On ancient Mars were suitable conditions for life underground

New research shows that ancient Mars probably had enough of the chemical energy that microbes could thrive underground. "Based on fundamental physical and chemical calculations, we showed that the subsurface layer of ancient Mars probably had enough dissolved hydrogen to power a global subsurface biosphere," says Jesse Tarnas, a graduate student at Brown University and lead author of the study published in Earth and Planetary Science Letters ".

On ancient Mars were suitable conditions for life underground

"The conditions in this potentially habitable zone could be similar to the earth a place where there is an underground life."

Where is life on Mars hiding?

Earth - home to the so-called subsurface lithotrophic microbial systems. In the absence of sunlight, these underground microbes often take their energy, taking the electrons from molecules in the environment. Dissolved molecular hydrogen - a fine electron donor. It nourishes such microbes on Earth.

New research has shown that radiolysis, a process during which radiation destroys the water molecule into its constituent hydrogen and oxygen, could create many ancient Mars hydrogen subsurface. Scientists estimate that the concentration of hydrogen in the cortex 4 billion years ago was to be roughly comparable to the Earth that feeds many bacteria today.

These findings do not mean that life is definitely existed on ancient Mars, but they suggest that if life there is really Martian subsurface would have the necessary components to support its over hundreds of millions of years. The work also has implications for the future exploration of Mars because the area where the ancient subsurface comes out, can be a great place to look for his former life.

go underground

Since then, as it turned out that Mars was once flowing rivers and lakes, the scientists obsessed with the possibility that the Red Planet may once store life. But while evidence of the existence of water in the past are undeniable, it is unclear for what part of the history of Martian water actually flowed. Most climate models of early Mars give temperatures that barely exceed the freezing point, which means wet periods of the planet could be very transient. It's not the best scenario for the maintenance of life on the surface for a long time, and so some scholars believe that beneath the surface of past Martian life might feel better.

"the question arises: what was the nature of the subsurface life, if it existed, and where she took her energy," says Jack Mustard, professor of Earth, the Faculty of Environmental and Planetary Sciences at Brown University, co-author of the study. "We know that radiolysis helps provide energy underground microbes on Earth, so Jesse has decided to continue the story with radiolysis on Mars."

The researchers examined data on gamma-ray spectrometer, which flies on board the Mars Odyssey system. They made a map of the distribution of radioactive elements thorium and potassium in the Martian crust. Based on the map, they were able to find a third radioactive element uranium. Disintegration of these three elements provides a radiation that causes radiolytic decomposition of water. Since these elements decay at a certain rate, the prevalence of the model can be used to calculate the presence of elements of 4 billion years ago. So the team had the idea of ​​radioactive outbreak, which actively pushed radiolysis. The next step was to estimate how much water was available for this radiation. Geological evidence suggests that in the porous rocks of ancient Martian crust was a lot of groundwater, breaks through the pores. The scientists used measurements of the density of the Martian crust to approximately estimate how much has been available for filling with water.

Finally, the team used geothermal and climate models to determine where there might be an ancient life. It was supposed to be so cold that not all of the water is frozen, but not too warm.

By combining these tests, the scientists concluded that Mars probably had a global subsurface potentially habitable zone of several kilometers thick. In this zone, the production of hydrogen in the process of radiolysis generated a more than enough chemical energy to sustain microbial life, if we assume that we know on Earth. And this area was saved hundreds of millions of years.

These findings persisted even when researchers simulate different climate scenarios - some warmer, some colder. Remarkably, according Tarnas number subterranean hydrogen available for energy grows in extremely cold climate scenarios. Because a thicker layer of ice over the habitability area serves as a cover which prevents escape of hydrogen subsurface.

"People have the idea that the cold climate of early Mars bad for life, but as we have seen, in colder climates greater chemical energy for life underground," says Tarnas. "We think that it can change people's attitudes to climate and past life on Earth."

The consequences of the study

Tarnas and Mustard said that these findings will help in the understanding of where to send the next spacecraft that will search for signs of life on Mars.

"One of the most interesting options for the study is to find megabrekchii blocks - pieces of rock that have been taken out of the earth in a meteorite impact," says Tarnas. "Many of them came from the depth of the habitable zone, but now are often untouched on the surface."

Mustard, who was actively involved in the selection process of the rover landing site Mars in 2020, says that this type of breccia units are present in at least two places who viewed NASA: Northeast Syrtis Major and Midway.

"The mission of the rover in 2020 will be to search for signs of life," says Mustard. "Areas where you may be the remains of an underground habitable zone - which was probably the biggest habitable zone on the planet - seem to be a good place to look."

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