Last week, we covered the latest piece of research to come out of the Rosetta mission studying comet 67P, which involved some interesting ice action in the shadows of the comet’s skinny “neck.” That action probably encourages extra erosion in the shadows, which may explain why the neck is so thin. It puts another mark in the column for the hypothesis that the comet’s strange shape is the result of sculpting from an initially conventional shape.

The other hypothesis is that comet 67P is actually two comets, long ago welded together after a chance meeting. New research published in this week’s Nature puts a rather large mark in the column for this hypothesis.

One of the many awesome things Rosetta’s cameras have detected on the comet’s surface is a myriad of small terraces reminiscent of layered rock outcroppings on Earth. There are a number of possible explanations for these features—after all, we still have much to learn about how comets form and evolve over time.

But by meticulously mapping the orientations of those terraces, a team led by the University of Padova’s Matteo Massironi has shown that the terraces are part of a coherent layered structure that extends at least a few hundred meters below the surface. Comets—and ogres—are like onions.

More to the point, comet 67P looks like two onions. The layers of each lobe close on each other rather than linking in one continuous set of layers interrupted by erosion. It looks like two independent comets were glued together—probably in the early stages of the formation of the Solar System, the researchers say.

Nature, 2015. DOI: 10.1038/nature15511 (About DOIs).