So much in our vast universe seems hopelessly faraway, but with NASA's FY2007 budget even relatively close planetary neighbors like Mars and Europa now seem more distant. The venerable space agency's cancellation of so many robotic exploration and observation projects dawns as a dark day for space science. It is sadly ironic, considering that a hefty 76 percent increase to $3.06 billion has been allotted for the long-term manned spaceflight initiative. This bodes well for the future of American manned space exploration. But the price has been high, way too high.

Most salient among the robotic mission cuts is the Europa exploration program that had been given the highest priority solar system science objective after Mars by the National Academy of Sciences and NASA advisory committees. And even planetary exploration's job-one that has seen the Martian landscape increasingly covered with rover tracks was also not immune: NASA's Red Planet research budget has been cut by $243.3 million to $700.2 million. This includes the cancellation or indefinite postponement of projects such as the Mars Sample Return Mission and the Mars Telecommunications Orbiter.

Not only did planetary geology suffer, but so did astronomy: Also delayed indefinitely was the Terrestrial Planet Finder (TPF) slated to detect and study Earth-like planets and, lest we still could get excited about discovering extrasolar planets, NASA also delayed by about three years the Space Interferometry Mission (SIM), set to map stars and also search for sister worlds; it will now launch no earlier than 2015. The list goes on and on. The most egregious budget lines are the two surviving programs that are being maintained on billions of dollars of life support—the space shuttle and the International Space Station (ISS). A question: In NASA's budgetary calculus, is it necessary or logical to maim the successful, scientifically productive and visionary part of the space program to feed the cost overruns of the Shuttle/ISS programs, the former of which is scheduled to be canceled in 2010 anyway? Put more metaphorically, this concern was voiced by Rep. Sherwood Boehlert (R–N.Y.), chairman of the House Committee on Science when he said that "Science funding should not be taking a backseat to operational programs that have much less impact. We have to be sure that we are not demonstrating that science is a 'crown jewel' of NASA by seeing how much we can get for it at the pawnshop."

There is no easy way to quantify the science returned by the robots, but there's no question it goes way beyond what the shuttle and ISS can do. Despite some nominal science done on some shuttle missions, and its invaluable employment to place and maintain in orbit one of the most productive telescopes in observatory astronomy, the Hubble Space Telescope, it is not much of a scientific or space exploration system. And as for the science output past, present and future on the ISS, only few scientists would consider it on the positive side of cost versus benefit.

So in trekking through Washington's lunar-cold budgetary landscape, NASA obviously had to make some hard decisions. We will go on with manned missions, our goal to return to the moon and then on to Mars. This is good, very good. But first there is that little hurtle: we have got finish up the shuttle program, which, apart from fixing Hubble, serves no greater purpose except to service and complete the ISS as it circles above, on its way to where it was 90 minutes ago, waiting to be completed in 2010 and probably decommissioned by 2016 (unless it is taken over by our international partners). No matter what the station's fate, the U.S.'s budgetary dedication to its science return is far from certain; it hasn't even been determined at this time if the crew will ever be larger than three.

Compare this to the robotic missions. Besides heavy science, there's the wonderment of it all. We go places with these probes. I'll always remember watching coverage at 2 a.m. in August 1989 when Voyager 2 sent back those first images of Neptune in all its stormy, azure glory. Or when Pathfinder unfolded its petals and as the predecessor of those two amazing rovers that still rove, took its first tentative sniff of Martian dirt since the more aggressive Vikings poked and prodded the Red Planet to stir up any lurking alien biology in the 1970s. And it is amazing to me to think that while we were concentrating on getting humans to the moon and back, we were also tossing off all sorts of flybys and landers that lived up to their ambitious names—Mariner, Ranger, Surveyor and Pioneer. They ventured to the moon and the planets, not as a sideshow, but rather, it seemed, as a vanguard for manned exploration to come in the ensuing decades.

There is no need to get into why and how human spaceflight got bogged down in LEO, but as for robotic missions, it seemed there was never a lack of vision at NASA, or at JPL, APL, etc. Let's see: we have 1970s-era spacecraft at the cusp of our solar system that continue to dutifully report back science data and are on the verge of exploring the heliopause. We have recently landed on an asteroid; mussed up another comet with an impactor; and soft-landed in Utah a scoop of over 4 billion-year-old primordial cometary detritus. Not to forget Galileo's extensive tour of the Jovian system. We have recently launched explorers named Messenger and New Horizons, which are zipping to opposite ends of the solar system—the former to orbit searing Mercury and the latter to flirt in a flyby with dark and frozen Pluto then forge on to the new territories of the Kuiper belt. We have seen the sun's polar regions with Ulysses, rely on regular space weather reports from SOHO and have been tantalized by Cassini-Huygens's glimpse through Titan's smoggy veils at its eerily earthly coastlines.

Budgetary threats to some of our greatest projects have almost become ritual, but we cannot assume there will be any public clamor or congressional saviors. Perhaps imaginative and innovative planning by NASA will be the way to save all this priceless science while maintaining NASA's international obligations. If there is anything worse than throwing good money after bad, it is taking it from the best.

Update: Among the other voices decrying this decision by NASA to "cannibalize" the agency in order to scrape together tight budget money for the shuttle and ISS are Wesley T. Huntress, Jr., and Louis Friedman of the Planetary Society. Read their forceful and articulate commentary here.