The Mars Curiosity rover suffered a setback on February 27, when an arm on the vehicle short circuited. However, NASA mission planners believe the problem may be repaired within a week.

Following a short circuit in the arm, on-board computers sent the vehicle into fail-safe mode, preventing any movement of the arm and locking it place. Investigators believe the short circuit took place within electronics used to operate a drill, designed to bore into rock. Samples were being transported from the drill to instruments inside the craft, in advance of testing.

Curiosity has not been moved since the initial incident, as mission planners attempt to diagnose the problem.

"Diagnostic testing this week has been productive in narrowing the possible sources of the transient short circuit. The most likely cause is an intermittent short in the percussion mechanism of the drill. After further analysis to confirm that diagnosis, we will be analyzing how to adjust for that in future drilling," Jim Erickson, Curiosity project manager at Jet Propulsion Laboratory, said.

The drill where the problem occurred uses both a rotating bit, as well as a hammer-like percussive action to obtain samples of powered rock, and bring them into the vehicle for analysis. At the time of the short circuit, percussive actions were taking place, in order to shake powder loose from the drill.

"Call me Johnny Five. Some ops on hold while my team investigates a short circuit," Curiosity managers tweeted on the day of the incident.

Curiosity was tested with 180 up-and-down repetitions of the percussive action of the drill. On the third of these runs, a small short circuit, lasting just 0.01, was observed. Such an incident, under normal conditions, would have triggered the computer to shut down the rover.

Further analysis will be aimed at determining the exact cause and nature of the short seen during testing, before the arm is moved. Mission planners want to run tests with the arm in its current position, in case the problem does not happen when the arm is aligned differently.

A striker in the arm is operated by a wire coil, generating a pulsating magnetic field. This may be the center of the problem, researchers are theorizing.

After the problem is identified and corrected, mission engineers are planning on continuing the transfer of the rock powder into Curiosity to run experiments on the sample. After that occurs, the rover will continue to climb up Mount Sharp. The short circuit is not expected to threaten the mission, although if it is not fixed, the drill may not be able to penetrate harder rocks.