Rutgers University has presented a new study, according to which the most habitable region on Mars is likely to be several kilometers below its surface. The results of the work are published in the journal Science Advances.
The most habitable area on Mars is underwater due to the subsurface melting of thick ice sheets fueled by geothermal heat.
The new study will help resolve the faint young sun paradox, an important part of Mars research.
The sun is a huge nuclear fusion reactor that generates energy by converting hydrogen into helium. Over time, these reactions occurred more and more, and the star gradually brightened and warmed the surface of the surrounding planets. About 4 billion years ago, the Sun was much weaker, so early Mars’ climate must have been too cold for liquid water to appear. However, geological indicators such as ancient river beds and minerals associated with water suggest that Mars was rich in liquid water from about 4.1 to 3.7 billion years ago. This apparent contradiction between the geological record and climate models is the faint young sun paradox.
On rocky planets – Mars, Earth, Venus, and Mercury – uranium, thorium, and potassium release energy (and heat) due to radioactive decay. In this scenario, liquid water can be formed by melting at the bottom of thick ice sheets, even with weak solar activity. On Earth, for example, geothermal heat forms subglacial lakes in West Antarctica, Greenland, and the Canadian Arctic. Such melting will likely explain the presence of liquid water on cold Mars 4 billion years ago.
Scientists wanted to find out if the planet was heated by geothermal heat in the past. The study found that the conditions required for subsurface melting were ubiquitous on ancient Mars. Even if the planet had a warm and humid climate 4 billion years ago, with a loss of magnetic field, thinning of the atmosphere, and a drop in temperature, liquid water could only be stable at great depths. Life, if it ever was on Mars, could “follow” liquid water to depths.
“It is in the depths of Mars that a long-lived habitable environment can survive as a result of hydrothermal activity (heating reaction),” concludes the study’s lead author, Lujendra Oja, assistant professor of Earth and planetary sciences at Rutgers University.