NASA's Mars rover Curiosity is expected to resume movements of its robotic arm this week while analysis of what appears to be an intermittent short circuit in the drill continues.
A fluctuation in current on February 27 triggered a fault-protection response that immediately halted action by the rover during the mission's 911th Martian day, or sol.
Since then, the rover team has avoided driving Curiosity or moving the rover's arm, while engineers have focused on diagnostic tests, NASA said.
Science observations with instruments on the rover's mast have continued, along with environmental monitoring by its weather station.
"Diagnostic testing has been productive in narrowing the possible sources of the transient short circuit," said Curiosity Project Manager Jim Erickson of NASA's Jet Propulsion Laboratory, Pasadena, California.
"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 analysing how to adjust for that in future drilling," said Erickson.
The sample-collection drill on Curiosity's robotic arm uses both rotation and hammering, or percussion, to penetrate into Martian rocks and collect pulverised rock material for delivery to analytical instruments inside the rover.
The short on Sol 911 occurred while the rover was transferring rock-powder sample from the grooves of the drill into a mechanism that sieves and portions the powder.
The percussion action was in use, to shake the powder loose from the drill.
Engineers received results on March 5 from a test on Curiosity that similarly used the drill's percussion action.
During the third out of 180 up-and-down repeats of the action, an apparent short circuit occurred for less than one one-hundredth of a second, researchers said.
Though small and fleeting, it would have been enough to trigger the fault protection that was active on Sol 911 under the parameters that were in place then.
The rover team plans further testing to characterise the intermittent short before the arm is moved from its present position, in case the short does not appear when the orientation is different.
After those tests, the team expects to finish processing the sample powder that the arm currently holds and then to deliver portions of the sample to onboard laboratory instruments. Next, Curiosity will resume climbing Mount Sharp.
