Scientists have reason to believe there must have been water on the surface of Mars at some point thanks to the imprints of structures on the planet which resemble fluvial steam networks on Earth.
It's thought that these imprints mean there must have once been enough water on the red planet to feed water streams that incised their path into the soil.
But for many years scientists have debated where this water originated from. Was it rainwater that caused streams and rivers to swell? Or did water ice in the soil melt due to volcanic activity, and seep out to form rivers? Whatever the outcome, they each lead to a completely different conclusion about the climatic history of the red planet.
However, a new study published in Science Advances by physicist Hansjörg Seybold, a professor at the Institute for Terrestrial Ecosystems, and planetary specialist Edwin Kite from the University of Chicago, suggests that the branching structure of the former river networks on Mars has striking similarities with terrestrial barren landscapes.
Recent research shows that there must have been much more water on Mars than previously assumed
Using statistics from all mapped river valleys on Mars, the researchers conclude that the contours still visible today must have been created by superficial run-off of water, or rain. What this means is that the influence of groundwater seepage from the soil wasn't a dominant process for shaping these features.
Conditions such as those found in terrestrial arid landscapes today probably prevailed on Mars for only a relatively short period about 3.6 to 3.8 billion years ago. In that period, the atmosphere on Mars may have been much denser than it is today.
"Recent research shows that there must have been much more water on Mars than previously assumed," said Seybold.
One hypothesis suggests that the northern third of Mars was covered by an ocean at that time. The researchers think that water evaporated, condensed around the high volcanoes of the highlands to the south of the ocean and led to heavy precipitation. As a result, rivers formed, which left traces that can still be currently observed on Mars.
Commenting on where the water disappeared to over time, Seybold added: "It's likely that most of it evaporated into space. But it could still be found in the vicinity of Mars […] but this is a question for a future space mission".
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