Martian teardrop carved in crater 18:04 24 August 04 NewScientist.com news service Wind sculpted basaltic sand dunes millions of years ago (Image: ESA/DLR/FU Berlin G. Neukum) Dark, rippling dunes of volcanic ash - similar to Hawaii's black sand beaches - cast a teardrop shape in an ancient Martian crater, reveal the latest images from Mars Express. Wind is likely to have carved the 12-kilometre-long tear shape a million or more years ago when the Martian atmosphere was thicker, says Gerhard Neukum, principal investigator of the High Resolution Stereo Camera on Europe's Mars orbiter. Now, the atmosphere has thinned so much...