Adapted from an ESA press release, July 17, 2014:
New images of Comet 67P/Churyumov-Gerasimenko reveal an extraordinarily irregular shape (see p. 213). It has become clear that this is no ordinary comet. Like its name, it seems that comet 67P/C-G is in two parts.
ESA scientists have made this movie, using a sequence of 36 interpolated images each separated by 20 minutes, providing a truly stunning 360-degree preview of the overall complex shape of the comet. It supports the presence of two definite components – one segment seems to be rather elongated, while the other appears more bulbous. Indeed, some people have already likened the shape to a duck, with a distinct body and head. Note that the comet’s surface features won’t be as smooth as these processed images imply.
Dual objects like this – known as ‘contact binaries’ in comet and asteroid terminology – are not uncommon. Indeed, Comet 8P/Tuttle is thought to be such a contact binary; radio imaging by the ground-based Arecibo telescope in Puerto Rico in 2008 suggested that it comprises two sphere-like objects. Meanwhile, the bone-shaped Comet 103P/Hartley 2, imaged during NASA’s EPOXI flyby in 2011, revealed a comet with two distinct halves separated by a smooth region. In addition, observations of asteroid 25143 Itokawa by JAXA’s Hayabusa mission, combined with ground-based data, suggest an asteroid comprising two sections of highly contrasting densities.
Is Rosetta en-route to rendezvous with a similar breed of comet? The scientific rewards of studying such a comet would be high, as a number of possibilities exist as to how they form.