Emily LakdawallaMay 15, 2015

Unseen latitudes of comet Churyumov-Gerasimenko -- revealed!

Every thing in the solar system spins, from the biggest planets to the smallest asteroids. And nearly everything that spins, spins at an angle to its orbit. Therefore, nearly everything in the solar system has seasons. Comet Churyumov-Gerasimenko is no exception. When Rosetta arrived there last year, it was summer in the comet's north. (I'd usually say "summer at the north pole," but with 67P's weird shape, does it have two north poles!?) Winter darkness covered the comet's south, leaving a large chunk of it invisible to Rosetta's cameras. The season has shifted since then, bringing sunlight to more and more of the southern hemisphere. As Mattias Malmer pointed out on Twitter, a recent Rosetta image has revealed a good part of that southern terrain to the public for the first time.

Equatorial view of comet Churyumov-Gerasimenko
Equatorial view of comet Churyumov-Gerasimenko In this photo, Rosetta is staring almost straight at the equator of comet Churyumov-Gerasimenko. Territory in the comet's southern hemisphere is receiving more sun than it did when Rosetta arrived in 2014, revealing its features.Image: ESA / Rosetta / NavCam

Mattias has been in the process of creating and improving a 3D model of the comet nucleus for some time, making a version available in his cool Rosetta Now website. I checked it just now, and look what an odd view of the comet Rosetta has at the moment!

Rosetta Now screen cap
Rosetta Now screen cap Visit http://mattias.malmer.nu/rosetta-now/ for a simulation of Churyumov-Gerasimenko as it currently appears to Rosetta, simulated from a shape model developed by Mattias Malmer from Rosetta NavCam images.Image: Mattias Malmer / ESA / Rosetta / Navcam

Anyway, the new image fills in a gap in Mattias' model, which shows up as a smooth area in the left image below.

Mattias recently published a new version of his shape model, much improved thanks to the bonanza of newly released Navcam images. His new model includes a global map of the surface to add to its realism. I thought the map alone was very cool; he has cut it along the boundaries that the OSIRIS image team drew among different cometary regions. I want to have this printed on fabric and try to assemble it into a soft model of the comet!

Surface map of comet Churyumov-Gerasimenko
Surface map of comet Churyumov-Gerasimenko A map of the surface of comet Churyumov-Gerasimenko based on Rosetta Navcam imagery. The pieces are cut along the boundaries of the regions named from OSIRIS imaging.Image: Mattias Malmer / ESA / Rosetta / NavCam

Here's a guide to those named regions. Keep up the good work, Mattias! And keep sending us great photos, Rosetta!

Map of comet Churyumov-Gerasimenko regions
Map of comet Churyumov-Gerasimenko regions The 19 regions identified on Comet 67P/Churyumov–Gerasimenko are separated by distinct geomorphological boundaries. Following the ancient Egyptian theme of the Rosetta mission, they are named for Egyptian deities. They are grouped according to the type of terrain dominant within each region. Five basic categories of terrain type have been determined: dust-covered (Ma’at, Ash and Babi); brittle materials with pits and circular structures (Seth); large-scale depressions (Hatmehit, Nut and Aten); smooth terrains (Hapi, Imhotep and Anubis), and exposed, more consolidated (‘rock-like’) surfaces (Maftet, Bastet, Serqet, Hathor, Anuket, Khepry, Aker, Atum and Apis).Image: ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA

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