New York Throwing fresh light on how much water once existed on the Red Planet, the rover Curiosity has taken pictures of over 120,000 measurements of surface rocks and soil on Mars.

Scientists have found that the weight of the dust they have sampled is two to four percent water.

For the first time, they have also confirmed that the common element fluorine exists on Mars.

“Curiosity has travelled nearly 6.5 km ever since the rover landed on Mars in 2012 and is more than halfway to its destination, Mount Sharp,” said Celia Arnaud, a senior editor at Chemical & Engineering News (C&EN).

The rover is equipped with an instrument called ChemCam (Chemistry & Camera) that not only takes high-resolution images of the barren landscape it passes, but also can figure out what's in the soil and rocks within about 23 feet of its location.

Back on Earth, scientists at NASA's Jet Propulsion Lab aim the ChemCam at targeted rocks and zap them with a laser beam.

The instrument reads the light that bounces back and can tell what atoms and molecules are in the rocks.

In the meantime, its on board equipment is collecting a treasure trove of information about the Red Planet's surface.

With about five km more to go before it reaches Mount Sharp, Curiosity is sure to keep adding new details to the emerging picture of our planetary neighbour, Arnaud noted.