Ancient Meteorites Show Early Earth’s Atmosphere May Have Had 1,000x More Carbon Dioxide Than Now


These tiny meteorites, about half a millimeter across, fell into the ocean and were collected from the deep sea. Like the samples used in the new study, these more recent micrometeorites are made of iron. Credit: Donald Brownlee/University of Washington

Very occasionally, Earth gets bombarded by a large meteorite. But every day, our planet gets pelted by space dust, micrometeorites that collect on Earth’s surface.

A University of Washington team looked at very old samples of these small meteorites to show that the grains could have reacted with carbon dioxide on their journey to Earth. Previous work suggested the meteorites ran into oxygen, contradicting theories and evidence that the Earth’s early atmosphere was virtually devoid of oxygen. The new study was published this week in the open-access journal Science Advances.

“Our finding that the atmosphere these micrometeorites encountered was high in carbon dioxide is consistent with what the atmosphere was thought to look like on the early Earth,” said first author Owen Lehmer, a UW doctoral student in Earth and space sciences.

At 2.7 billion years old, these are the oldest known micrometeorites. They were collected in limestone in the Pilbara region of Western Australia and fell during the Archean eon, when the sun was weaker than today. A 2016 paper by the team that discovered the samples suggested they showed evidence of atmospheric oxygen at the time they fell to Earth.

That interpretation would contradict current understandings of our planet’s early days, which is that oxygen rose during the “Great Oxidation Event,” almost half a billion years later.

Knowing the conditions on the early Earth is important not just for understanding the history of our planet and the conditions when life emerged. It can also help inform the search for life on other planets.

“Life formed more than 3.8 billion years ago, and how life formed is a big, open question. One of the most important aspects is what the atmosphere was made up of — what was available and what the climate was like,” Lehmer said.

The new study takes a fresh look at interpreting how these micrometeorites interacted with the atmosphere, 2.7 billion years ago. The sand-sized grains hurtled toward Earth at up to 20 kilometers per second. For an atmosphere of similar thickness to today, the metal beads would melt at about 80 kilometers elevation, and the molten outer layer of iron would then oxidize when exposed to the atmosphere. A few seconds later the micrometeorites would harden again for the rest of their fall. The samples would then remain intact, especially when protected under layers of sedimentary limestone rock.

The previous paper interpreted the oxidization on the surface as a sign that the molten iron had encountered molecular oxygen. The new study uses modeling to ask whether carbon dioxide could have provided the oxygen to produce the same result. A computer simulation finds that an atmosphere made up of from 6% to more than 70% carbon dioxide could have produced the effect seen in the samples.

“The amount of oxidation in the ancient micrometeorites suggests that the early atmosphere was very rich in carbon dioxide,” said co-author David Catling, a UW professor of Earth and space sciences.

For comparison, carbon dioxide concentrations today are rising and are currently at about 415 parts per million, or 0.0415% of the atmosphere’s composition.

High levels of carbon dioxide, a heat-trapping greenhouse gas, would counteract the sun’s weaker output during the Archean era. Knowing the exact concentration of carbon dioxide in the atmosphere could help pinpoint the air temperature and acidity of the oceans during that time.

More of the ancient micrometeorite samples could help narrow the range of possible carbon dioxide concentrations, the authors wrote. Grains that fell at other times could also help trace the history of Earth’s atmosphere through time.

“Because these iron-rich micrometeorites can oxidize when they are exposed to carbon dioxide or oxygen, and given that these tiny grains presumably are preserved throughout Earth’s history, they could provide a very interesting proxy for the history of atmospheric composition,” Lehmer said.

Reference: “Atmospheric CO2 levels from 2.7 billion years ago inferred from micrometeorite oxidation” by O. R. Lehmer, D. C. Catling, R. Buick, D. E. Brownlee and S. Newport, 22 January 2020, Science Advances.
DOI: 10.1126/sciadv.aay4644 

Other co-authors are Donald Brownlee, a UW professor emeritus of astronomy; Roger Buick, a UW professor of Earth and space sciences; and Sarah Newport, a former UW undergraduate who is now at Rutgers University. The research was funded by NASA, the UW Astrobiology Program, the UW Virtual Planetary Laboratory and the Simons Foundation’s Collaboration on the Origins of Life.

5 Comments on "Ancient Meteorites Show Early Earth’s Atmosphere May Have Had 1,000x More Carbon Dioxide Than Now"

  1. “Scientists” of today are fiction writers who don’t go in for all that scientific method stuff, gets in the way of a good story and funding. Morons the lot of them.

  2. We’re oxygen breathers, more than a little CO2 kills us. Sure, its interesting to known 2.7-B years our atmosphere had 1000X CO2. I’m happy to pay taxes for the sake of knowledge for its own sake, but this finding (IF correct) not going to get us anywhere right now. Sorry I’m being grouchy, I havent had a single M&M today because I ran out and the new order hasn’t arrived, and I’m in a terrible mood.

  3. As James Hansen explains, yes there was a lot of co2, 4.6 bn years ago. But the sun was a lot dimmer, so it didn’t matter.

    I am trusting James Hansen here.

  4. The Earth could put up with a lot of different stuff millions of years ago because the Sun was weaker than it is today. Venus and Mars were able to be different back then. But today the power of the Sun is stronger and is affecting our planet in a whole different way. Also back then we humans didn’t do things that added heat or pollution to our atmosphere so us humans weren’t affecting the deterioration of our planet in any way! However today we humans are putting up 90,000 to 200,000 things are gigantic vacuum machines that are also extreme heating machines that emit massive amounts of pollutants and heat into the atmosphere which destroys our atmosphere. These things are called jet engine airplanes, rockets and weapons that we launch daily into the Earth’s atmosphere! On top of that we humans are also driving these things called automobiles that also vacuum up moisture out of the environment closer to Earth as they also heat up and pollute the planet thus reducing the ability for nature to make clouds and rain. These things are all polluting our atmosphere with chemicals that make it very difficult for nature to make clouds. Then these things also vacuum up our Earth’s water molecules from the Earth leaving less moisture in the atmosphere to produce clouds. These jet planes we are told can suck in, heat up and pollute enough air about every 2 minutes to fill an enclosed Supper Size football stadium! Go check out a site on the computer called On there you will see the amount of passenger planes in the air worldwide at that given moment. This site doesn’t include any military planes from any country on that site. There are about 80,000 to 90,000 passenger jet planes flying around the earth every day. Averaging out that these jet planes are spending about 3 hours flying then we humans are flying jet planes that are vacuuming up, heating up and polluting enough of the Earth’s air to fill up 194,400,000 enclosed supper size football stadiums DAILY worldwide! And that is a low estimate because jet plane flights are on the average longer that 3 hours considering how long the planes are running their engines on the ground and also circling airports waiting to land. And this figure doesn’t include military jets and weapons and also private and military rockets whose exhaust is way higher that jet engine planes.
    Folks, clouds are the ONLY thing that Earth has that can prevent the Sun’s rays from reaching the Earth’s surface and heating up the Earth! Clouds are actually the Earth’s umbrella. To form clouds the earth must have a certain level of moisture in the Earth’s atmosphere. In certain parts of the earth, like desserts, there is not many clouds ever and look at what happens there in the desserts. Desserts get not much rain at all and live doesn’t exist for most living creatures and plant life in desserts and also on planets where there is no clouds or water or atmosphere like Mars and Venus.The Earth needs clouds to survive because clouds produce rain. The Earth also needs trees and vegetation to produce atmospheric moisture to the point where enough moisture is in the air to produce enough clouds so that those clouds can produce rain. If there isn’t enough clouds then the Sun will evaporate the water from the Earth while also heating up the Earth so that the Earth becomes hotter which is what probably happened to Venus and Mars.
    Folks, we have to go back to using propeller airplanes to fly because they don’t suck in, heat up and pollute the air in our atmosphere like jet engine airplanes do. Also we have to stop driving combustion engine vehicles and start driving electric power automobiles. Then we have to better design our buildings so that they don’t need air-conditioning and heat as much because heating and cooling a building is taking a lot of moisture out of the atmosphere. The Earth’s trees and vegetation can’t produce daily the amount of moisture to offset the amount of moisture that we humans take out of the atmosphere daily!
    Folks, we have about 10 to 15 years to either fix this global warming situation before it is too late fix our global warming problem! Right now today the permafrost in the North Pole region around Russia and North America is melting rapidly and all this melted water from the permafrost is draining into the Pacific Ocean in the North Pole region. This warmer permafrost water is melting the ice in the North Pole area and recent videos made by someone shows that this melting has been going on since the 1960’s which was about the time that jet engine airplanes, rockets, air-conditioning, more combustion engine vehicle traffic and China’s massive polluting industry buildup all started! In this video you will see that water runoff from permafrost melting water was every year to today melting the North pole. In about 10-15 more years of this melting the North Pole will have all or most of it’s ice and glaciers and snow covered mountains melted. This melted water in the Pacific Ocean is travelling around the water and heating up the water in the South Pole which is causing the South Pole to also melt!
    In about 15 to 20 years when the North and South Poles are mostly melted and the glaciers and snow covered mountains are all melted the Earth’s atmosphere will change dramatically! There will be less clouds then which means less rain and more heat reaching the Earth from the Sun. The water from the Earth will evaporate into nothing as desserts form around the world. Mass starvation and droughts will become the norm as people will not be able to grow crops on a massive scale as they do today to feed the people of the world. Streams, creeks and rivers and lakes will dry up and all animal and human live around them will leave the area or die. Insects will take over the world as they can survive a little longer because they only need droplets of water to survive. Whatever animals and humans left on Earth will have to survive on under ground water or cave water to live. Trees and vegetation will all die from lack of water and too much heat from the Sun. All of this happening now and will get a lot worse in about 10-15 years! You ALL better stop this now before it’s TOO LATE!!!! And the Republicans and all other politicians better stop denying any of this because as time goes on people will react to this global warming and vote the Republicans out of political office for not doing anything but obstruct us from doing anything!

  5. That makes sense, the carbon in me and my dog had to come from somewhere and I am a lot more dense than gas. I’m a little surprised it was only 1000x.

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