According to NASA, billions year ago there is liquid water in Martian surface. Today Mars is dry, cool and a dead planet. The Martian atmosphere is very thin today (almost 1% of the Earth atmosphere). Billions year ago Martian atmosphere was not so thin.
NASA’s recent study has found a reason for this. The reason is Solar Wind. Normally the planet with a developed magnetic field can protect its atmosphere from Solar Wind. But Mars’ magnetic field is became off billions years ago, so its atmosphere became heavily exposed by Solar Wind. Mars atmosphere is stripping away by Solar Wind and became very thin now.
Measuring Mars’ Atmospheric Loss
You can find the full program below from NASA. This program is about ‘Measuring Mars’ Atmospheric Loss’ and if the same thing can happen with Earth?