Why probe the planets? A new rationale

Man's quest into the solar system may be more down to earth in the years ahead.

Planetary probes were once driven by a thirst to know the unknown, to explore the unexplored. But in the future they may well be fueled by a need to begin using what scientists have learned from the planets to help solve such pressing earthbound problems as changing climatic conditions.

That, at least, is the prediction of Bruce Murray who, as head of the Jet Propulsion Laboratory here, has spent the past six years overseeing the nation's unmanned space shots -- and who recently announced he will step down from his post later this year.

''Inner solar system research may well have more of a utilitarian flavor,'' said Dr. Murray in interview with the Monitor shortly after announcing his decision to resign.

''It will also be a unifying, internationalizing thing, because all the people on Earth have a stake in the Earth's climate change and in understanding it,'' he continued. ''By the year 2000, I believe it will be a national imperative of many countries in the world to really understand the total set of physical factors, both man-made and natural, that influence the global climate. Because there's an awful lot at stake.''

Murray, like many other scientists, believes that the polar regions of Mars may contain important geological records that will help man understand short-term and long-term climatic changes, particularly those relating to changes in the Earth's atmosphere.

A similar utilitarian push may also be a factor if the United States ever decides to launch another mission to the moon, says Murray. No such missions are now in the offing, but Murray suggests that the US may someday explore the moon with an eye to establishing bases there.

''The issue of potential resources or potential utilization of the moon will be a driver,'' he predicts. ''The next round of lunar missions will carry a component that is related to potential utilization, not just pure scientific exploration.''

Murray's predictions represent a marked change from the philosophy that powered the US planetary program through its stupendous years of discovery in the 1960s and 1970s. It is a change wrought, in large part, by the Reagan administration's substantial cutbacks in the planetary program.

Murray's resignation announcement, in fact, was met with widespread speculation that the act was one of discouragement -- prompted by the current bleak outlook for planetary exploration. Although the JPL chief admits ''there has been a lot of personal emotion and turmoil,'' he insists he never intended on staying longer than five to 10 years. And he makes it clear that he is parting with JPL on a decidedly optimistic note.

Significantly, says Dr. Murray, although many proposed planetary projects were lost in budget battles, JPL succeeded in saving the late-1980s Galileo mission to Jupiter. That means, he says, ''the outer planets program will be going through this decade. The flywheel is still turning.''

He also points with satisfaction to the charting of a new course for JPL. In the face of declining government support for the civilian space program - a decline which many worried would induce JPL's highly trained specialists to look for jobs in the private sector - Murray pushed for, and received, permission to seek Department of Defense contracts accounting for up to one-third of JPL's work. That work will include satellite projects and helping the Army design automated battlefields, where perilous roles will be filled by machines, not soldiers.

Despite this partial shift in JPL's focus, however, Dr. Murray says the US should not overlook three major areas of solar system exploration: discovering what the cloud-cloaked surface of Venus looks like, exploring comets, and studying asteroids that cross the Earth's orbit.

''We have to rebuild some kind of a more modest inner-planet program,'' he says, ''but clearly, we're not going to dominate the inner planets the way we did. I believe that program will be more internationalized because we're no longer top dog. And that's not all bad.''