Are large asteroids hidden in this annual meteor shower?
- The Taurid meteor showers in June and November happen because Earth plows into debris left behind by Comet Encke. These showers appear to emanate from the constellation Taurus the Bull.
- Larger chunks of debris may be hiding in the Taurid meteors. Every few years, we pass through a Taurid swarm, or a denser concentration of comet debris. And in fact, it’s possible the Tunguska event of 1908, when a large space rock flattened forest in Siberia, was from the Taurid swarm.
- The Taurid swarm – if it exists – should be close to Earth in 2032 and 2036. That might mean the moon, and perhaps Earth, could be pelted again in those years.
By Mark Boslough, University of New Mexico
Could large asteroids hidden among meteors harm Earth?
Have you seen any meteors or fireballs lately? They might have been Taurid meteors. The North Taurid meteor shower runs until around December 2. These meteors are a result of debris left behind by Comet Encke. And there’s a weaker Beta Taurid meteor shower in June, which is also the remains of Comet Encke. Taurid meteors appear to emanate from the constellation Taurus the Bull.
Beyond the light show, there is something that scientists as well as onlookers have long wondered about: the possibility that bigger chunks are in the Taurid meteor streams. These chunks might be the size of boulders, buildings or even mountains.
And if that’s true, could one of those monster-sized Taurid objects collide with Earth? Could they wipe out a city, or worse? Is it possible that’s already happened, sometime in our planet’s past?
As a physicist who researches the risk that comets and asteroids pose to the Earth, I’m aware that this is a subject where pseudoscience often competes with actual science. So let’s try to find the line between fact and fiction.
Comet Encke
Comet Encke is the so-called parent comet of the Taurid meteors. It’s relatively small, just over 3 miles (almost 5 kilometers) in diameter. And it crosses inside Earth’s orbit and back out every 3.3 years.
As Encke moves, it sheds dust wherever it goes, like the Peanuts character Pig-Pen. A meteor shower occurs when that dust and debris light up while entering Earth’s atmosphere at high speeds. Ultimately, they vanish into an incandescent puff of vapor with a glowing tail, creating the illusion of a “shooting star.”
But dust isn’t all that breaks off the comet. So do bigger chunks, the size of pebbles and stones. When they collide with the air, they create the much brighter fireballs, which sometimes explode.
Doomsday showers
The coherent catastrophism hypothesis suggests that comet Encke was created when an even larger comet broke up into pieces. Encke survived as the largest piece. The hypothesis also suggests that other mountain-sized chunks broke off and coalesced into a large swarm of fragments. If such a swarm exists, there is a possibility those large chunks could one day hit Earth as it passes through the swarm.
But just because something might be physically possible doesn’t mean that it exists. Mainstream astronomers have rejected this theory’s most catastrophic predictions. Among other reasons, scientists have never observed high concentrations of these mountain-sized objects.
Despite the lack of evidence, researchers on the fringes of science have embraced the idea. They claim Earth experienced a global catastrophic swarm 12,900 years ago. The impact, they say, caused continent-wide firestorms, floods and abrupt climate change that led to the mass extinction of large mammals, such as woolly mammoths, and the disappearance of early Americans known as the Clovis people.
The evidence for a catastrophic cause of these events, most of which did not happen, is lacking. Nevertheless, the idea has gained a large following and formed the basis for British author Graham Hancock’s popular TV series, Ancient Apocalypse.
The Tunguska event
But even outlandish ideas can have elements of truth, and there are hints that some objects – more than just dust and debris, but less than doomsday size – indeed exist in the Taurid meteor stream … and that Earth has already encountered them.
One clue comes from an event on June 30, 1908. On that day, an enormous explosion in the sky blew down millions of trees in Siberia. This was the Tunguska event, an airburst from an object that may have been up to 160 feet (about 50 meters) in diameter.
The collision unleashed several megatons of energy, which is roughly the equivalent of a large thermonuclear bomb. What happens is this: The incoming object penetrates deep into Earth’s atmosphere, and the dense air slows it down and heats it up until it vaporizes and explodes.
Could this object have been a Taurid? After all, the Taurids cross Earth’s orbit twice a year – not just in November, but also in June.
Evidence for a Taurid causing the Tunguska event
Here’s the evidence: First, the descriptions of the trajectory of the Tunguska airburst, as reported by eyewitness observers, is consistent with that of an object coming from the Taurid stream.
What’s more, the pattern of blast damage on the ground beneath an airburst depends on the trajectory of the exploding object. Supercomputer simulations show that the shape of the surface blast that would be caused by an exploding Taurid object matches the pattern of fallen trees at Tunguska.
Finally, during the Taurid meteor shower in 1975, people observed large fireballs. And seismometers, that Apollo astronauts had previously placed on the moon, detected seismic events on the lunar surface. Scientists interpreted those events as impacts, presumably made by the Taurid meteors.
Could large asteroids hidden in the Taurids still hit us?
In 2032 and 2036, the Taurid swarm – assuming it exists – is predicted to be closer to Earth than any time since 1975. That might mean the moon, and perhaps Earth, could be pelted again in those years.
There is time to figure this out. Scientists can expand their astronomical surveys to look for Tunguska-sized objects at the locations where they are predicted to be the next time they are in our vicinity.
Most scientists remain skeptical that such a swarm exists, but it’s the job of planetary defenders to investigate possible threats, even if the risk is small. After all, a Tunguska-sized object could conceivably demolish a major city and kill millions. An accurate count of objects on a potential collision course is essential.
Put doomsday scenarios and ancient apocalypses aside. The real question, and still an open one, is whether a Taurid swarm could deliver more Tunguska-sized objects than we would otherwise expect. This would mean we have underestimated the risk from future airbursts.
Mark Boslough, Research Associate Professor of Earth and Planetary Sciences, University of New Mexico
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Bottom line: Large asteroids hidden in the Taurid meteors could be a threat to Earth. One of them might be responsible for the 1908 Tunguska event.
Read more: How likely is a doomsday asteroid swarm from Comet Encke?
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