Gravel On Mars

NASA's Curiosity rover has come upon an ancient riverbed on Mars.  Large, rounded stones firmly placed in a conglomerate is strong evidence that water not only once existed on the surface, but that at some point water flowed swiftly enough, strongly enough, and long enough to smooth and round the stones.  Scientists calculate the water in the river was once about three feet deep.

The discovery of what is essentially gravel is simply the latest in a solid line of evidence supporting the thesis that Mars was once a warmer, wetter place than it is today.  That, in turn, increases the possibility that life arose on Mars, and may still exist there.