NASA's current plan for manned space exploration focuses on establishing a base on the moon, as a vital stepping stone for a visit to Mars. The initiative has been trumpeted by the Bush administration, which wants the first mission to launch by 2020. But trouble is brewing as a growing group of former mission managers, planetary scientists and astronauts argues against any manned moon mission at all. One alternative, they say: Send astronauts to an asteroid as a better preparation for a Martian landing.

In January 2004 President Bush announced his plan to send Americans back to the moon and onto Mars. Those bold goals—which NASA estimates it could achieve by 2018 and 2030, respectively—would at last free the nation of the 25-year drudgery of the shuttle program. The idea raised eyebrows--not least because of its price tag, distant target dates and suspicious initial timing, at the start of the 2004 election cycle. In the two years since, however, funding has been forthcoming and design work has begun, with aerodynamic testing on scale models under way at the Marshall Space Flight Center in Huntsville, Ala. While political and fiscal obstacles could still scuttle the whole plan, the ships taking shape in the NASA labs are winning deserved raves.

(CNN) -- NASA Administrator Michael Griffin rolled out NASA's plan for the future Monday, including new details about the spaceship intended to replace the shuttle and a timeline for returning astronauts to the moon in 2018.

MOSCOW - Rivals for lunar conquest four decades ago, Russia hopes to join the U.S. moon exploration program with technology and know-how, a Russian space agency spokesman said Thursday.