So going back to some geology: in October I had the opportunity to attend the Meteor Crater Field Training and Research Program led by Lunar and Planetary Institute scientist Dr. David Kring. It was a program aimed at planetary geology graduate students. Our group of 24 consisted of students from lots of different universities, and different countries. Two guys hailed from Germany, two students from Austria, one from England, and one from Canada. Of the 18 students from the US, the universities represented were pretty prestigious: MIT, Harvard, Washington U. in St. Louis, University of Arizona, Arizona State, Purdue, Case Western, University of Texas - Austin, University of Colorado - Boulder, and, of course, University of Tennessee! There were two of us from UT, and I felt like that made our department and university look really good to be rubbing shoulders with the Ivy leaguers :) Most of the students (ok, all but me and Matt) were studying some aspect of impact crater formation, either on Earth or other bodies. I was mainly there to skip school (with a good excuse), find a real meteorite, and to get the behind-the-scenes tour of the crater with an expert. I definitely learned a lot about impact cratering - like how much I still don't know! I also learned about how COLD and WINDY Arizona can be in October!!
For starters, here's a picture of me on the crater rim:
Something that I had known before going and had even taught in Geology 104 lab (introduction to the planets) was that a defining feature of a crater is its uplifted rim. However, I hadn't given the word "uplifted" much thought until going there. Northern Arizona is pretty flat, and when you're driving up to the crater, it's definitely noticeably higher than the surrounding area!
The crater is actually "small" by impact crater standards; it's less than a mile across. It's also really young geologically - only about 50,000 years old!! For comparison, the Chesapeake Bay impact structure is 35 million years old and much much larger. Meteor Crater, however, is much better preserved than pretty much any other crater on Earth, making it ideal for study. It was first "discovered" in the late 19th century and was purchased by a fellow named Barringer. Barringer was into mineral exploration/resources and was primarily a businessman, having only an undergraduate degree in geology. He was essentially the first person to call the site a meteorite crater (others, including the head of the US Geologic Survey at the time, thought it was a volcanic feature) so he suspected that the meteorite that produced it may lie at least in pieces in the crater walls or under the crater floor. Basically, he thought he was going to make tons of money from unearthing an enormous iron meteorite. The crater became his obsession for basically the rest of his life. He made amazingly detailed and astute observations. In fact, many of his hypotheses still hold up even now with all kinds of new ways to collect information from the site. Just goes to show that you can learn a lot just by hanging out somewhere and walking around!
There were, however, some key aspects of crater formation that he didn't grasp. He thought the entire meteorite would be buried, intact, underneath the crater floor. He also thought the meteorite would be roughly the size of the hole. Wrong. Meteors that form craters are only a fraction of the size of the craters they form. The crater is formed from pressure and shock waves resulting from the fast-moving meteor crashing into the surface. Usually, the meteorite is either vaporized (if it's small) or broken into many tiny pieces and scattered. So while lots of meteorite fragments have been recovered from the site over the past 100 or so years, no enormous iron blob has been unearthed! But other than that, he pretty much got the story right. Yay for amateur scientists being awesome! Also, the Barringer family still owns the crater. It's actually not a national park/site, which is pretty amazing.
Some things about Meteor Crater that make it unique:
1) It's roughly square-shaped with rounded corners. Most craters on any planet are circular. This is due to the pre-existing perpendicular joints in the rock. When the impact occured, those weaknesses already existed in the rock, so the walls formed along relatively straight lines.
2) After impact, a lake formed in it. This is thought to be not uncommon in very ancient (4.5 - 3.75 billion year old) Martian craters.
3) A few areas around the rim are higher due to huge chunks of rock being shoved into the crater walls as they were forming. Weird.
4) Astronauts train there!
5) All the rubble/old mining equipment has been left the way it was after mining efforts ceased, so it's completely historically accurate.
6) It was a filming location for the 1980's movie, Starman. We watched it one night... I would not necessarily recommend.
Apollo-era astronauts did a lot of training at Meteor Crater. On the crater floor (off-limits to tourists, but we got to go down), there is an American flag set up with a wooden astronaut cut-out next to it. Here's a picture of me and the astronaut:
Apparently rovers are trained there, too! Here's a Canadian Space Agency group testing a rover:
We spent the first two days basically hiking around and through the crater, which was pretty cool. Dr. Kring told us that taking samples from the crater was prohibited for tourists. Scientists were permitted to take samples that had already fallen to the crater floor to use for research, but each piece must be documented and registered. Any meteorite chunks that are found have to be left alone if they're still in the crater wall. They can be collected by meteorite scientists after they've weathered out, but Dr. Kring said that usually they would get lost in the material that had been rained down the slopes during the rainy season. He did show us a nice sample still stuck in the wall. We weren't even allowed to sit less than 5 feet away from it! Here he is pointing it out to us (it's the dark blob in the pinkish rock to his left):
Even though we weren't allowed to collect our own meteorites, we still ended up with samples anyway! A professor from Arizona State drove up and talked to us about meteorites and gave us goody bags with teeny meteorites from Meteor Crater in them!
We camped in tents at the Meteor Crater RV Park. Our fellow RV park residents were pretty colorful characters. We were the only group in tents, with the exception of a group of three hunters. They were pretty old and woke up at 4 AM every morning. Good campfire entertainment. Here's a picture of our tents lit up at night:
Our main project while there was to contribute to a research project Dr. Kring was heading up. We did all the data collection for the project and took lots of good pictures for the paper that will result. Admittedly, I didn't understand a ton of what we "discovered" but I did contribute by making very detailed rock descriptions!
At the end of the day, I learned a lot. I networked with my planetary peers, which is never a bad thing. I also learned though, that if you're going to Arizona in October, bring LOTS OF WARM CLOTHES and an alpine-grade sleeping bag. Consider yourselves warned! Sadly, we missed the Grand Canyon (not enough time!) but the trip definitely whet my appetite to explore the southwest!
Vaya con Dios!
Sarah
