Red planet Mars ‘once had huge sea’

A single large ocean once covered much of the northern half of Mars, supplied with water from a belt of rain-fed rivers, new research suggests.

Scientists have produced a new map showing that Martian valley networks are more than twice as extensive as had previously been thought, indicating that they were carved by rivers.

They are concentrated in a belt circling the planet's equator and mid-southern latitudes.

Experts believe they mark the paths of rivers that once flowed from the planet's southern highlands into a huge ocean.

The evidence suggests that billions of years ago much of Mars had an “arid continental climate” similar to drier areas of the Earth.

Rain would have fallen regularly, swelling the rivers and topping up the ocean basin. Such a wet period early in the planet's history would have greatly increased the chances of life.