Mercury probe spies odd formation

0 Comments | USA TODAY, January, 2008 | by Elizabeth Weise

Thirty-three years after NASA got the first clear pictures of the surface of the planet Mercury, the Messenger spacecraft has transmitted surprising information and images of a mysterious formation that no one can yet explain.

From 125 miles up, Messenger sent home pictures of an enormous formation that NASA scientists have dubbed "The Spider." It's a 26- mile-wide crater with more than 50 steep-sided, flat-bottomed valleys radiating out from it.

What created it and the relationship between the crater and the troughs is unknown. Did the crater come first and the troughs afterward? Is it the result of volcanic activity or the movement of dust? Scientists have not been able to even hazard a guess.

"It's not entirely clear what created them," says...