Well, the UFOlogists won't like it, but UCLA scienstists have come up with an explanation for the giant white arrow observed on the surface of Titan, Saturn's largest moon - and it's not an 'X marks the spot' from aliens.
A mission to sail the seas of Titan is one of three projects shortlisted by NASA for its next Discovery mission.
Liquid methane has been raining down on Titan, say NASA scientists, who have observed the equatorial weather on Saturn's largest moon for the first time.
Scientists have created organic macromolecules by zapping a Titan-like atmosphere with UV rays. The discovery supports the idea that the moon of Saturn could support life.