Meteorite that hit Earth 3 billion years ago dwarfed rock that caused dinosaur extinction: study

As It Happens6:19Meteorite that hit Earth 3 billion years ago dwarfed rock that caused dinosaur extinction: study

Over three billion years ago, a meteorite bigger than the city of Toronto struck the Earth. It ripped open the planet's crust and generated so much heat on impact the oceans started to boil.

It's a good thing the only living creatures at the time were bacteria and other tiny organisms.

According to a new study published in the scientific journal Proceedings of the National Academy of Sciences (PNAS), the meteorite known as S2 struck near present-day South Africa and was up to 200 times bigger than the rock that wiped out the dinosaurs.

As It Happens host Nil Köksal spoke to the study's lead author, Harvard University researcher Nadja Drabon. Here's part of their conversation.

I know you've asked people to sort of imagine they're standing on an island or maybe the coast of Cape Cod at that moment. Describe what you believe happened next.

Taking the time machine back in time, you land on this small little volcanic island. You see that massive space rock crashing towards Earth. And so the first thing you would see is a flash of light from the impact event. And then the impact would release a massive air blast and the seismic waves — a really strong earthquake that would travel across the globe.

But now, besides producing this shockwave, the impact actually released so much energy that the ... crust and the sediments that it landed on would actually vaporize to form a rock vapour cloud. So we're injecting that rock vapour cloud into the atmosphere, putting a lot of dust into the atmosphere. So the skies will actually start turning dark.

And in the process, you're putting so much heat into the environment that the atmosphere really started heating up above the boiling point of water, so that the uppermost layers of the oceans actually started boiling off. 

A totally relaxing day.

Yeah, a relaxing day! If that's not enough for you, on top of that — because Earth back then was a water world — this huge ball over 40 to 60 kilometres in diameter was likely to hit the ocean.

So this would initiate an enormous tsunami, quite possibly bigger than anything humans have ever seen. And this tsunami would just sweep across the globe, rip up the ocean floor, inundate coastlines and have been really devastating.

So, you know, if you were a human back then, you know, if you weren't killed by the heating or by the tsunami ... with the darkness and the heating, you know, the food chain would have really collapsed and it would have been really hard to get nutrients.

Clearly this was not a small event, not a small rock. How does this meteorite, though, for our listeners, just so they can, you know, visualize it a little bit more even in their minds, how does it compare in size and mass to the one that contributed to the extinction of the dinosaurs?

Yeah, the one that led to the extinction of the dinosaurs really pales in comparison. So the S2 meteorite was a carbonaceous chondrite, and it was between 40 to 60 kilometres in diameter. So this is huge in terms of mass. That means that the S2  impact was between 50 to 200 times bigger than the one that killed the dinosaurs.

I saw one article describe it as "four Mount Everests?"

Yes, that's the lower estimate.

We should stress, your research suggests that that very vivid moment of impact you describe, it's not all bad news. There's a silver lining to this meteorite, if we could say. What were the benefits?

After all of these devastating events, we certainly believe that a lot of microbes died off. So anything that was on land but got really hard on the shallow water, you know, any life that relied on photosynthesis would have probably died off.

But there were enough little refugia left — so like in cracks on the rocks or potentially in the deeper ocean where life could survive for quite a while. And then once the conditions returned back to normal, so that would be within a few years to perhaps a few decades, life not only survived and bounced back right away, but we actually think that it really bloomed.

And this is for two reasons. So firstly, carbonaceous chondrites, so this type of meteorite that hit, they can actually contain quite a bit of phosphorus. And we think of the early oceans as being really starved of phosphorus. So we don't think that there was a lot of life around; there was some, but not a lot. So this meteorite, you can almost picture it like a fertilizer bomb that just put a lot of phosphorus like across the entire globe. And this is a very important nutrient for life.

Then the second thing that helped microbes thrive in the aftermath of the impact is that with the tsunami traveling across the globe, it really ... brought waters from the deep oceans that are rich in iron and nutrients up to the surface where life is living.

So those two things together, the injection of phosphorus from the impact itself and the water masses from the deep ocean coming to the surface, we think that life actually, you know, really benefited from the impact for for quite a while.