Updated

NASA has delayed two programs that search for planets capable of supporting life as the space agency instead focuses on developing a new manned spacecraft to return to the moon in the next decade.

The delayed SIM PlanetQuest and Terrestrial Planet Finder missions, managed by NASA's Jet Propulsion Laboratory, aim to determine whether there are Earth-like planets beyond our solar system with conditions suitable for life or developing in that direction.

President Bush's budget proposal released Monday seeks to give the National Aeronautics and Space Administration $16.8 billion for fiscal year 2007, a 3 percent increase from the year before. Of that, about $5.3 billion in funding will go toward the space agency's science missions.

NASA is trying to fulfill Bush's space exploration vision to build the new Crew Exploration Vehicle that would replace the aging space shuttle fleet and enable a return to the moon by 2018. NASA Administrator Michael Griffin told a news conference that the budget reflects that priority.

Under the proposed budget, the SIM PlanetQuest project would receive $98.5 million in fiscal year 2007, but its original launch date of 2011 was pushed back to no earlier than 2015.

The goal of SIM is to measure the distances and positions of stars to locate Earth-like planets out to 100 light years away using a technique called interferometry where light from multiple telescopes is combined to create images.

The dual Terrestrial Planet Finder telescopes, originally scheduled to lift off in 2016 and 2019, will use the information by SIM to photograph those planets to look for evidence of life. That program has been indefinitely postponed.

Geoffrey Marcy, an astronomer at the University of California, Berkeley, and an investigator for SIM, expressed disappointment that "our society can't put more resources into answering the glorious question of whether we humans are alone in this universe."

Despite the delays, other JPL-managed projects including sending the next generation of spacecraft to roam Mars remain on track.

The NASA budget allocated $90.5 million toward the launch of Phoenix Mars lander in 2007. The stationary probe will land on Mars' north pole and use its robotic arm to dig into the icy terrain for signs of water.

Another $348 million went to the Mars Science Laboratory, which will roam the Red Planet collecting soil samples and rock cores for analysis. The Mars Science Laboratory is scheduled to launch in 2009.

The Pasadena-based NASA center, which laid off about 300 workers last year as part of an agency-wide cut, said its workforce will remain stable in light of the proposed budget. The center currently has about 5,000 workers.