Oh yes. Like Bone On Mars!
The above photo, taken by the Martian rover Curiosity, appears to contain a thigh bone.
An interview with a man claiming to be a former Lockheed Martin scientist surfaced after the man's death. In it are details about Area 51 and interactions with aliens, including photos like the one above. The interview,incredibly, claims that aliens currently work for the US government.
Snopes.com has declared the video a hoax, pointing out that the alien figure shown looks an awful lot like a toy on sale at Walmart.
A UFO blog picked out what looks a little bit like a sideways sideways art on a rock from a photo captured by the Curiosity rover. The blog suggested that it looks an awful lot like some inscriptions on columns from ancient Egypt.
Want to send conspiracy theorists into orbit? Send an unmanned space plane into orbit for two years and keep its mission classified. Theories about what the X-37B did was looking for aliens, commandeering abandoned alien bases on other planets or flying around communicating with extraterrestrials.
Malaysia Airlines conspiracy theorists claimed that radar readings showed a UFO interfered with the missing airliner flight, while others suggested it might have been swallowed by a black hole
When Philae "landed" on a comet, an anonymous "ESA whistle-blower" sent around an email claiming the comet was actually anything but and that the Rosetta mission was all about making contact with extraterrestrials, perhaps by a rendezvous at this secret spacecraft/base posing as a big rock