As he was looking over the designs for instruments to be carried aboard NASA's 2001 Mars Surveyor Lander, Nye noticed that the solar-panel calibration device for the lander's Pancam panoramic camera -- a small aluminum square with an upright post in the center of it -- looked familiar.

"I said, 'Hey you guys, this has got to be a sundial. It'll be great.' They said, 'Bill, this is a space program. We have a lot of clocks. Thanks for your input.' Everybody was skeptical at first, but later thought it would be kind of cool," Nye recalls.

The launch of the Surveyor Lander was canceled after the disappearance of the Mars Polar Lander in December 1999 following its descent into the Martian atmosphere for a landing on the planet's south polar region. But the first interplanetary sundial finally is expected to make it to the red planet on Jan. 4, 2004. Identical sundials, each about 3 inches square, are being carried by the two Mars Exploration Rovers, the first of which was launched from Cape Canaveral Air Force Station on June 10. The second rover launched one month later, on July 7.

The sundial design team ultimately included Nye, a 1977 Cornell engineering graduate, Rhodes Class of '56 Professor and host of the now-ended PBS show "Bill Nye the Science Guy"; Steven Squyres, Cornell professor of astronomy and principal investigator for the Athena suite of science instruments carried by the rovers; Jim Bell, Cornell assistant professor of astronomy and lead researcher for the high-resolution stereo Pancams carried by both rovers; Woodruff "Woody" Sullivan, sundial enthusiast and professor of astronomy at the University of Washington; Tyler Nordgren, Cornell Ph.D. '97, an artist and astronomer at the University of Redlands in California; Jon Lomberg, an artist and creative consultant to the Mauna Kea Center for Astronomy Education, University of Hawaii at Hilo; and Louis Friedman, executive director of the Planetary Society.

Schoolchildren across the country also contributed to the project, submitting illustrations for the sundial to Sheri Klug, director of Arizona State University's Mars Education and Outreach Program. Some of those drawings are included on the sundials.

Unlike ordinary sundials, the Mars sundials have no hour marks -- the rovers carrying them will be changing position frequently, rendering permanent hour lines meaningless. Instead, the Athena team will add hour marks electronically onto Pancam photos of the sundial. The Athena Web site sundial page will be updated every couple of days with new photos of the sundials, and one full day of the mission will be devoted to sundial observation.

The sundials, positioned on each rover's rear solar panel, are there not only to tell the hours but also to help the Athena team adjust the rovers' panoramic cameras. Scientists will use the colored blocks in the corners of the sundial to calibrate the color in images of the landscape so that Mars can be seen in its true colors. And pictures of the shadows that are cast by a sundial's center post -- in sundial terminology, the gnomon -- will allow scientists to properly adjust the brightness of each Pancam image.

"On Mars, you don't know what color anything is," Nye points out. "The Martian sky is so pink that it makes everything pink, and so you want to know if the object you're looking at is really pink or if it's pink light bouncing off the sky."

The grayscale calibration rings surrounding the gnomon represent the orbits of Mars and Earth, with two dots representing the planets. A keen observer might note that the dots are in the positions that Mars and Earth would have been in at the time of the Surveyor landing.

Each sundial is inscribed with the words "Two Worlds, One Sun" and bears the name "Mars" in 17 languages, including Bengali, Inuktituk, Lingala and Malay-Indonesian, as well as ancient Sumerian and Mayan. Four gold panels along the sides of the sundials are inscribed with stick-figure drawings of people, as well as a message to future Mars explorers:

"People launched this spacecraft from Earth in our year 2003. It arrived on Mars in 2004. We built its instruments to study the Martian environment and to look for signs of life. We used this post and these patterns to adjust our cameras and as a sundial to reckon the passage of time. The drawings and words represent the people of Earth. We sent this craft in peace to learn about Mars' past and about our future. To those who visit here, we wish a safe journey and the joy of discovery."

Another important piece of terrestrial culture is represented on the sundial: baseball, since both Nye and Sullivan are fans. To save weight, six holes in the shape of home plate were cut out of the underside of the aluminum base.

Nye, whose contagious passion for science made him a television star, is boundlessly enthusiastic about the Athena mission. Nye said: "I'm very proud of the sundial, and I'm honored to be part of the team." What's Next Nozomi, a Japanese (ISAS) Mars probe, has also completed its final Earth swingby operation on June 19 (JST), and is on its way to Mars. Nozomi, which means Hope, passed within 18,000 km of the Earth in a manuever designed to use the planet's gravity to slingshot the probe toward Mars. Nozomi, launched in July 1998, is Japan's first attempt to explore Mars. Its mission is to orbit Mars and gather data on the Martian atmosphere and its interaction with solar wind for up to two years.

The European Space Agency, ESA, launched its own probe June 2nd, called the Mars Express, with a lander, named after the famous voyage, Beagle, that carried Englishman Charles Darwin on his world tour in search of how life evolved on Earth. With a landed mass of less than 30 kg, Beagle 2 represents the most ambitious science payload-to-systems mass ratio ever attempted. Almost a third of the payload will carry out various types of analysis or be used to manipulate and collect samples for study on the surface of Mars. One of its main tasks will be the step-wise heating of martian soil in a kind of oven, to determine the elemental composition of any volatiles including organic compounds.

Each of the quartet of current Mars missions has its own challenges and rewards. Beagle is smaller and will perform some of the first biology detection experiments since the 1976 Vikings first injected microbial nutrients in hopes of seeing evolved gases and byproducts of martian metabolism. Beagle will be less mobile, relying on a mole-like digging tool to burrow for its soil samples just below the dusty top-layers. The Mars Exploration Rovers, Opportunity and Spirit, will have panoramic cameras and much greater mobility to travel beyond where they initially come to rest. Late this year and early next will give focus to the international science effort to explore whether the 'wetter and warmer' Mars can be viewed up close.

In looking back on the success of the 1997 Mars rover, Pathfinder project scientist, Dr. Matthew Golombek, of the Jet Propulsion Laboratory, reflected that: "Power for a solar spacecraft must be managed very carefully. Managing the lag in knowledge from one day to the next is also important. Better autonomy placing instruments against rocks and targets and more autonomous roving could help look at more materials on the surface and visit more sites. For deep space missions, all it takes is one mistake for the mission to fail. Every launch has a 5 times out of 100 chance of blowing up. Part of exploration is confronting the unknown and risk can never be removed completely. In cases like Pathfinder taking a little risk can result in an enormous payoff."

Orbital projections of where Mars Express and the Mars Exploration Rovers are right now, can be continuously monitored over their half-year journeys.

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