LOS ANGELES, Jan 28: As Nasa scientists pored over striking new photos from Mars revealing finely layered formations of ancient bedrock, engineers labored on Tuesday to diagnose problems with two robotic rovers on opposite sides of the Red Planet.

Besides a serious malfunction that has idled the first rover, Spirit, since last Wednesday, mission controllers at NASA's Jet Propulsion Laboratory said they are now contending with a power drain on Spirit's newly arrived twin, Opportunity.

Mission manager Jim Erickson told reporters said the power loss appeared to be from one of the craft's heating units that keeps turning itself on and running overnight without receiving commands from NASA to do so.

While engineers do not believe the faulty thermostat will overheat the vehicle, the long-term consequences of the glitch and whether it can be fixed are not yet known, Erickson said.

"I'd like to have a little more information on what we're seeing from the vehicle before we make any judgments there," he said. Otherwise, the rover was "in pretty good shape" as a new martian day, its fourth, dawned over Opportunity's landing site on a wide, flat plain known as the Meridiani Planum.

The area is of interest to scientists because it is believed to contain large deposits of an iron-bearing crystalline mineral called hematite, which on Earth usually forms in the presence of liquid water.

Both Opportunity and Spirit are equipped with a laboratory of geologic tools designed to search for evidence that the martian surface was once wetter and more hospitable to life, than it is now.-Reuters