NASA's Mars Reconnaissance Orbiter will be kept in its safe mode — suspending its science observations of the red planet for several weeks — while engineers try to investigate what is plaguing the spacecraft.

The 4-year-old orbiter has mysteriously rebooted its main computer three times this year, most recently on Aug. 26. It also inexplicably switched to a backup computer last month in a different malfunction.

During analysis of the four safe-mode events, NASA engineers have identified a vulnerability of the spacecraft to the effects of subsequent events. They are currently developing added protection to eliminate this vulnerability while they continue analysis of the string of incidents.

NASA launched the Mars Reconnaissance Orbiter toward the red planet in 2005. It is the most powerful orbiter ever sent to Mars and has beamed home more data and images than all other missions to the red planet combined.

The orbiter completed its primary mission in late 2008 and is currently in the middle of an extended mission that runs through mid-2010.

Continuing science observations are planned when the spacecraft is brought out of its current precautionary mode.