'Thigh Bone' on Mars Is Just Another Rock, NASA Says

A rock spotted by NASA's Curiosity rover on Mars may look like a femur bone, but is actually just a weathered Martian rock formation.
A rock spotted by NASA's Curiosity rover on Mars may look like a femur bone, but is actually just a weathered Martian rock formation. (Image credit: NASA/JPL-Caltech/MSSS)

A photo from NASA's Curiosity rover on Mars set the Internet abuzz this week with claims that the robot had found a "thigh bone" on the Red Planet. But not so fast. That so-called bone? Just a weathered Martian rock, NASA says.

The erroneous bone claim first appeared on a UFO blog and was quickly picked up by media outlets. So much so, that NASA released Curiosity's "thigh bone" Mars rock photo with a science explanation on Thursday (Aug. 21).

In the photo description, NASA officials wrote that while "this Mars rock may look like a femur thigh bone," it is not the fossilized remains of a mysterious Martian. "Mission science team members think its shape is likely sculpted by erosion, either wind or water."

The Curiosity rover has found evidence that Mars was once a habitable place in the ancient past, but there is no evidence that creatures large enough to leave a bone behind ever existed on the planet.

"If life ever existed on Mars, scientists expect that it would be small simple life forms called microbes," NASA officials wrote 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."

There is a long tradition of seeing shapes in Mars rocks that don't reflect reality. The phenomenon in which the human brain perceives faces, animals or other shapes that aren't really there is known as pareidolia.

Since the "Face on Mars," photos from Mars orbiters and rovers have captured shapes resembling a lizard, a rat and even a jelly donut — all of them just illusions or strange rock formations on the Red Planet.

NASA's 1-ton Curiosity rover has been exploring Mars since its arrival in August 2012.

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Tariq Malik
Editor-in-Chief

Tariq is the Editor-in-Chief of Space.com and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became Space.com's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining Space.com, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at Space.com and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.