This amount is comparable to the volume of water on Earth
Exploration of the Jezero Crater on Mars confirms that the planet had vast pools of water, leaving traces of rivers, streams and lakes. About three billion years ago, the ocean could cover most of the planet. At that time, Mars was not rusty red — its vast regions were blue.
How much water there was on Mars remains an open question, but new research suggests it is comparable to Earth.
Scientists including Bruce Jakosky, a planetary scientist at the University of Colorado and principal investigator for NASA's MAVEN (Martian Atmosphere and Evolution) mission, have calculated how much water was lost, absorbed into Martian rocks and minerals, frozen in the polar caps, hidden in the ice of the ancient ocean, and also how much could have remained in the crust of Mars.
A significant part of the water loss ended up in space — Mars, thanks in part to solar radiation, gradually lost its insulating atmosphere. As a result, the once dense atmosphere of Mars was significantly reduced and more water evaporated — without the insulating blanket of atmosphere, the planet dried out. Today, Mars is 1,000 times drier than the driest desert on Earth.
The researchers concluded that Mars lost between 380 and 1,970 meters of water, assuming that all of this was evenly distributed on the surface of Mars, forming a giant ocean. Previous studies based on other methods have provided lower estimates of the amount of water. One of the reasons for the large range in the estimate is related, among other things, to how much water may currently be located in the pore spaces of the planet's crust. This can be a huge amount, reaching 1000 meters.
To understand the volumes, you can use the Earth as a reference point. If we take into account all the waters of the Earth and scale them in proportion to the size and mass of Mars, then the thickness of the water layer on it would be about 1400 meters.
Thus, Mars, in all likelihood, contained colossal volumes of water in the past, comparable to those on Earth. However, it is unlikely that all this water was simultaneously present at any point in the planet's history. However, these data, combined with Mars's landscapes of dry canyons and evidence of past rivers and lakes, suggest that early Mars was raged by water. There is no clear evidence yet for the existence of microbial life on Mars, but it is likely that all that water created an environment favorable to the evolution of primitive organisms.
Missions to Mars, such as the Perseverance rover, continue to explore the now deserted planet for traces of past life, such as molecules or cell fragments.