SCIENTISTS HAVE ALREADY known that there was water on Mars – but now they’ve found evidence of an entire ocean.

New results from a European Space Agency (ESA) radar have given the strongest evidence yet that there was once an ocean on the red planet.

The ESA’s MARSIS radar on board the Mars Express, which has been investigating the planet since 2005, detected sediments reminiscent of an ocean floor within the boundaries of previously identified ancient shorelines on Mars.

“We interpret these as sedimentary deposits, maybe ice-rich,” said Jérémie Mouginot, one of the researchers who have analysed more than two years of data from the radar. “It’s a strong new indication that there was once an ocean here”.

The ocean is believed to have existed three or four billion years ago, but may have existed for less than a million years. Mouginot estimates that the water could have either frozen in place and been preserved underground or else turned into vapour and gradually lifted into the atmosphere.

However it’s unlikely that there would have been evidence of life. “I don’t think it could have stayed as an ocean long enough for life to form,” said Mouginot.

However, the research provides some of the strongest evidence yet that there were once large bodies of liquid water on Mars, said Olivier Witasse, ESA’s Mars Express Project Scientist. It also raises questions, he added, saying:

This adds new pieces of information to the puzzle but the question remains: where did all the water go?