Credit: Paul Fleet / 500Px Plus / Getty Images Plus.
A recent analysis of ocean sediments has uncovered geochemical hints that the Northern Hemisphere was hit by a disintegrating comet 12,800 years ago.
The research suggests this comet may have triggered a rapid cooling of Earth’s air and oceans.
The Younger Dryas Impact Hypothesis is a theory which says during this time period Earth passed through debris from space which destabilised ice sheets and caused temperatures to drop. During the cooling event, temperatures dropped to about 10°C for 1,200 years.
Prior to the new study there was no evidence that Earth was impacted by a comet during this period of cooling, known as the Younger Dryas event.
Many researchers instead believed that glacial meltwater triggered the cooling. This meltwater is believed to have caused a freshening of the Atlantic Ocean which significantly weakened the currents that transport warm water to the Northern Hemisphere, leading to the cooler temperatures.
The researchers analysed the geochemistry of 4 seafloor cores from Baffin Bay, near Greenland to investigate what actually caused the Younger Dryas event.
“The sites were significant because they were a considerable distance from potential anthropogenic contamination, and in most cases, the cores were highly laminated, indicating that the record was relatively undisturbed,” says Dr Christopher Moore from the University of South Carolina (USC), USA.
The team used radiocarbon dating to determine which sediments were deposited when the cooling event began. They analysed the sediments further using scanning electron microscopy and energy dispersive spectroscopy.
“The other significant finding of this research is the novel application of single-particle inductively coupled plasma time-of-flight mass spectrometry to identify elemental abundances,” says Moore.
“This revolutionary new technology allows the determination of mass and concentrations of virtually all elements present within individual nanoscale particles in a sediment sample.”
The team uncovered small nano-particles that contained high levels of platinum, iridium, nickel and cobalt, all of which hint towards extraterrestrial origin.
Examples of Fe-rich and silica-rich impact microspherules (a and b) and metallic dust particles (MDPs; c and d) interpreted as cometary dust from Baffin Bay cores. Yellow arrows show particles of FeSi, FeS, and FeCr on microspherules (a and b) and NiFe, low-O2 Fe, and native Fe on metallic particles (c and d). Note folded edges of MDP in panel d. Credit: Moore et al., 2025, PLOS One, CC-BY 4.0.
“It is great to implement our unique nano-analytical tools in a new area of study,” says Dr Mohammed Baalousha from the Centre for Environmental Nanoscience and Risk at USC.
“We are always happy to implement our tools to support our colleagues and explore new frontiers.”
Analysis of these samples detected metallic debris whose geochemistry is consistent with comet dust.
These samples were found alongside particles of mostly terrestrial origin.
The authors suggest the comet exploded just above or upon hitting the ground, melting the materials and particles together.
“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,” says Dr Vladimir Tselmovich from the Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences.
While these findings indicate a “geochemical anomaly” at the beginning of the cooling period, further research is needed to provide direct evidence of impact and then linking it to the cooling.
“We are expanding our research to include other marine cores collected from all the world’s oceans, to test the hypothesis that the Younger Dryas impact was a global phenomenon,” says Moore. “This research is highly relevant to our times because such impact events, whether small or large, pose substantial risks to our modern civilisation.”