A study published in Science Advances reveals that Mars' underground may have been habitable billions of years ago, despite the planet's surface being a dry, frigid wasteland. Researchers suggest that ancient geothermal heat could have melted the bases of thick ice sheets, generating large amounts of potentially life-supporting groundwater.
The study addresses the decades-old mystery of the faint young sun paradox, which questions how Mars could have supported a warm and wet environment 4 billion years ago, given the sun's reduced energy output at the time. Climate models struggle to support a long-term warm and wet Mars, even with increased greenhouse gases.
The researchers propose that high geothermal heat in Mars' past could have reconciled the paradox. They modeled the thickness and behavior of ancient ice sheets in the Martian southern highlands, using data from NASA's Mars Odyssey orbiter. The results suggest that heat flowing from the Martian mantle and crust could have melted the bottom layers of thick ice sheets, creating potentially habitable environments underground.
The study's findings imply that life could have thrived in these underground environments, sustained by hydrothermal activity and rock-water reactions. The subsurface may represent the longest-lived habitable environment on Mars, with pockets of groundwater potentially persisting to the present day.
The research has significant implications for understanding life's emergence on Earth and the potential habitability of exoplanets. Radiogenic heat may have played a crucial role in making our planet habitable, and similar processes could apply to other worlds.
While the study provides a partial solution to the faint young sun paradox, the heat flow numbers are uncertain and require further investigation. The researchers emphasize the need for actual measurements of Martian subsurface heat flow to confirm their findings.
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