Rover experiences instrument glitch

A US rover despatched to investigate the surface of Mars has a glitch in one of its instruments.

The US has sent identical vehicles to Mars

The problem in a spectrometer on the Spirit vehicle was picked up during a routine checkout.

But officials at the American space agency's (Nasa) Jet Propulsion Laboratory say they are not unduly concerned at this stage.

They believe the rover instrument will still be able to do its job of gathering data about iron in Martian rocks - even if scientists have to play around with the information to make the best sense of it.

Spirit was launched by a Delta II rocket from Florida on 11 June and has already travelled more than 150 million kilometres to its destination.

Iron study

It is one of a pair of identical twin vehicles - the other is called Opportunity - that will study the geology of the Red Planet when they get down on to its surface in early 2004.

Nasa's people have been checking through the vehicles' systems since launch to see how they coped with the stress of being thrown into space on a rocket.

We'll be able to get scientific information out of the data it sends us from Mars Dr Steve Squyres, Cornell University

All the systems - cameras and instruments - appear to be working well - apart from the Mössbauer spectrometer on Spirit.

It is one of three spectrometers on the rovers and is designed to study the arrangement of iron atoms in geological samples. It is housed on an extending arm so that it can get a close-up view of rocks and soil.

A Nasa statement said the checkout on Spirit's Mössbauer spectrometer returned some unexpected data.

Working it out

"The Mössbauer results we just received from Opportunity are helping us interpret the data that we've been analyzing from Spirit," said Dr Steve Squyres of Cornell University, principal investigator for the suite of science tools on each rover.

"Some of the theories we had developed for what might be causing the anomalous behaviour of the Mössbauer instrument on Spirit have been eliminated by looking at the data from the one on Opportunity."

Spirit left Earth in June

The remaining theories focus on an apparent problem in movement of a mechanism within the instrument that rapidly vibrates a gamma-ray source back and forth.

"The Mössbauer spectrometer on Spirit is working, and even if we don't come up with a way to improve its performance, we'll be able to get scientific information out of the data it sends us from Mars," Dr Squyres said.

"But it's a very flexible instrument, with lots of parameters we can change. We have high hopes that over the coming months we'll be able to understand exactly what's happened to it and make adjustments that will improve its performance."