An artist's concept of large extrasolar planet. Photo: Greg Bacon, STScI

On beat with its "faster, better, cheaper" rhythm, NASA on Thursday announced the selection of three proposed low-cost missions for further in-depth study, including one that seeks to find habitable planets outside our solar system.

Ranging from asteroids, Jupiter's atmosphere and detecting distant planets, one of the chosen three will be approved later this year for development and a mid-decade launch.

The trio of possible Discovery missions were chosen from among 26 proposals that were submitted to NASA from various scientific organizations in August. A team of scientists and engineers has been assigned to each would-be space probe to study the feasibility of such missions to see if the plan for each mission would work. Each group will get $450,000 in funding from NASA during the upcoming four-month study period.

The selected missions include an asteroid-orbiting mission called Dawn that would circle two of the solar system's largest asteroids -- Vesta and Ceres. The two space rocks to be probed by the $271 million, UCLA-led mission have very different backgrounds, thus making the mission ideal for looking back into the early years of the solar system.

Another probe in this batch of proposed Discovery missions includes a Jupiter orbiter called the Interior Structure and Internal Dynamical Evolution of Jupiter spacecraft, or "INSIDE Jupiter" for short. The most expensive mission of the group at $296 million, this JPL-headed craft would look into the atmosphere of the gas giant to study the internal structure and processes of the planet.

A drawing of the proposed Kepler spacecraft. Photo: NASA-Ames

A space telescope named Kepler rounds out the tri-fecta of proposals, and its mission is to seek out extrasolar planets around the same size as Earth in orbits around nearby stars. By monitoring 100,000 stars over a four-year mission, Kepler could detect up to 500 Earth-sized planets and up to 1000 Jupiter-sized planets. The mission would be the first NASA probe to be fully focused on the search for planets outside our solar system. Kepler would cost NASA $286 million and would be led by the NASA Ames facility.

An extra program, officially deemed a Mission of Opportunity, includes a previously planned U.S. commitment to the French NetLander mission, set for touchdown on Mars in 2007. NASA will build a wind sensor and seismometers on each of the four landers in the mission, as well as a geodesy instrument on the orbiter of the mission for a total cost of $35 million.

"The diversity of science represented in these three mission proposals is outstanding. NASA will have its hands full picking only one for flight," said Dr. Jay Bergstralh, acting Director of Solar System Exploration at NASA Headquarters in Washington.

A launch date for the main Discovery Program mission that is selected is set for no later than September 30, 2006.

The three missions are part of NASA's Discovery Program, which utilizes small, focused missions that feature a cost to NASA of no more than $299 million. The goal of the program is to have a launch of a Discovery mission at least once every two years.

The program already such successful missions as the NEAR Shoemaker probe currently orbiting asteroid Eros, the Mars Pathfinder mission of 1997 and Lunar Prospector. Four more Discovery missions have been selected and will launch in the next few years. One so-called Mission of Opportunity has been selected as well; NASA will place an experiment on ESA's Mars Express orbiter, which is due for launch in June of 2003.