Magellan Renews Venus Mapping Effort : Space: Scientists hope to complete a topographic picture and analyze any changes found in the planet’s surface since the first images were taken.

The Magellan spacecraft has begun its second mapping of the planet Venus, and scientists are hoping that not everything looks the same the second time around.

Scientists will be looking for areas where something has changed since the same region was first mapped several months ago. Changes could reveal active volcanoes and other geological or atmospheric processes on the planet.

“We’re coming back around to some of the places we’ve seen before,” project scientist Steve Saunders told the staff of the Jet Propulsion Laboratory Tuesday. Magellan is in a near-polar orbit around the planet, and sends back a nearly continuous strip of images that are being melded together to form a mosaic of Venus.

Saunders said 78% of the planet has been mapped since Magellan began snapping its first radar images last August. During the second phase of the mission, Magellan is to fill in gaps missed during the first phase and re-examine areas that might have changed.

Magellan uses radar to pierce through the dense clouds that hide the surface of Venus. The radar beam then bounces back to the orbiting spacecraft. Scientists at the Pasadena lab use that data to create the sharpest images ever made of the surface of Venus, the planet that is most like the Earth in size and distance from the sun.

What Saunders and other scientists would most like to see is evidence of active volcanism. Nearly all the scientists associated with the project believe Venus is still active volcanically, but the snapshots captured by Magellan in its first phase do not show that.

Now scientists will be looking for changes in the landscape that could have been caused by flowing lava, or crustal deformation, resulting from recent volcanic activity.

Scientists compare the images to features seen on the Earth, where they have a clearer understanding of the evolutionary processes.

Saunders said some images reveal hills that appear to be similar to the Kelso sand dunes in the Mojave Desert. Sand dunes are formed primarily by wind erosion, and the wind at the surface of Venus is so mild that many scientists were doubtful that they would find evidence that wind has helped shape some of the planet’s features.

If there are sand dunes, that leaves scientists wondering where the sand came from. Sand on the Earth is created by erosional processes such as rivers and strong winds, and there is nothing like that on Venus.

Other patterns indicate that the wind has swept some material away from impact craters, leading to speculation that sand is created when a meteorite strikes the surface. Others suggest that an object striking Venus could be so hot it could produce localized winds that might cause some erosion.

“The puzzle is whether the impact produced the winds or whether it produced the sediment,” Saunders said.