Another evidence can prove that there was once water on Mars. A team of scientists identified fossilized river channels in the Martian region, Arabia Terra.

Joel Davis from the University College London and a group of international researchers found out that there are over 10,500 miles (17,000) km of ancient fossilized river channels in the said Martian region. Earlier this year, NASA's Mars Curiosity Rover was tasked to investigate the dark streaks on the slopes in Mars to see if it were influenced by flowing water. Today, this new study suggests that river systems may have existed on the planet.

The study also suggests that the Martian climate may be different from what it is today. "We've now found evidence of extensive river systems in the area which supports the idea that Mars was warm and wet, providing a more favorable environment for life than a cold, dry planet," Joel Davis, lead author said in a statement.

Scientists knew the canyon systems and valleys since the early 1970's and say that they resemble the ones found on Earth. These channels suggest the presence of water. But the Arabia Terra region does not exhibit similar properties until Davis and the team analyzed a huge part of the region by examining the data obtained by NASA's Mars Reconnaissance Orbiter.

Their study identified the existence of fossilized riverbeds in inverted channels. The riverbeds are composed of sand and gravel, remnants when the river dried out.

"The networks of inverted channels in Arabia Terra are about 100 feet (30 m) high and up to 0.6-1.2 miles (1-2 km) wide, so we think they are probably the remains of giant rivers that flowed billions of years ago," Joel Davis, lead investigator of the study said in a statement. "We think the rivers were active 3.9-3.7 billion years ago (Noachian period), but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present," Davis added.

Other experts suggest that since the presence of fossilized rivers were identified, the Arabia Terra is now a good candidate to search for signs of past life on Mars.