Everything We've Discovered So Far About the Rosetta Comet

It's been a little over two months since the Rosetta mission pulled o​ff its historic landing on Comet 67P/Churyumov–Gerasimenko (C-G), and a lot of experimentation has gone on during that time. Today, an enormous data dump of new insights an​d information about the comet is published in the journal Science. This flood of new research provides the most in-depth look at a comet ever achieved, revealing all kinds of previously unknown complexities about these mysterious ice worlds.

"Comets have always surprised humanity," said Murthy Gudipati, a planetary scientist and lead author of one of the seven studies appearing today, in a statem​ent. "C-G seems to be no exception."

In other words, there is a lot of new information to parse, so I'm only going to outline the major finds of each of the seven papers. First up is a report le​d by experimental physicist Nicolas Thomas, whose team created an incredibly detailed infrared map of C-G using Rosetta's OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) camera. The diverse and extraordinary surface features of the comet are described in great detail, as well as the processes that may have formed them.

"Although we are still in a relatively early phase of the mission, the following conclusions appear to be robust," Thomas and his co-authors wrote. "The presence of airfall, dune/ripple-like structures, wind tails, and smooth depressions with ponded dust suggests that surface dust transport is of major importance in defining the uppermost surface layer in many regions."

Thomas's study is definitely worth reading through if you want to get a better sense of C-G's contours and landscapes. It also gets extra points because the comet's regions have an Egyptian mythological naming scheme, in keeping with the Rosetta orbiter and Philae lander. It's pretty fun to read about the smooth plains of Imhotep, the interfaces between Ma'at and Ash, or the cliffs of Hathor. This comet sounds like a badass place to visit.

The second of the Science ​papers is also based on OSIRIS data, but instead of mapping the surface, the researchers focused on C-G's nucleus. Led by OSIRIS principal investigator Holger Sierks, the team found that the core was filled with dust, rock, frozen gas, and what the paper calls "goosebumps"—previously unknown slopes along the nucleus.

The team also addressed the C-G's intriguing "rubber ducky" shape. The comet has two main lobes connected by a narrow neck, suggesting that it might have formed from two separate planetesimals—the tiny building blocks o​f planets—some 4.5 billion years ago. In the end, Sierks's team concluded they needed more data to determine whether such an event, called a "contact binary," formed C-G, or whether it was always one object, and simply suffered erosion at the neck.

The third study is based off of d​ata obtained by ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis), and unveiled a lot of surprises about C-G's coma—a term for the nebulous runoff surrounding comets. The report, led by planetary scientist Myrtha Hässig, showed that the composition of the coma fluctuates significantly depending on its orientation and distance from the Sun. The water vapor, carbon dioxide gas, and other materials surrounding the comet are not homogeneous and static, suggesting that the relationship between the comet nucleus and coma is more complex than previously thought.

You may have noted that so far, the studies have described C-G's broad features and composition. The fourth study, in contrast, delved into the​ formation of the comet's magnetosphere, and how it is enhanced by solar wind flux. Led by Hans Nilsson, principal investigator of Rosetta's Ion Composition Analyzer, the researchers reconstructed C-G's magnetic history by studying its shell of atmospheric water ions, which evolved to "define its boundaries," according to Nilsson and his co-authors. That's how "a magnetosphere is born," the team wrote. Incidentally, Rosetta also reco​rded the song of C-G's magnetic field, which is well worth listening too.

Moving along, the fifth study identified the pre​sence of organic compounds in C-G's nucleus. Lead author Fabrizio Capaccioni and his team used VIRTIS (the Visible and Infrared Thermal Imaging Spectrometer) to identify the carbon-bearing molecules on the comet's surface and in its core. The findings provide valuable context for the "panspermia" theory, which posits that comets rich in orga​nic compounds might deliver the building blocks of life to countless planets.

The sixth paper used the ​the MIRO (Microwave Instrument on the Rosetta Orbiter) to get a closer look at the subsurface properties of C-G. Led by MIRO principal investigator Samuel Gulkis, the team found that the neck of the comet was the major contributor to the "outgassing" of water vapor and other gases. The authors also discovered that C-G "sweats" the equivalent of about two glasses ​of water every second, and corroborated the findings of Hässig's team regarding the seasonal fluctuations on the comet.

Finally, the seventh ​and last paper focused on the composition of C-G's dust runoff, revealing that the dust-to-gas ratio is higher than expected. The paper, led by physicist Alessandra Rotundi, represents a collaboration between several Rosetta teams, including OSIRIS, ROSINA, and MIRO. It also includes an in-depth analysis of individual dust grains captured by Rosetta.

You see what I mean about this being a massive data dump? As the wealth of new research has shown, ambitious missions like Rosetta aren't just about conquering untouched territories. They also deliver vital information about the worlds that share our solar system, and shed light on the development of our modest cosmic neighborhood.

Along those lines, keep in mind that this sophisticated mission has only just begun. These papers represent research completed over the last ten odd weeks. How much more will we know after another two months, or six, or a full year? Here's to looking forward to the next exciting dispatch from everyone's favorite cometary explorer.