NASA Mars: Both orbiters are down for the count

The Red Planet is experiencing a partial radio blackout this week, as both of NASA's Mars orbiters have been felled by technical glitches. Until one of the probes can be brought back online later this week, the outages will delay operation of the twin Mars rovers, which use the orbiters to efficiently relay data back to Earth.

The main blow to rover operations comes from NASA's Mars Odyssey, which reached the Red Planet in 2001 and has been the prime communications relay for the rovers Spirit and Opportunity since they landed in 2004.

Odyssey has been down since 28 November, when its computers registered a memory error and sent the spacecraft into "safe mode", which minimises spacecraft operations.

Odyssey's most natural communications backup, NASA's Mars Reconnaissance Orbiter (MRO), has been kept on standby since August, when the spacecraft spontaneously rebooted for the fourth time this year.

Fast connection
The solar-powered Mars rovers can communicate with antennas on Earth directly, but the orbiters can relay information from the rovers to Earth at more than 10 times that speed, using a fraction of the energy.

The outages could delay attempts to free the Spirit rover from a sand pit that has been its home for more than six months (see Mars rover battles for its life). The rover team has been given until February to extricate Spirit.

"The rovers are safe. However, future activities are likely delayed, roughly on a day-for-day basis until Odyssey returns to relay operations," says John Callas, the rover programme manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.