Software Glitch May Have Doomed Probe

Jan. 11, 2007 — NASA is investigating whether human error caused the loss of Mars Global Surveyor, a 10-year-old probe credited with finding signs of liquid water on the planet's surface.

The spacecraft fell silent in November after a problem with one of its solar array panels. Preliminary findings indicate software that was uploaded to Global Surveyor earlier in the year may have contained an error that set off a chain of events leading to the probe's demise.

Global Surveyor had already lasted four times longer than its design lifetime, but was about to embark on what might have been its most critical observations yet.

Scientists had hoped to fly the spacecraft over parts of Mars previously imaged to look for topographical changes. It was not just wishful thinking: Scientists had already found two locations showing signs of very recent water flows on the planet's surface.

It will be up to NASA's new spacecraft, the Mars Reconnaissance Orbiter, to pick up the surveys, as engineers have virtually no hope of recovering Global Surveyor.

"We still listen for it, but that's really the extent of it," NASA's Mars Exploration Program director Doug McCuistion told Discovery News.

The agency has set up a investigation board to try to figure out what happened to Global Surveyor. McCuistion said the software glitch is among the possible scenarios.

"Something may have occurred that we may never know," he added.

The board also will be looking into how the faulty software slipped through NASA's safety and quality control reviews. The program was intended to improve Global Surveyor's computer, but it had an error that may have caused the probe's solar array panel to jam.

The spacecraft then went into an automated emergency standby mode awaiting instructions, but engineers believe the battery, which was facing the sun, overheated and failed.

NASA used MRO as well as one of its rovers on the planet's surface to try to locate Global Surveyor, but the spacecraft could not be found.

Even with Global Surveyor's demise, Mars is still well-populated with robotic probes: two rovers have been scouring opposite sides of Mars' equator for signs of past water and three orbiters, including Europe's Mars Express, are circling the planet searching for water-bearing minerals and water-carved geologic formations.

NASA's next Mars mission is a lander named Phoenix that will touch down on the planet's north pole to study if the icy terrain could have — or possibly still does - support life. The Phoenix launch is scheduled for August.