Phys.org’s Leah Burrows examines the question of how early Mars, at a time in the solar system’s history when it should have been cold, was warm enough for liquid water.
Researchers from the Harvard John A. Paulson School of Engineering and Applied Science (SEAS) suggest that early Mars may have been warmed intermittently by a powerful greenhouse effect. In a paper published in Geophysical Research Letters, researchers found that interactions between methane, carbon dioxide and hydrogen in the early Martian atmosphere may have created warm periods when the planet could support liquid water on the surface.
“Early Mars is unique in the sense that it’s the one planetary environment, outside Earth, where we can say with confidence that there were at least episodic periods where life could have flourished,” said Robin Wordsworth, assistant professor of environmental science and engineering at SEAS, and first author of the paper. “If we understand how early Mars operated, it could tell us something about the potential for finding life on other planets outside the solar system.”
Four billion years ago, the Sun was about 30 percent fainter than today and significantly less solar radiation—a.k.a. heat—reached the Martian surface. The scant radiation that did reach the planet was trapped by the atmosphere, resulting in warm, wet periods. For decades, researchers have struggled to model exactly how the planet was insulated.
The obvious culprit is CO2. Carbon dioxide makes up 95 percent of today’s Martian atmosphere and is the most well-known and abundant greenhouse gas on Earth.
But CO2 alone does not account for Mars’ early temperatures.
“You can do climate calculations where you add CO2 and build up to hundreds of times the present day atmospheric pressure on Mars and you still never get to temperatures that are even close to the melting point,” said Wordsworth.