An American spacecraft 44 million miles from Earth intercepted a comet for the first time today and raced harmlessly through its gaseous, 14,000-mile-wide tail in 18 minutes, finding many surprises that may force scientists to revise their textbooks.
The five-foot-long robot craft, traveling at 46,000 m.p.h., sliced into the glowing tail of Comet Giacobini-Zinner at 3:53 a.m. PDT and emerged unscathed 18 minutes later, climaxing a billion-mile, seven-year voyage.
“It’s another of those firsts that this country enjoys making,” said NASA Administrator James Beggs, who was on hand at the Goddard Space Flight Center for the event. “It is significant indeed and we’re proud of it.”
Accelerates Charged Particles
One big surprise from the initial preliminary results radioed back was that the comet is very active from a space physics standpoint and is able to accelerate electrically charged particles.
“We’re quite at a loss to understand what’s going on,” said Fred Scarf, a physicist from TRW Inc. in Redondo Beach, Calif. “We thought of a comet as a rather benign object. It turns out to be extremely active.”
The probe’s passage through the tail, which was expected to take only five minutes, indicated that the tail is 14,000 miles thick--three times what was anticipated.
“Mankind’s first encounter with the comet has to be ranked as an unqualified success,” said Edward Smith of the Jet Propulsion Laboratory in Pasadena, Calif.
“The data are full of surprises,” he said. “I think it’s going to cause people to rethink what’s going on (regarding comets).”
Concern for Survival
There was considerable concern that the craft, called the International Cometary Explorer, or ICE for short, might not survive the encounter, but project scientist Tycho von Rosenvinge said the probe reported no evidence of any dust impacts, the primary concern.
“I’m very pleased that we’re still alive,” flight director Robert Farquhar said.
The first indication that the probe was nearing the tail came when instruments aboard the spacecraft detected a strong magnetic field. That in itself was a major discovery.