After journeying for a decade and about 6.4 billion kilometers through the solar system, the Rosetta spacecraft on Wednesday became the first in history to rendezvous with a comet, marking a milestone in space exploration and big moment for European science.
Rosetta and the comet are now hurtling along at nearly 55,000 kilometers (34,000 miles) an hour, locked in a common orbit around the sun, some 405 million kilometers from Earth, according to the European Space Agency, which masterminded the mission. The comet’s 6½-year orbit will eventually take it far beyond Jupiter, and Rosetta will accompany it for a year on that journey.
“We are delighted to announce finally ‘we are here,'” said Jean-Jacques Dordain, ESA’s director general.
The mission is a significant test of Europe’s spacefaring ambitions. Scientists had to plan the 10-year trip in minute detail. Orbiting and landing on a comet, whose surface properties are largely unknown, is no easy task either. The comet is small—about 4 kilometers in diameter—and irregularly shaped. Its gravity is hard to predict.
More than scientific credibility is at stake. The mission has cost €1.3 billion ($1.74 billion), including the launch, the spacecraft and the various instruments on board. Contractors from 14 European countries and the U.S. were involved in the industrial aspects of the project.
Wednesday’s maneuver, which was accomplished by firing rocket thrusters on the spacecraft, has brought Rosetta within a mere 100 kilometers of the target. “After the maneuver we’ll be at a walking pace alongside the comet,” said Matt Taylor, project scientist at ESA.
The scientists hope to release a small lander onto the icy nucleus in November. At that stage, the mothercraft will itself be in close orbit of the comet, about 30 kilometers above its surface. That will allow an unprecedented view of how the comet changes as it approaches the increasing intensity of the sun’s radiation. It is expected to develop a typical “coma”—gaseous material boiled off the comet’s icy nucleus—and two characteristic ion and dust tails.
With Rosetta now locked in early-stage orbit around the comet, ESA scientists are awaiting the first of many several images offering a close-up view of the surface of the comet, known 67P/Churyumov-Gerasimenko.
Comets are primitive visitors from the outer reaches of the solar system, and they carry vital chemical clues about how our solar system was created and how it evolved. So scientists are salivating at the opportunity to embark on a lengthy exploration of 67P from close quarters.
Rosetta may not be much more than a big black box but it is bristling with scientific instruments and 11 experiments. On board are devices that will study the comet’s dust, take high-resolution images of its nucleus and study the materials of which it is composed.
Images taken from a distance of about 12,000 kilometers suggested that comet comprised two segments joined by a “neck,” giving it a duck-like appearance. It isn’t clear that means 67P was a single comet that was eroded into this unusual shape, or whether it was the result of two separate comets coming together.
The scientists hope to identify five possible landing sites by late August, and identify the best one by mid-September.
Source: Wall Street Journal
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