By working out how much water has been lost to space, researchers claim that they now know that the Red Planet was covered in more water than the Earth is now. An ocean, which was over a mile deep in some places, covered half of the northern hemisphere of Mars around 4.3 billion years ago, writes Andrew Griffin for The Independent.

Mars Was Habitable For Longer Than Thought

Losing water into space

“Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,” said lead study author Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “With this work, we can better understand the history of water on Mars.”

Our belief that Mars has always been an inhospitable planet should be changed by this latest study. As a young planet, it appears that Mars was much more welcoming than it is now.

Up until around 10 years ago scientists believed that water on Mars was only present sporadically, and only covered small areas of the planet. This latest data reveals that far more water was lost from Mars than previously expected.

Mars habitable for longer than thought

“With Mars losing that much water, the planet was very likely wet for a longer period of time than was previously thought, suggesting it might have been habitable for longer,” said Michael Mumma, a senior scientist at Goddard.

The researchers used observations made by the Very Large Telescope at the European Southern Observatory to estimate the amount of water lost from Mars. In this way scientists were able to find out how much water is on Mars, and compare it with the amount of water found in a 4.5 billion-year-old meteorite from Mars.

They were also able to work out how the amount of water on Mars changed over years and seasons. NASA’s Mars Exploration Program aims to find out more about the climate and environment of the Red Planet, and the European Space Agency is also planning to send a rover to the planet in the next few years.