From marbles to meteorites


Ok, so, meteorites. I’m gonna do a post with multiple items this time, because I’m trying to make a kickass point. In general, there are several different general types of meteorite. They are either stony (chondrites), iron (iron), a mix of iron and rock(stony/iron, including pallasites), or a funky 4th category(carbonaceous chondrites) that are crazy carbon rich. I’ve got a few meteorites, but not all the ones I want. I’m gonna include some pictures from things I don’t have yet, just to demonstrate my overall point, and to show why I must own them.

Now as we all know, the Earth’s interior is differentiated into different layers, with different properties. We have the rocky outer crust, where we live, which is ridiculously thin, between 2 and 30 miles thick or so. Considering the Earth is about 8000 miles in diameter, that’s pretty damned thin. Next, we have the still rocky, but now fluid mantle. Here the pressure and temperature has melted the rock and turned it into a sort of super-sticky fluid. The mantle can be further subdivided into an upper/lower, but that’s not really relevant, so I’ll just say the mantle is about 1800 miles thick. Beneath that we have the outer and the inner core, both consisting primarily of iron and nickel. Almost everyone knows about the iron, but most people don’t know there’s quite a bit of nickel too. Why, you might ask?

Well, back in the olden days, before the Earth, or the Sun existed, a really big star blew up somewhere pretty near to the cloud of gas that was eventually to be our solar system. This star blew up because it had started fusing iron in it’s core, and for stars, this is the end of the road. Fusing iron doesn’t produce energy, it consumes it. It starts sucking energy out of everything around it, and the outward radiation pressure drops. Gravity starts to win. But the star does not go quietly. As it simultaneously implodes, and explodes, its core becomes a black hole, while the rest of its innards, get ejected at a significant fraction of the speed of light in the kind of explosion that’s visible across the Universe. In the process, pretty much every chemical element from iron on up in the periodic table is created, all within a few seconds. That’s where uranium is made. That’s where gold is made.

Eventually the shockwave, followed later by the ejected bits collide with a gas cloud, and cause a part of it to collapse, just like blowing into a cloud of smoke. Now, the important thing, is that these supernova explosions are very rich in a particular isotope of iron called Iron-60. Iron-60 is radioactive, and it decays into…Nickel-60! This is where all that nickel came from. So, when you’re looking at an iron meteorite, you’re looking at the pieces of a dead star. The ratio of iron to nickel tells you something about the neighbors during the period when it formed. It tells you something about the stars that gave birth to it. When that meteorite formed, it was probably mostly iron. Over time, the radioactive Iron-60 in it decayed and turned into very stable Nickel-60, where it has remained ever since.

So, then some shit happened, a star formed, and along with it, a bunch of planets. Some of those planets are still with us today. Others, well…they didn’t make it. Our solar system was one crazy place back then, with a whole lotta shit flying around in a whole lotta directions, colliding, accreting, etc. Point is, planets are being assembled. Violently. Sometimes they get disassembled by accident. And that’s how meteoroids are born!

Korra Korrabes meteorite from Namibia

This is a stony meteorite, technically known as a chondrite. There are many different varieties of these, just like there are many different varieties of rock on Earth. This particular one is an “H3 Chondrite” named Korra Korrabes (after where it was found). It’s a breccia, which basically means it’s composed of loose gravel filled with finer dirt, and then compacted. It’s a bit like a natural concrete, I guess. This one came to earth in Namibia, and was later discovered in 1996 in a dry river bed by a farmer. It is a piece of the crust/mantle of a planet that’s no longer with us.

A piece of the Sikhote-Alin fall

A piece of the Sikhote-Alin fall

This is an iron/nickel meteorite. It’s from Sikhote-Alin, which is a mountain range in Siberia. It’s technically classified as “coarsest octahedrite”, which refers to the crystalline structure of the metal it’s composed of. The dimples in the surface are called regmaglypts, and they’re basically the result of air pressure on the molten outer surface of the meteorite after it meets the atmosphere and heats up. It’s a lot like what would happen if you pursed your lips and blew really hard into a bowl of ice cream. If you cut it open(the meteorite, not the ice cream,) it would look something like this.

Toluca-IAB iron meteorite w/widmanstatten pattern

Toluca-IAB iron meteorite w/widmanstatten pattern

It’s called a “Widmanstatten Pattern” and it is unique to iron/nickel meteorites. It can only be created when a molten chunk of iron/nickel floating in zero gravity under a near perfect vacuum, is allowed to cool veeeerrrry slowly over millions of years, giving these amazing crystals time to form. The bands basically represent different nickel/iron alloys. Because the ratio of iron:nickel is different between the stripes, the crystal structures they form are slightly different. This manifests itself as a series of criss-crossing lines throughout the body of the meteorite. This particular one is from the Toluca, Mexico meteorite. When it was found, in 1776, the locals were turning chunks of it into farm equipment, cuz, hey, free iron! Its constituent atoms were born in an ancient star that went supernova. It got its shit together, and became the core of a planet that’s no longer with us. It died in its youth, victim of a driveby planet. RIP, little meteor. RIP.

Imilac Pallasite

Imilac Pallasite

This is a pallasite. These things are fucking beautiful, and I MUST own one. It’s strange, it’s got a whole crapload of iron, but it’s not pure iron/nickel like the other ones. Why? Well, I’ll tell you. That’s the boundary between the mantle, and the core of a planet that’s no longer with us. Why is it all gemstoney? Well, that’s how gemstones are made. Immense heat + immense pressure + a stocking full of coal = diamonds. In this case, it’s Olivine, also known as Peridot. Are you born in August? How’s that for a birthstone to make your friends jealous?

Each of these things is older than any rock, anywhere on Earth. They’re all about 4.5 billion years old, a bit older than the Earth itself. They’re the shattered remains of planets that just didn’t quite make it. They survived long enough to differentiate into an iron core, with a rocky outer crust, and that incredible boundary layer. They just couldn’t quite hang in there for the long haul though. Those early few hundred million years were pretty hazardous. Imagine how hazardous it has to be for an object the size of a planet to be routinely obliterated? It’s like that.

Flash back to Starwars, Vader is destroying himself some homeworlds just to make the princess cry, cuz he’s hard like that. Remember that planet exploding? This is like that. Only for real. And on a massive scale, like “OH FUCK, LOOK OUT! HERE COMES A PLANET!” If you find yourself in such a situation, it’s probably best that you grab your ankles, and think of England.

When you look up at the moon, and you see these giant scars, those were some pretty massive bodies smashing into it at pretty incredible velocities. It was such an impact that created our moon in the first place, when one of those mars-sized erstwhile planet wannabes picked a fight with the erstwhile planet wannabe Earth, and lost. The impact was sorta oblique, so it happened to fling big chunks of both bodies into orbit around the new Earth + 1. Those chunky bits coalesced into our Moon.

Oh, the 4th category, Carbonaceous Chondrites? Those are basically comets. They formed in the outer solar system, around Pluto’s neighborhood. They’re chock full of water and carbon, just the kind of thing a growing planet needs to establish a biosphere. The Tagish Lake meteorite is an excellent example of a carbonaceous chondrite.

Ok, so anyway, my point. Science rules, Natural Selection doesn’t just apply to monkeys and Creationists, and meteorites aren’t just rocks from space. They tell you something about where you came from, and where they came from, where the Earth, and the Sun themselves came from. Every time I think about what these represent, it puts me into a state of awe that words just can’t convey. And yet, it’s just a rock, or just a lump of metal. Hell, I bet you could make some damned fine farm equipment out of it.

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