Johannesburg: Researchers suggest that Mars` thin atmosphere might have led to its cold, dry conditions.
The results are important because they shed light on how habitable Mars was billions of years ago, and how long any surface water persisted.
Planetary geologist Edwin Kite of the California Institute of Technology and his team measured craters made on Mars by asteroid collisions to get an idea of its past atmospheric pressure, News24 reported.
Kite`s team took a look at 319 craters in Aeolis Dorsa - a 3.6-billion-year-old region showing evidence of past rivers.
The scientists found that the craters were formed when Mars had an atmospheric pressure of up to 0.9 bar, which is close to the pressure that Earth has.
However, Mars is far more distant from the Sun and at that time the star was less brighter, as a result Mars may have required pressures of at least five bar for its surface to keep above the freezing point of water.
The study has been published in the journal Nature Geoscience.