It’s been 66 million years since something very large and possibly angry flew to earth, killing all the dinosaurs, and for a long time now we’ve been looking for something to blame.
Scientists have finally found us a scapegoat—the planet Jupiter. Not that the planet did it on purpose—that we know of.
Here’s what we already knew: The Chicxulub Impactor, which left a giant crater in Mexico nearly 150 km across and almost 20 km deep was the devastating aggressor that killed almost 75 per cent of life on earth, blacked out the sky and caused fire to rain from above for a year and a half.
What we didn’t know is what caused it, or what it was exactly.
A new study may have given us the answer. Published in Scientific Reports, two Harvard professors Avi Loeb and Frank Baird Jr and Amir Siraj, graduating in 2021 with a concentration in astrophysics, have a new theory on what exactly happen.
Let’s get back to why this is Jupiter’s fault exactly—on the edge of the solar system is a sphere of debris called the Oort cloud, which sounds like an Adventure Time villain. A piece of debris in that cloud was bumped off-course by Jupiter’s gravitational field during the cloud’s orbit of the solar system and became a comet, hurtling towards the sun. the sun’s tidal force broke apart piece of the rock, sending one piece to earth.
This happens once every 250 million to 730 million years. Rest easy, as that’s a long way off.
“Basically, Jupiter acts as a kind of pinball machine,” said Siraj, who is also co-president of Harvard Students for the Exploration and Development of Space while simultaneously pursuing master’s degree at the New England Conservatory of Music, as one does. “Jupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.”
These kind of long-period comets are called “sun grazers” according to Siraj.
“When you have these sun grazers, it’s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that’s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force” said Siraj.
“You get what’s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there’s a statistical chance that these smaller comets hit the Earth.”
Their calculations increase the chances of long-period comets impacting earth by a factor of approximately 10, with about 20 percent becoming sun grazers, which lines up with researchers in their field.
Their theory also lines up with the age of the Chicxulub crater, which makes it a fair explanation for where it came from.
“Our paper provides a basis for explaining the occurrence of this event,” said Loeb, the Harvard scientist and professor.
“We are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.”
Loeb and Siraj’s hypothesis might also explain the makeup of many of these impactors.
“Our hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive [carbonaceous chondrite] composition than expected from the conventional main-belt asteroids,” the scientists wrote in the published paper.
We’re getting a bit too sciency here, but bear with us: The theory that’s long held is that whatever hit Chicxulub is a fragment of a much larger asteroid that came from the main belt between Jupiter and Mars. Only 10 percent of the main-belt astroids have this composition, while most long-period comets have it. The evidence shows the Chicxulub crater was caused by something from that same material. That evidence would support their model.
The new Vera Rubin Observatory in Chile should be able to see smaller fragments once it comes online in 2022.
“We should see smaller fragments coming to Earth more frequently from the Oort cloud,” Loeb said. “I hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.”
Then we will not only be able to study these events to understand the past—we can see more clearly if one is ever coming our way again. And then we’ll need to turn on the Aerosmith, and hope Ben Affleck and Bruce Willis are willing to help.
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