Two teams, one centered at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA, and the other at Lockheed Martin Astronautics, Denver, CO, will conduct separate, intensive two- month studies to further define the concepts. In the studies the teams also will evaluate risk, cost, and readiness for flight, allowing 36 months of development leading to a May 2003 launch date.

The reports will be submitted for review to Mars Program Director Scott Hubbard at NASA Headquarters, Washington, DC. Dr. Ed Weiler, Associate Administrator for Space Science at NASA Headquarters, will make the final decision of which mission -- if any -- to launch in the 2003 opportunity. If selected, the cost of the 2003 mission will be about the same as the successful 1997 Mars Pathfinder mission (adjusted for inflation).

"Our budget will support only one of these two outstanding missions for the 2003 launch opportunity, and it will be a very tough decision to make," said Dr. Weiler.

"Following this decision, later in the year we will have a more complete overall Mars exploration program to present to the American public which will represent the most exciting, most scientifically rich program of exploration we have ever undertaken of the planet Mars."

"These two mission concepts embody the requirements we have learned through the hard lessons of two recent Mars mission failures, and either one will extend the tremendous scientific successes we have had with the Mars Global Surveyor and Mars Pathfinder," said Hubbard.

The Mars Surveyor Orbiter is a multi-instrument spacecraft similar in size to the currently operating Mars Global Surveyor. It is designed to recapture all the lost science capability of the Mars Climate Orbiter mission as well as to seek new evidence of water-related materials.

The orbiter's mission will be to study the martian atmosphere and trace the signs of ancient and modern water. Its instruments potentially will include a very high- resolution imaging system, a moderate-to-wide-angle multicolor camera, an atmospheric infrared sounder, a visible-to-near- infrared imaging spectrometer, an ultraviolet spectrometer, and possibly a magnetometer and laser altimeter. Telecommunications relay equipment that could be used to support Mars missions for 10 years also would be included.

The return of the beach ball

The rover is a based on the Athena rover design, which already has been operated in field tests and previously was considered for the cancelled 2001 lander mission.

The concept being proposed for the 2003 mission involves packaging the 286- pound (130-kilogram) rover in a system similar to the 1997 Mars Pathfinder structure, which would be cushioned on landing by airbags.

Unlike the 1997 mission, however, the four-petal, self- righting enclosure would serve only as a means to deliver the rover to the surface and not function as a science or support station.

After landing, the Mars Mobile Lander would serve as a self- contained mission, communicating directly with Earth or with an orbiting spacecraft band as the rover traverses the martian terrain.

The rover would be capable of travelling up to 100 yards (100 meters) a day, providing unprecedented measurements of the mineralogy and geochemistry of the martian surface, particularly of rocks, using a newly developed suite of instruments optimized to search for clues about ancient water on Mars.

The mobile surface-laboratory will be able to gain access to a broad diversity of rocks and fine-scale materials for the first time on the surface of Mars, in its search for evidence of water-related materials. The rover's mission would last for at least 30 days on the surface.

"We are opening up a new frontier on the Red Planet, and we can't afford to overlook anything," Weiler added. "We have to make sure we plan it well, provide our people with the tools they need, and do whatever it takes to ensure the best possible chances for success."