On Wednesday, for the first time ever, a human spacecraft made a controlled rendezvous with a comet. This is what it saw as it approached:
For generations of people raised on sci-fi movies, the video might not look like a huge deal. But it's pretty amazing to realize that this choppy little clip is an actual image of a real comet — the most detailed look we've ever had.
The spacecraft is the European Space Agency's Rosetta probe, and the comet is 67P/Churyumov–Gerasimenko, a roughly 2.5 mile-wide chunk of rock, dust, and ice that's currently 250 million miles away from Earth, about halfway between the orbits of Mars and Jupiter.
A close up, taken on August 6th. (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
The probe was launched in 2004 specifically to study this comet, and is now within about 62 miles of it. Rosetta traveled nearly 4 billion miles to get there, looping around Earth and Mars several times in order to use their gravity to add momentum to its flight path.
Two previous probes have briefly flown by comets, but neither came nearly as close as Rosetta. Additionally, in 2005, NASA's Deep Impact Probe was intentionally crashed into a comet to analyze its interior.
Rosetta, though, will be the first mission to study a comet close-up for an extended period of time. The plan is for the probe to begin orbiting the comet within the next six weeks and accompany it for about a year, deploying a small landing craft in mid-November to analyze soil and rock samples.
A detail of the comet's surface, taken on August 6th. (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
Scientists hope that measurements collected by Rosetta will help us learn more about the composition of comets in general. This sort of information could be quite relevant to understanding the formation of all planets, and even the development of life on Earth: comets formed during the earliest stages of the solar system, and some scientists believe that the water on Earth was originally delivered by comets and asteroids.
A rear view of the comet, taken on August 3rd. (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
Update: For an idea of how big this comet is, we bring you a nice image from the European Space Agency comparing it to some well-known buildings and mountains:
Click to enlarge. (European Space Agency)
