Scientists seek cause of 'soft short' electrical problem in Mars rover

NASA says science observations by its Mars rover Curiosity have been suspended while engineers look for possible causes of a voltage change detected Sunday. "The vehicle is safe and stable, fully capable of operating in its present condition, but we are taking the precaution of investigating what may be a soft short," Mars Science Laboratory Project Manager Jim Erickson at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said. A "soft" short is a leak of electrical current through something that's partially conductive, rather than a "hard" short such as what occurs when one electrical wire contacts another. The rover team detected a change in the voltage difference between the chassis and the 32-volt power bus that distributes electricity to systems throughout the rover, JPL said. From 11 volts since the rover landed, the level has dropped to about 4 volts, it said. While shorts reduce the level of robustness for tolerating other shorts in the future, the rover's electrical system is designed with the flexibility to work properly throughout such changes in voltage, using a design feature called a "floating bus," rover managers said. Operations planned for Curiosity for the next few days are designed to check some of the possible root causes for the voltage change, they said.