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Mars is arid and inhospitable today, but billions of years ago the red planet had water and a very dynamic global weather system. We know that the planet once hosted oceans of water and river systems. Now, according to a new study, Mars may once have even been subjected to powerful megafloods.
About four billion years ago, an asteroid impact melted ice stored on the Martian surface, triggering a cascade of effects that could have unleashed gigantic megafloods. Although the water has long since disappeared, the signs of the floods are still on Mars in the form of megariples, also known as antidunes.
“We identified megafloods for the first time using detailed sedimentological data observed by the Curiosity rover,” said co-author Alberto G. Fairén, a visiting astrobiologist at Cornell University’s College of Arts and Sciences. “The deposits left by the megafloods had not previously been identified with the orbiting data.”
Just like on Earth, today’s geological features on Mars bear the marks of the passage of water and wind, the touches of which have remained frozen over time.
These include megaripples in the Gale crater – wave-shaped features etched into the sedimentary layer that can reach up to 9 meters (30 feet) in height spaced 135 meters (145 feet) from each other.
According to the Cornell researchers, these ripples are nearly identical to those formed on Earth by the melting of ice about two million years ago.
Four billion years ago, a large impact generated copious amounts of carbon dioxide and methane – both powerful greenhouse gases – that warmed the climate, eventually melting Mars’ ice reserves. The water vapor trapped even more heat in the atmosphere, causing the red planet to experience a brief period of warm, humid conditions.
Clouds of water vapor formed through condensation likely triggered torrential rain on a planetary level. Some of the water fell on the Gale Crater, then combined with the water flowing downhill from Mount Sharp, producing gigantic flash floods.
Previously, scientists had determined that Gale Crater was once the site of persistent lakes and streams in Mars’ ancient past. Along with the present findings, the authors of the new study state that both Gale Crater and Mouth Sharp were able to support microbial life.
“Early Mars was an extremely active planet from a geological point of view,” Fairén said in a news release. “The planet had the necessary conditions to support the presence of liquid water on the surface and on Earth, where there is water, there is life.
“So the first Mars was a habitable planet,” he said. “Was it inhabited? This is a question that the next Perseverance rover … will help answer. “
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