(9 of 10)
The flood of data from Pioneer 10's different instruments will require weeks and even months of detailed analysis, but project scientists last week had already made some preliminary conclusions. For one thing, Jupiter's magnetic field—only about ten times stronger than the earth's—follows what the scientists variously dubbed a "Saturn ring" and "Hula-Hoop" model; that is, the lines of magnetic force seem to stretch outward near the equator but are more rounded at the poles. The average temperature of Jupiter's cloud tops is somewhat above 200°F. with no apparent variations on the day and night sides; this fact tends to confirm the widely accepted idea that Jupiter—which is so large that it barely missed generating its own nuclear fires and becoming a star —is giving off some internal heat. There was also additional proof of Jupiter's powerful gravity. During the brief flyby, Pioneer was suddenly hit by ten tiny meteoroids, after a rate of only one hit every 25 days during its journey; this indicated that the Jovian gravitational field scoops up and concentrates the particles as the planet whirls round the sun.
To the chagrin of Pioneer's photographic team, there was a loss of several close-up pictures, including one of the Jovian moon lo, an object of particular interest to astronomers because of its extraordinary brilliance. But other data and the color shots of Jupiter, including a closeup of the Red Spot during the flyby, fully met expectations.
After the Jupiter flyby, astronomers —including the Skylab astronauts —turned their attention back to Kohoutek. "She's still coming at us," reported Skylab Commander Gerald Carr, noting that the fuzzy blob was getting bigger all the time. In the weeks ahead, the Skylab crew will keep Kohoutek under virtually constant watch in order to spot any structural changes in the comet as quickly as possible. The astronauts will also lug some of their cameras outside to get the best possible pictures during three space walks—on Christmas Day just before the comet ducks behind the sun, on Dec. 29 after it reappears, and again just before the end of the mission in February.
Bit of Luck. Skylab's presence in orbit during the comet's passage is an incredible bit of luck. If the comet had arrived a month or so later, or Skylab had been launched only slightly earlier, the space station would not have been available for the important observations. Says Astronaut-Scientist Karl Henize: "All through the space program, we've been looking for a Rosetta stone—what is the primordial material out of which the solar system is made? We looked for it on the moon and we didn't find it; we found other things instead. Now we're down to our last chance—the comets. It's something of a miracle that we have Skylab up there just when a bright comet like Kohoutek comes along."