With only less than a week to go before it enters into orbit with Comet 76P/Churyumov-Gerasimenko, the European Space Agency's Rosetta spacecraft reveals more photos that provide a closer view of the comet's odd-shaped, two-lobed nucleus.
The images, which were taken by Rosetta's Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), were taken with a resolution of 300 feet per pixel and confirms what earlier images have shown. From a distance, Comet 67P looks like a "rubber duckie," with a bigger body and a smaller head, but the resemblance diminishes as Rosetta closes in. The newest and most intriguing discovery to date is a bright ring that emanates from the link between the two lobes. Scientists believe this bright "neck" indicates that something interesting could be taking place in the link between the comet's lobes.
"The only thing we know for sure at this point is that this neck region appears brighter compared to the head and body of the nucleus," says Holger Sierks of Germany's Max Planck Institute for Solar System Research and OSIRIS principal investigator.
One possible explanation for the strikingly bright neck is that the area could have a different surface composition. It could also have a variation in the size of dust and ice grains covering the surface. Topographical effects could also account for the peculiar feature.
Astronomer and author of Death from the Skies: The Science Behind the End of the World Phil Plait speculates that Comet 67P is the result of one large comet that shattered into pieces after colliding with another object. The combined gravity of the pieces pulled them back together into a bunch of rocks dominated by the two biggest pieces. Plait says the comet's bright neck could be a low-gravity area where rocks, dust and pebbles flow to leave behind the ice that forms a bright ring.
Although Plait says his explanation is pure speculation, it seems to coincide with NASA's findings about Comet 103P/Hartley, which went into rendezvous with the flyby EPOXI mission in 2010. Images from the mission revealed that Comet 103P's smoother-than-usual middle was characterized by a gravitational low where material from the comet is prevented from leaving the gravitational field.
Of course, not much can be done but wait for Rosetta to close the 2,000-kilometer gap between it and Comet 67P and link up with the four-kilometer comet in its journey around the sun, before its Philae lander touches down on the surface of the comet in November.
By this time next week, Rosetta will be 100 kilometers away from the surface of Comet 67P's nucleus and the first image from OSIRIS' detailed mapping of the comet will be available on August 6.
Rosetta is the first mission to rendezvous with a comet, travel with it around the sun and eject a lander on its surface.
