The Rosetta mission of the European Space Agency started in 2004 and finally reached its destination, Comet 67P/Churyumov-Gerasimenko, in 2014. While its Philae lander ended up in a ditch on the comet's surface and cannot recharge its batteries due to insufficient sunlight, Rosetta itself had been sending back a stream of data that scientists have been studying ever since.

For instance, one of the most interesting points for researchers is the "rubber ducky" shape of the comet. There were already many theories circulating before on how it came to be this way, but it is only now that humanity can say with certainty that a slow collision fused two smaller comets into the one we know now, according to CBS News.

High resolution images taken from August 2014 to March 2015 were used to study the different layers of the comet. Researchers first identified 100 terraces on the comet's surface. They also noticed parallel layers of material from exposed cliff walls and other pits. Next, a 3D model was used to determine the direction that these walls sloped and how much they extend into the subsurface.

"You can imagine the layering a bit like an onion, except in this case we are considering two separate onions of differing size that have grown independently before fusing together," said Matteo Massironi, lead author of the study from the University of Padova, Italy. He is also an associate scientist for the Optical, Spectroscopic, and Infrared Remote Imaging System or OSIRIS team.

The 3D images were used to make cross-sections of the comet, BBC reported. The cross-sections show that there are two distinct sets of layers. "You don't know the structure of an onion until you cut across it," Massironi said. He adds, "What we have seen is that this stratification is really continuous - and that [the one in the tail] doesn't match that of the head."

Studies on the gravity field of the head and body of the rubber ducky-shaped comet further supports this confirmed theory. Also, other comets that have been observed up close, like Halley, Borrelly, and Hartley-2, showed a similar lobed structure. The next question is whether these comets' shapes were created using the same slow collision that resulted in 67P/Churyumov-Gerasimenko.

The Rosetta mission is proving to be very enlightening on the form and function of comets zipping past our planet. If you find this as fascinating as us, then hit share to get your friends' inputs too!