According to new research scientists believe Mars' atmosphere used to be much denser than it currently is today. Mars' current atmosphere is extremely thin (1% of Earth's density at sea level)

At the EGU 2013 General Assembly today in Vienna, researchers revealed NASA's Curiosity rover has uncovered compelling evidence that Mars' original atmosphere is currently floating in space, after escaping many years ago.

Curiosity is equipped with the Sample Analysis at Mars (SAM) tool, which allows the rover to analyze a sample of the planet's atmosphere. Last week week's results led to the breakthrough discovery.

"We found arguably the clearest and most robust signature of atmospheric loss on Mars," said SAM co-investigator Sushil Atreya of the University of Michigan.

Because Mars has no global magnetic field to keep atoms and molecules attached to the planet, large amounts of Mars' gas was stripped from the upper atmosphere by solar wind.

"We've been seeing the same kind of behavior in the carbon dioxide isotopes and the water isotopes - they're all telling us the same story; that gases have been escaping from Mars over time, and the argon isotope just really nails it," Atreya added.

The breakthrough forces scientists to reconsider possible life sustainability from a past Mars atmosphere. If Mars possessed a thicker atmosphere, like Earth, it may have been able to sustain bodies of water.

Because Mars' atmosphere is currently so thin, and air pressure so low, any water on the red planet's surface would immediately evaporate.