From the October 2007 Scientific American:
To a child of the Space Age, books about the solar system from before 1957 are vaguely horrifying. How little people knew. They had no idea of the great volcanoes and canyons of Mars, which make Mount Everest look like a worn hillock and the Grand Canyon like a roadside ditch. They speculated that Venus beneath its clouds was a lush, misty jungle, or maybe a dry, barren desert, or a seltzer water ocean, or a giant tar pit—almost everything, it seems, but what it really is: an epic volcanic wasteland, the scene of a Noah’s flood in molten rock. Pictures of Saturn were just sad: two fuzzy rings where today we see hundreds of thousands of fine ringlets. The giant planet’s moons were gnats, rather than gnarled landscapes of methane lakes and dusty geysers.
All in all, the planets seemed like pretty small places back then, little more than smudges of light. At the same time, Earth seemed a lot larger than it does now. No one had ever seen our planet as a planet: a blue marble on black velvet, coated with a fragile veneer of water and air. No one knew that the moon was born in an impact or that the dinosaurs died in one. No one fully appreciated that humanity was becoming a geologic force in its own right, capable of changing the environment on a global scale. Whatever else the Space Age has done, it has enriched our view of the natural world and given us a perspective that we now take for granted.
Since Sputnik, planetary exploration has gone through several waxing and waning phases. The 1980s, for instance, might as well have been the dark side of the moon. The present looks brighter: dozens of probes from the world’s space programs have fanned out across the solar system, from Mercury to Pluto. But budget cuts, cost overruns and inconsistency of purpose have cast long shadows over NASA. At the very least the agency is going through its most unsettled period of transition since Nixon shot down the Apollo moon missions 35 years ago.
“NASA continues to wrestle with its own identity,” says Anthony Janetos of the Pacific Northwest National Laboratory, a member of a National Research Council (NRC) panel that scrutinized NASA’s Earth observation program. “Is it about exploring space? Is it about human exploration, is it about science, is it about exploring the outer universe, is it about exploring the solar system, is it about the space shuttle and station, is it about understanding this planet?”
In principle, the upheaval should be a happy occasion. Not only are robotic probes flying hither and yon, the human space program is no longer drifting like a spent rocket booster. President George W. Bush set out a clear and compelling goal in 2004—namely, to plant boots in lunar and Martian soil. Though controversial, the vision gave NASA something to shoot for. The trouble is that it quickly turned into an unfunded mandate, forcing the agency to breach the “firewall” that had traditionally (if imperfectly) shielded the science and human spaceflight programs from each other’s cost overruns.
“I presume it is not news to you that NASA doesn’t have enough money to do all the things it’s being asked to do,” says Bill Claybaugh, director of NASA’s Studies and Analysis Division. Cash doesn’t exactly flow like liquid hydrogen at space agencies in other countries, either.
NRC panels periodically take a step back and ask whether the world’s planetary exploration programs are on track. The list of goals that follows synthesizes their priorities.
1 Monitor Earth’s Climate
Amid all the excitement of buggying around Mars and peeling back the veil of Titan, people sometimes take the mundane yet urgent task of looking after our own planet for granted. NASA and the National Oceanic and Atmospheric Administration (NOAA) have really let it slide. In 2005 Janetos’s NRC panel argued that the “system of environmental satellites is at risk of collapse.” The situation then deteriorated further. NASA shifted $600 million over five years from Earth science to the shuttle and space station. Meanwhile the construction of the next-generation National Polar-Orbiting Operational Environmental Satellite System ran seriously over budget and had to be downsized, stripping out instruments crucial to assessing global warming, such as those that measure incoming solar radiation and outgoing infrared radiation.