Martian doings

Two Mars vehicles—an orbiting spacecraft and a robot on the planet’s surface—have reached new milestones in their missions. Seven months after its arrival, the Mars Reconnaissance Orbiter, NASA’s most recent envoy to that planet, has finished reshaping its orbit into the nearly circular, low-altitude path that will give it a close view of the Red Planet. During the maneuvers, flight engineers sent the craft sailing through the upper layers of Mars’ atmosphere 426 times, using friction to gradually decrease Orbiter’s highest altitude from 45,000 kilometers to 486 km.

During its 2-year study, set to begin in November, Orbiter is expected to return more data about Mars than all previous Mars missions combined. For example, the craft will view the 70-meter-deep crater Victoria and will map the mineral content of that region.

In the meantime, the rover Opportunity, one of the twin field geologists that have explored the planet since January 2003, is approaching the rim of Victoria, the widest and deepest crater that the vehicle has visited. Scientists intend to use Opportunity’s first images of the rim to determine how the rover might descend into the crater. “Victoria has been our destination for more than half the mission,” says rover scientist Ray Arvidsen of Washington University in St. Louis. Information about the rocks that are exposed on the crater’s walls will provide new information on past conditions, including whether shallow water once covered that area.

While Opportunity rolls along, its twin—Spirit—isn’t faring as well during the planet’s winter. Its solar batteries have been depleted by low light. Spirit continues to take measurements but since April has remained parked in an outcrop called Low Ridge Haven.