ONLY 12 ASTRONAUTS set foot on the moon in half a dozen landings between 1969 and 1972¿here Apollo 11¿s Buzz Aldrin shows off his boot. A new NASA plan calls for sending astronauts back to the moon by 2020, but some critics doubt the feasibility of the scheme. Image: NASA
When President George W. Bush declared in January that NASA would set its sights on returning astronauts to the moon by 2020, scientists quickly lined up on opposing sides. Although Bush's plan promises more funding for researchers studying the moon and Mars, other branches of space science are already feeling the pinch. The most prominent loser by far is the Hubble Space Telescope. Just two days after the president presented his initiative, NASA announced that it would cancel a shuttle flight to install new gyroscopes, batteries and scientific instruments to the Hubble. If NASA does not reverse the decision, its premier space observatory will cease operating when its current equipment fails in the next few years.
The problem arises from the Bush administration's strategy of financing the moon effort through the early retirement of the space shuttle. During the phaseout, targeted for 2010, much of the shuttle's $4-billion annual budget will be shifted toward designing a crew exploration vehicle that could take astronauts to the moon. In the meantime, shuttle missions will focus on assembling the International Space Station.
NASA officials insist that they canceled the Hubble mission strictly because of safety concerns. To prevent a repeat of last year¿s Columbia catastrophe, NASA will require all shuttles to dock with the space station, where astronauts can inspect and repair damage to the vehicles or, if necessary, await a rescue effort. A shuttle bound for the space telescope would not be able to rendezvous with the station. But two reports written by a dissenting NASA engineer, who declined to be identified for fear of losing his job, claim that the agency could perform the Hubble mission safely by developing alternative repair methods and preparing a rescue mission in advance.
Although ground telescopes equipped with adaptive optics can match Hubble¿s resolution, they cannot duplicate all of the space telescope¿s abilities. For example, Adam G. Riess, an astronomer at the Space Telescope Science Institute, notes that ground telescopes cannot accurately measure the brightness of distant type Ia supernovae, which are used to gauge the expansion history of the universe [see "From Slowdown to Speedup," by Adam G. Riess and Michael S. Turner; Scientific American, February]. "It¿s frustrating," Riess says. "It will be a long while before we have a way of doing this science again."
The biggest winners are the lunar geologists, who argue that the Apollo missions left many questions unanswered and that continued exploration of the moon could reveal much about the evolution of the solar system. The Bush plan earmarks $1.3 billion for unmanned missions to the moon over the next five years, including a lunar orbiter to be launched by 2008 and a robotic lander scheduled for 2009. Although both craft would pave the way for manned missions¿by investigating potential landing sites, for in-stance¿ they would also provide researchers with a treasure trove of new data. "The moon is still mostly unexplored," says Alan Binder, the principal investigator for the Lunar Prospector orbiter that studied the moon in the late 1990s. "So lunar science can make a giant leap forward."
In some ways, planetary scientists know more about Mars than they do about the moon. The orbiters sent to the Red Planet in the past few years have thoroughly mapped its topography and mineralogy; in comparison, the moon maps obtained by Lunar Prospector and the earlier Clementine spacecraft are fuzzy and incomplete. The 2008 lunar orbiter could fill in the gaps by charting the moon¿s surface with radar imaging, laser altimetry and high-resolution spectroscopy. One probable goal of the mission will be to carefully delineate the permanently shadowed areas at the moon¿s poles, where some scientists believe that bits of water ice may be mixed in with the lunar dirt.
James Head, a planetary geologist at Brown University, hopes that the 2009 mission to the lunar surface will be the first in a series of unmanned landers. That craft may well carry a robotic rover similar to the Spirit and Opportunity vehicles that are now roaming the Martian surface. The moon mission, though, is more likely to be focused on applications that will aid human spaceflight¿ such as finding ice and learning how to extract it for life support or to produce rocket fuel by breaking the water into liquid hydrogen and oxygen.