Published online 14 May 2008 | Nature | doi:10.1038/news.2008.821

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Spot the spacecraft

Scientists hope the public can help find the Mars Polar Lander's resting place in released images.

Mars imageCan you spy any doomed spacecraft?NASA/JPL/Univ. Arizona

Back in 1999, the Mars Polar Lander (MPL) went missing as it entered Mars’s atmosphere, and its fate has been a mystery ever since. But now there is a chance for a member of the public to locate the missing spacecraft and help work out what went wrong.

The High-Resolution Imaging Science Experiment (HiRISE), based at the University of Arizona in Tucson, has a raft of images of the MPL’s projected landing area, but scans of the huge images came up blank.

So now, the HiRISE team’s blog has published 18 images, and has challenged the public to find the lost lander.

“You may in fact be the first person to see MPL in the nearly 10 years since it left Earth,” reads the blog entry. The team also provides pictures of parts of the lander as it would appear to HiRISE, to help identification. The challenge is to scan the pictures and see if you can spot the MPL, or its remains, somewhere near the intended landing area.

Some enthusiastic lander-spotters have already claimed to have the machine in their sights. One visitor to the blog gives two grid references: one for something “a bit weird-looking”; another for something “a bit machine-like”.

Another describes “something resembling a half-buried parachute at about the right size”. HiRISE scientists will now try and verify these initial 'sightings'.

Massive task

Other aspiring spotters should not, however, be discouraged — there is still plenty of ground to cover. “These are big images and there are a lot of them,” says Alfred McEwen, HiRISE principal investigator. Each picture is 20,000 by 80,000 pixels (1.6 gigapixels) — about the size of 1,600 computer screens. And to get the best chance of spotting the lander, there's no substitute for the human eye: automating the process would need a hugely complex algorithm, and would churn out unmanageable amounts of data.

For similar reasons, several other recent science projects have called on public eyes for help. Stardust@home has asked the public to look for interstellar dust grains from the Stardust spacecraft mission’s encounter with a comet in 2004. And Galaxy Zoo is a project that asked members of the public to classify a million galaxies, attracting more than 125,000 participants.

Calling on public support makes a lot of sense, says Kevin Schawinski, an astrophysicist and Galaxy Zoo scientist at the University of Oxford, UK. “Modern data sets are so big,” he says, for a single person, or small team of scientists, to scan properly.

False positives

“More eyes looking at it might turn up something,” says McEwen. But he expects false alarms, especially for a planet as geographically varied as Mars: “These regions are covered with little bright spots,” he says.

Spotting the MPL in one of the images is only going to be possible if the lander did actually crash somewhere near its intended landing site. Uncertainty surrounds its disappearance. Communication with the spacecraft, which was heading to Mars to look for water, ceased as it entered the martian atmosphere on 3 December 1999.

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Spotting the lander on the planet’s surface, and seeing what state it is in, might offer clues as to what went wrong. The favourite current theory is that the central mechanism was so sensitive that the jolt it got when the legs deployed for landing tricked the system into thinking that it actually had landed, so the thrusters were turned off 40 metres above the ground.

“This is probably the only way they’ll ever find [the MPL],” says Schawinski. McEwen is cautious about the chances of seeing the missing lander this way, giving it a “small but not zero” chance of success. And if they don’t find it, HiRISE will need to try and focus in on the landing area again next summer — something that McEwen hopes won’t be necessary. “It’d be great if someone found it — then we don’t have to take all those new images.” 

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