Curiosity Suggests Water on Mars: NASA’s Previous Expeditions to Mars [SLIDESHOW]

Recently taken photographs of the surface of Mars, by NASA's Curiosity rover, which has been exploring the red planet for two months now, seem to offer evidence water once flowed on the planet's surface.

NASA confirmed Rover captured photographs of rock and ancient streambed gravel and the scientists said the size and shape of the stones suggested they could have only been created and carried by flowing water. There is prior evidence to the presence of water on Mars but each piece of speculation points towards a different phenomenon. The scientists claimed this evidence is the first of its kind.

In 2006, the Mars Global Surveyor spacecraft, which began orbiting Mars in 1997, provided images of two gullies on Mars that suggested water carried sediment through them. In yet another expedition in 2008, laboratory tests aboard NASA's Phoenix Mars Lander identified water in a soil sample. More recently, in July last year, scientists claimed to have found traces of water under a thin varnish of iron oxide, or rust, similar to conditions found on desert rocks in California's Mojave Desert.

And in early August 2011, NASA scientists claimed the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter found flowing salt water, which appears only in spring and summer, on a slope inside Mars' Newton crater. Through the discovery they concluded that salt deposits or such brines were abundant over much of Mars in the past and may form still today in limited times and places.

Start the slideshow to know about more such major past Mars missions suggesting evidence of water on the Martian surface