A Rutgers-led study has concluded that the subsurface of Mars would have been the most habitable region on the planet for simple life forms, likely due to geothermal heat melting the bottom of thick ice sheets, according to an article from Rutgers Today.
Available evidence for the former presence of liquid water on Mars suggests that the planet was once warm and wet, therefore capable of supporting life, according to an article from NASA. This idea has led to debate, since climate models suggest early Mars should have been extremely cold, according to the study.
The sun has brightened, and in turn, warmed the surfaces of planets over time, but it was much fainter approximately 4 billion years ago, according to Rutgers Today. That Mars had liquid water regardless marks a seeming contradiction that is called the faint young sun paradox.
“Even if greenhouse gases like carbon dioxide and water vapor are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to support a long-term warm and wet Mars,” said lead author Lujendra Ojha, an assistant professor in the Department of Earth and Planetary Sciences, according to the article. “I and my co-authors propose that the faint young sun paradox may be reconciled, at least partly, if Mars had high geothermal heat in its past.”
The researchers analyzed Mars datasets to determine whether subsurface melting via geothermal heat would have been feasible, according to the article. They demonstrated that the required conditions were readily fulfilled.
The drop in Mars’ temperatures over time combined with other planetary changes may have made it so liquid water lay primarily in the subsurface, according to the study. If life existed on Mars, it likely would have gone to increasingly lower depths along with the water.
“At such depths, life could have been sustained by hydrothermal (heating) activity and rock-water reactions,” Ojha said. “So, the subsurface may represent the longest-lived habitable environment on Mars.”