Orbiter (MRO), frequently in unexpected places.
Scientists believe that Mars’ atmosphere was mostly stripped away and its magnetic field burnt out billions of years ago, whence Earth’s magnetosphere still exists. This implied that not much could be done to stop water from evaporating and vanishing into space. Due to its thin atmosphere, modern Mars is also subjected to the sun’s intense UV radiation, which is lethal to life and breaks down the intricate molecules required for it.
“Unlike Earth, Mars lacks a protective ozone shield, so there is 30% more harmful ultraviolet radiation at the surface in comparison with our planet,” Khuller stated. “Thus, on Mars, the areas where photosynthesis could occur are more likely to be within dusty ice because the overlying dusty ice blocks the harmful ultraviolet radiation at Mars’ surface, and liquid water is highly unstable at the surface of Mars due to its dry atmosphere.”
The scientists discovered through computer simulations that the shallow liquid water beneath the surface of dusty Mars ice can melt from within, shielded from evaporating into the dry Martian atmosphere by the ice covering it.
“So, the two key ingredients for photosynthesis can be present within dusty Martian ice in the mid-latitudes,” Khuller stated. “For photosynthesis to take place, there must be sufficient sunlight and liquid water. Previous independent models of dense Martian snow have shown that if dust particles (less than 1 percent) are present in the snow, melting below the surface can still happen in the Martian mid-latitudes today.
“By discovering dusty ice exposed within buried dusty snowpacks associated with Martian gullies a few years ago, there is a mechanism for them to melt below the surface to form shallow subsurface liquid water.”
According to Khuller, the researchers discovered that the surrounding ice can shield the exposed dusty ice from the damaging UV rays that reach the surface of Mars. Additionally, enough sun energy can pass through this ice below the surface to support photosynthesis.
The concentration of dust in the ice determines the depths at which these radiative habitable zones are found. According to the team’s models, ice that is very dusty would obstruct too much light. On the other hand, a radiative zone might occur in ice containing 0.01% to 0.1% dust at a depth of 2 to 15 inches (5 to 38 centimeters). At a depth of seven to ten feet (2.2 to 3.1 meters), a wider and deeper radiative zone would be possible with less “polluted” ice.
The team believes that a lack of subsurface melting would make the polar regions of Mars, where most of the planet’s ice is found, too cold for these radiative habitable zones to exist. The Red Planet’s mid-latitude regions would be more prone to experience this kind of melting.
The observable evidence that the team has gathered comes from Earth rather than Mars, lending some credence to their theory.
“I was surprised to find out that there are potentially similar analogs for life within ice on Earth that contains dust and sediment,” Khuller said. “These are called ‘cryoconite holes’ and form when dust and sediment on top of the ice melt into the ice because it is darker than the ice.”
The study went on to say that every summer, even though the ice above is frozen, liquid water forms surrounding the black dust within the ice as a result of heating from sunshine. This occurs as a result of the ice’s transparency, which lets light through below the surface.
“People have found microorganisms that live in these shallow subsurface habitats on Earth,” Khuller stated. “The microorganisms typically go dormant in the winter when there is not enough sunlight to form liquid water within the dusty ice.”
Naturally, none of this suggests that there is or ever was photosynthetic life on Mars. However, it’s exciting and might encourage more research into the possibility that the Red Planet has subterranean radiative livable zones.
“I am working with a team of scientists to develop improved simulations of if, where, and when dusty ice could be melting on Mars today,” Khuller said. “Additionally, we are recreating some of these dusty ice scenarios in a lab setting to examine them in more detail.”
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