A new study shows that ancient Mars likely had enough chemical energy to microbes could flourish underground. “Basing on fundamental physical and chemical calculations, we showed that the subsurface layer of ancient Mars probably had enough of the dissolved hydrogen to power the global subsurface biosphere,” says Jesse Tarnas, graduate of brown University and lead author of the study published in Earth and Planetary Science Letters”.
“The conditions in this potentially habitable zone could be like earth where there is an underground life.”
Where Mars is hiding life?
The land is home to the so-called subsurface autotrophic microbial systems. In the absence of sunlight, these underground microbes often take their energy, taking electrons from molecules in the environment. Dissolved molecular hydrogen — the perfect donor of electrons. He has such microbes on Earth.
A new study shows that the radiolysis, the process by which radiation breaks the water molecules into their component hydrogen and oxygen, could create a lot of hydrogen in an ancient Martian popularnosti. Scientists estimate that hydrogen concentration in the crust 4 billion years ago should have been roughly comparable to the earth that feeds many germs today.
These findings do not mean that life definitely existed on ancient Mars, but they suggest that if life did, indeed, Martian popularnosti would have the necessary components to sustain it for hundreds of millions of years. This work also has implications for future Mars exploration because of the region where the ancient popularnosti comes out, can be a great place to search for former life.
Since then, as it became clear that Mars once had flowing rivers and lakes, scientists are obsessed with the possibility that the Red planet could once to keep life. But although evidence of the existence of water in the past is irrefutable, it is not clear for which part of Martian history, water was actually flowing. The best climate models of early Mars give temperatures that barely exceed the freezing point, and then wet periods of the planet could be very fleeting. It’s not the best scenario for maintaining life on the surface for a long time, and so some scientists believe that beneath the surface of past Martian life might feel better.
“The question arises: what was the nature of this subsurface life, if any existed, and where did she get her energy?”, says Jack mustard, Professor of Earth, environmental and planetary Sciences brown University, co-author of the study. “We know that the radiolysis helps to provide energy to the underground of germs on the Ground, so Jessie decided to continue this story of radiolysis on Mars”.
Researchers examined data on gamma-ray spectrometer which flies on Board the spacecraft Mars Odyssey. They made a map of the prevalence of radioactive elements of thorium and potassium in the Martian crust. Starting from the cards, they managed to find a third radioactive element, uranium. The collapse of these three elements provides a radiation, which leads to radiolytically the disintegration of the water. And since these elements decay at a certain speed, the model prevalence can be used to calculate the presence of elements 4 billion years ago. So the team had the idea of a radioactive flash that was actively pushed by the radiolysis.
The next step was to estimate how much water was available for this radiation. Geological evidence suggests that in the porous rock of ancient Martian crust had a lot of ground water, erupting through the pores. The researchers used a measurement of the density of the Martian crust to a rough estimate of how long it was available for filling water.
Finally, the team used geothermal and climate model, to determine where could be the ancient life. Not supposed to be so cold that not all the water is frozen, but not too warm.
By combining these tests, the researchers came to the conclusion that Mars probably had a global subsurface potentially habitable zone several kilometers thick. In this area the production of hydrogen in the process of radiolysis would generate more than enough chemical energy to sustain microbial life, assuming that we know on Earth. This area should have been saved hundreds of millions of years.
These findings remained even when the researchers simulated various climate scenarios — some warmer, some colder. Remarkably, according to Tarnas, underground hydrogen available as an energy source, grows in extremely cold climate scenarios. Because a thicker layer of ice above the zone of habitability is the lid which does not allow the hydrogen to escape from popularnosti.
“People have the notion that cold climate of early Mars is bad for life, but as we have seen, in colder climates more of the chemical energy for life underground,” says Tarnas. “We think that it can change people’s attitudes to climate and past life on Earth.”
Implications of the study
Tarnas and mustard say that these findings will help in understanding where to send the next spacecraft, which will search for signs of life on Mars.
“One of the most interesting options research is the search for blocks of megabreccia — rock pieces that were torn from the ground in the process of a meteorite impact,” says Tarnas. “Many of them came from the depth of the habitable zone, and now are often intact on the surface.”
Mustard, who was deeply involved in the process of selecting the landing site of the Mars 2020 Rover, says that such blocks of breccia are present in at least two places that were considered at NASA: Northeast Syrtis Major and Midway.
“The mission of the 2020 Rover will be to search for signs of life,” says mustard. “The area where you can have the remains underground in the habitable zone — which was probably the largest inhabited area on the planet — seem like a good place to search”.
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