It seems too round to be true the Curiosity rover has found a ball-shaped object among the craggy rocks in its picture. This image was taken on Sol 746 of the rovers mission on Mars, which so far has extended over two Earth years.

No, its not the leftover of a Martian baseball game and nor is it aliens. In fact, according toDiscovery News(who is quoting NASA) its a kind of rock that shows evidence of water in the ancient past.

Ian ONeill writes:

According to MSL scientists based at NASAs Jet Propulsion Laboratory (JPL) in Pasadena, Calif., the ball isnt as big as it looks its approximately one centimeter wide. Their explanation is that it is most likely something known as a concretion. Other examples of concretions have been found on the Martian surface before take, for example, the tiny haematite concretions, or blueberries, observed by Mars rover Opportunity in 2004 and they were created during sedimentary rock formation when Mars was abundant in liquid water many millions of years ago.

Curiosity isnow at the base of Mount Sharp (Aeolis Mons) its main science goal and scientists are hoping to find more signs of habitable environments as the rover slowly prepares for the climb up the slope. Mission managers will need to be careful as therover has battered wheelsfrom rougher terrain than expected.

The rover already has found other evidence of water in its landing site of Gale Crater, such as thisancient lakebed that could have supported life.

Elizabeth Howellis the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter@howellspaceor contact her ather website. FollowElizabeth Howell on Google+.

Originally posted on Universe Today.

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Mysterious 'ball' on Mars: Where did it come from?