Floods may have been far more important on ancient Mars than we thought. The Red Planet is criss-crossed by valley networks that once held flowing rivers聽and the deepest of them seem to have formed quickly from cataclysmic flooding.
Up until about 3.5 billion years ago, many of the craters that pock the Martian surface were full of water. at the University of Texas at Austin and his colleagues mapped out how often those lakes overflowed, creating ravines as they did so.
Generally, we assume that riverbeds are mostly carved out by slow erosion, but some large floods on Earth have been seen to create canyons quickly and violently. 鈥淚nstead of forming a river valley over tens of thousands or hundreds of thousands of years, you might be forming them catastrophically over weeks or months, really rapid timescales for geology,鈥� says Goudge.
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The researchers found that Martian ravines that formed rapidly from the overflow of lakes were rare 鈥� they only represented about 3 per cent of the total combined length of all the valleys in the areas they examined. But with an average depth of 170 metres, those ravines were more than twice as deep as the other valleys on average, meaning they were responsible for a huge amount of erosion.
鈥淚f you look at the landscape and map these valleys out, they look pretty sparse, but when you look at the volumes, what you see is that these catastrophic outlet canyons actually represent about one-quarter of the total valley erosion,鈥� says Goudge.
That means these valleys were probably far more important to the landscape on ancient Mars than we realised, redirecting the flows of the other rivers as water poured into the new canyons.
鈥淥ur understanding of how much water was available at the surface and for how long really feeds into our understanding of how Mars might have been able to sustain life or evolve life,鈥� says Goudge. This work is a step towards reconstructing the history of water 鈥� and therefore habitability 鈥� on Mars.
Nature
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