Interview with Dr. Christopher R. Moore, University of South Carolina, U.S.

Interview with Dr. Christopher R. Moore, University of South Carolina, U.S.

Author of PLOS One paper: 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

Can you tell us what The Younger Dryas Impact Hypothesis is, how it related to other Younger Dryas hypotheses, and what first drew you to studying it?

The Younger Dryas Impact Hypothesis (YDIH) proposes that around 12,800 years ago, Earth was struck by fragments of a disintegrating comet or asteroid, triggering widespread wildfires, abrupt climate cooling, and significant ecological disruptions. This event is believed to have initiated the Younger Dryas (YD), a sudden return to near-glacial conditions during an otherwise warming period. Evidence for the hypothesis includes microspherules, platinum anomalies, nanodiamonds, and charcoal-rich layers found at many sites across several continents.

The YDIH is often cited as an alternative to the Meltwater Pulse Hypothesis. What many don’t understand is that the YDIH proposes the impact event (potentially involving many thousands of impacts and airbursts globally) would destabilize the glacial ice sheet in the Northern Hemisphere, leading to the collapse of massive glacial meltwater lakes and subsequently shutting down the ocean’s conveyor belt. This shutdown of oceanic circulation is the most likely cause of YD climate change. In this regard, the YDIH is the trigger for the meltwater pulse. Another hypothesis suggests a volcanic trigger for the YD; however, there is no evidence for volcanic eruptions within ±50 years of the YD onset.

What did you choose to investigate in this study, and why?

We chose to analyze marine cores from Baffin Bay to determine if YD impact proxies reported from dozens of terrestrial sites globally were present in ocean cores. 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.

What are the key findings from your research?

The key finding of this research is the replication of findings from terrestrial sites within ocean cores, located as deep as 2,300 meters below the sea floor, with cores reaching depths of 6.3 meters. The other significant finding of this research is the novel application of single-particle inductively coupled plasma time-of-flight mass spectrometry (SP-ICP-TOF-MS) to identify elemental abundances (such as platinum, iridium, and nickel) and elemental ratios consistent with an extraterrestrial impact. This revolutionary new technology allows the determination of mass and concentrations of virtually all elements present within individual nanoscale particles in a sediment sample.

Metallic dust particles (MDPs) are a new discovery from Baffin and have chemistry consistent with that of cometary and meteoritic material. Some of these particles comprise low-oxygen iron and high-nickel content. The other primary impact proxy found at Baffin Bay is iron and silica-rich microspherules, which we show to have formed primarily from terrestrial material with minor amounts of impactor material, most likely from low-altitude airbursts or “touchdown” events where the airburst plume reached the ground.

What most surprised or interested you about your findings?

The discovery of metallic dust particles (MDPs) in the core samples, along with the microspherules, meltglass (melted terrestrial sediment), and nanoparticle evidence. MDPs are a new proxy for the YD impact that have gone unrecognized in earlier studies.

How do your findings provide potential evidence in support of the Younger Dryas Impact Hypothesis, and what additional evidence is still needed?

The YD sediment layer in the Baffin cores contains multiple proxies consistent with an impact event. Microspherules, twisted and deformed metallic dust particles (MDPs) with chemistry consistent with comet or meteoritic material, meltglass, and identification of nanoparticle peaks in key elements (e.g., platinum and iridium) suggest an impact event. This evidence is supported by the findings on terrestrial sites on multiple continents in both hemispheres. This work builds on other evidence that the YD impact event was likely global in scale. For future work, we plan to investigate whether these particles have a terrestrial or extraterrestrial origin by measuring oxygen isotopes and helium-3.

How do your findings fit into existing conversations about the The Younger Dryas Impact Hypothesis?

After analyzing narrowly constrained stratigraphic intervals of four ocean cores dating to ~12,800 cal BP, we present multiple lines of evidence, including spherules, metallic dust particles, meltglass, and PG-rich nanoparticles. Although a few critics dismiss the coeval abundance peaks in this material as being coincidental, the most plausible explanation is that they represent an airburst/impact event.

Our findings from Baffin Bay are the first instance of YD impact proxies recovered from marine cores. In our view, this puts to rest the idea that what we have found in shallow terrestrial sites is due to anthropogenic contamination. This study is also the first to identify metallic particles that have chemistry consistent with cometary or meteoritic material. We interpret these particles as likely of cometary origin, resulting from Earth's passage through the dust and debris stream of a fragmented comet. 

What do you hope your findings might lead to, and what are the next steps for your research?

We are expanding our research to include other marine cores collected from all the world’s oceans, to test the hypothesis that the YD impact was a global phenomenon. This research is highly relevant to our times because such impact events, whether small or large, pose substantial risks to our modern civilization. Small but devastating impacts are projected to recur every few hundred to a few thousand years.

Interview edited by PLOS staff for clarity and concision.