What Space Dust Reveals About Earth's Ice Age

Summary

Podcast Summary: Short Wave – What Space Dust Reveals About Earth’s Ice Age

Date: November 11, 2025
Host: Regina Barber (NPR)
Guest: Frankie Pavia (Geochemist, University of Washington)
Duration: ~15 minutes

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Episode Overview

This episode of Short Wave explores how fragments of space dust, or “cosmic dust,” are offering new insights into the history of ice coverage in the Arctic Ocean—and what that can teach us about climate change today and in the future. Host Regina Barber speaks with geochemist Frankie Pavia about the surprising ways interplanetary particles deposited on Earth's surface are helping researchers reconstruct ancient climate transitions—such as the last Ice Age—and sharpen predictions about the fate of Arctic sea ice in a warming world.

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Key Discussion Points & Insights

1. Setting the Scene: Earth During the Last Ice Age

• Around 20,000 years ago, Earth was much colder, with temperatures averaging 10°F colder than today and thick ice sheets covering much of North America.

  “There’s places where the ice is a kilometer thick, sitting on top of North America, the northern U.S. and Canada.”
  — Frankie Pavia (01:12)

• In the millennia that followed, CO₂ levels rose, the planet warmed, and ice coverage changed dramatically.

  “The Earth’s climate began to change.”
  — Regina Barber (01:43)

2. The Mystery: How Has Arctic Sea Ice Responded to Climate Change?

• The present rapid decline in sea ice motivates scientists to better understand past transitions as a guide for what’s next.

  “We would like to be able to predict what ice is going to be like in the future as we continue to warm the planet with fossil fuels.”
  — Frankie Pavia (02:27)

3. Cosmic Dust: An Out-of-This-World Proxy

• Cosmic dust is debris from asteroids and comets; it falls steadily to Earth, blanketing the surface at a near-constant rate over vast timescales (02:42).
• The unique “helium fingerprint” in the dust, altered by the solar wind, allows scientists to track its presence in sediment layers over time.

4. How to Read the Past: Sediment Core Sampling

• Researchers use specialized tubes attached to ships to extract columns of mud from the ocean floor; the oldest layers are at the bottom, newest at the top.

  “Essentially what you’re doing is you’ve got a big tube … and you basically ram a big tube into the sea floor, fill it up with mud with the oldest mud at the bottom and the youngest mud at the top...”
  — Frankie Pavia (04:33)

• Each centimeter of sediment corresponds to a window into past Earth conditions, with some Arctic sediment samples going back about 30,000 years (06:52).

5. The Cosmic Dust-Ice Connection

• Cosmic dust’s journey is interrupted if thick sea ice covers the ocean; the dust accumulates on the ice rather than in seabed mud, leaving a measurable deficit in sediment layers formed during icy eras.

  “When you have ice covering the Arctic, that cosmic dust that’s coming in through space and then through the atmosphere gets intercepted by the ice and can’t reach the seafloor.”
  — Frankie Pavia (08:04)

• By comparing the amount of cosmic dust (via helium signals) to other chemical markers, Pavia’s team detected a startling difference: a 300% deficit in cosmic dust for intervals corresponding to the last Ice Age, indicating an extended period of thick ice coverage (10:49).

  “There was, like, a 300% deficit in how much [cosmic dust]. ... In the world of geochemistry and paleoclimate, that is ... a real big signal.”
  — Frankie Pavia (10:49)

6. Why Does Ice Age Coverage Matter for Today?

• Knowing how Arctic sea ice responded to ancient warming helps validate and improve climate models for the future.

  “Ice coverage in the Arctic has dropped by about 40% over the last 40–45 years.”
  — Frankie Pavia (11:26)

• The implications stretch from global shipping and geopolitics to local coastal communities and global climate feedbacks (11:45).

7. How Did the Ice Melt? Ruling Out Heat Sources

• Three hypotheses for past sea ice melt: heat from Pacific waters, Atlantic waters, or atmospheric warming.
  • Findings: Warming from Pacific waters did not match the timing of the melting; atmospheric or Atlantic-origin heat remain the prime suspects (13:00).

  “We could show that heat from Pacific waters entering the Arctic was not the cause of ice breakup. ... We can’t conclusively make a call between Atlantic sourced heating and atmospheric heating.”
  — Frankie Pavia (13:13)

8. The Path Forward: More Data, Holistic Understanding

• The method using cosmic dust will continue to refine our understanding of Arctic climate transitions.

  “It takes a really holistic understanding of a lot of different things in the climate system and how they all operate together.”
  — Frankie Pavia (14:06)

• Anticipation for expanded use with more sediment samples and new analytical approaches.

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Notable Quotes & Memorable Moments

• “So naturally, Frankie wondered, what if space could help us know more about Earth, specifically using something called cosmic dust?”
  — Regina Barber (02:35)

• “You do have to be like, this is, you know, marine mud. It has no commercial value, blah, blah, blah. It doesn’t look as insidious or suspicious as you might think.”
  — Frankie Pavia, on shipping sediment samples (09:54)

• “There was, like, a 300% deficit in how much [cosmic dust]. ... In the world of geochemistry and paleoclimate, that is ... a real big signal.”
  — Frankie Pavia (10:49)

• “Our goal is to figure out where there are major changes in climate in the geologic past that can help us supplement the record of ice change that we’ve seen from satellites over the last 40 years.”
  — Frankie Pavia (11:45)

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Key Timestamps

• 01:12 – Ice Age conditions in North America
• 02:10 – Why study past climate change?
• 02:42 – Introduction to cosmic dust
• 04:33 – How sediment cores are collected
• 06:52 – How far back sediment records go
• 07:12 – Cosmic dust and helium fingerprints
• 08:19 – How ice blocks cosmic dust from being deposited
• 10:49 – Discovery of the 300% deficit in cosmic dust during last Ice Age
• 11:26 – Relevance for present-day climate change
• 13:13 – Eliminating potential sources of past Arctic warming
• 14:06 – Need for a holistic approach and next steps

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Conclusion

This episode delivers an engaging, accessible look into how something as small and cosmic as interplanetary dust can help answer massive questions about Earth’s climate future. Frankie Pavia and Regina Barber demystify complex geochemical detective work using curiosity and humor, revealing how deep time and deep mud can inform humanity’s response to climate change.

For science fans, policymakers, and anyone interested in climate or planetary mysteries—this episode is a journey from the stars, to the seafloor, to our rapidly changing Arctic.

Transcript

[Announcer]

This message comes from Memorial Sloan Kettering Cancer center, working to change the story of pancreatic cancer. And during Pancreatic Cancer Awareness Month, your support goes twice as far to accelerate breakthrough treatments. Donate [e-mail] give hey, short waivers.

[Regina Barber]

Could you do us a favor right now on the app or platform where you're listening? Could you leave us a quick review or rating like this one from Lindsay Lou, who says, love the podcast. It's so fun learning new everyday knowledge. Great info and conversation starters to have in your back pocket, too. Reviews like this really help new listeners find our show. So thank you, Lindsay, and thank you for listening and for taking a second to also leave a review and share us with your friends. Okay, onto the show. You're listening to short wave from NPR. Around 20,000 years ago, the world was cold. Temperatures around the world averaged 10 degrees Fahrenheit, cooler than they are today. And most of North America was covered in ice. Humans were surviving, though, mastering fire and making friends with wolves.

[Frankie Pavia]

There's places where the ice is a kilometer thick, sitting on top of North America, the northern U.S. and Canada.

[Regina Barber]

That's Frankie Pavia and a geochemist at the University of Washington. And he says because the Earth's climate was so different during that time, the winds and oceans move differently than they do now.

[Frankie Pavia]

And the sort of background state of Earth's climate. Right. Is just different. As a result, both of these changes to the Earth's surface and. Right, because there's 100 parts per million less carbon dioxide in the atmosphere during this time.

[Regina Barber]

But in the couple thousand years to follow, carbon dioxide levels in the atmosphere and temperatures started to climb and. And the Earth's climate began to change.

[Frankie Pavia]

It's a transition period. It's trying to get itself back to sort of a stable baseline state.

[Regina Barber]

Today, our climate is changing, too. But to understand that and the amount of ice we're losing, we need to know more about the past. That's where Frankie comes in.

[Frankie Pavia]

We're trying to figure out how ice coverage in the Arctic Ocean responds to climate change events in the past. Sea ice in the Arctic is a really fundamental part of the Arctic system as a whole, and it's declining quite quickly. And we would like to be able to predict what ice is going to be like in the future as we continue to warm the planet with fossil fuels.

[Regina Barber]

So naturally, Frankie wondered, what if space could help us know more about Earth, specifically using something called cosmic dust?

[Frankie Pavia]

Cosmic dust is debris that forms from collisions of things like asteroids and comets in the solar system.

[Regina Barber]

Cosmic dust blankets Earth's surface at a constant rate. And Frankie realized that this material from space could be key to finding out how the Arctic ice is melting now. So today on the show, what space dust is telling scientists about the history of ice in the Arctic and what that could tell us about the Earth's future. I'm Regina Barber, and you're listening to Shortwave, the Science podcast from NPR.

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[Regina Barber]

So, Frankie, in a new study, you and your team tried to figure out how Arctic ice basically covered the Earth and how it's impacted by climate change. How do you get the sediment to study that?

[Frankie Pavia]

Yeah. So to get the sediment, you have to send a boat out, right? To the, to the part of the ocean where you want to collect mud. And essentially what you're doing is you've got a big tube on the end of a long wire with some weight on top of it and a little device that self closes at the end of it so that when you fill up that tube with mud, the mud doesn't all come sliding out when you raise it back up. And so you basically ram a big tube into the sea floor, fill it up with mud with the oldest mud at the bottom and the youngest mud at the top, and then you haul that sediment back up to the ship that you're on.

[Regina Barber]

If I was to look at these tubes, how big would they be?

[Frankie Pavia]

The diameter of the tube is probably a little bit smaller than your or my face. And the length of the tube can vary from anywhere from like a foot to hundreds of feet long.

[Regina Barber]

How are you analyzing these? Like, are they like in a lab and you're like, looking at them? Or like, how are you Studying them.

[Frankie Pavia]

Okay. So these sediments are taken, you know, raised up. They're processed either on the ship or on land. They're sort of sliced up about a centimeter at a time. And each layer. Right. Each of those centimeter layers is analyzed to figure out what time period that that mud is from and what sort of characteristics of the environment are recorded in the chemical signatures of that sediment.

[Regina Barber]

Okay. So you're basically, like, going into the database and, like, looking at, like, information from all of these, like, centimeter thin disks.

[Frankie Pavia]

Yeah. So there's, you know, there's a. There are repositories. There's basically huge libraries of mud that's been collected at the sea floor since the 1950s, more or less. Arctic mud hasn't been getting collected quite as long as that. But right across the global ocean, you know, since the 1950s and even back to, like, the Challenger expedition in the 1800s, people were taking samples of seafloor mud.

[Announcer]

Wow.

[Regina Barber]

How much time is represented in this database of these, like, centimeter disks from.

[Frankie Pavia]

These sediment cores, specifically that we worked on in this paper?

[Regina Barber]

Yeah.

[Frankie Pavia]

We are going back about 30,000 years.

[Announcer]

Wow.

[Regina Barber]

Okay. And in your study, you looked at something called cosmic dust inside these sediment cores. And cosmic dust is that debris that forms from collision of things like asteroids and comets in the solar system. And how does this debris help you determine the age of ice?

[Frankie Pavia]

Yeah, so when that debris forms. Right. It gets bombarded with the solar wind, which is. Right. Blowing out from the sun, and it's enriched in rare forms of helium because the sun is burning hydrogen to make helium. And so that helium, with a sort of a distinct fingerprint, gets implanted into these cosmic dust grains. And those cosmic dust grains enter the Earth's atmosphere. So when they come in, they get heated, and only the really tiny grains, you know, less, you know, about 1/100th of a millimeter, keep their distinct helium fingerprint. And, you know, these cosmic dust grains then blanket Earth's surface at a constant rate in space and time over hundreds of thousands of years. And we can use measurements of that distinct, distinct helium fingerprint to tell us about how much cosmic dust is in sediment layers in the past.

[Regina Barber]

And knowing how fast it settles on the sea floor depends on how much ice was covering that area. How do you figure that out?

[Frankie Pavia]

So I was actually studying cosmic dust in a part of the ocean that had nothing to do with ice. And I was using it in concert with one other sort of chemical index that we measure that nominally both tell you the same thing about how sediments accumulate at the seafloor. But they have different sources. So cosmic dust comes from space, through the atmosphere to Earth's surface. And the other index chemical marker that we are looking at is produced in seawater. And when you have ice covering the Arctic, that cosmic dust that's coming in through space and then through the atmosphere gets intercepted by the ice and can't reach the seafloor. And we can detect that by measuring both our radioactive index and our helium Fingerprint for cosmic dust.

[Regina Barber]

Yeah. What'd you find?

[Frankie Pavia]

Yeah, so. Right. I got together with my main sort of collaborator on this, Jesse Farmer, who's a professor at UMass Boston, and he had been working on Arctic climate change in the past for some years. And we were sort of spitballing this idea, and I was like, jesse, is this. Is this, like, a good idea? Is this really dumb? Is there some way to, like, that we can get some Arctic sediments to test this? And Jesse, like, had. Jesse sort of had the ideal set of samples for us to give this.

[Regina Barber]

A whirl with, just sitting around.

[Frankie Pavia]

Yeah, truly. And so he sent me some little bags that had powdered sediment in them. Yep.

[Regina Barber]

And the postal service was not mad about that at all.

[Frankie Pavia]

You know, this is. This is sort of a funny thing. When you're shipping these sorts of things, you do have to be like, this is, you know, marine mud. It has no commercial value, blah, blah, blah. It doesn't look as insidious or suspicious as you might think. But there are geologic samples that do.

[Regina Barber]

So you're looking at these baggies, you're looking at these samples, and you're like, is this method going to work?

[Frankie Pavia]

So we maybe measured, like, 10 samples to compare the top of the core. Right. The most recent interval with samples that were from the last ice age. Right. 20,000 years ago. And we found sort of immediately that there is a big deficit in the amount of cosmic dust based on helium. Right. That we would have expected during the ice age.

[Regina Barber]

Okay. So that amount that you would just assume would be, like, just accumulating on the, you know, on the ocean surface was just not right.

[Frankie Pavia]

Yeah. There was, like, a 300% deficit in how much.

[Guest or Additional Announcer]

Wow.

[Frankie Pavia]

Yeah, exactly. And so that's like, in the world. In the world of, like, geochemistry and paleoclimate, that is like. That is a real. That is a real big signal. Right. And so that was like. That's what set us off to the races of like, okay, we are. We might be on to something here.

[Regina Barber]

So this deficit in cosmic dust says there, you know, or Implies that there's. There was ice there. Why do we as a human race need to, like, know about the ice coverage during the Ice age?

[Frankie Pavia]

Yeah. So that helps us say, okay, we've had these major shifts in climate, including conditions in the Arctic that were a little bit warmer than today. How does sea ice coverage respond? Because we've seen that over that last 40, 45 years, ice coverage in the Arctic has dropped by about 40%.

[Announcer]

And. Right.

[Frankie Pavia]

Climate models try and make predictions of when the Arctic will be ice free. And an ice free Arctic has consequences for things like shipping and navigation, for geopolitics of Arctic bordering countries that are jostling for superiority there, for fisheries, for coastal erosion, of communities that live on Arctic coastlines. And so our goal is to figure out where there are major changes in climate in the geologic past that can help us. Right. Supplement the record of ice change that we've seen from satellites over the last 40 years.

[Announcer]

Right.

[Frankie Pavia]

With longer timescales, with changes in climate that might be akin to where we're heading in the not so distant future.

[Regina Barber]

So one of the findings that kind of surprised me is that what was melting the ice was maybe more clear than you thought.

[Frankie Pavia]

Well, it was and it wasn't. We were able to rule out one. Right. So in order to melt this ice, you gotta bring heat in from somewhere. Right. That's what's gonna melt the ice. And we had a few options. Right. One was heat from warm waters entering the Arctic from the Pacific, one was heat from warm waters entering the Arctic from the Atlantic, and one was heat from the atmosphere. And based on the timing of when the Bering Land bridge opened up and allowed Pacific waters to enter the Arctic, we could show that heat from Pacific waters entering the Arctic was not the cause of this ice breakup. And so that left us with atmospheric warming. So direct atmospheric heating or heat coming in from Atlantic waters, and we can't conclusively make a call between Atlantic sourced heating and atmospheric heating. But more work that tries to unpack the mechanism for how you deliver heat to break up sea ice coverage during past Arctic climate change events would be really, really important to understand how that might be affecting ice coverage today.

[Regina Barber]

So we're going to use your method more and we're going to find out more.

[Announcer]

Yeah.

[Frankie Pavia]

And other methods.

[Announcer]

Right.

[Frankie Pavia]

Like other reconstructions that are looking at how different processes in the Arctic work. It takes a really holistic understanding of. Right. A lot of different things in the climate system and how they all operate together.

[Regina Barber]

Frankie, thank you so much for talking with us today.

[Announcer]

Yeah.

[Frankie Pavia]

Thank you. This is fun.

[Regina Barber]

This episode was produced by Rachel Carlson with a little bit of help from Hannah Chin. It was edited by our showrunner Rebecca Ramirez. And Tyler Jones checked the facts. Robert Rodriguez was the audio engineer. Beth Donovan is our vice president for podcasting. I'm Regina Barber. Thank you for listening to Short Wave from N.

[Frankie Pavia]

Foreign.

[Guest or Additional Announcer]

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