Venus Bares Its Soul in New Radar Images : Space: Latest photographs show craters large enough to swallow Los Angeles. JPL scientists search for clues telling why planet turned out to be so different than Earth.

Venus, a planet that started out like the Earth but took a dramatic turn somewhere along the way, is turning out to be a geological candy store as it lays bare its soul for the Magellan spacecraft.

Photographs released Tuesday by the Jet Propulsion Laboratory show a planet that is pockmarked with giant impact craters large enough to swallow Los Angeles and a twisted, tormented landscape that has been molded by forces that are still not understood.

“These are extremely jazzy images,” said Gordon H. Pettengill of the Massachusetts Institute of Technology, principal investigator for Magellan’s radar science team. The images were captured by an electronic “camera” that uses radar beams to pierce through the dense atmosphere that normally hides the surface of the hot, barren planet.

Scientists hope that Magellan will help them understand why Venus--the planet that is most like the Earth in size, mass and distance from the sun--turned out to be so different: devoid of life, with surface temperatures hot enough to melt lead and a heavy atmosphere rich in carbon dioxide.

After a troubled beginning, Magellan seems to be doing its best to help unravel the mysteries, but some of the images produce more questions than answers.

The spacecraft has mapped the surface for more than 80 orbits as it flies in a polar trajectory around Venus. The problems that caused the craft to sever its communications with Earth twice are not fully understood, said chief engineer John P. Slonski Jr., so Magellan is not completely safe yet.

“The problems may happen again,” Slonski told a press conference at the Pasadena lab. He said that even if the “root cause” of the blackouts has not been determined, engineers have at least narrowed the range of probabilities and taken steps to protect Magellan as much as possible.

Scientists said Tuesday that the images captured by Magellan have demonstrated that Venus is an extraordinary laboratory in which to test geological theories because the photographs are clear and reveal a geological record spanning hundreds of millions of years.

On Earth, the evidence of earthquakes and volcanoes disappears over time because of vegetation and erosion. On Venus, where there is no vegetation and very little erosion, the geological record stands out in brilliant clarity.

One of the new images shows an extraordinary pattern of what appears to be a crosshatching of faults.

“It’s an extremely regular pattern,” said James W. Head II of Brown University, co-investigator on the radar science team. “The regularity is so remarkable,” he said, that “we have no idea how these (patterns) would form.”

It is possible that there are similar areas on Earth, he said, but they must be hidden by vegetation or erosion.

As expected, “erosion does not appear to be a fundamental process” on the surface of Venus, Head said. That is because there is no water to wash away the soil and produce sediments that could be transported by the wind, and the wind amounts to little more than a slight breeze.

“We’re so used to water eroding the surface of Earth,” Head said. “It’s astonishing to see all this detail. When you create (a geological feature on Venus) it stays there a long time.”

If Magellan can capture a photo of an active volcano on Venus, it would answer whether the planet is alive in a volcanic sense, but nothing in the images transmitted to Earth shows that.

Head pointed out that Magellan has covered only 1 1/2% of the surface of Venus so far. If you looked at that much of the Earth’s surface, you probably would not see any active volcanoes either, he said.

Head indicated that he believes he already knows the answer. “It’s very much alive,” he said of Venus.

The images from Magellan reveal a surface that could be changing even as the spacecraft zips overhead. In addition to faulting and cratering, the newly released images show a “river” of lava hundreds of miles long. The images also show giant volcanoes similar to those in Hawaii.

The most spectacular image is a mosaic covering an area about half the size of California. It was displayed at JPL as a 10-foot-by-12-foot mural, and it shows giant craters up to 30 miles in diameter.

One image shows an impact crater that is nearly two miles deep. All of the impact craters are at least five miles in diameter. Scientists said that is because only the largest objects survive the long journey through space to Venus’ surface. Smaller meteoroids apparently break up as they crash through the dense atmosphere.

Magellan is expected to spend nearly a year mapping Venus, and scientists said Tuesday that they expect far more images and a lot of surprises.

“Don’t touch that dial,” Head said. “We think we’ve got a blockbuster fall season coming up.”