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It's just dirt and rocks to you, but Mars bedrock is cool to scientists

Scientists on Tuesday unveiled an image revealing fine-scale layering in the flat, tabular martian bedrock close to the newly arrived rover Opportunity, saying they are on the verge of "arguably the coolest geologic field trip in human history."

Notwithstanding the jibes of late-night comedians about so much boring rock and dirt, rover chief scientist Steve Squyres of Cornell University could not contain his eagerness for a closer look at the formation in the rim of the small crater where Opportunity landed over the weekend.

"Look at that wonderful layer-cake structure in there," Squyres rhapsodized. "It's going to be fascinating _ beyond words _ to get up close and personal with this thing."

The rock formation, the first bedrock encountered by the five U.S. landers that have reached Mars, is less than about 30 feet from the rover, a short drive away.

Using Opportunity's field geology tool kit, scientists are anxious to find out whether the layering is sediment, formed by water, when the planet was billions of years younger, or the result of volcanic ash deposits or other processes. The goal of Opportunity and its twin, Spirit, resting on what might be an ancient lake bed on the opposite side of the planet, is to search for signs that Mars once had liquid water long enough for life forms to develop.

Narrating as the black and white panorama unfolded on a big screen at the Jet Propulsion Laboratory, Squyres noted the left to right progression around roughly half of the crater rim, showing flat, tabular outcrops of rock, then the first ribbons of layering in the rock surfaces, then a different looking segment higher up, where the rocks are more massive and rounded, with sharp, jutting overhangs and, finally, even more distinct layering.

Mission scientist Andrew Knoll of Harvard noted that each layer records a different period of history, a type of geological "document" familiar on Earth. "Probably every geologist in the world is developing opinions about" the martian outcrops now, he said.

The six-wheeled, golf-cart-size rover sat perched on its lander as engineers prepared it to start the process of extending its six wheels and "standing up." In about two weeks, they expect to command it to roll down the exit ramp onto the fine, dark soil on the crater floor.

The rover was in good health, although engineers were analyzing a small, 15-watt power loss believed to stem from a heater in a joint of its robotic arm, said mission manager Jim Erickson. The heater seemed to be turning on when temperatures drop, even though the heat is needed only when the arm active.

At first, Squyres said, rover drivers went "Yikes!" when they saw the rough, rocky formations reaching halfway around the crater rim, fearing they would impede the rover's mobility. Then the team realized how small the outcrops are: about 1{ feet from top to bottom.

Opportunity beamed back this panoramic image of a layered martian bedrock. Each layer is roughly the width of a human finger. For more photos from the Mars rovers, visit