This image shows a digital terrain model of the crater investigated by the University of Arizona's Ali Bramson. Image released August 26, 2015. A giant slab of ice as big as California and Texas combined lurks just beneath the surface of Mars between its equator and north pole, researchers say. This ice may be the result of snowfall tens of millions of years ago on Mars, scientists added. Mars is now dry and cold, but lots of evidence suggests that rivers, lakes and seas once covered the planet. Scientists have discovered life virtually wherever there is liquid water on...