Huge rivers seem to have been flowing across Mars relatively recently, scientists said.

The flowing water came in rivers much bigger and more powerful than those seen on Earth, they said. And they seem to have stuck around far longer than we had realised.

The raging water courses carved deep channels into the Martian surface at "hundreds of locations", said scientists.

Satellite images and data from Nasa's Curiosity rover indicate that many of the rivers were twice as wide as those on Earth.

They may also have persisted until less than one billion years ago, the evidence suggests.

Signs of ancient rivers on Mars revealed in new images Show all 13 1 /13 Signs of ancient rivers on Mars revealed in new images Signs of ancient rivers on Mars revealed in new images Perspective view of ancient river valley network on Mars These images taken by the European Space Agency’s Mars Express satellite show the marks that an ancient network of rivers have left on the planet’s surface. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Ancient river valley network on Mars The valleys formed as they would on earth, with a strong flow of water carving its way through the landscape. What is less clear is where the water came from. Due to a lack of knowledge about the past climate of Mars, scientists can not tell whether it came from groundwater, precipitation, melting glaciers or something unheard of. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Ancient river valley network on Mars This colour-coded topographic view shows the relative heights of the terrain in and around the network of dried-up valleys on Mars. Lower parts of the surface are shown in blues and purples, while higher altitudes show up in whites, yellows, and reds, as indicated on the scale to the top right. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Ancient river valley network on Mars This image shows the landscape in and around a network of dried-up valleys on Mars. The region outlined by the bold white box indicates the area photographed by the Mars Express. NASA MGS MOLA Science Team/FU Berlin Signs of ancient rivers on Mars revealed in new images Eberswalde crater delta This dried-up ancient river delta once carried liquid water across the surface of Mars. The photographed area is 31 x 7.5km. Released on February 4 2019. ESA/Roscosmos/CaSSIS Signs of ancient rivers on Mars revealed in new images Eberswalde crater delta Eberswalde crater formed more than 3.7 billion years ago. The rim of the crater is only intact in the north-eastern part, the rest has been buried by debris from the nearby, more recently formed Holden crater. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Eberswalde crater delta In the left of the image is the Holden crater, which is 140km across. To the right is the Eberswalde crater, which is 65km across. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Korolev crater A perspective view of the Korolev crater, an 82-kilometre-across crater filled with ice found in the northern lowlands of Mars. Taken by the European Space Agency's Mars Express satellite. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Korolev crater The Korolev crater, an 82-kilometre-across crater filled with ice found in the northern lowlands of Mars. Taken by the European Space Agency's Mars Express satellite. ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Korolev crater DisThis colour-coded topographic view shows the relative heights of the terrain in and around Korolev crater, an ice-filled crater in the northern lowlands of Mars. Lower parts of the surface are shown in blues and purples, while higher-altitude regions show up in whites, browns, and reds, as indicated on the scale to the top right. The crater’s thick deposit of ice can be seen at the centre of the frame. Released December 20 2018 ESA/DLR/FU Berlin Signs of ancient rivers on Mars revealed in new images Water buried under the south pole of Mars ESA’s Mars Express has used radar signals bounced through underground layers of ice to identify a pond of water buried below the surface. ESA/NASA/JPL/ASI/University of Rome Signs of ancient rivers on Mars revealed in new images Water buried under the south pole of Mars The brighttop line represents the icy surface of Mars in this region. The south polar layered deposits – layers of ice and dust – are seen to a depth of about 1.5 km. Below is a base layer that in some areas is brighter than the surface reflections, highlighted in blue, while in other places is rather diffuse. The details of the reflected signals from the base layer yield properties that correspond to liquid water. ESA/NASA/JPL/ASI/University of Rome Signs of ancient rivers on Mars revealed in new images Water buried under the south pole of Mars The 200km square study area is shown in the left image and the right image shows the radar footprints on the surface of Mars. ESA/NASA/JPL/ASI/University of Rome

The findings are a mystery, because scientists had thought the Red Planet was losing its atmosphere and drying out during this time.

Dr Edwin Kite, from the University of Chicago, said: "It's already hard to explain rivers or lakes based on the information we have. This makes a difficult problem even more difficult."

The amount of water gushing through the river channels was estimated at between three and 20 kilograms per square metre per day.

The team studied more than 200 ancient Martian river beds criss-crossing the planet.

The width and steepness of the channels and size of rounded pebbles they contained provided clues about the volume and force of water that once flowed through them.

Oddly, the rivers appeared to have been flowing until the "last geological minute" before the planet became a desert, said the researchers writing in the journal Science Advances.

"You would expect them to wane gradually over time, but that's not what we see," said Dr Kite. "The rivers get shorter - hundreds of kilometres rather than thousands - but discharge is still strong.

"The wettest day of the year is still very wet."

One possibility is that the Martian climate had an "on/off" switch that tripped back and forth between dry and wet cycles, he added.