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The San Diego Supercomputer Center (SDSC) is helping to ensure that everyone who wants to get an online look at the latest mission to Mars will be able to access up-to-the-minute information on America's return to the red planet. It all starts January 3, when two robot rovers, each the size of a golf cart, are expected to begin their explorations of Mars. Millions of people will watch their progress on the World Wide Web, creating the potential for a massive Internet traffic jam. SDSC will host a mirror site on two separate server computers for MarsQuest Online, which will cover the landings of the two spacecraft and the rovers' subsequent exploration of the planet's surface.

As new data comes in, it will be relayed to SDSC and to other high-capacity Web servers across the country. A single URL, http://www.marsquestonline.org/, will handle all requests for information from the public in "round-robin" fashion. As website hits are received, they will be handled in sequence by servers at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, at SDSC, at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, and at other mirror sites, so no single site has to handle the entire load.

"We are delighted to assist the space science community in conveying the excitement of planetary exploration to the public," said Joshua Polterock, Group Leader for SDSC's Server Systems. "In 1997 we aided NASA on the Mars Pathfinder mission, when the Sojournerrover landed on Mars. Our server helped take over the load when the main JPL website was swamped. We handled more than four million hits back then. This time we expect to be able to serve several times as many users with much more information - including animations - and much less effort. SDSC's two servers will be on gigabit data links, only one hop away from the main Internet border routers, so we expect to be able to provide smooth, fast data transfers."

NASA's twin robot explorers, christened Spiritand Opportunity, were launched toward Mars this past summer, and are scheduled to land on Mars on January 3 and January 24, 2004. Their main mission is to investigate the terrain, rocks, and soils that hold clues to the present and past geology of Mars, and in particular the possible role of water in the evolution of the planet. The two spacecraft are targeted to sites that appear to have been affected by liquid water - Spiritwill land at Gusev Crater, a giant impact crater that may once have held a lake, and Opportunitywill explore Meridiani Planum ("the plains on the meridian"), where sensors on orbiting spacecraft have indicated the presence of the mineral hematite, which on Earth is usually formed in a wet environment.

When the two probes enter Mars' atmosphere, nestled inside aeroshell entry capsules, they will be slowed in four minutes from 12,000 miles per hour to 960 mph by atmospheric friction (which will heat the aeroshells to 2,600 degrees Fahrenheit). The aeroshells will break open and the landers will descend on parachutes to 50 feet above the surface, where retro rockets will fire. Airbags will inflate around the landers, and the probes will drop to the ground. If all goes well, the airbag-cushioned landers will bounce several times and roll to a stop, perhaps as far as half a mile from their touchdown points.

The rovers will roll out to take panoramic images with their stereoscopic cameras, to give scientists the information they need to select promising geological targets. Then the rovers will drive to those locations to perform on-site scientific investigations, using cameras, microscopes, spectrometers, rock grinders, magnetic particle collectors, and robot arms.

NASA scientists hope that each rover will travel up to 40 meters (more than 120 feet) per day over the course of three months of exploration - hardly comparable to the journey of Lewis and Clark, but not bad at all for a machine in a hostile, cold, gritty environment with no repairmen within sixty million miles.

Additional information about the Mars Exploration Rover mission is available at http://www.marsquestonline.org/ and at http://marsrovers.jpl.nasa.gov/.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington. See http://jpl.nasa.gov/ for more information.

MarsQuest Online is funded by the National Science Foundation's Division of Informal Science Education ( http://www.ehr.nsf.gov/esie/programs/ise/ise.asp), which promotes public interest, understanding, and engagement in science, technology, engineering, and mathematics. It is supported by the Jet Propulsion Laboratory (http://www.jpl.nasa.gov/), NASA's lead center for robotic exploration of the solar system, by the Space Science Institute ( http://spacescience.org/), which integrates research in Earth science, space physics, planetary science, and astrophysics with education and public outreach, and by TERC ( http://www.terc.edu/), a not-for-profit education research and development organization based in Cambridge, Massachusetts that seeks to improve mathematics, science, and technology teaching.

Image credits: NASA/JPL.