Scientists have invited the public to trawl high-resolution images for signs of NASA's Mars Polar Lander, which went silent on arrival at Mars in 1999. Finding the wreckage might explain why the mission failed.

"If we can find the Mars Polar Lander and be convinced we understand what we're looking at, it might provide some clues as to what went wrong," says Alfred McEwen of the University of Arizona in Tucson, US. "There could be lessons there that are applicable to future landers."

The Mars Polar Lander was supposed to study the Martian climate as well as soil and ice close to the planet's south pole. But mission controllers lost contact with the probe when it landed. An investigation suggested it probably smashed onto the surface at high speed because the engines that should have slowed the craft's descent shut down too quickly.

Scientists thought they saw the dead lander in images taken by the Mars Global Surveyor satellite in 2000, but these turned out to be a mirage. Now images taken by the Mars Reconnaissance Orbiter are offering another chance for the probe to be found.

Southern summer

In mid-2007, an instrument called the High Resolution Imaging Science Experiment (HiRISE) on the orbiter snapped sharp images of about half of the likely area where the failed lander touched down. "This was also the southern summer on Mars, so the site was well illuminated," says McEwen, who leads the HiRISE team.

Now, HiRISE software developer Guy McArthur, also at the University of Arizona, has invited the public to scan these images for signs of the Mars Polar Lander. It's a huge challenge because although there are only 18 images, each of them is enormous – typically 1.6 billion pixels.

"If your computer screen is 1000 by 1000, that means you need 1600 screenshots to view one image," says McEwen. "On the HiRISE team, we haven't put much effort into looking for this – we're too busy with other things."

The lander certainly won't be easy to spot. "We just don't know exactly what it will look like," says McEwen. He estimates that any spacecraft features that might be visible – the lander, its heat shield or the backshell with a parachute attached, if the parachute actually opened – will only be a few pixels across.

Years gone by

And the local landscape is troublesomely speckled with bright and dark features roughly the same size as the spacecraft components. "It's a terrible place to look for things like this," says McEwen. "And years have gone by, so some dust will have settled – it may not stand out now."

However, keen volunteers can take some tips on what to look for from Tim Parker at

NASA's Jet Propulsion Laboratory, who has analysed HiRISE images of other spacecraft components on Mars.

NASA is hoping for a better outcome on 25 May, when its Phoenix Mars Lander is due to touch down on Mars. The lander uses similar technologies to the Mars Polar Lander, but its design has been thoroughly tested for any flaws.

Mars – The Red Planet is full of surprises; learn more in our continually updated special report.

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