WASHINGTON -- A spaceborne telescope to detect Earth-sized planets around other stars. A spacecraft to orbit Jupiter and study the giant planet's internal structure. And a mission to circle two of the largest asteroids in the solar system.

NASA announced today several candidate low-cost Discovery missions, culling through over two dozen proposals that were submitted to the space agency last August.

Also included in the prospective Discovery missions selected, NASA has given a go-ahead to fund American participation in a 2007 mission to Mars. The French and Italian space agencies will team with NASA for this project.

The French-led NetLander mission is to create the first science network on Mars to study the Red Planet's internal structure. The U.S. will contribute seismometers and wind sensors on the landers. W. Bruce Banerdt of the Jet Propulsion Laboratory (JPL) in Pasadena, California will lead U.S. involvement in the French Mars project.

Today's trio of Discovery-class candidates:

• The Kepler mission is a space telescope specifically designed to detect Earth-sized planets around stars in the Sun's neighborhood of the galaxy. Some 100,000 stars over Kepler's four-year mission are to be scanned. The spaceborne observatory could detect up to 500 Earth-sized planets and up to 1,000 Jupiter-sized planets. William Borucki of NASA's Ames Research Center near San Francisco, California will lead the Kepler mission.
• The Interior Structure and Internal Dynamical Evolution of Jupiter (INSIDE Jupiter) mission would study how planetary systems originate and evolve, as well as how both physical and chemical processes determine the characteristics of the planet. Edward Smith of JPL will lead INSIDE Jupiter;
• The Dawn mission intends to orbit the asteroids Vesta and Ceres. Each space rock is expected to be very different in composition. Christopher Russell of the University of California at Los Angeles would lead Dawn.

Following detailed studies of each of the new candidate Discovery missions, NASA will pick one of the three proposals late in 2001 for full development. The selected mission should be launched around 2005 or 2006.

Early Discovery-class spacecraft include the Stardust mission now en route to comet Wild 2; the Lunar Prospector; the Mars Pathfinder and Sojourner mini-rover; the Near Earth Asteroid Rendezvous (NEAR) craft now orbiting asteroid Eros; along with the still-to-fly Contour, Genesis, Messenger and Deep Impact missions.

Among the proposals not selected, NASA elected not to support projects to further explore the Moon and Venus.