The best region for life on Mars was well below the surface

The region most habitable for life on Mars would have been up to several miles below its surface, possibly due to the underground melting of thick ice caps fed by geothermal heat, a study by Rutgers concludes.

The study, published in the journal Scientific advances, can help solve what’s called the weak young sun paradox – a lingering key question in Mars science.

“Even though greenhouse gases like carbon dioxide and water vapor are pumped into the early Martian atmosphere during computer simulations, climate models still struggle to sustain a hot and humid Mars in the long run. ”Said lead author Lujendra Ojha, assistant professor in the Department. of Earth and Planetary Sciences in the School of Arts and Sciences at Rutgers University-New Brunswick. “My co-authors and I propose that the weak young sun paradox can be reconciled, at least in part, if Mars had high geothermal heat in its past.”

Our sun is a massive nuclear fusion reactor that generates energy by fusing hydrogen into helium. Over time, the sun has gradually brightened and warmed the surface of the planets in our solar system. About 4 billion years ago, the sun was much weaker, so the climate at the start of March should have been freezing. However, the surface of Mars has many geological indicators, such as ancient riverbeds, and chemical indicators, such as water-related minerals, which suggest that the Red Planet had abundant liquid water around. 4.1 billion to 3.7 billion years ago (the Noachian era). This apparent contradiction between geological data and climate models is the weak paradox of the young sun.

On rocky planets like Mars, Earth, Venus, and Mercury, heat-producing elements like uranium, thorium, and potassium generate heat through radioactive decay. In such a scenario, liquid water can be generated by melting at the bottom of thick ice caps, even though the sun was weaker than it is now. On Earth, for example, geothermal heat forms subglacial lakes in the ice cap areas of West Antarctica, Greenland and the Canadian Arctic. It is likely that a similar fusion may help explain the presence of liquid water on cold, frozen Mars 4 billion years ago.

Scientists looked at various datasets from Mars to see if heating via geothermal heat would have been possible during the Noachian era. They showed that the conditions necessary for underground fusion would have been ubiquitous on ancient Mars. Even though Mars had a hot and humid climate 4 billion years ago, with the loss of the magnetic field, the thinning of the atmosphere, and the consequent drop in global temperatures over time, liquid water does not may have been stable only at great depths. Therefore, life, if ever born on Mars, may have followed liquid water to progressively greater depths.

“At such depths, life could have been supported by hydrothermal (heating) activity and rock-water reactions,” Ojha said. “So the basement may represent the oldest habitable environment on Mars.”

NASA’s Mars InSight spacecraft landed in 2018 and could allow scientists to better assess the role of geothermal heat in the habitability of Mars during the Noachian era, according to Ojha.

Scientists from Dartmouth College, Louisiana State University, and the Planetary Science Institute contributed to the study.