Torrential rainfall on early Mars eroded the network of deep valleys still visible on the surface of the planet today, new research claims

• Experts found river networks on Mars have parallels with waterways on Earth 
• Heavy rainfall over a prolonged period may have run off quickly over the surface 
• This is how river valleys develop in arid regions on Earth, such as in Arizona
• One hypothesis is the northern third of Mars was once covered by an ocean
• Water evaporated, condensed around volcanoes and led to heavy rainfall 

Torrential downpours of rain on the surface of Mars formed a network of deep valleys still visible on its surface today, experts say.

Mars bears the imprint of canyons and ravines – similar to rivers on Earth – that formed billions of years ago and crisscross the surface of the planet.

Exactly how they were created has long been debated, but scientists assume there must once have been enough water to feed streams that cut channels into the soil.  

Now, a new study claims to prove that rainwater must have been behind the erosion of the largely dry Martian surface.

A giant ocean that once covered a third of the surface of Mars may have been responsible for the waters evaporating and condensing in the atmosphere, researchers claim.

Torrential downpours of rain on the surface of Mars formed a network of deep valleys still visible on its surface today. This image shows the central portion of Osuga Valles, which has a total length of 100 miles. In some places, it is 12 miles wide and plunges to a depth of 3,000 ft

Experts from the Swiss Federal Institute of Technology (ETH) in Zurich determined the branching structures of the former river networks on Mars have parallels with waterways that run through arid regions on Earth.

The distribution of the branching angles of the river valleys on Mars are strikingly similar to those in places like Arizona.

Researchers observed the same valley network patterns in a landscape in the US state where astronauts are currently training for future Mars missions. 

Sporadic heavy rainfall on Mars over a prolonged period of time may have run off quickly over the surface, shaping the valley networks.

This is how river valleys develop in arid regions on Earth.

Using statistics from all mapped river valleys on Mars, the team concluded that the contours still visible on Mars today must have been created by similar surface run-off of rainwater.

'Recent research shows that there must have been much more water on Mars than previously assumed,' said physicist Hansjörg Seybold from ETH. 

'It’s likely that most of it evaporated into space. Traces of it might still remain in the vicinity of Mars, but this is a question for a future space mission.' 

Mars' bears the imprint of canyons and ravines, similar to rivers on Earth, that formed billions of years ago and crisscross its surface. The angles of valley branches - here a section of the Warrego Valles region - on Mars are narrow and correspond to those of arid regions on Earth

The angle of a river branch is determined, among other things, by how dry an area is and whether groundwater emerges from the ground. Experts observed the same valley network patterns in Arizona, where astronauts are training for future Mars missions

The branching angles on Mars are comparatively low, so the team ruled out the influence of groundwater seepage on Mars.

River networks that are strongly affected by re-emerging groundwater - as found, for example, in Florida - tend to have wider branching angles between the two tributaries and do not match the narrow angles of streams in arid areas.

Conditions such as those found in arid landscapes on Earth today likely prevailed on Mars for only a relatively short period, between 3.6 and 3.8 billion years ago.

In that period, the atmosphere on Mars may have been much denser than it is today.

One hypothesis suggests the northern third of Mars was covered by an ocean at that time.

Water evaporated, condensed around the volcanoes of the highlands to the south of the ocean and led to heavy rainfall there. 

As a result, rivers formed, which left the traces that can be observed on Mars today. 

The full findings of the study were published in the journal Science Advances.

Exactly how the valleys visible on the surface of Mars (pictured) were created has long been debated, but scientists assume there must once have been enough water to feed streams that cut channels into the soil (stock) 

One hypothesis suggests that the northern third of Mars was covered by an ocean at that time. This image taken by the Mars Pathfinder mission in 1999 shows the surface of the red planet as it appears today (stock)

DO SCIENTISTS BELIEVE WE COULD EVER FIND LIFE ON MARS?

Over the years, scientists have found a number of promising signs that life may have been present on Mars, including evidence of water, chemical reactions, and expansive ice lakes beneath the surface.

Life on Mars is unlikely to have flourished on the surface, given the harsh conditions – including radiation, solar winds, and frigid temperatures.

As a result, many scientists believe organisms evolved to live beneath the surface of the Red Planet.

In November 2016, Dr Christian Schröder, an environmental science and planetary exploration lecturer at Stirling University, said: ‘For life to exist in the areas we investigated, it would need to find pockets far beneath the surface, located away from the dryness and radiation present on the ground.’

This is supported by evidence of water beneath the surface.

Researchers have identified mudstones and sedimentary bands on Mars, which only form when there is water present for thousands of years.

Vast oceans of ice have also been uncovered, lying just below the surface of the planet.

The presence of ice and water beneath the Red Planet greatly increases the chances that there was once at least microscopic life on Mars and that some form of the organism could be living there today.

'Any place on Earth we find liquid water we find life,’ Jim Crocker, vice president of Lockheed Martin's Space Systems said in August 2016.

‘It's very exciting to understand the possibility that life could possibly have started on Mars before it lost its atmosphere, and perhaps even in the deeper surfaces, where water is still liquid because of the heat of the planet, perhaps there's bacterial life.'

Having water just below the surface also means that human colonies could survive and even thrive on the planet and indicates that fuel for manned spaceflight could be manufactured there.

In 2017, Nasa's Curiosity rover also found evidence of boron on the red planet's surface.

This is another key ingredient for life, and scientists say the find is a huge boost in the hunt for life.

Boron was unearthed in the Gale Cater, which is 3.8 billion years old, younger than the likely formation of life on Earth.

That means the conditions from which life could have potentially grown may have existed on ancient Mars, long before organisms began to develop on Earth.

A controversial 2001 study into a 4.5 billion-year-old meteorite, dubbed ALH84001, which was found in Antarctica's Allan Hills ice field in 1984, claimed it had definitive prove of life on Mars.

Meteorite ALH84001 was blasted off the surface of Mars by a comet or asteroid 15 million years ago, and Nasa researchers said it contains proof the Red Planet was once teeming with bugs which lived at the bottom of shallow pools and lakes.

They also suggested there would have been plants or organisms capable of photosynthesis and complex ecosystems on Mars.

However British experts said at the time that the evidence, though exciting, had to be treated with caution and could not be taken as conclusive, since many non-biological chemical processes could also explain what was found.