Earth has a lot going for it.

But there’s one thing a bunch of other planets have that ours doesn’t, and that’s a ring. I mean, Saturn has seven, and we’ve got none.

But that may not always have been true. There are signs that Earth had its own bling once, and we just missed out on seeing  it by a few hundred million years. It wasn’t just a cool decoration either.

This ancient ring could  have been connected with one of the biggest leaps of biodiversity  in our planet’s history. Meaning it helped make Earth what it is today. [♪INTRO] For a long time, we used to think  rings were just Saturn’s thing, but they’re actually pretty  common in our solar system. All four of our giant planets have them, and there are hints that  Mars had a ring once, too.

But for whatever reason,  we didn’t have any evidence of rings closer to the Sun than that… until a team of scientists in  Australia picked up on something funny. They’d been trying to understand one of the most tumultuous times in Earth’s history, called the Ordovician Period, which began around 485 million years ago. And there was a lot happening back then.

Tectonic plates were on the move. Carbon dioxide levels shot up to  multiple times what they are today. Sea levels got so high that almost all of what’s now North America was underwater.

And then, out of nowhere, temperatures plunged, leading to a lot of the Earth freezing over. As you can imagine, there were big things happening with living things, too. At this point, our planet had just  gone through the Cambrian Explosion, which is when the tree of life hit a growth spurt.

And if the Cambrian is when we got the branches, the Ordovician is when they started to fill in. So in the midst of all this geological turmoil, new species were exploding into existence. Basically every modern fish and marine invertebrate traces its  origin back to the Ordovician, making this one of the most important periods of biodiversification in  the history of our planet.

The big question has always been… what happened? One intriguing clue is that  the explosion of new life happened right around the same time that Earth was bombarded by a sudden shower of space rocks. We can still see remains of these meteorites and the craters they made in the fossil record.

They’re thought to be pieces of an asteroid that broke up in the Asteroid  Belt 466 million years ago. And researchers have hypothesized that all these meteorites wreaked havoc on existing ecosystems, forcing organisms to evolve into new life forms. Others suggested that dust  from the meteorites blocked out the sunlight, which then caused  the temperature to plunge.

Either way, the general  consensus was that a run-in with this asteroid’s debris  somehow stirred things up on Earth and triggered the  rapid diversification of life. But there were some issues with the  idea that the breakup of a far-off asteroid caused the sudden  bombardment during the Ordovician. One big sticking point was the  fact that there’s no sign that Mars or the Moon got a shower  of meteors at the same time, which seemed to suggest that whatever happened, it was localized just to Earth.

Which led to someone on that  Australian team developing a hunch that a big chunk of that asteroid  had broken up a lot closer to Earth. And to explain why that matters, we need to talk about something called a Roche limit. When you have a small object like an asteroid approaching a large object like a planet, there’s an invisible line between the two of them that’s determined by their  relative gravitational forces.

Every planetary body is basically  held together by its own gravity, so when the larger object starts  to pull on the little one, there’s a tug of war between  those two centers of gravity, and the closer they are, the  harder the big object can pull. And if they get too close, that big object can essentially disintegrate the  smaller one, piece by piece. So the Roche limit is the line that determines how close is too close, so to speak.

And objects crossing over that Roche limit is actually how lots of planets get their rings — by demolishing big chunks of  rock that get too close to them. And now, here’s a little chunk of  information from one of our sponsors. Thanks to Brilliant for  supporting this SciShow video!

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That link gives you 20% off an annual  premium Brilliant subscription. And you’ll get the first 30 days for free. So in light of all that, the team of  researchers started to wonder if a big chunk of that far-off asteroid might  have wandered too close to Earth.

If that did happen, Earth’s  gravity could have ripped the asteroid to shreds, creating  our planet’s very own ring. It was a wild idea, but not impossible. Remember what I said about  how Mars used to have a ring?

We think this same thing happened to Mars, and then that the ring debris un-shredded and formed one of Mars’s moons. And if that same thing happened to our planet, the objects forming the ring could  have gradually fallen to Earth, explaining this mysterious bombardment  during the Ordovician Period. One way to test this idea is to look at where the impact craters were, relative to the equator.

See, because planets bulge out  a bit around their equators, that’s usually the best place for a ring to form. So they needed to map all of the  impact craters from this time period, but also needed to do that on a projection of where the continents were way back then. Because continental drift is a thing.

And the results were mind-blowing. They showed that most of  the craters dotted land that would have been within just  30 degrees of the equator. That suggests that meteors weren’t  just falling on Earth willy-nilly, in a shower of debris hailing  from the Asteroid Belt.

It seemed like they’d fallen out of  a ring that was circling the equator. This hypothetical ring probably  didn’t survive for too long, geologically speaking. It formed  around 466 million years ago and may have lasted about 40  million years before burning through the atmosphere, piece  by piece, and falling to Earth.

Aside from being an awesome piece of bling, this ring made of shredded  asteroid would have helped steer the evolution of our planet  and every living thing on it. It would have cast a shadow  on whichever hemisphere was in winter, making things even colder. At the same time, it would  have reflected light onto the summer hemisphere, making summer even hotter.

Meanwhile, dust kicked up  by meteorite impacts would have blocked some sunlight,  cooling the whole planet — and possibly explaining Earth’s sudden freeze. And all the environmental  changes may have been the key to the explosion in diversity  that came along at this time. The increased seasonality –  hotter summers, colder winters, and average temperature shifts  – all of that creates lots of new extremes, and more  distinctions between habitats.

When the range of temperatures  expanded, that meant there were all sorts of new niches for living  things to adapt and radiate into. Which would put pressure on all those critters to diversify into the groups that we see today. Unfortunately, we came along  about 400 million years too late to know what life  was like on a ringed planet, or to see a glowing ring up in the sky.

But if this ring really did  exist, we just might owe our existence to the biodiversification  it helped set in motion. So it was fashionable and  very functional. Win-win! [♪OUTRO]