Effect of a giant meteorite impact on Paleoarchean environment and life

> Drabon and her colleagues went in search of evidence of ancient major impacts in a remote area south of Kruger National Park in South Africa. There they sought out rocky outcrops containing a layer of spherules – molten droplets formed following a major meteorite impact that rained down over huge swathes of the planet. There are eight such spherule bands in this area, each preserving an ancient impact event.

> While the impact crater itself is long gone, analysis of rocks from 3.26 billion years ago tells a tale of planetary devastation. The layer of spherules from this huge impact was 15 to 20cm thick in places, compared with less than a centimetre for the famed dinosaur-killing meteorite, says Drabon.

Publications are institutionally incapable of publishing an article (and readers incapable of appreciating) that says, A Paper Investigates How Early Archean Impacts Might Have Possibly Affected The Development of Nascent Life

I love this type of articles where we can reconstruct what happened so long ago just based on careful observations.

Some other instances I've come across:

* The K-Pg extinction event that wiped off dinosaurs had the impact it did because the asteroid happened to impact a shallow water region. This kicked up a lot of sulfur (in gypsum) that further affected global climate: https://en.wikipedia.org/wiki/Chicxulub_crater#Effects

* Earth likely had rings ~466M years ago. We deduced this by looking at impact craters from that time period, and seeing that they all lie near the equator (accounting for continental drift): https://www.sciencedirect.com/science/article/pii/S0012821X2...

* Earth's rotation period was probably frozen at 21h, ~600M years ago, likely due to interaction between lunar and solar tides. This resonance could have been broken by ice ages (!!!). Amazing to think that global climate affects earth's rotation: https://en.wikipedia.org/wiki/Earth%27s_rotation#Resonant_st...

Yep. Good ol' observing, questioning, hypothesizing, experimenting, analyzing and concluding.

The paper also mentions that, at the time, "dinosaur killer"-sized objects hit the Earth every 15 million years on average, which must have been sort of disruptive.

Likely due to this: https://en.wikipedia.org/wiki/Late_Heavy_Bombardment

The purpose of scientific papers is to explain that, starting with observations.

What these authors claimed recently was that prior LHB estimates were low by a large factor. https://www.nature.com/articles/s41561-021-00835-9

Thanks for the paper link!

Vote for Giant Meteor 2028!

https://votegiantmeteor.com/

The downvotes are misplaced. This is a good question.

The value of HN is when people-who-know help curious folks understand the validity of a story. Surely someone here is more capable of assessing this story and I agree that skepticism is in order at first.

When is the next one coming? Or what is the probability distributuon like?

Except the article explains in fairly easy to understand terms how the study came to this theory, and the original paper is linked from that article. The question here gives the impression that the asker read only the headline.

> it's just a theory that tries to fit this data

What do you feel is missing? You might find that if you read the paper, it goes through the evidence, prior evidence, and their hypothesis.

It's a poisson distribution.

> reconstruct what happened so long ago just based on careful observations.

Me too! My book is filled with them. Like how minerals in lava, affected by Earth's magnetic field, lock into place while cooling, which provides us with yet another cross-check for radiometric dating. See page 23:

https://impacts.to/downloads/lowres/impacts.pdf

> Yeah, but it's just a theory that tries to fit this data. Doesn't mean it is correct.

Yes. What else do you expect from science, or really from any human attempt to find truth? Are you just upset they don't include the caveat "subject to potential future evidence or better theories" on literally every single piece of science journalism? Are you upset that people do their best to make sense of weird situations and then tell people about their work, even if it's not absolute truth? What do you want to happen here?

I hope that your reaction is because the headline is way more sensational (to the extent of probably being incorrect) than the actual paper's abstract (https://www.pnas.org/doi/10.1073/pnas.2408721121)

Here's what the actual paper says:

> [...] Thus, the S2 impact likely had regional, if not global, positive and negative effects on life. The tsunami, atmospheric heating, and darkness would likely have decimated phototrophic microbes in the shallow water column. However, the biosphere likely recovered rapidly, and, in the medium term, the increase in nutrients and iron likely facilitated microbial blooms, especially of iron-cycling microbes.

Which sounds and - if I understand it correctly - means something kinda different than how "reset early life" is ordinarily understood, huh.

The downvotes are because people are reading the question as rhetorical rather than being asked out of genuine curiosity. It's only a good question if the person asking it is doing so with an open mind.

(That and the article answers the question.)

Have you got a better theory that fits all available data and has predictive power?

Have the data actually been fit a Poisson distribution? Or is this is just a guess assuming constant rate and independence?

I imagine it is more of an exponential decay mixed with poisson since strikes were far more common back in the day. Also, I'd guess an exponential decay in the expected size of impactors over time as they've been smashing themselves into pieces.

Skepticism should begin with the skeptic's own motives. A skeptic's second question (after "Really?" or "Why?") should be, "Why am I asking?"

Do they want to test the claim to learn something, or to dismiss it, just to dismiss it?

If they're asking questions which are literally answered as part of the claim, they need to start over, and start with themselves.

No natural phenomena ever exactly fits any probability distribution.

The article claims that 363 billion tons of phosphorous were dropped on earth 3.26 billion years ago during a decade of darkness.

I’m completely incapable of making sense of that claim because it’s so far outside of my expertise.

But my fundamental problem is that I don’t trust the source’s incentives to deliver reliable information and I want someone independent to help me understand if this is a how strong or weak this science is.

And my starting point for that is “it’s very hard to know anything specific about the deep past. And I’m tired of scientific retractions.”

Right but I'm saying do we have data showing it's even close? (Genuinely asking, I have no idea.)

Not to nitpick but the dinosaurs were on already on the way out, the asteroid merely finished them off early.

https://www.theatlantic.com/magazine/archive/2018/09/dinosau...

There's no one stop shop for instantly correct science, think less about retractions and more about incremental advances toward better understanding.

> The article claims that 363 billion tons of phosphorous were dropped on earth 3.26 billion years ago

The article correctly reports that a series of papers claim that a bolide (large mass) of an estimated diameter of 37 to 58 km across impacted some time ago.

There's a slew of paths forward for anyone interested in knowing more and questioning these claims.

The 96 references cover such things as estimating the impact crater, spray field, and impactor size.

You might want estimate for yourself the mass of a spherical cow some 40km in diameter if the material were to be (say) nickel iron .. and then perhaps back of the envelope determine what fraction of that would 363 billion tonne be.

It may or may not help to know that W.Australia move a billion tonne of iron ore per annum, that's a certain volume of mesa uprooted and moved to China, and 363 years of that would be a similar mass and volume.

This goes to having a feel for the paper's methodology in estimating P mass.

You may also wish to review papers and books on the K-Pg bolide, the one that "killed the dinosaurs" which is estimated to be some ~50 to 200 times smaller by mass than the one discussed here.

There's also a body of work on theories of planet formation via big rocks smashing into each other, sticking together, and planets slowing growing as stray rocks get hoovered up.

> Sealioning (also sea-lioning and sea lioning) is a type of trolling or harassment that consists of pursuing people with relentless requests for evidence, often tangential or previously addressed, while maintaining a pretense of civility and sincerity ("I'm just trying to have a debate"), and feigning ignorance of the subject matter. It may take the form of "incessant, bad-faith invitations to engage in debate", and has been likened to a denial-of-service attack targeted at human beings. The term originated with a 2014 strip of the webcomic Wondermark by David Malki, which The Independent called "the most apt description of Twitter you'll ever see".

https://en.wikipedia.org/wiki/Sealioning

The comic strip in question is actually adorably absurd:

http://wondermark.com/1k62/

except the emission spectra from atoms :)

Thank you!

I have been trying to remember the name for that comic for years, and no amount of searching has ever yielded anything.

Aww! I love that for you. Finding things people are searching for is a bit of a hobby of mine, so I’m happy I was able to have helped you.

Just going through the numbers:

363 BB tons / (1 ton / cu m) / (1 BB cu m / cu km) is the mass of a 9-km-diameter ice ball, smaller for rockier materials.

363 BB tons / 10 years = 100 MM tons / day.

By comparison, Mount St Helens (1980) and Eyjafjallajökull (2010) each produced 500 MM tons of ash. So the amount of material is about equivalent to having a similarly-sized volcano eruption every few days for ten years straight.

The Earth's surface area is 500 MM sq km. If we were to distribute 363 BB tons uniformly, that would be an average of 1000 tons per sq km. If the layer had a density of 1 ton per cu m (same as water), the resulting layer would be 1/1000 of a meter thick. This seems to be thinner than the spherule layers described.

Please don't take the bait. It's fine to let us know when a headline is sensational/distorted so we can change it. It's not fine to take to the comments about it, because that is likely to produce a shallow and less interesting discussion, which is what happened here.

Edit: I've changed the title to that of the paper.

The paper is at https://www.pnas.org/doi/10.1073/pnas.2408721121. We've adopted its title above.

I meant that "you" like the general you, not iambateman you. Sorry if that wasn't clear. I couldn't figure out a better phrasing at the time. Hopefully it's better now.

I'm nobody to lecture people. I don't matter. I just really dislike seeing epistemic nihilism framed as skepticism, and that's the vibe I was getting from the top of the thread.

Science is the proven process for investigating nature while dealing with questions like "What if you're wrong about everything?" The comment at the top reads, out of context, like an absolutely wild example of someone asking, "What if you're wrong?" as if it's something new that's never been asked.

> And my starting point for that is “it’s very hard to know anything specific about the deep past. And I’m tired of scientific retractions.”

There's no way to prove the past without doubt. It's always going to be conjecture.

What people do is that, they observe current phenomenon, and see what kind of artifact it produces and leaves behind. They then work backward from that, if we see the same artifacts, they connect that back with a similar cause from the past.

Generally, people consider this even more reliable than human written artifact, because, well, human write a lot of BS. But when there are also written texts or drawn glyphs, those are looked at for corroboration.

All of that is added up to gain some level of certainty, but it'll never be for sure, because we'll always be working with incomplete information, and we'll use today's assumption to interpret the information from the past, but even the wildest things might be possible, like that the very nature of physics was different 1 billion years ago, and the same phenomenon would not result in the same kind of artifact as they do today for example.

You have to decide for yourself if this inherent uncertainty makes you more skeptical of historical claims, or if you feel the methodology is still reliable enough for practical purposes.

And I'd like to contrast this with science about the present, where once we assume something to be true, we can test it by predicting the future with it, and then seeing if that future materializes. If it does, it reinforces the validity of our truths, the more it can accurately predict the future, the truer it is, and where it fails to do so, we know it's not as accurate as it needs to be.

Science is about using the best methodology to get us as close as possible to the truth as we can be. Historical sciences have less to work with, but this might still be the best methodology if you want to be as close to the truth. Experimental sciences are able to have even better methodology that allows us to be even closer to the truth.

To the best of my knowledge not everyone agrees to that hypothesis. One of the strongest arguments against it is that paleontological evidence is always incomplete. Holes in it that are treated in favor of the hypothesis are actually smaller or comparable to holes that appear just due to incompleteness.

Likely it isn't, because the Solar system today and 3Bln years ago are two very different systems.

The dinosaurs were not “wiped off”, by which I mean they are not extinct. This is an extremely widespread misconception that popular science articles like this one keep perpetuating. We should do better and help people understand that (some) dinosaurs survived and evolved into modern birds. Birds are dinosaurs. Dinosaurs are alive today.

The article perpetuates the widespread misconception that dinosaurs are extinct. In reality, (some) dinosaurs survived and evolved into modern birds. Everything from penguins to ostriches, hummingbirds to albatrosses and woodpeckers to eagles is a dinosaur.

Science communication should do better and clear up this misunderstanding.

It would be so much cooler to say that the asteroid killed the pterosaurs. Not only is it factually correct, it also opens doors to more curiosity. Why do they say pterosaurs instead of dinosaurs? Turns out they are separate clades. The pterosaurs, plesiosaurs and mosasaurs are all extinct as best as we can tell. The dinosaurs are not.

Dinosaurs are delicious. They taste like chicken.

When referring to dinosaurs, most people are thinking about non-avian, teethed dinosaurs anyway.

Proof we live in a simulation. Everything tastes like chicken!

This is fascinating. Although I'm having trouble mapping your comment onto this: https://opengeology.org/historicalgeology/case-studies/dinos...

What is the complete set and which are extinct?

Here is the Chixculub impact effect in realtime simulated as happening in today's world: https://youtu.be/ya3w1bvaxaQ?si=S-jmFegMo63HKzID

We're assuming an even average distribution, and comparing ash to spherules - which would have different patterns of sedimentation depending on how far from epicenter one is. Although, for a large enough impact, the distribution radii overlap around the planet so there may be quite a bit of averaging as the sun+atmosphere provides a mixing medium and the energy to do so.

If things go sideways in 2029, the next one comes in 2036.

> What is the complete set and which are extinct?

That's as good a complete tree as you're likely to get, down to the class level. Some species in the class Aves survived, and progenitor species with Aves are still around today. There's no significant evidence of species in other classes of the clade Dinosauria surviving much past the impact boundary.

You can push this up one level to the clade Avemetatarsalia (including Pterosaurs along with Dinosaurs) and the statement above would still be true; but pushing it further to Archosauria would not be valid, because crocodilians survived (and survive) as well.

Read the article. That's the subplot. We get to see just how non-scientific science really is. The true and current evidence points to an asteroid being the final blow to an already declining environment. But the status quo narrative so strong that egos and biases override facts.

The diagram in your link only shows the dinosaurs, not the entire tree of animals alive at the time. Within that diagram, everything except Aves (which, incidentally, is the Latin word for birds) is believed to be extinct.

The article makes no mention of other clades that lived during the Cretaceous, such as the pterosaurs, or indeed the mammals. Just as birds are descendants of the few surviving dinosaurs, we are descendants of the few surviving mammals.

I get that, but most people don't know that birds evolved from dinosaurs that survived the asteroid (which I think is both interesting and important to know) and I think it's the responsibility of science communicators to... communicate that.