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Clickworkers on Mars

Michael Szpir

In graduate school I spent many months staring into a microscope and drawing the outlines of neurons and axons as part of my thesis research. It was mind-numbing and hand-cramping work. (The only thing that saved me from blowing out my own neurons was the daily broadcast of the Iran-Contra hearings on NPR.) At the time I considered the task to be a necessary evil, just a pound of flesh that science sometimes demands of its practitioners. Other scientists have undoubtedly felt the pain of such tedium and perhaps also wondered whether there wasn't a better way. As it happens, there is.

Can you rate this congenial Martian crater? . . .Click to Enlarge Image

A group of planetary scientists at NASA's Ames Research Center in Moffet Field, California, have created a Web site,, where they invite Web surfers to take over some of the more onerous tasks of studying our solar system—in this instance, measuring and classifying impact craters on Mars—by drawing circles around craters or estimating a crater's age based on its appearance. The task is usually undertaken by someone trained in the art and science of rating craters, but there are many thousands of craters on the planet and, well, most scientists (even graduate students) have better things to do.

Enter the general public. NASA scientists believe that the average person has enough common sense to make accurate assessments of the craters. In fact, the real trick is our species' finely tuned perceptual abilities, which are far superior to the capabilities of the current generation of computers and image-recognition algorithms. Volunteering humans are also cheaper. The question is, would human beings donate their time and eyes to the task? And if so, would the results be scientifically useful?

Surprisingly, the answer is yes to both questions. A pilot study conducted on the Web site between November 2000 and September 2001 attracted more than 80,000 people who marked nearly 2 million craters for measurement and classified the relative age of another 300,000. Their averaged results proved to be just as good as those produced by an expert crater rater—who would have had to dedicate several months of continuous effort to produce the same amount of data.

The NASA scientists have submitted a proposal to acquire further funding, which they are slated to hear about as this magazine goes to press. If it's funded, the scientists will be looking for gullies, among other things, in the images and data that will be sent back by the Mars Odyssey spacecraft. Eventually, the project will be expanded to other worlds.

For those who think they'd like to give it a shot, the Mars Clickworkers Web site is still in operation. I tried my hand at measuring a few craters and estimating their ages. It was simple and sort of interesting at first, but the novelty wore off after about a dozen or so craters. It reminded me a lot of grad school.—Michael Szpir

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