Northern Hemisphere cooling 12,800 years ago generally thought to be caused by glacial meltwater; new geochemical evidence might support comet impact.
Analysis of ocean sediments has surfaced geochemical clues in line with the possibility that an encounter with a disintegrating comet 12,800 years ago in the Northern Hemisphere triggered rapid cooling of Earth’s air and ocean. Christopher Moore of the University of South Carolina, U.S., and colleagues present these findings in the open-access journal PLOS One on August 6, 2025.
During the abrupt cool-off—the Younger Dryas event—temperatures dropped about 10 degrees Celsius in a year or less, with cooler temperatures lasting about 1,200 years. Many researchers believe that no comet was involved, and that glacial meltwater caused freshening of the Atlantic Ocean, significantly weakening currents that transport warm, tropical water northward. In contrast, the Younger Dryas Impact Hypothesis posits that Earth passed through debris from a disintegrating comet, with numerous impacts and shockwaves destabilizing ice sheets and causing massive meltwater flooding that shut down key ocean currents.
However, the impact hypothesis has been less well supported, lacking any evidence from ocean sediments. To address that gap, Moore and colleagues analyzed the geochemistry of four seafloor cores from Baffin Bay, near Greenland. Radiocarbon dating suggests the cores include sediments deposited when the Younger Dryas event began. To study them, the researchers used several techniques, including scanning electron microscopy, single-particle inductively coupled plasma time-of-flight mass spectrometry, energy dispersive spectroscopy, and laser ablation inductively coupled plasma mass spectrometry.
The analysis detected metallic debris whose geochemistry is consistent with comet dust. These occurred alongside microscopic spherical particles whose composition indicates a mostly terrestrial origin, with some materials believed to be extraterrestrial—suggesting these microspherules could have formed when comet fragments exploded just above or upon hitting the ground, melting materials together. The analysis also uncovered even smaller nanoparticles with high levels of platinum, iridium, nickel, and cobalt, which can be signs of extraterrestrial origin.
Together, these findings indicate a geochemical anomaly occurring around when the Younger Dryas event began. However, they do not provide direct evidence supporting the impact hypothesis. More research is needed to confirm whether the findings are indeed evidence of impact, and to firmly link an impact to climate cooling.
Dr. Christopher R. Moore adds: “Our identification of a Younger Dryas impact layer in deep marine sediments underscores the potential of oceanic records to broaden our understanding of this event and its climatological impacts.”
Dr. Mohammed Baalousha adds: “It is great to implement our unique nano-analytical tools in a new area of study, namely the analysis of nanoparticles generated or transported to the Baffin Bay core site during the Younger Dryas. We are always happy to implement our tools to support our colleagues and explore new frontiers.”
Dr. Vladimir Tselmovich adds: “Collisions of the Earth with comets led to catastrophes leading to climate change, to the death of civilizations. One of these events was a catastrophe that occurred about 12,800 years ago. Having studied in detail the microscopic traces of this disaster in Baffin Bay, we were able to find multiple traces of cometary matter, which was identified by the morphology and composition of the microparticles found. The amount of comet dust in the atmosphere was enough to cause a short-term “impact winter,” followed by a 1,400-year cooling period. The results obtained confirm the hypothesis that the Earth collided with a large comet about 12,800 years ago.”
Citation: Moore CR, Tselmovich VA, LeCompte MA, West A, Culver SJ, Mallinson DJ, et al. (2025) A 12,800-year-old layer with cometary dust, microspherules, and platinum anomaly recorded in multiple cores from Baffin Bay. PLoS One 20(8): e0328347. https://doi.org/10.1371/journal.pone.0328347
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Thanks for the good read, Anthony. Randall Carlson has put a couple podcasts on YouTube going over these possibilities. Makes a lot of sense due to the global change in such a extremely short period of time.
A good read and argument-who knows? The “cosmic” traces found are quite plausable, as is a sudden melt-tho why who knows? Cause and effect, poor correlation, coincidence? Again, who knows? This old planet of ours has had the S beat out of it for a few billion years from comets, asteroids, big rocks-whatever-again, who knows? And we still have bits and pieces of stuff falling on us. Fascinating. Personally, I favor comets or really big rocks based on history and current events. But, again…?
There have been fewer large comet or asteroid impacts than might otherwise have been expected. For all of the 4.5 billion years since the Earth was formed,it has had a much bigger brother protecting it Jupiter has a mass of more than 300 times that of Earth. It thus has a huge gravity well compared to other planets. And for all of those 4.5 billion years, Jupiter has been drawing very large numbers of comets and asteroids into itself. We saw this happening in our lifetimes in 1992-94 when Comet Shoemaker-Levy 9 was first dismantled by Jupiter’s gravitation and its pieces fell into Jupiter.
This is very far from the first such impact which Jupiter has absorbed over the past 4.5 billion years. Jupiter has been functioning effectively as a giant vacuum cleaner sweeping up large numbers of much smaller objects and preventing them from hitting much smaller planets like ours.
Because of the gravitational protection of Jupiter, this is likely to be a key reason why Earth-impactors like Chicxulub 65 million years ago. These long periods of relative calm has allowed life on Earth to evolve into complex forms.
That makes sense.
But it should be testable.
The frequency of impacts should have a periodicity related to Earth’s position, relative to Jupiter. The two planets have different years so there ought to be periods of lesser and greater protection.
How does the bombardment periods fit into your post?
https://science.nasa.gov/moon/lunar-craters/what-is-the-late-heavy-bombardment/
It’s generally consistent. The so-called Late Heavy Bombardment period takes place not long after the Moon was formed from the Earth by a collision with a very large asteroid. It should be noted that the incidence of crater formation declines over time. A reasonable speculation is that, over this time, Jupiter has been absorbing more and more of the assorted orbital material in solar orbit. There should be a decline over time of asteroid impacts as Jupiter thins out the number of such asteroids and other particles of all sizes.
Why meltwater or comets. The more plausible explanation, backed by observation, is freeing up of grounded ice sheets as the water level rose. Once these monsters were roaming the oceans in both hemispheres, they would keep the oceans cool for centuries.
There is evidence of icebergs scrapping at depths of 700m now so about 600m when they were broken from land masses as the ocean level rose.
And I am certain there would be space debris accumulate on ice over the 100kyr period of the glaciation that would be spread across the oceans as they melted..
Iceberg A-23A is now grounded again. It has an area of 3460km^2. And this is an interglacial with close to zero change in ocean level. Imagine the amount of ice hanging off land masses during the depths of glaciation.
“ The amount of comet dust in the atmosphere was enough to cause a short-term “impact winter,” followed by a 1,400-year cooling period.”
An” impact winter” seems quite plausible, but it’s not clear to me why a 1400 year coo “cooling period” would follow, and why would it suddenly end? It’s also not obvious why it would be limited to the Northern hemisphere.
It shows up in some Antarctic ice cores, but greatly attenuated compared to the north.
The chart at the top is confusing. The numbered circles 2, 4, and 5 show three periods of cooling that lasted from (about) 14,700 to 12,800. [Is #6 indicative of this entire episode, not the same years as 5?]
#5 seems to be what most call the Younger Dryas cooling but the cooling started at the apex of #1 and #2, at 14,700 bp.
My attempt to interpret the chart has cooling well before the 12,800 years ago of the comet encounter.
The red line between 4 and 5 is warming. Then the comet hits, causing rapid cooling. What caused the cooling of #2? Was that natural cold melt water cooling or was there more than one comet?
While being impressed by the use of the nano-analytical tools, I hope more can be learned of all the ups and downs from 15,000 to 11,000 bp.
Other’s comments will likely help with my confusions.
I had roughly the same questions. Seems something else was in play.
Britannica and other sources usually showed most or all of the cooling right before 12 kya to be the Younger Dryas, so I always assumed it was the whole thing. I never reeally looked into it. The effects of meltwater would make sense, but an asteroid or comet impact occurring around the same time would certainly act as a force multiplier. A small impact (non-Chicxulub-size) by itself should only have a short-term (few years) influence.
Sharing my “had to look it up” result:
“The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico… The crater is estimated to be 200 kilometers (120 miles) in diameter and 30 kilometers (19 miles) in depth. It is one of the largest impact structures on Earth”
Not a “Comet” debris from a disintegrating comet: copy/paste: the Younger Dryas Impact Hypothesis posits that Earth passed through debris from a disintegrating comet, with numerous impacts and shockwaves destabilizing ice sheets and causing massive meltwater.
The YD was caused by ice sheet meltwater outburst from proglacial lakes into the Arctic Ocean. One of numerous papers presenting irrefutable evidence confirming this inescapable conclusion:
https://www.nature.com/articles/s43247-022-00428-3#:~:text=Abstract,the%20disintegrating%20Laurentide%20Ice%20Sheet.
The prior Dryas cold snaps were caused by previous such freshwater floods earlier in the glacial termination, just as in previous deglaciations and Heinrich Events.
Irrefutable?
A supported hypothesis, which is what is presented, is NOT irrefutable.
It is irrefutable that there was an outwash flood precisely at the YD onset. Also at the Older and Middle Dryas, and iceberg armadas at each and every Heinrich event. Plus the same in every other glacial termination for 2.5 million years.
“Precisely at the YD onset.”
Would that be to the microsecond or the picosecond?
There may be the correlation you identify, but that does not define cause and effect.
Your statement infers consensus is irrefutable.
“Why 100? If I were wrong, one would have been enough”
— Albert Einstein
It implies no such thing. If you imagine it’s refutable, please provide a single shred of evidence doing so. Thanks!
So under the hypothesis what caused the meltwater? Any chance you’re confusing cause and effect?
The same things that cause all outwash floods. The ice dam floats up or is broken, or the lake overtops the topography.
See the Missoula Floods and Lake Agassiz, for instances. The Icelandic word is jökulhlaup.
Another interesting question is what caused that significant warming around 14500, some 25 F(?)/C(?).
YD the same time as peoples started to populate the Amazon basin – fascinating!
13,800 years ago
Looks right. But be cautious.
The correlation between two dates with such huge uncertainties is of limited significance when compared with the duration of a human life.
And migration is a human decision.
Some astronomers have proposed that the Earth encountered the comet Swift-Tuttle in a skip impact event at Lake Michigan that kicked off the Younger-Dryas period. The oval shaped Carolina Bays lend credence to the idea as the result of the ejections from the event. Throw in the extinction of the North American mega fauna, the massive fires discovered in that period and the paper reference in the post; I think it is only a matter of time before the scientific consensus centers on this.
I think it is also possible that millions of tons of ice was ejected into a polar orbit around the Earth creating a ring around the Earth. The ring reduced the amount of sunlight causing the 1400 year temperature drop until the ring eventually disintegrated as the material eventually returned to Earth.
Even original proponents of the YDIH no longer cite the Carolina Bays in support.
Nor do megafauna extinctions fit. Those occurred before, during and after the YD. The last American megafauna, ie giant ground sloths, weren’t wiped out until humans reached Caribbean islands some 4000 years ago.
All perfectly reasonable conjectures.
I appreciate the analysis of alternatives, even if I support none of them (or only some of them).
Doubtless, the comet was attracted to the earth by the CO2 in the atmosphere. Another reason for net-zero. Right?
LOL.
I posted similar a day or 2 ago.
Oh that evil CO2 is responsible for everything!
Volcanos affect climate/weather too…..around 536 and 1516 there was volcanic activity that cooled enough to leave evidence….and is likely to happen again. The earth has no doubt been bombarded by asteroids as much as the moon…..and will be hit again.
One possibility, not part of the analysis in the article and unrelated, is the kinetic energy released by comets or comet fragments striking ice sheets (or air burst above) would contribute or, unlikely by themselves, explain the ice sheet melts.
Eyeballing the graph leads to the conjecture that had there been no external influence, such as a comet, the temperature might have risen in a relatively linear fashion from ~15K bp to ~11K bp.
It is also possible (conjecture) that the interval, given all the significant ups and downs, could be the result of multiple events, such as comet strikes.
I looked in the referenced paper and did not find what the identifiers in the graph above indicate.
Good thinking, that giant crater near Winslow, AZ was formed by an explosion above the surface not a physical strike to the surface.
I once worked with kinetic energy “tools.”
KE = ma = 1/2 mv^2
Analysis of alternatives is a very useful tool.
I also recall the Tunguska event, a massive explosion that occurred in Siberia, Russia, in 1908, a likely (not proven) comet air burst.
The explosion flattened an estimated 80 million trees over an area of 2150 square kilometers (830 square miles).
“The analysis detected metallic debris whose geochemistry is consistent with comet dust.”
If I analyze a woodchip from my back yard the samw way, what are the odds I find “metallic debris whose geochemistry is consistent with comet dust”?
Low as the “metallic debris” more likely had chemistry consistent with your sawblade.
There should have been a grand solar minimum starting from close to 12,870 years ago.