US scientists awe-struck by Soviet space-exploration plans. Pasadena meeting also produces hints of cooperation in future

The Soviet Union is throwing down the gauntlet to the rest of the world in the area of exploration of the solar system. It is moving ahead with plans to send unmanned missions to Mars and other parts of the solar system at a pace that is producing both awe and anxiety among scientists in the West.

While the general outlines of the Soviets' Mars missions have long been known, fresh details have emerged on the scale and timing of their program. It includes plans to send up to eight unmanned spacecraft to the red planet within the next decade. (America needs balanced space program, Page 25.)

The Soviet launches would start in 1992 and culminate before the turn of the century with the return of rocks and soil samples - one of the most coveted prizes in planetary exploration.

One knowledgeable United States space scientist, after hearing details of the Soviet plan, called it not so much a program as an ``assault.''

And Bruce Murray, a planetary scientist at the California Institute of Technology (Caltech), says: ``It would be by far the biggest science mission flown by any nation, ever.''

The Soviet plans were outlined at a meeting here last week on solar system exploration sponsored by the American Institute of Aeronautics and Astronautics and Caltech's Jet Propulsion Laboratory (JPL). It drew top space officials from around the world.

The meeting was considered significant for several reasons. One was what US scientists call the ``unprecedented'' degree of openness by the Soviet delegation, which included the first visit to the United States by Roald Kremnev, who oversees the USSR's unmanned spacecraft activities and is a top official in the country's scientific establishment. American scientists say the Soviets have been more forthcoming about their plans in recent years, but that the practice seems to have accelerated under the glasnost (openness) policy of Soviet leader Mikhail Gorbachev.

Second, and more important, is what the Soviets revealed about their planned assault on Mars.

Plans currently call for sending two spacecraft, probably in 1992, to explore the planet. The mission would include balloons that would drift around the atmosphere during the day and land on the surface in the cool of night.

It may also include a small, automated vehicle that would roam the surface.

US scientists say what's new here is the possible 1992 launch date (the Soviets were looking at 1994) and the possible use of a rover.

This mission, however, would just be a precursor to the far more ambitious launches in 1996 or 1998 intended to bring back a sample from Mars. According to Soviet scientists, these might involve two sets of two launches (the Soviets conduct parallel launches to provide backup in case one rocket fails) or four launches at once. The Soviets are also considering putting a large rover on the planet.

These double shots would involve launching more than 60,000 pounds of scientific equipment, instruments, and fuel into space. ``That's more than the US has put into planetary missions in total,'' says Dr. Murray.

The announcement of Soviet plans comes at a time when the US space program has been set back several years because of the Challenger disaster and budgetary restrictions continue to hamper plans to explore the solar system. The National Aeronautics and Space Administration (NASA) has announced, however, that the Magellan Venus Radar Mapper will be launched in 1989 as planned. It had been threatened with a two-year delay.

On the other hand, a modest Mars atmospheric probe that JPL scientists were hoping to launch around 1990 doesn't look like it will make it before its previously planned 1992 liftoff.

At present, US scientists are hoping to launch a sample-return mission to Mars in 1998. That mission, however, is still in the earliest planning stages.

``The upshot of all this is that the Soviets have made a major commitment to a Mars sample return, and we're still trying to develop what we should do,'' says John Casani, head of JPL's Galileo project, which hopes to send a spacecraft toward Jupiter in 1989.

Like the US space program, the Europeans' is struggling to get back on its feet after the failure last year of an Ariane rocket. Buoyed by their successful encounter with Halley's comet last year, however, European scientists are putting a high priority on visiting another comet as part of their budding interplanetary exploration program. The Japanese, meanwhile, are just beginning to outline a modest space-exploration program.

Though separate programs are being fashioned, there is a growing call for cooperation among spacefaring nations. Scientists contend that planetary exploration is too risky and costly, and the expected benefits too large, to pursue individually.

``International cooperation in solar system exploration is essential,'' says Burton Edelson, a former NASA official.