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.

Exploring and Defining Planetary Systems

Now that we’re about a decade and a half into the “new” century, it’s not a bad time to look at where we are as we explore the cosmos. Planetary science has always been one of my great interests, so I’ll take a look at that in this musing (and then explore other aspects of astronomy in the 21st Century in other musings).

Planetary science is, essentially, the study of the origin and evolution of solar system objects and is now embracing the study of exoplanets as well.  There are BIG stories in planetary science, ranging from the continued characterization of objects we know about and the continued discovery of others far out in the distant reaches of our solar system. This week the AAS Division of Planetary Sciences is meeting, and I know there are some very cool stories to be shared! Due to these stories, I think that planetary science has more than come into its own as a discipline. It’s more than dividing planets into rocky ones and gas giants, or (in the extreme) getting upset about the planetary status of Pluto.

I’ve written several times in the past few years about Pluto and the whole “is it or isn’t it a planet” discussion that has been raging since the 2006 vote at the International Astronomical Union that supposedly stripped Pluto of its planet status. There are many questions about why the vote was held, what the IAU’s authority was to hold a vote, and why so few planetary scientists (who are also IAU members) were involved in a decision that is squarely in their domain (and not in the stellar astrophysics domain, for example). It’s an ongoing controversy and one that does call in to question the IAU’s actions at that time and since then.

The IAU is an international coordinating body that is charged (among other things) with doing the cosmic bookkeeping necessary so that we don’t (for example) have three planets named Saturn, or two asteroids with the same name, or misnumber a comet. In that sense, they provide a valuable service. The group has also waded into the whole “definitions” arena, and this is where it has been less than successful in terms of serving science. Lately, the group has also stepped into arenas (such as the Pluto vote) that call into question its self-assumed authority over something so simple as naming a crater on Mars or naming exoplanets.

It has always been my understanding that the IAU’s responsibility over names was simply to make sure there were no duplicates, or that a suggested name was appropriate within a theme. For example, craters on Venus are named after famous names or bear other female names. In recent years, the IAU has taken on a role wherein it assumes it has sole and undisputed authority, not to mention the moral high ground, to name things, rather than simply being the bookkeeper. It has gone as far as to sponsor an event to name exoplanets, but bristles if any other group wants to do the same thing. Seems rather curious for an organization that is supposed to serve science and scientists. I won’t go into details here. If you’d like to read the rather extensive analysis I did a couple of years ago, you can find articles here.

I digress a bit. Let’s get back to Pluto and the magnificent importance of planetary science.

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