WASHINGTON - The launch of NASA's Dawn spacecraft, a mission that will explore the two largest objects in the asteroid belt in an effort to answer questions about the formation of our solar system, has been rescheduled to September.

The decision was made today to move the launch to September after careful review by NASA's Science Mission Directorate officials, working with Dawn mission managers, the Dawn principal investigator, and with the concurrence of the NASA Administrator.

Primary reasons for the move were a combination of highly limited launch opportunities for Dawn in July and the potential impact to launch preparations for the upcoming Phoenix Mars Lander mission, set for early August. A September launch for Dawn maintains all of the science mission goals a July launch would have provided.

NASA will hold a news briefing at 11:30 a.m. EDT on Monday, July 9, to preview the launch of the Phoenix Mars Lander. Prior to the Phoenix presentations, media will have the opportunity to learn in more detail about the rescheduled Dawn launch. The briefing will originate from the NASA Headquarters auditorium, 300 E St., S.W., Washington. It will air live on NASA Television and be streamed online at:

http://www.nasa.gov/ntv

The Phoenix mission, scheduled for liftoff in early August from Cape Canaveral Air Force Station, Fla., will examine whether the icy soil on Mars could have been a habitable environment for microbial life.

For more information about the Phoenix mission, visit:

http://www.nasa.gov/phoenix

For more information about Dawn, visit:

http://www.nasa.gov/dawn