The roving vehicle Sojourner, the first mobile explorer of another planet, began prospecting the soil and rocks of Mars on Sunday and transmitting a flood of data to overjoyed scientists, their dreams of knowing what Mars is made of about to come true.
As its first task, Sojourner pressed the head of its principal scientific instrument to the powdery surface at the base of the Mars Pathfinder landing craft. The readings from this first examination of the chemical composition of Mars were radioed to Earth Sunday afternoon for analysis by geologists.
Then Sojourner, which is about the size of a microwave oven, prepared to crawl a few feet to begin a 10-hour study of a pitted, knobby rock that geologists are calling Barnacle Bill.
“We have a fully functional spacecraft,” Dr. Matthew Golombek, the chief project scientist, said. “Everything is working just perfectly.”
Overcoming communications trouble and other setbacks, the Sojourner left the Pathfinder lander on Saturday shortly before 11 p.m. Pacific time.
When Sojourner came to a stop on the surface, Richard Cook, the mission manager here at the Jet Propulsion Laboratory, set off cheers in the control room with the announcement: “The rover is on the surface of Mars. We’ve got some great images back, and all the scientists are in heaven.”
As they studied the panoramic views of the landing site produced by Pathfinder’s color camera, scientists got a clearer picture of what Mars looks like up close on the flood plain of Ares Vallis, near ancient highlands. They could hardly wait for Sojourner to navigate the field of rocks and drift sand out to larger boulders and hills in the distance.
At a news conference, Dr. Dan Britt, a geologist at the University of Arizona at Tucson, echoed the excitement and anticipation of the project’s science team. “We’ve got a cornucopia of rocks and processes.”
Dr. Ronald Greeley, a planetary geologist at Arizona State University in Tempe, said, “We chose this site because we wanted to see geological diversity on Mars, and we have not been disappointed.”
In all directions from Pathfinder, scientists could see rocks: small and large, rounded and jagged and blocky, some coated with rust-colored dust and others bare and gray. The more rounded ones appeared to have been eroded as they tumbled from the highlands in ancient floods.
A study of the rounded rocks, Greeley said, could enable geologists to determine the amount of water that carried them from the highlands to the plain. “Their appearance is definitely consistent with transport by water,” he said.
The blocky rocks - one is rectangular, like a solid stone table, and another looks like a couch - could be bedrock ejected when an asteroid gouged out the crater less than a mile from the lander, geologists said. The crater’s rim is barely visible.
Two hills, each several hundred feet high, stand out about a mile to the southwest. Scientists are calling them Twin Peaks.
Of particular interest are apparent horizontal bands on the face of one hill, which could be evidence of sediments laid down by ancient flooding.
There is no liquid water on the Martian surface now, but scientists figure that the planet is water-rich. Vast amounts of frozen water exist in the north polar cap and beneath the surface as permafrost, and some liquid water might lie at greater depths. Judging from pictures of Mars returned by the two Viking orbiters in 1976, water washed vast expanses of the landscape several billion years ago, carving wide channels like Ares Vallis. Rocks from that time and place, scientists suspect, could contain evidence of that warmer, wetter environment - a time when life might have gotten a start on Mars.
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