The National Aeronautics and Space Administration says there was once more water on the planet Mars than in the Arctic Ocean on Earth.
In a new study in the journal Science, space agency researchers say they compared the ratio of two different types of water found in the Martian atmosphere with the ratio of those waters trapped in a Martian meteorite dating back 4.5 billion years.
They say more than 4 billion years ago, Mars was covered with water 137 meters deep and that nearly all of it has since evaporated.
The scientists say water may have covered Mars for a greater period than previously thought, meaning there may have been some form of life on Mars longer than what has been believed.
The planet is now largely a desert.