Elemental Geology 2 - Iridium, the Meteorite Tracer

[00:00:00] Dr. Jesse Reimink: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.

[00:00:14] Chris Bolhuis: Hey doc, how we [00:00:15] doing today?

[00:00:15] Dr. Jesse Reimink: Good. Chris, how are you? Welcome back.

[00:00:18] Chris Bolhuis: I'm thanks. Thanks. You were kind to me yesterday. Um, that means a lot. I mean, you could have really taken some jabs at me in my absence and, uh, I'm, I'm, I'm thankful that you

[00:00:28] Dr. Jesse Reimink: Oh, you think I held

[00:00:29] Chris Bolhuis: [00:00:30] that. I appreciate you.

[00:00:30] Dr. Jesse Reimink: think I held back a little bit too much

[00:00:32] Chris Bolhuis: Yeah. . I'm just gonna say that I would not have been so kind, so I was off gallin and, uh, we just couldn't make the timing work to do our little intro to this. [00:00:45] And, and so you, you did it all by yourself. You're a big boy. I, I appreciate that. You did a good job and you were kind to

[00:00:50] Dr. Jesse Reimink: I could have taken a lot more shots across the bow, but you know, I tried, wanted to

[00:00:53] Dr. Jesse Reimink: hold back in a new year here and uh, you know, it's all

[00:00:57] Chris Bolhuis: Oh, I appreciate that. I was a little worried. I was, I [00:01:00] was concerned, like, what I, what am I gonna listen to when I listen to this live? What's gonna happen?

[00:01:04] Dr. Jesse Reimink: Giving up control. It's a dangerous thing. Dangerous thing.

[00:01:07] Chris Bolhuis: today, Jesse, what are we re-releasing

[00:01:09] Dr. Jesse Reimink: The geology of Iridium, which is a really cool element. It's a short, this is a [00:01:15] relatively short episode, uh, that we recorded, about a year ago, and it's just a really cool episode. I love Iridium's. Really interesting one. And, and it, you kind of brought this up because you know you really like the meteorite impact story. The end flirtatious mass extinction.

[00:01:28] Chris Bolhuis: Yeah. that's right. Yeah.[00:01:30]

[00:01:30] Dr. Jesse Reimink: and uh, and so, you know, you kind of were like, Hey, let's talk about Iridium. And so we threw this together and it's a really interesting element.

[00:01:35] Chris Bolhuis: I enjoyed doing it, like you said. Uh, it, it got me excited because of the, the tie in to meteorites and, you know, a little bit of earth formation and why the crust is so [00:01:45] low in Iridium then, and that dives back into your deep background on early Earth. So fun episode. I loved it. I hope you enjoy it.

[00:01:52] Dr. Jesse Reimink: Yeah, that's right. You can follow us on all the social medias. We're at Planet Geo Cast. You can visit our website, planet geo cast.com. Send us an email, [00:02:00] planet geo cast gmail.com and uh, what else Chris?

[00:02:04] Chris Bolhuis: Uh, give us a rating we really appreciate that. Helps with the algorithms, helps searchability and all that good stuff. And also, check out our camp courses@geo.camp courses.com [00:02:15] and let us know what you

[00:02:15] Dr. Jesse Reimink: That's right.

[00:02:16] Chris Bolhuis: Let's get to,

[00:02:17] Dr. Jesse Reimink: Enjoy.

[00:02:18] Dr. Jesse Reimink: Uh, check your audio. Check, check, check. And with that, we're off

[00:02:29] Dr. Jesse Reimink: Chris, we're [00:02:30] back. We're back. Here we go. Face-to-face. Face-to-face. Still. It's so good. It is. It's good. Really good. Really good. We've gotten a lot done. We've been cranking, man. We have. It's good. Yep. All right. So what are we doing today? We're following up from last week's episode. Yeah. We're gonna follow up on

[00:02:43] Chris Bolhuis: the, uh, meteor. [00:02:45] impact and flirtatious event. Totally. Okay. And so the, you know, we've spent a lot of time talking about Iridium in that, because that was an important part of the discovery. Yeah. And so today we're gonna talk about Iridium.

[00:02:56] Dr. Jesse Reimink: Yeah. Dive into a little bit more details, like why is this a [00:03:00] meteorite tracer, basically? And iridium is an element. Okay. So if you look on the periodic table, one of the boxes is iridium, it says ir. That's iridium, right? Yep. Yep. And uh, the question is, why do we use Iridium? Like why is Iridium this. [00:03:15] Tracer of meteorite impacts. That's kind of the question here.

[00:03:17] Chris Bolhuis: Yeah. Okay. Well, Iridium is a higher concentration in meteorites. It's. Not really high, but it's higher. Right.

[00:03:25] Dr. Jesse Reimink: Okay. So than earth. Than Earth, than like background

[00:03:27] Chris Bolhuis: earth. Right? Yeah. To put it in perspective, it [00:03:30] has a concentration in meteors of about 500 parts per billion , so that's not a lot. You take a billion atoms of a meteor, right? A billion, yeah. And wait a minute.

[00:03:42] Dr. Jesse Reimink: Yep. Yeah.

[00:03:42] Chris Bolhuis: 500, 500 of them. . [00:03:45]

[00:03:45] Dr. Jesse Reimink: It feels very small. The numbers, 500

[00:03:47] Chris Bolhuis: of them would be iridium. Yeah. So not a really high concentration, which when you, when you think about that, actually it's really interesting because this played such a big role in the discovery of this event. Okay. [00:04:00] And, and, uh, the concentration is not exceedingly high like you might want to think.

[00:04:05] Dr. Jesse Reimink: Right. You know, so it's very. To imagine 500 parts per billion, like 500 out of a billion. So I don't know. Sometimes it's easier to think of it with a, you know, probability. Like [00:04:15] if you just grabbed one atom of a meteorite randomly, one atom, you'd have less than a million, one in a million chance of pulling out an iridium atom. So very small chance of finding one iridium

[00:04:25] Chris Bolhuis: atom. Which is like, okay, let's, let's put this in perspective, maybe even a little further. [00:04:30] You talk about a very important gas. We've t we've had a episode on it, the Greenhouse effect. Okay. Carbon dioxide, the concentration of carbon dioxide in our atmosphere, this very important, controversial greenhouse effect. Gas has a concentration of about 420 parts per [00:04:45] million. Yes. In our atmosphere. So a hundred times more concentrated in our atmosphere than what

[00:04:51] Dr. Jesse Reimink: you would find in meteors. Right. And it just, I mean, that's a great point, Chris. It kind of shows how small concentration Yeah, that's, I'm full of great points.

[00:04:59] Dr. Jesse Reimink: Yeah. May [00:05:00] emphasize that , uh, I think, you know, it shows this like low concentration stuff has a big impact in earth. Mm-hmm. , like the, you know, it's kind of an interesting, uh, It is take home point there, huh? Um, but the question then is, okay, it's high in meteorites or it's higher in Earth than [00:05:15] meteorites.

[00:05:15] Dr. Jesse Reimink: It's still pretty low in meteorites, but it's higher than Earth. The question is why, and that question is important because Earth is actually made up of meteorites, right? Like Earth was formed from a whole bunch of meteorites that came together to form Earth. So why don't we have as much iridium? Well, earth

[00:05:28] Chris Bolhuis: is differentiated.

[00:05:29] Chris Bolhuis: [00:05:30] Okay. And so bingo, we're we're layered, and basically it goes from the least dense minerals exist on the surface of the earth, the crust, and it gets denser and denser and denser as you go down to the core. So [00:05:45] iridium is not high concentration in meteors, but it's much higher. in this clay layer than anywhere else in the

[00:05:55] Dr. Jesse Reimink: crust.

[00:05:55] Dr. Jesse Reimink: So iridium is not actually high in meteorites. 500 parts per billion is not [00:06:00] high, but it's higher than an Earth's crust. In an earth's crust. It's very, very, very low. And so earth's crust, the, the sort of tippy top layer of earth Yeah. Has 3.2 parts per billion. So meteorites have 500. Mm-hmm. Earth's crust has [00:06:15] 3.2 parts per billion.

[00:06:16] Dr. Jesse Reimink: So if you, a meteorite comes in and hits the crust, You know, it spreads iridium all over the place, and in these clay layers it can be a lot closer to 500 parts per billion than 3.2.

[00:06:27] Chris Bolhuis: Yes. So why didn't this iridium. [00:06:30] like the rest of the iridium sink to the core.

[00:06:33] Dr. Jesse Reimink: Right. So iridium is what's called a cile element, and cile means iron loving.

[00:06:39] Dr. Jesse Reimink: And this goes back to like some of the earliest geochemistry. No. Is, hold on, hold on. I'm sorry to [00:06:45] interrupt. No. Is that not what you meant? No.

[00:06:46] Chris Bolhuis: Ciro goes back to the ancient Greek, which means the iron. Oh, I think I want you to call me from here on out. , can you just refer to me as Ciro?

[00:06:56] Dr. Jesse Reimink: Yeah, . That's a good [00:07:00] one.

[00:07:00] Dr. Jesse Reimink: I like that. That's a funny one. Okay. Ciro. Oh, dear Ciro, can you tell me why that's, that's quite good. I like that so, It is cile. It loves iron like ciro, but uh, it [00:07:15] means that it is happier bonding with iron than bonding with anything else. Mm-hmm. And so it likes being with iron, which means that when Earth differentiated, you said, you know, earth is differentiated.

[00:07:26] Dr. Jesse Reimink: It separates out into density because it was all molten. It was all [00:07:30] molten. Iron is very dense, so the liquid iron sank to the bottom, formed Earth's core irid. Went with it cuz Iridium likes to form metallic bonds with iron. It does not like to bond with silica or oxygen, which are the main elements that [00:07:45] make up the mantle and the crust.

[00:07:47] Chris Bolhuis: And so when this meteor event happened, it happened after the differentiation of the earth

[00:07:53] Dr. Jesse Reimink: happened, right? So that's a great point. The differentiation of the earth. This forming the core that happened, you know, 4 billion [00:08:00] years ago, more than 4 billion years ago. So this meteorite impact is a much later event.

[00:08:04] Dr. Jesse Reimink: Earth's crust and mantle already lost all of the iridium, and so that's all in the core. Now. We will never really have access to that iridium in any high concentration. Yeah. So these sinking, [00:08:15] when that differentiation happened, these sink, these blobs of iron, when the earth was entirely molten, you th kind of visualized these big blobs of iron sinking down through silicate liquid.

[00:08:25] Dr. Jesse Reimink: And they just soaked up all of the iridium. Mm-hmm. . And now it's in the core.

[00:08:28] Chris Bolhuis: So one of the [00:08:30] interesting things about Iridium. is that it is the most corrosion resistant substance known on

[00:08:35] Dr. Jesse Reimink: Earth. That's really amazing. I didn't actually know that before we started looking into this. Right. This is, that's very cool.

[00:08:40] Dr. Jesse Reimink: Even at very high temperatures.

[00:08:41] Chris Bolhuis: But that makes sense with what you just said because you said [00:08:45] that. . Iridium loves iron, but it hates oxygen. And oxygen. Is it? Well, it oxidizes, it rusts things. Totally. And so this hates oxygen. Doesn't corrode

[00:08:55] Dr. Jesse Reimink: cuz it doesn't rust. Yeah. So like iron, you know, rusts, it forms heide.

[00:08:58] Dr. Jesse Reimink: That's, that's iron [00:09:00] bonding with oxygen, just like you said. Iridium doesn't do that. So it's used in things that need to be very corrosion resistant. Compass needles, pen tips, contacts in spark plugs, any sort of high voltage electrical contact. Usually has some iridium in it [00:09:15] because it's so corrosion resistant.

[00:09:16] Dr. Jesse Reimink: And

[00:09:17] Chris Bolhuis: it's also used in radiation treatment for cancer

[00:09:19] Dr. Jesse Reimink: patients, isn't it? Yeah. Right. So you can, uh, there are some isotopes of iridium. Usually they're synthetically produced, but they decay and they produce radiation that we can use for medical treatment things. Yeah. But [00:09:30] the total amount of iridium, like mind and used on a yearly basis is very small.

[00:09:34] Dr. Jesse Reimink: It's like three tons or something, which is tiny at the global scale. It's a very, very sort of small amount. Um, so

[00:09:40] Chris Bolhuis: how much does that go? Yeah, Ian's so

[00:09:43] Dr. Jesse Reimink: rare. I don't know. [00:09:45] I, the one number I saw was like $4,200, $4,000 per 100 grams of iridium, which is very expensive. I don't know how that compares really to other certain metals.

[00:09:56] Dr. Jesse Reimink: That's

[00:09:56] Chris Bolhuis: even, that's even

[00:09:56] Dr. Jesse Reimink: close to a pound. Yeah. No, no, it's, it's like, [00:10:00] uh, you know what is that quarter pound or something like that? Maybe? Yeah.

[00:10:02] Chris Bolhuis: Yeah. Close somewhere around there. All right. So just to be. I wanna make sure we're clear in this, right? Did we hit it well enough with why Iridium is so, so rare in

[00:10:14] Dr. Jesse Reimink: the crust?

[00:10:14] Dr. Jesse Reimink: I think [00:10:15] so. I mean, yeah, I think it kind of, in this earth distillation process, Iridium ends up getting distilled out or ends up down in the mantle or down in the, in the core. Actually it just sinks cuz it's denser. It's it bonds with the denser

[00:10:27] Chris Bolhuis: stuff. Yeah, it, it goes with the denser things. It goes with ciro.

[00:10:29] Dr. Jesse Reimink: [00:10:30] Exactly. With the iron one. So what we see on the surface does not have any, So it makes it a great tracer of meteorites. It's, it's a beautiful element for tracing meteorite impacts because it's so rare on the

[00:10:40] Chris Bolhuis: surface. That's a good point, is that iridium was [00:10:45] not, , uh, it wasn't the only time it was used as a tracer for meteors.

[00:10:49] Chris Bolhuis: There are other events that, like, there's an event that happened 2.5 million years ago that we use Iridium to

[00:10:56] Dr. Jesse Reimink: trace that event to exactly, and then you can go back all the way back to [00:11:00] 3.4 billion years ago, there's a Sphero bed that is high iridium concentrations in it. And, uh, people have used this to say, yeah, there's a 3.4 billion year old now, not million billion year old meteorite impact that occurred because we can see this iridium.

[00:11:14] Dr. Jesse Reimink: [00:11:15] Concentration spike or this iridium anomaly as we call it. Yeah, that's crazy. So it's this great tracer because of these sort of various chemical properties, which explain why it's useful in like compass needles. That was kind of interesting. I didn't know that Compass needles had iridium. I didn't either.

[00:11:27] Dr. Jesse Reimink: There we go. Now we do. We all learned something. Hey, the more you [00:11:30] know, the more you know . Alright Chris, I think that that nails it. We good? We're good. Let's wrap it up. Uh, follow us all the social medias. We are at Planet Geo Cast, planet geo cast gmail.com. Give us a review and a rating. We love that. That really helps us And share with your friends.

[00:11:44] Dr. Jesse Reimink: That's the [00:11:45] most important indeed. Cheers.[00:12:00] [00:12:15] [00:12:30] [00:12:45] [00:13:00] [00:13:15] [00:13:30] [00:13:45] [00:14:00] [00:14:15] [00:14:30] [00:14:45] [00:15:00]