Heavy bouts of rain may have frequently punctuated Mars' early climate, as evidenced by the complex network of valleys slithering their way through the Martian ground.
New findings by a team of researchers show that the deep channels on the surface of the Red Planet may have been carved into place by rainfall nearly 4 billion years ago.
The research draws upon earlier studies done on similar geographic structures on Earth that show the terrestrial channels were caused by huge streams of rainwater.
Channel Networks On Mars
Scientists have long known that Mars harbors an intricate web of deep valleys, some going as wide as 12 miles and plunging almost as deep as 3,000 feet. These valleys branch out from each other, much like the tributaries of a great river splitting off from the main channel.
The discovery led experts to assume that Mars must have had enough water to sculpt the valleys into the Martian soil. However, where the water that created these channels came from has remained a mystery.
Some theories point to a large body of water, such as a lake, that must have been there once while others believe it could be water emerging from the ground. Yet other scientists think it could be from the melting ice on Martian highlands caused by heat coming from the volcanoes.
A team of researchers from ETH Zurich and the University of Chicago says heavy rain that fell in huge spells 3.6 to 3.8 billion years ago created the channel networks.
Rainfall On Mars
In a new study published on the open-access website Science Advances, the researchers used similar structures on Earth as a model for examining the network of branching valleys on Mars.
By looking at two datasets collected by other researchers investigating the Martian valleys, the researchers were able to conclude that the dryness of a region provides a lot of clues as to what created the channels The angle at which the tributaries split off from each other was also significant.
In places with a harsh dry climate, such as the deserts of Arizona, the researchers found that the networks of valleys were caused by rainwater sculpting waterways into the ground. The branches in these channels are marked by a low angle.
On the other hand, valley networks caused by water seeping from the ground, such as those in Florida, have wider angles between their branches.
The channel networks on Mars resemble the narrow-angled valleys on Earth, which means they must have been made by rainwater creating paths in the ground for it to flow through.
The findings led the scientists to conclude that there must have been a significant amount of rain that fell on Martian soil in the planet's early days. They also assume that Mars may have had an atmosphere far denser than it is today.
"Recent research shows that there must have been much more water on Mars than previously assumed," says physicist Hansjörg Seybold, lead author of the study.
As heavy rainfall pummeled the surface of the planet, the increasing amounts of rainwater cut deeper into the ground to reach the channels' current depths.
Mars Must Have An Active Water Cycle
The study also presupposes that Mars must have had a very active water cycle. One theory is that one-third of the entire area of Mars was covered by a large body of water.
Heat being spewed by active volcanoes located near the theoretical Martian ocean caused large amounts of water to turn into a vapor that later fell to the ground as rain.
Of course, this also raises the question: Where has all that water gone?
"It's likely that most of it evaporated into space," says Seybold. "But it could still be found in the vicinity of Mars."