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Just Wait a Martian Second

21 April 1999 6:00 pm
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Suppose there's a sundial somewhere in the desert, but to read the time, you'd have to go to another planet. Sounds silly? Not if everyone lives on the other planet. The sundial in question is to be shipped to the martian desert in 2001, but only people on Earth will be able to read off the date and time.

The martian sundial is the brainchild of Bill Nye, host of the public television children's science program, "Bill Nye the Science Guy." Nye unveiled the design today at a press conference at Cornell University in Ithaca, New York. The sundial will be part of APEX (Athena Precursor Experiment), a suite of four science instruments on NASA's Mars Surveyor 2001 lander, which is due to touch down on Mars in January 2002. Designed with the help of children from all over the United States, the colorful device shows the orbits of Earth and Mars and contains a message for future martian explorers (see below). Measuring 7.5 centimeters square, the anodized aluminum instrument will also act as a color calibration device for Pancam, the Mars lander's panoramic camera.

There's one problem with the sundial, however: You wouldn't be able to read the time from it if you were on Mars. That's because NASA can't calibrate it until the craft has reached the martian surface. "We will only know the exact orientation [of the sundial] after the spacecraft has landed," says Woody Sullivan, an astronomer at the University of Washington in Seattle, who helped design the instrument. Because the pattern of lines is dependent on the location, orientation, and possible tilt of the lander, it can't be etched onto the sundial before launch. Instead, the calculated line pattern will be superimposed on electronic pictures of the sundial that will be made available through the Internet.

But does a shadow pole without any reading device deserve to be called a sundial? "It will be a device on the surface of Mars that will accurately (and easily for any Web viewer) indicate the martian time and date by the shadow of the sun," says Sullivan. "I'd say that qualifies as a sundial."

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