Bill Nye's sundial hitches a ride to Mars

Mars is about to be invaded by three successive spacecraft carrying sophisticated scientific instruments, six-wheeled robotic "rovers" and two sundials from Seattle.

The planned landing on Christmas Day of Britain's Beagle 2 will be followed by two NASA probes, Spirit and Opportunity, which will land on different days in January. The general purpose of the missions is to find evidence of life, or past life.

What does a sundial have to do with this and why on Earth would it come from soggy, cloudy Seattle?


	Nye

"When I first suggested the sundial to the (Mars) team, they said to me, 'Bill, dude, this is for NASA, the space program. We have a lot of really good clocks,' " said Bill Nye The Science Guy, cracking that wry smile familiar to those who have seen his antics on television.

But Nye persisted and, if Spirit survives its Jan. 3 landing, the Red Planet will be home to the first extraterrestrial sundial -- known as a MarsDial -- thanks mostly to him and fellow "gnomonocist" (sundial enthusiast) University of Washington astronomer Woody Sullivan. The Opportunity is planned to follow Jan. 25.

Nye and Sullivan hope the events will help them recruit others to build "EarthDial," a planet-wide network of sundials tracked by Webcam to create on the Internet a real-time, visual reckoning of "solar time" across the two worlds.

"A sundial is all about place on the planet and your relation to the cosmos," said Sullivan, who said he's already sparked interest in EarthDial from around the world.


		Karen Ducey / P-I
	A replica of the MarsDial which is en route to the Red Planet on board NASA's Mars Rover.

Nye was able to convince NASA that they needed a sundial on their Martian rover during the project planning phase in 1998, after he learned they were already going to attach a device to better determine colors.

Remote digital images taken during past Mars missions have had no reference, or calibration scale, to help scientists accurately determine the correct "tint" of the images.

How red, exactly, are those Martian rocks? Is the sky, if not blue, yellow-orange or orange-yellow? It's not just a matter of aesthetics. Color indicates mineral content and atmospheric composition.

NASA had planned to calibrate using an erect post set in a color chart. The idea was to compare various colors in shadow and direct light to accurately adjust the natural tint.

A post? A shadow?

When Nye saw the color-calibration method planned for the rover, he realized it would just take one small step for mankind to transform the device into a sundial. He could add function without adding weight. Eureka! Nye was ecstatic.

The Cornell University team hired by NASA to construct the Mars rover agreed to do it as a matter of public education and outreach. Nye asked Sullivan and his UW colleague, precision machinist Larry Stark, to help design and build it.

Made of anodized aluminum, the Mars sundial is a work of art. Around the center post (gnomon) are concentric rings, a blue and red dot representing the orbits of Earth and Mars. Though just 3 inches square, it is laser-engraved with a lengthy statement of purpose, the word "Mars" in 17 languages and tiny stick-figure humans.


	Karen Ducey / P-I
Bill Nye, left, and UW astronomer Woody Sullivan hold a mock-up of the MarsDial, the first extraterrestrial sundial, which they helped design and build. MarsDial will be aboard the rover Spirit on its planned Mars landing.

But it now appears the Seattle sundial may be much more than an artistic color calibrator and timepiece. It's a necessary backup.

"NASA engineers orient the Mars rover by looking at the sun through the panoramic camera," Sullivan explained. But they only recently recognized they had no orientation system to back up the camera should it fail, he said.

Each rover is expected to cruise the Martian surface for three months, collecting samples of rock and soil, and each vehicle's success depends upon having its bearings.

"Then the engineers realized they could orient using the sundial," Sullivan said. "Our sundial is now the official backup for orienting NASA's rover."

The related EarthDial project is being launched by Sullivan and Nye to pair the tracking of solar time on the Red Planet with a network of sundials spread across the Blue Planet.

Anyone willing to dedicate some personal computing time, a Webcam and a few hours of craftwork (to construct your Earthdial, according to specifications) can participate in this unprecedented project sponsored by The Planetary Society.

The EarthDials are designed by Nye and Sullivan to look similar to the MarsDials aboard the Spirit and Opportunity rovers.

Both dials feature the motto "Two Worlds One Sun."

Images of each EarthDial around the world will be posted on a Web site every five to 10 minutes. As described on the EarthDial Web site:

"As your eye sweeps across the images on this page, the Sun's shadow will sweep across the faces of the dials. Kids and grownups, classrooms and clubs, around the world will gain a palpable sense of how the Sun illuminates the round globe that is our Earth -- and how the sun's passage across the sky controls time around the world."

In addition, the site will feature images of the MarsDials.

"People around the world will be able to look at solar time passing on both Earth and Mars," said Nye. "It's amazing."

Sullivan said it shouldn't surprise anyone that two of the world's sundial worshippers live in Seattle.

"We don't take the sun for granted here," he said.

A moment with ... Bill Nye, the Science Guy