sciencehabit writes: The Curiosity rover has entered a martian terrain offering clear signs of ancient water and tantalizing hints of a scientific bonanza. In a press teleconference, NASA rover team members reported the discovery of mineral-filled veins and small mineral spheres that require that water once saturated the muddy floor of Gale crater. But geologists are particularly enticed by the sedimentary rock that Curiosity has roved across on its way from its landing site. As it descended deeper into the exposed strata and farther back in geologic time, it first encountered pebbles and cobbles laid down in deep torrents of water, then sandy sediments deposited by less turbulent currents, and finally fine, silty sediments. The silty sediments speak of a far quieter time in Gale, perhaps when a placid lake filled the crater. Lake sediments are the ideal place to look for organic matter lingering from ancient martian life, which is what Curiosity will do when it begins rock drilling in a few weeks.