... SUN MOON MERCURY VENUS MARS, JUPITER SATURN . ... Mars . ... Mars rover finds Yellowstone-like hot spring deposits . ... Deposits of nearly pure silica discovered by the Mars Exploration Rover Spirit in Gusev Crater formed when volcanic steam or hot water (or maybe both) percolated through the ground. ... That's a record high for silica on Mars." ... The best fit we got was with siliceous sinter," he says, referring to deposits of "opal," a type of amorphous silica laid down by hot springs. ...