Did a Second Asteroid Finish off the Dinosaurs?

Probably not. There is a trend toward academic clickbait in scientific publishing that requires a “hook” to get media attention. The very unlikely relationship between the Nadir structure and the dinosaur-killing Chicxulub event does not represent the scientific significance of this paper. But that’s what made it newsworthy to the media.

This week, a new paper “The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure” was published in Science Advances. I found nothing wrong with the paper in terms of the science. The authors provided strong evidence in seismic reflection data on the sea floor in the eastern Atlantic for a ≥8.5-km-wide structure that looks like an impact crater, and they presented sophisticated computational simulations that showed how such a crater could have formed. This is a notable scientific contribution, because confirmed craters at the bottom of the ocean are rare.

Unfortunately the authors buried their lede in favor of highlighting the rarity of binary craters and impact clusters in the first sentence of their abstract, which they closed by stating, “We hypothesize that this formed as part of a closely timed impact cluster or by breakup of a common parent asteroid.” In my opinion, creative speculation should be encouraged in science and this idea has a legitimate place in this paper, as long as it’s clearly labeled as a hypothesis and not a finding (as the authors of this paper did). My only disagreement with the authors was the prominence they gave to this peripheral notion.

Scientists are not immune to the desire to get media attention for their work. Neither are their sponsors and institutions. It is well established that “clickbaity” academic papers are shared more widely. My own research has benefited from promotion by connections that are secondary to the science. One notable example was the opportunity I got to model the formation of Libyan Desert Glass because public interest was piqued after the discovery that King Tut had a carved piece of it in his tomb. Two weeks ago, I wrote an intentionally clickbaity blog post to draw attention to the existence of “academic clickbait.” In part because I chose a clickbaity title, it led to a discussion on Reddit that resulted in media attention.

My problem with academic clickbait isn’t the fact that it gets media attention, it’s that it has the potential to distort the significance (or non-significance) of the science. Scientists, institutional public affairs organizations, sponsors, journalists, and media consumers all need to be aware of this and work together to minimize this negative effect. For the record, I also used a clickbaity title and image on the present blog post to increase the likelihood that someone will actually read it.

Last week I was asked to answer five questions about the Nadir Crater paper for a CNN story published the day it was released. Here are the questions with my answers.

• Do you agree with the findings of the paper?

I agree with the findings with the following strong caveats: 

1) The paper did not declare that it found an impact crater, only that it found evidence for a candidate impact structure. This was the main finding. I agree that it's a good candidate and is likely to be conformed when it is drilled, but until then it's only a candidate as the authors correctly stated.

2) The paper offered a speculative hypothesis that (if the Nadir structure is confirmed as an impact structure with a date close to the K/Pg) this would be evidence for a closely-timed impact cluster. The authors make it clear that this is speculative and contingent, and I do not consider this to be a finding.

• How significant is the discovery of a crater of this size and age?

The discovery of a terrestrial impact crater is always significant, because they are very rare in the geologic record. There are fewer than 200 confirmed impact structures on Earth and quite a few likely candidates that haven't yet been unequivocally confirmed by the presence of diagnostic features such as shocked mineral phases which, in this case, will require drilling. The authors were careful to point this out. The most significant aspect of this discovery, in my opinion, is that it would be a submarine impact structure, for which there are few examples. The opportunity to study an underwater impact crater of this size would help us understand the process of ocean impacts, which are the most common but least well preserved or understood.

Regarding the size and age of this structure, it is unremarkable. As pointed out by the authors, impacts of objects this size could as frequent as one every hundred thousand years, meaning there have probably been hundreds of such impacts since the time of Chicxulub, and it should not be surprising that there were at least a few within a million years of that event. Having found evidence for one is the part that is significant.

• Do you agree it was caused by an asteroid?

I agree that it probably was, but confirmation will require drilling as stated by the authors.

• Was this asteroid strike linked to the Chicxulub impact?

I am very skeptical of that hypothesis, and I believe the authors are (rightly) skeptical too. They offered it as a speculative hypothesis but I think it's a real stretch given the limited information they have about its age and its lack of proximity to Chicxulub. Some elements of their hypothesis (e.g. a tidal breakup on a previous encounter with Earth with subsquent impact many years later) would be difficult if not impossible to test.

• Could the discovery change our understanding of why (non-avian) dinosaurs went extinct?

I don't think so. Even if they were simultanious impact events, the Chicxulub impactor had more than 10,000 times the mass and energy of the Nadir impactor. It's like the difference between a hummingbird and an adult human, and it implies that if .001% of the asteroid broke off and hit somewhere else on Earth it would change the outcome of the resulting extinction event.

The bottom line for me is that working to encourage media promotion of findings for public engagement is fine, as long is it doesn’t distract from or misrepresent the actual science.

Mark Boslough is a Fellow of the Committee for Skeptical Inquiry and chair of the Asteroid Day Expert Panel.