New research sheds light on subsurface melting of thick ice billions of years ago.
The most habitable region Mars it would be even a few miles below the surface, possibly due to the subsurface melting of thick ice sheets fueled by geothermal heat, concludes the Rutgers study.
Study published in the journal Scientific progress, can help solve the so-called weak young sun paradox – a key question in the science of Mars.
“Even though greenhouse gases such as carbon dioxide and water vapor are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to keep Mars long-term warm and wet,” said lead author Lujendra Ojha, assistant professor at the Department of Earth and Planetary Sciences at the School of Arts and Sciences at Rutgers University – New Brunswick. “My co-authors and I propose that the weak young sun paradox could be reconciled, at least in part, if Mars had a history of high geothermal heat.”
Our Sun is a huge fusion reactor that produces energy by converting hydrogen into helium. Over time, the sun 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 of early Mars should have frozen. However, the surface of Mars has many geological indicators such as ancient river beds and chemical indicators such as water-related minerals that suggest that the red planet had abundant liquid water around 4.1 billion to 3.7 billion years ago (the era Noahs). This apparent contradiction between geological data and climate models is a weak paradox of young sun.
On rocky planets like Mars, Earth, Venus and mercury, heat-generating elements such as uranium, thorium and potassium, generate heat through radioactive decay. In such a scenario, liquid water could be produced by melting at the bottom of thick layers of ice, even if the sun was fainter than it is now. On Earth, for example, geothermal heat creates subglacial lakes in the West Antarctic, Greenland and Canadian Arctic ice sheet areas. It is likely that a similar melting could help explain the presence of liquid water on cold, freezing Mars 4 billion years ago.
Scientists examined various datasets from Mars to see if heating with geothermal heat would be possible in the Noah era. They showed that the conditions needed for a subsurface melting would be ubiquitous on ancient Mars. Even if Mars had a warm and humid climate 4 billion years ago, with the loss of the magnetic field, the decrease in atmospheric and the subsequent decline in global temperatures over time, liquid water could only be stable at great depths. Therefore, life, if it ever originated on Mars, could follow liquid water to ever greater depths.
“At these depths, life could be sustained by hydrothermal activity (heating) and water-rock reactions,” said Ojha. “So the substrate may represent the longest-lived environment on Mars.”
NASAAccording to Ojh, the Mars InSight spacecraft landed in 2018 and could allow scientists to better assess the role of geothermal heat in Mars habitability during the Noah era.
Reference: “Groundwater Production from Geothermal Heating in Early Mars and Implications for Early Martian Habitats” Lujendra Ojha, Jacob Buffo, Suniti Karunatillake, and Matthew Siegler, December 2, 2020, Scientific progress.
DOI: 10.1126 / sciadv.abb1669
Researchers from Dartmouth College, Louisiana State University, and Planetary Science Institute participated in the study.