Life associated with ice on Mars?

Scientists have concluded that pockets of meltwater may exist on Mars, at shallow depths under surface ice, capable of supporting microbial life.

Through simulations in digital models, the team of Aditya Khuller of NASA and Phil Christensen of Arizona State University, both institutions in the United States, has shown that the amount of sunlight that can pass through water ice would be enough to photosynthesis to occur in shallow pools of water under that thin layer of ice. Similar pools of water have been found on Earth, forming inside blocks of ice and teeming with life, including algae, fungi and cyanobacteria, all of which derive energy from photosynthesis.

In Khuller’s opinion, these shallow Martian pools beneath the surface ice are probably the most accessible places in the universe that could harbor life.

Mars has two types of ice: frozen water and frozen carbon dioxide. In the new study, Khuller and his colleagues focused on water, large amounts of which formed from snow mixed with dust that fell to the surface during a series of Martian ice ages. That old powdery snow has since turned into ice, which holds the dust motes.

Although dust particles can obscure light in the deeper layers of ice, they are the key to how shallow pools of water can form beneath the surface ice when exposed to the Sun: dark dust absorbs more sunlight than the surrounding ice, potentially causing the ice to heat up and melt at depths of a few metres. That ice can melt from the inside out, letting in sunlight that warms it as if it were a greenhouse, instead of melting from the outside to the inside.

The results of the new study indicate that dusty ice allows enough light to pass through for photosynthesis to occur up to 3 meters below the surface. In this scenario, the upper layers of ice prevent shallow subsurface water pools from evaporating, while protecting them from harmful radiation. This is important because, unlike Earth, Mars lacks a magnetic field that protects it from both particles from the Sun and those coming from other parts of the cosmos.

The white material seen inside this Martian ravine is believed to be dusty water ice. Sites like this could be an excellent place to look for microbial life on Mars. This image, showing part of a region called Dao Vallis, was captured by NASA’s MRO (Mars Reconnaissance Orbiter) space probe in 2009. (Photo: NASA JPL / Caltech / University of Arizona)

The study’s authors believe that the water ice most likely to form underground lagoons is in the tropics of Mars, between 30 and 60 degrees latitude, in both the northern and southern hemispheres.

The study is titled “Potential for photosynthesis on Mars within snow and ice.” And it has been published in the academic journal Nature Communications Earth & Environment.

Khuller hopes to recreate some of Mars’ dusty ice in a laboratory to study it up close. Meanwhile, he and other scientists are starting to map the most likely places on Mars to look for shallow meltwater, places that could be scientific targets for possible human and robotic missions in the future. (Fountain: NCYT by Amazings)