A Flip-Flopping Climate Could Explain Mars's Watery Past

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Source:  By Shannon Hall, Earth & Space News (EOS; AGU)

Excerpt: ...A new hypothesis might reconcile two opposing theories that have tried to explain Mars's mysterious history... suggests that lush periods just long enough to form water-created surface features, such as canyons, punctuated much longer, planet-wide frozen spells. ...In the 1970s, images of Mars taken by the Mariner and Viking spacecraft revealed enormous channels and valley networks—both of which are reminiscent of catastrophic floods and river drainage systems on Earth. The fluvial features were the first sign that 3.8 billion years ago, the planet was once a lush oasis, awash with oceans, lakes, and rivers. ...a 40-year-long debate that has divided planetary astronomers into two camps: those that think Mars must have once contained a thicker and warmer atmosphere—which made the Red Planet hospitable to liquid water and potentially the evolution of life—and those that think Mars was mostly cold save for short bursts of warmth. ...In a study accepted for publication in Earth and Planetary Science Letters, Natasha Batalha, a graduate student from Pennsylvania State University in University Park, and her colleagues suggest that Mars flip-flopped between a deep-freeze climate and a habitable one. ...the cycle begins on a world coated with glaciers. Volcanoes spew greenhouse gases into the atmosphere, increasing the temperature until it’s finally warm enough to rain. Downpours then scrub the potent gases from the atmosphere rapidly, shutting down the greenhouse and plunging the planet back into its glaciated state. Whereas on Earth the cycle acts as a built-in temperature control system, keeping our planet habitable on million-year-long timescales, the team’s simulations showed that on Mars it forces the planet to oscillate between a glaciated world and a habitable one. “You get these dramatic climate cycles that give you about 10 million years of warmth in between these 120-million-year frozen states.”

https://eos.org/articles/a-flip-flopping-climate-could-explain-marss-watery-past

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