Washington, December 3
If life ever existed on ancient Mars, it would have lived up to several miles below the surface of the Red Planet, likely as a result of the melting of thick ice sheets under the ground fed by geothermal heat, according to a study.
The research, published in the journal Science Advances, examined several Mars datasets to see if heating via geothermal or underground heat would have been possible 4.1 billion to 3.7 billion years ago or in the Noachian era.
They showed that the conditions necessary for subsurface melting would be ubiquitous on ancient Mars.
Even if Mars had a warm and wet climate 4 billion years ago, with the loss of the magnetic field, atmospheric thinning, and the subsequent drop in global temperatures over time, liquid water may have been stable only at great depths, found the researchers. Therefore, if life ever originated on Mars, it may have followed liquid water to ever greater depths, they said.
“At such depths, life could have been sustained by hydrothermal (heating) activity and rock water reactions. So the subsurface may represent the longest-lived habitable environment on Mars,” said lead author Lujendra Ojha, an assistant professor at Rutgers University. -New Brunswick in the USA.
The study may help solve what is known as the faint young Sun paradox – a lingering key question in Mars science.
“Even if greenhouse gases such as carbon dioxide and water vapor in computer simulations are pumped into the early atmosphere of Mars, climate models still struggle to support a sustained warm and wet Mars,” said Ojha.
“I and my co-authors propose that the faint young solar paradox could be reconciled, at least in part, if Mars had high geothermal heat in its past,” he said.
The researchers noted that our sun is a huge nuclear fusion reactor that generates energy by fusing hydrogen into helium. Over time, they explained, the sun has gradually brightened and warmed the surface of planets in our solar system.
According to the researchers, the sun was much fainter about 4 billion years ago, so the climate of early Mars should have been freezing.
However, the surface of Mars has many geological indicators, such as ancient river beds, and chemical indicators, such as water-related minerals. These suggest that the Red Planet had abundant liquid water in the Noachian era, the researchers said. This apparent contradiction between the geologic record and climate models is the faint young solar paradox, they said.
On rocky planets such as Mars, Earth, Venus and Mercury, heat-producing elements such as uranium, thorium and potassium generate heat through radioactive decay. In such a scenario, liquid water could be generated by melting at the bottom of thick ice sheets, even if the sun was weaker than it is now.
On Earth, for example, geothermal energy forms subglacial lakes in areas of the West Antarctic Ice Sheet, Greenland and the Canadian Arctic.
The researchers noted that it is likely that similar melting could explain the presence of liquid water on cold, icy Mars 4 billion years ago. PTI