A humble sundial to mark the passage of the Martian day is set to be part of NASA's next mission to red planet. A team at Cornell University in New York, the University of Washington in Seattle and Arizona State University in Tempe will put together the tiny aluminium device for the Mars Surveyor mission set to begin in 2001. The sundial will be three inches square and weigh slightly more than two ounces. It will need to be configured differently from Earth sundials, said Mr Woodruff Sullivan, an astronomy professor at the University of Washington.

The Martian year is nearly twice as long as Earth's, and its seasons are more pronounced because its orbit is more elliptical. But the planets are tilted away from the sun to a similar degree. The scientists say they hope the sundial will have its image sent back to Earth for anyone to monitor via the Internet.