By Jane E. AllenAssociated PressPASADENA, Calif. _ Mars is looking more Earthlike and less like the moonwith Pathfinder scientists' every new observation, including a football-sizedmartian rock that fits the profile of a kind common on Earth.The first chemical analysis of the martian rock _ nicknamed Barnacle Billby Pathfinder scientists _ shows that at least one rock on the dusty redplanet is rich in silica, the quartz material found in sand.Such a rock _ which could have been brought to the surface by volcanic activityor a meteorite impact _ could only be formed by repeated heating in an activecrust, scientists said Tuesday.``The Earth is a very unusual place, at least we thought that until lastnight,'' said Hap McSween, a meteorite specialist from the University ofTennessee. ``Now it appears Mars, too, has a crust that ... contains quartz.''Examination of a second rock was expected to begin today, with its chemicalsignature taken overnight by the Mars Pathfinder's robot geologist Sojourner.Data from the rover suggest that Barnacle Bill might be a kind of andesite,the second most common type of lava on Earth. It gets its name from theAndes Mountains.The latest evidence hints that water may have existed on Mars more than4 billion years ago, the same era when life began on Earth.It was too early to tell if Barnacle Bill is andesite. But because sometypes of andesite only form in the presence of water, the new results eventuallymay lead to the demonstration that early Mars had water in its interior,said Allan Treiman, a planetary scientist at the Lunar and Planetary Institutein Houston.``It completely changes most people's views of Mars. Mars becomes a placethat had water from the beginning and the water was very active in the planet,''Treiman said in a telephone interview just as scientists were finishinga news conference at NASA's Jet Propulsion Laboratory.Matthew Golombek, the Pathfinder project scientist at JPL, was far morecautious in his assessment. But he was excited just to see that Mars' crustwas a ``much more dynamic'' place than originally perceived, ``more likeEarth than the moon,'' with re-melting of rocks that heated away elementslike iron and left more silica.``What we don't know is whether that's an andesite,'' he said, and not someother rock types, like a mix of granite and basalt, the most common typeof lava on Earth.On Monday, Pathfinder scientists presented evidence of massive floods 1billion to 3 billion years ago on Mars' now bone-dry salmon-colored surface.With other rocks named Yogi, Scooby Doo, Casper and Crab due for similarup-close encounters with Sojourner, scientists' conclusions could strengthenwith numbers.``This site really is a rock festival,'' quipped McSween.