New findings are offering prospect of water on Mars, an issue that has been puzzling scientists for long time now.

Traces of water on Mars are under a thin varnish of iron oxide, or rust, similar to conditions found on desert rocks in California's Mojave Desert, NASA said in a statement on Friday.

According to NASA scientists, many more outcrops of carbonates that form mainly in large water bodies have been spotted on Mars surface. These patches are more in number than originally expected.

It's possible that an important clue, the presence of carbonates, has largely escaped the notice of investigators trying to learn if liquid water once pooled on the Red Planet, Janice Bishop, a planetary scientist at NASA's Ames Research Center at the SETI Institute at Moffett Field, California, said.

The new findings that appeared in the Friday July 1, online edition of the International Journal of Astrobiology, were similar to observations provided by NASA's Mars Reconnaissance Orbiter (MRO) spacecraft, which revealed “the strongest carbonate signature ever found” on an ancient region of Mars called Nili Fossae.

Another spacecraft for Mars mission called Spirit identified a small carbonate outcrop at a crater called Gusev in 2010, scientists said.

More recently, NASA's newest and most capable rover, the Mars Science Laboratory Curiosity, which is schedule to launch in November, will study whether Mars had environmental conditions favorable for supporting microbial life.

NASA’s findings in the past have also heightened speculations about the potential for microbial life on Mars. In 2006, Mars Global Surveyor spacecraft, which began orbiting Mars in 1997, provided images of two gullies on Mars that suggest water carried sediment through them.

In 2008, laboratory tests aboard NASA's Phoenix Mars Lander identified water in a soil sample.

As scientists continue to launch various Mars missions to know if life existed on the Red Planet, here are a few pictures from NASA’s past Mars expeditions suggesting evidence of water on the Martian surface:

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A handout picture taken by Mars Express, January 15 from a height of 273 km shows a channel (Reull Vallis) once formed by flowing water east of the Hellas basin on Mars January 23, 2004. REUTERS/NASA

 

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An image shown by NASA officials March 2, 2004, shows a detail of the planet Mars that they claim shows evidence that parts of the planet were once covered in water, at a NASA press conference in Washington. NASA officials have concluded that the part of Mars that NASA's Opportunity Rover is exploring was soaking wet in the past. REUTERS/NASA

 

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This image, taken by the microscopic imager on the Mars Exploration Rover Opportunity, shows a geological region of the rock outcrop at Meridiani Planum, Mars dubbed El Capitan. El Capitan, which is pocked with indentations about a centimetre (0.4 inch) long, has the distinctive texture familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. Parts of Mars were once drenched with so much water that life could easily have existed there, NASA said on March 2, 2004. REUTERS/NASA

 

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An undated photo released by NASA February 15, 2007 shows the surface of Mars displaying the effects of ancient underground fluids. New images of a craggy, fissure-filled canyon on Mars provide evidence of long-term underground water flows that may have provided a suitable environment for microbial life, scientists said. REUTERS/NASA

 

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An artist's conception shows what NASA's Mars Reconnaissance Orbiter has revealed, vast Martian glaciers of water ice under protective blankets of rocky debris at much lower latitudes than any ice previously identified on the Red Planet. Scientists analyzed data from the spacecraft's ground-penetrating radar and report in the November 21, 2008 issue of the journal Science that buried glaciers extend for dozens of miles from edges of mountains or cliffs. REUTERS/NASA

 

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Gully channels in a crater in the southern highlands of Mars, taken by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter, are shown in this image released by NASA September 20, 2007. The gullies emanating from the rocky cliffs near the crater's rim (upper L) show meandering and braided patterns typical of water-carved channels. REUTERS/NASA

 

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A new gully deposit in a crater in the Centauri Montes Region. NASA PHOTO

 

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A small crater on the rim of a large crater as shown in image captured by Mars Global Surveyor spacecraft in 2006. NASA PHOTO

 

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A pair of gully channels that emerged, as shown in image captured by Mars Global Surveyor spacecraft in 2006. NASA PHOTO