How Rosetta’s 67P comet got its ‘rubber duck’ shape

Some said it looked like a giant rubber duck.

According to a paper published Monday in Nature, Comet 67P’s lobes were once two totally separate objects.

A file handout photo released on September 19, 2014 by the European Space Agency shows a four-image NAVCAM mosaic of Comet 67P/Churyumov-Gerasimenko.

Finally, he notes, “Comets are also known to carry organic compounds and are thought to be one type of vehicle that delivered water and organic chemicals to Earth – chemicals that could serve as building blocks for more complex molecules underpinning organic life”.

Initially, says lead author Matteo Massironi, of the University of Padova, in Italy, astronomers saw a lot of material spewing from the “neck” of the comet, suggesting that prolific erosion from this region created 67/P’s peculiar shape.

What ultimately convinced Massironi and his co-authors that 67P had originally been two independent bodies was a careful analysis of what the scientists call “terraces”-distinct layers of the comet’s interior exposed by the partial stripping of outer layers over 67P’s 4.6-billion-year lifetime”.

“The big news is that the layers of each lobe wrap independently, indicating that the two lobes grew separately and only joined together later in their history, gently “docking” together during an ancient encounter that apparently did little damage to either partner”, he said. Indeed, scientists are saying, “Two independent and primitive envelopes of the bilobate nucleus of comet 67P”. Both parts of the comet have similar layering.

The team found that the orientation of a given layer and the direction of the local gravity are closer to perpendicular in the model with two separate objects, rather than with one.

Dr. Massironi said the fusion likely occurred in the early years of the solar system, while dust was still coagulating into larger bodies on the outskirts of the system and planets were still forming in the interior of the system.

He added the “two pieces were probably not formed in the same place, but formed in the same way”. However, the layers are oriented so that they surround the cores of each lobe, not the core of what would have been a single original body.

Scientists don’t know if comet twins are common, or if 67P is an oddity, but the results may provide an important clue about how comets – and the planets – formed.

Scientists suspect the bodies merged during the solar system’s early years.