If you’re like me and involved in planetary sciences or meteorites, or just a space-buff in general, this week must have seen like mana from whatever god you may or not believe in. There were a couple big news items that made this week all the more fun to be involved in space science.
First up: Planetary Resources. In my opinion, this has been the biggest news of the week because of the players involved. When you hear about an asteroid mining company being funded by the tech titans at Google (among other wealthy people) and R&D being headed by engineers from NASA/JPL, you can be sure that Planetary Resources doesn’t plan on being the one-hit wonder of the nascent private space sector.
With that being said, I’m cautiously optimistic that this entire venture will succeed. Do I think they’ll find all this platinum that they’re looking for? Not entirely. When I look at meteorites (which come from asteroids) I don’t do a modal abundance of platinum; I’m looking at iron/nickel abundance. Since they’re not looking at the meteorites themselves, I can only assume that they’re using spectral analysis to determine how much platinum is available in a given asteroid. While this is a fairly useful tool, spectral analysis has a tendency to give false readings based on the degree of space weathering an object has suffered.
Now, with all that being said, I still think it’s a great idea and we’ll hopefully see many technological advances come out of this. And who knows- this sort of venture may lead to other job opportunities for those such as myself that study meteorites, and by extension, the asteroids from which they come.
The second cool piece of news: brand new meteorites from the California fireball from last Sunday!
The new Sutter's Mill Meteorite. Aren't they pretty? (Image from NASA Lunar Science Institute)
I don’t know much about these meteorites yet. However, from the picture I can say that it’s a carbonaceous chondrite with some CAI’s (calcium aluminium inclusions). Those would be the white specks found scattered in the body of the meteorite. Carbonaceous chondrites tend to be on the rare side in our collections, so it’s always nice when we’re able to find more samples to augment our current crop of CC’s. Even more exciting is that these little beauties will possibly tell us more about the origins of solar system than what our collection of meteorites tell us now.
A tektite and shatter cone from the Cascadia Meteorite Lab display case
My inspiration for this post came while I was working on the meteorite case for the lab. Initially we were going to put a relatively cheap meteorite in the display, but then we decided that wasn’t such a good idea. So, the next best idea was the throw in a few impactites. These are rocks that had the rather unfortunate (or fortunate depending on how you wanna look at it) luck to be in the zone of a rather large meteor impact. The extreme heat and pressure from these events really plays hell on the surrounding rocks.
An Australite tektite from the Australasian strewnfield (image from Wikipedia)
Impactites come in two flavors: tektites and shatter cones. Tektites are rocks that instantly melted and were flung into the air from the meteor impact. While airborne, the molten rock quickly cooled and took on an aerodynamic shape. Such shapes include tear drops, dumbells or even that of an inverted button found among Australites. Tektites are found only at four impact craters across the planet. As such, they can almost be as expensive as the meteorites themselves. The origin of tektites has been hotly debated in the past. In the 1950’s and 1960’s, researchers suggested that tektites were actually of lunar origin. However, tektites lack certain noble gases that are common to lunar meteorites (1).
Shatter cones are formed in the bedrock underneath the impact zone. They form at a relatively low pressure of less than 2 gigapascals (GPa). To put that into perspective, 2 gigapascal translates into approximately 290,000 psi. A shatter cone outcrops is a good sign that one is standing in an impact crater (2).
Shatter cone from the Wells Creek in Tennessee (Image from Wikipedia)
1. Schneider, D.M., Tektites. The Meteoritical Society. Accessed on 10/17/2011
2. French, B.M. 1998. Traces of Catastrophe. Lunar and Planetary Institute. Retrieved on 10/17/2011
These images of Enceladus were released just a few minutes ago by Carolyn Porco, the awesome principal investigator for the Cassini Mission. They haven’t been through photoshop or cleaned up in anyway, but they still look gorgeous in their unprocessed state. These pictures are made available through CICLOPS (Cassini Imaging Central Laboratory for Operations) which is the team responsible for gathering all the visual goodness that Cassini acquires. I highly recommend checking out their website as they have a ton of great information and pictures concerning the Saturnian system.
Enceladus and the rings of Saturn (Image from NASA/JPL)
Relatively smooth surface of Enceladus gives way to craters in the bottom portion of the image (Image from NASA/JPL)
This image shows the stark difference in terrain- older craters in the center juxtaposed against the younger, sinew like ridges on the left (Image from NASA/JPL)
It’s a great time to be a space science geek. Today NASA launched JUNO, it’s satellite mission to Jupiter that will further our understanding of the largest planet in the solar system. It’s scheduled to arrive at Jupiter in the summer of 2016 and will help us understand the formation of the solar system. In 2015, New Horizons will be snapping the first up close pictures of Pluto and possibly other members of the Kuiper belt.
Yesterday, JPL announced (again) further evidence for water on Mars with this gorgeous picture.
Gullies with dark streaks indicate the possible existence of water. (Image from JPL/NASA)
Let’s not forget the MESSENGER mission to Mercury either. I feel that of all NASA’s robotic missions, this one gets the least amount of attention, yet it churns some really nice pictures that display Mercury’s violent past.
Young portions of Mercury's crust display fewer impact craters than the darker areas along the edges (Image from NASA)
As exciting as the aforementioned are, what really gets me going are the pictures sent back from the Dawn Mission. Dawn is studying two protoplanets in the asteroid belt- Ceres and Vesta. A group of meteorites called HED’s- Howardites, Eucrites, Diogenites- are thought to come from Vesta and this mission will fill in the gaps of information that the meteorites can’t. This mission, along with JUNO, will greatly further our understanding of the evolution of the solar system. It’s thought that Jupiters formation basically stunted the growth of Vesta, Ceres and even Mars by sucking up material needed for accretion.
Vesta as seen from Dawn. The south pole is basically an impact crater from which the HED's possibly originated. (Image from NASA)
These images barely scratch the surface of what we’re accomplishing in our neck of the galaxy. There’s a long list of satellites that take beautiful images of our own planet, the moon and the sun. I didn’t even mention all the awesome information we’re getting back from the Cassini mission. Things may seem bleak for the science community with funds becoming more scarce, but we still have some reasons to celebrate what we do and further reasons to fight for what we do.
Before I move too far into this post I should define two important terms so that we’re all on the same page:
- Chondrite- basically the sedimentary rock of the solar system. It’s an aggregate of the left over material from the formation of the solar system.
- Chondrule- Kind of the vagabonds of the proto solar system. They started off as molten spheres of either pyroxene, olivine or another silicate mineral that glommed onto the nearest asteroid, cooled and became the round features so prominent in ordinary chondrites.
If you have further questions (or even corrections/critiques) post it in the comments and I’ll do my best to address it.
The term “ordinary chondrite” is a bit misleading. Rocks that formed during or even before the formation of the solar system are anything but ordinary. Rather, they are the most commonly found meteorite on the earth. Their stony composition makes them more resilient than their carbonaceous brethren and as such, there is a ton of material about them that one can study. I don’t want to get into the details in this post because I need a little more time to study it and do the topic justice. However, I will list the three classes of ordinary chondrites (from Wikipedia):
- H Chondrites- Highest total iron, high metal, but lower iron oxide in the silicates
- L Chondrites- Lower iron total AND metal content, but higher iron oxide in the silicates
- LL Chondrites- Low iron total and low metal content, but higher yet in iron oxides
So basically, what separates the three classes is the iron and iron oxide content. As one goes up the other goes down.
Ordinary Chondrite Northwest Africa 1756- image from Northern Arizona University
Those round blobs in this image are the chondrules. In a later post I’ll give more information about this particular chondrite.
This post marks the first of, what I’m hoping to be many, a weekly series about various meteorites. I love space rocks as much as I love their terrestrial cousins because they recount the history of our solar system. In the simplest of terms meteorites are basically chunks of natural space debris (i.e., not from man made objects) that survived their descent through the earths atmosphere and the resulting collision. These objects come primarily from asteroids such as Vesta 4, but a few have been found of lunar and martian origin.
Allende, Mexico Carbonaceous Chondrite
A carbonaceous chondrite is basically a big ball of space mud that can contain up to 20% water (I’m not remembering where I read that, so that number may change when I find the source). They are fairly soft and don’t survive their sojourn on the earth to well. These chondrites also represent the most primitive matter drifting through the solar system and have undergone the least amount of chemical and physical change when compared to ordinary chondrites. It’s estimated that they represent roughly 5% of the meteorites that are observed and collected upon entry to the atmosphere (1).
The Orgueil Meteorite from the Hoover study
As of last month a carbonaceous chondrite found itself in the center of a controversy when a NASA astrobiologist, Richard Hoover, declared that he found fossilized bacteria in a specimen discovered in the late 1800’s. I won’t go into his claims here because this isn’t a biology blog and I don’t have the expertise to handle such a topic. If you’re really interested you can click here and read the abstract. Also a quick google search will bring up all the arguments for and against Hoover’s claims.
- Bischoff, A.; Geiger, T. (1995). “Meteorites for the Sahara: Find locations, shock classification, degree of weathering and pairing”. Meteoritics 30 (1): 113–122.