Comet Discoveries Take Center Stage

Planetary Science on a Small (But Important) Scale

The first day of the AAS Division of Planetary Sciences meeting (beginning today) was filled with amazing science talks. Some of the most eagerly awaited were about the Rosetta mission and its up-close-and-personal study of Comet 67P/Churyumov-Gerasimenko. Every instrument team for the mission had a report.  The OSIRIS camera team members described the comet, and point out that there are five different morphologies (think of them as “body types”) for the surface of the comet: a dust-covered surface, a mantled area, deposits on various parts of the surface, smooth terrains, and other features. One of the scientists presenting a media briefing commented that the surface material is dusty with a consistency somewhere between hard-packed snow and cigarette ashes. In particular, this is what the landing site for the Philae (FEE-lay) probe is like.

It seems that the comet is most active in its “neck” region, and I saw some discussion on Twitter (among scientists and others following the stream) that this could indicate the comet is some sort of “conglomerate” of materials mashed together, instead of one big chunk shaped like a lumpy rubber duckie. Interestingly, even though the comet is an icy body, there doesn’t seem to be much (if any) ice on the surface, which is very dark. So, all the volatiles (gases and ices) are contained under that cracked, cratered, lumpy and dune-covered skin. As the comet gets closer to the Sun, those volatiles will be warmed and they’ll escape to space through the action of jets spewing from under the crust.

There is, of course, more to come about this comet — which the Philae lander  will be visiting. I all goes well, the actual “settling down” will occur on Wednesday morning. NASA TV will provide live coverage from 9-11:30 a.m. EST (6-8:30 a.m. PST) of the European Space Agency (ESA) Rosetta mission’s scheduled landing of a probe on a comet on Wednesday, Nov. 12. NASA’s live commentary will include excerpts of the ESA coverage and air from 9-10 a.m. NASA will continue carrying ESA’s commentary from 10-11:30 a.m. ESA’s Philae lander is scheduled to touch down on comet 67P/Churyumov-Gerasimenko at 10:35 a.m. ESA will also be streaming the landing, and you can watch that here:

I encourage you to follow along. How many times will you ever get to watch as a spacecraft sets itself down on a rotating comet? Check it out!

Just to give you a taste of what else was discussed today at the DPS, the recent passage of Comet Siding Spring past Mars resulted in some intriguing reports on how the tail materials may have sprouted the mother of all meteor showers over Mars. The Mars MAVEN mission also found that debris scattered by the comet added a temporary ionized layer of charged particles to the Martian ionosphere. This is the first time that anyone has seen anything like this at any planet, including Earth. That’s pretty amazing and shows us that (once again) good discoveries often come from some of the most unexpected events.

As I’ve said before, comets are an important key to understanding the early solar system, as well as the regions of the solar system where they come from: the Kuiper Belt and/or the Oort Cloud. The materials contained in comets existed when the Sun and planets formed — and there’s some evidence that some of their ices actually predate the Sun! We’re talking about materials that are at least 4 to 5 BILLION years old. The dust they contain, along with other gases, may have formed when ancient stars exploded, scattering their elements to space. If you want to know what things were like a long, long time ago, comets are going to be your key to that amazing past. And, they’re playing a growing role in planetary science.