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Ancient Mars was only intermittently hot and humid, a new study suggests.
Although the Martian surface is dry today, it is clear that liquid water flowed into it billions of years ago. The planet is marked by river channels and ancient lakes lurk on the floor of several craters – including Gale and Jezero, which are currently being explored by Curiosity and Perseverance Rovers, respectively.
But this remains unclear, and a subject of considerable scientific debate, what ancient Mars really looked like. Was the planet hot and humid long ago, or has it almost always been freezing cold, with only sporadic gentle expanses allowing transient water flows?
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A new study reinforces the latter point of view, suggesting that it took dramatic events to warm the cold heart of Mars, and that such ancient deviations never lasted long.
“Mars was intermittently warmed when its atmospheric composition was altered by the input of gases derived from volcanism and meteorite impactors,” said co-author Joel Hurowitz, a geoscientist at Stony Brook University in New York City, in a press release.
These heat waves “allowed water to flow over the surface, forming rivers and lakes and the rocks and minerals we associate with water on. MarchHurowitz said.
The new study, led by Robin Wordsworth of Harvard University, presents a new climate model of ancient Mars. The model takes into account various factors, including the effects of volcanic eruptions, which released greenhouse gases into Martian air, and the leakage of hydrogen from the atmosphere into space.
This hydrogen escapes, driven by solar wind, increased dramatically after Mars lost its global protective magnetic field. About 3.7 billion years ago, the once thick Martian atmosphere was barely 1% as dense as that of today’s Earth, and the era of rivers and lakes on the surface of the Red Planet was drawing near. its end.
The new study, which was published online today (March 8) in the journal Geoscience of nature, helps to flesh out this era and the hosting potential of the Red Planet. For example, this suggests that “wet” March was still very cold, with average annual surface temperatures below minus 28 degrees Fahrenheit (minus 33 degrees Celsius).
“The dynamic history of Martian environments proposed here suggests opportunities for the emergence of life during hot and humid intervals when reducing conditions would have favored prebiotic chemistry, but also challenges for the persistence of surface life in the face. at frequent extensions and, over time, intervals of predominantly cold and dry oxidizing environments, ”Wordsworth and colleagues wrote in the new study.
“Reducing conditions” refer to an atmosphere in which oxidation – the removal of electrons from atoms and molecules – is prevented or minimized. In contrast, oxidation is prevalent in “oxidizing environments”.
Oxygen is a biosignature – a possible sign of life to look for in the atmospheres of extraterrestrial planets. Interestingly, the new model predicts that Mars had an oxygen-rich atmosphere for long periods “in the middle of its history without requiring the presence of life, indicating that the detection of O2 alone may be a” false positive “for life under certain circumstances, “the researchers wrote in the new study.
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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