Mars is an incredibly inhospitable and arid desert, devoid of any signs of life, past or present. Scientists are, however, certain the Red Planet once resembled Earth, with vast lakes, rivers and seas. Geographical scans of ancient river beds and winding canyons all across Mars are all strong indicators of a liquid past. Today, almost all water on Mars exists in the form of ice and small amounts of water vapour in the planet’s carbon dioxide-rich atmosphere.
A new study, which is yet to be published, has now suggested Mars’ ancient waters were formed during powerful asteroid impacts billions of years ago.
The study, penned by climatologist Martin Turbet at the Sorbonne University in France, is yet to be peer-reviewed but was published on the arXiv online archive, organised by Cornell University, US.
Dr Turbet proposed asteroid impacts four billion years ago generated enough heat, molten rock and steam to kick start a deluge in the atmosphere.
The scientist and his team of researchers used computer modelling for asteroids bigger than 60 miles (100km) across hitting the planet.
The researchers found such impacts would generate extreme conditions of climate change for half-a-year, followed by intense rain lashing the planet.
Dr Turbet told Space.com: “Using sophisticated three-dimensional global climate-model simulations similar to the ones used, for example, to simulate global warming on Earth, we were able to simulate for the first time in three dimensions the climate change induced by the very large impacts that hit Mars about four billion years ago.”
Asteroids bigger than 60 miles (100km) are large enough to explain the large impact craters peppered around Mars.
The biggest crater, the Hellas Impact Crater, measures an incredible 1,400 miles (2,300km) across and is up to five miles (nine kilometres) deep.
The researchers found a “large impact” in an early Martian atmosphere would produce around 8.5ft (2.6m) of rain fallout per one Earth year.
After impact, the immediate surface conditions on Mars would make it impossible for liquid water to exist.
The amount of heat degenerated by the crash would instantly vaporise any liquid water and send it into the atmosphere.
But once this period of heating subsided, the vaporised water would return to the surface en mass in the form of torrential rain.
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After the deluge, Mars would most likely cool off in a relatively quick manner of 1,000 to 100,000 years, causing the water to freeze over.
Then over the course of millions of years, intense radiation from the Sun would vaporise the ice again and release it into the atmosphere.
The study reads: “The origin of the presence of geological and mineralogical evidence that liquid water flowed on the surface of early Mars is now a 50-year-old mystery.
“It has been proposed that bolide impacts could have triggered a long-term climate change, producing precipitation and runoff that may have altered the surface of Mars in a way that could explain, at least part of, this evidence.
“Here we use a hierarchy of numerical models to test that hypothesis and more generally explore the environmental effects of very large bolide impacts on the atmosphere, surface and interior of early Mars.”