The European Space Agency achieved a space exploration first on Wednesday when its Rosetta probe rendezvoused with Comet 67P/Churyumov–Gerasimenko, currently 405 million kilometers from Earth. Rosetta is currently 100 kilometers from the comet, moving at 55,000 kilometers an hour. The comet is in a six and a half year elliptical orbit that takes it from beyond the orbit of Jupiter to a point between the orbits of Mars and Earth and back again.
Rosetta’s journey began over ten years ago and involved three gravity assist flybys of Earth and one of Mars to keep it on course toward the comet. Along the way it passed by asteroids Šteins and Lutetia, returning invaluable data from both objects. Starting in May it began a series of ten maneuvers that allowed it to match trajectory and speed with the comet.
Comet 67P/Churyumov–Gerasimenko, like all comets, is thought to be composed of stuff left over from the birth of the Solar System. It likely originated from the Kuiper Belt, an area of icy objects located beyond the orbit of Neptune. Its orbit is heavily influenced by Jupiter, hence its relatively short orbit compared to most other comets. “The density of the nucleus seems to be much lower than that of water, indicating a loosely packed or porous object. Like other comets, its nucleus is generally blacker than coal, indicating a surface layer or crust of carbon-rich organic material.”
The plan is for Rosetta to accompany the comet for at least a year as it swings around the sun and heads back out toward Jupiter. The probe will conduct remote sensing operations of the comet, eventually going into orbit around it at a distance of about 30 kilometers depending on conditions. The highlight of the mission will take place when Rosetta deployed the Philae lander which will attach itself to the comet with harpoons in November and will attempt to take and examine samples from the object.