"The US Spirit rover on Mars has seen a UFO streak across the Red Planet sky." Man, you just know that is the most-fun lead the science editor at the BBC online has ever written in his entire life.

Apparently, Spirit snapped this picture recently; it's particularly rare given that the rover mostly has it camera focused downwards, and almost never points it at the sky. But what, precisely, is in the picture? As the BBC notes:

Astronomers say it could be the first meteor seen from the surface of another world, or a redundant orbiting spacecraft sent to Mars 30 years ago.

"We may never know, but we are still looking for clues," said Dr Mark Lemmon, from Texas A&M University.

Of course, the really fun thing is that the BBC isn't actually stretching the truth by calling it a UFO -- since "UFO" is just something you saw in the sky that hasn't been identified.

(Thanks to Plastic for this one!)