The 'thigh bone' that was found on Mars is not what it appears to be. NASA says that the photo of what appears to be Martian fossils is just weathered rock.

NASA's Curiosity rover captured a photo on Mars that went viral after appearing on a UFO blog. The image shows fragments on Mars' dirt surface, one particular elongated rock resembling a leg bone.

The media picked up news of the potential evidence and concluded that there is life on other plants, which led to NASA to officially provide an explanation.

"No bones about it! Seen by Mars rover Curiosity using its MastCam, this Mars rock may look like a femur thigh bone," NASA writes. "Mission science team members think its shape is likely sculpted by erosion, either wind or water."

NASA's photo description is a disappointment to fans of extraterrestrials, but this is not the first time people thought there was proof of life on Mars. Astronomers in the 1800s reported seeing canals from telescope views. Shadow and light in a photo that was taken on the Red Planet made it look like there was a "Face on Mars" in 1976.

The Curiosity rover found concrete evidence that Mars was once habitable; however, no creatures were big enough to leave any fossilized remains.

"If life ever existed on Mars, scientist expect that it would be small simple life forms called microbes," NASA officials writes in the photo description. "Mars likely never had enough oxygen in its atmosphere and elsewhere to support more complex organisms. Thus, large fossils are not likely."

All photos captured by Curiosity are available for free online.

In February, a rock suddenly appeared in previously empty ground close to the rover Opportunity. Many believe that alien life moved the rock. NASA says that Opportunity's wheels had kicked up the rock as it traveled.

A strange light could be seen in an image Curiosity shot back in April. The lights in the photo appear to be coming from an artificial source. This was linked to lighting effects from the sun beaming off of rocks.

There has not been confirmed extraterrestrials on Mars yet, but for science fiction fans, other life forms can still be lurking in the unknown.  

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