An artist's concept of SCIM. The mission would collect millions of dust particles and about a quart of atmospheric gas from Mars during a fast flythrough of the martian atmosphere for return to Earth. Credit: Arizona State University

In the first step of a two-step process, NASA selected four proposals for detailed study as candidates for the 2007 "Scout" mission in the agency's Mars Exploration Program.

NASA's Mars 2007 Scout selection process is the first fully competed opportunity for scientific missions to the Red Planet.

"This Scout selection will serve as a trailblazer for what we plan to be a continuing line of a small, yet exciting, class of Mars missions," said Orlando Figueroa, Director for the Mars Exploration Program at NASA Headquarters, Washington.

"These four outstanding proposals represent innovative ideas for exploring Mars on a modest budget to answer several priority questions about the Red Planet," said Dr. Ed Weiler, Associate Administrator for Space Science at NASA Headquarters. "I'm very pleased that this competition produced such a wide range of incredibly exciting ideas and I congratulate all members of the science teams involved," he said.

Following detailed mission-concept studies, due for submission by July 2003, NASA intends to select one of the mission proposals by August 2, 2003, for full development as the first Mars Scout mission. The mission developed for flight will be launched in 2007.

The selected proposals were judged to have the highest science value among 25 proposals submitted to NASA in August 2002 in response to the Mars Scout 2002 Announcement of Opportunity. Each will receive up to $500,000 to conduct a six-month implementation feasibility study focused on cost, management and technical plans, including educational outreach and small business involvement.

"Each of the selected missions pursues some of the greatest unknowns about potential biological activity on Mars, including such issues as the presence of organic molecules or their byproducts," said Dr. Jim Garvin, NASA's Lead Scientist for Mars Exploration in Washington.

The selected mission concepts, and the Principal Investigators, are:

• SCIM (Sample Collection for Investigation of Mars): Professor Laurie Leshin, Arizona State University, Tempe. This innovative mission would sample atmospheric dust and gas using aerogel and use a "free-return trajectory" to bring the samples back to Earth. Such samples could provide breakthrough understanding of the chemistry of Mars, its surface, atmosphere, interior evolution and potential biological activity.
  
  
• ARES (Aerial Regional-scale Environmental Survey): Dr. Joel Levine, NASA Langley Research Center, Hampton, Va. ARES offers to provide the first in situ measurements of the near- surface atmospheric chemistry within the Mars planetary- boundary layer, thereby providing critical clues to the chemical evolution of the planet, climate history, and potential biological activity.
  
  
• Phoenix: Dr. Peter Smith, University of Arizona, Tucson. This mission proposes to conduct a stationary, in situ investigation of volatiles (especially water), organic molecules and modern climate. It aims to "follow the water" and measure indicator molecules at high-latitude sites where Mars Odyssey has discovered evidence of large ice concentrations in the Martian soil.
  
  
• MARVEL (Mars Volcanic Emission and Life Scout): Dr. Mark Allen, NASA Jet Propulsion Laboratory, Pasadena, Calif. This mission proposes to conduct a global survey of the Martian atmosphere's photochemistry to search for emissions that could be related to active volcanism or microbial activity, as well as to track the behavior of water in the atmosphere across a full annual cycle.

The Mars Scout competition is designed to augment or complement, but not duplicate, major missions being planned as part of NASA's Mars Exploration Program or those under development by foreign space agencies. The selected Scout science mission must be ready for launch before December 31, 2007, within a total mission cost cap of $325 million.

The Mars Scout Program is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for the Office of Space Science, Washington.