LIKENED in shape to a giant rubber duck speeding towards the Sun at 34,000mph, Comet 67P Churyumov-Gerasimenko has journeyed alone for 4.6 billion years. Tomorrow, it will get a companion as a small, boxy spacecraft becomes the first to enter a comet’s orbit and chase alongside.
Rosetta, an unmanned probe managed by the European Space Agency, has journeyed four billion miles through deep space to catch up with the comet, a so-called “dirty snowball” of ice, rock and dust left over from the formation of the universe 4.6 billion years ago.
Tomorrow’s rendezvous, which will involve mission controllers in Germany sending commands to slow Rosetta’s speed and drop it into a triangular orbit around the comet, will be the culmination of two decades of work by scientists.
“It’s incredibly exciting to go from something theoretical to reality, to go from having only ground-based observations to getting there and seeing the nucleus in close-up,” said Matt Taylor, a Rosetta project scientist.
Spacecraft have performed high-speed fly-bys of comets before, but never made a rendezvous. By flying in 67P’s orbit, and at virtually the same speed, Rosetta will be able to study the comet like never before, taking images and readings in unprecedented detail to give scientists an intricate understanding of its composition, the physical processes taking place on and around it, and its history.
“This is a primordial leftover from the Solar System that’ll provide us with an extraordinary window on the past,” said Mr Taylor.
Rosetta will accompany 67P for the next year as the comet speeds towards perihelion – its closest approach to the Sun – and, this November, will release a landing craft named Philae to touch down on its surface, drill for samples and test them.
“That will be the cherry on top for this mission,” said Mr Taylor.
Since its launch in 2004, Rosetta has performed three “slingshot” manoeuvres around the Earth and one around Mars to fling itself sufficiently far into space to chase down the comet.
Scientists have described it as akin to a “cosmic billiard ball” as it bounced around the inner solar system, circling the Sun nearly four times, entering the asteroid belt and harnessing gravitational “kicks” from the Earth and Mars.
The comet is currently 252 million miles from Earth and travelling at more than 34,375mph. Because of the distance involved, communications between Earth and the spacecraft take 22 minutes to travel one way.
“All systems on the spacecraft are performing well and the entire team is looking forward to a smooth arrival,” Sylvain Lodiot, Rosetta’s operations manager at ESA, reported yesterday.
Rosetta’s mission – built with contributions from ESA’s member states and from the US space agency, Nasa – has cost €1.3 billion.
As it closed in on 67P, the probe took the comet’s temperature for the first time. The results surprised scientists, revealing that the comet has an average surface temperature of minus 70C – around 30C warmer than predicted and indicative of a dusty, rather than exclusively icy, surface.