Meteor swarm could be loaded with surprises in June

On June 30, 1908, an object the size of an apartment building came hurtling out of the sky and exploded in the atmosphere above Siberia. The Tunguska event, named for a river, flattened trees for 800 square miles. It occurred in one of the least-populated places in Asia, and no one was killed or injured. But the Tunguska airburst stands as the most powerful impact event in recorded human history, and it remains enigmatic, as scientists don’t know the origin of the object or whether it was an asteroid or a comet.

One hypothesis: It was a Beta Taurid.

The Taurids are meteor showers that occur twice a year, in late June and late October or early November. The June meteors are the Betas. They strike during the day, when sunlight washes out the “shooting stars” that are visible during the nighttime meteor shower later in the year.

A new calculation by Mark Boslough, a physicist at Los Alamos National Laboratory, shows that the tree-fall pattern in Siberia is consistent with an asteroid coming from the same area in the sky as the Taurid meteor swarm. Boslough and physicist Peter Brown of Western University in London, Ontario, gave a presentation at the American Geophysical Union fall meet- ing in Washington this month in which they called for a special observation campaign this June to search for Tunguska-class or larger objects embedded in the Taurids.

In some years, Earth passes near the densest cluster of material in the Taurid stream - and 2019 will be such a year. The scientists say it presents potentially the richest batch of incoming material since 1975, when seismometers left on the moon by Apollo astronauts recorded a spike in impacts during the Taurid swarm.

“If the Tunguska object was a member of a Beta Taurid stream . . . then the last week of June 2019 will be the next occasion with a high probability for Tunguska-like collisions or near misses,” their AGU presentation stated.

“While we are not predicting another Tunguska airburst, an enhanced population of small NEOs [near-Earth objects] in the Beta Taurids would increase the probability of another such event on or near next year’s Tunguska anniversary,” they concluded.

To be clear, no one is saying that June should be declared National Wear a Helmet Month. Even if there is an “enhanced” number of Tunguska-class objects in the Taurid stream, the probability of one hitting Earth remains very low. Space rocks rarely come even as close as our moon.

Experts have a simple explanation for this: Space is big. It’s so much easier to miss the Earth than to hit it. Of course, it can happen, and it did in 2013, when an object smaller than the Tunguska impactor slammed into the atmosphere in Russia near the city of Chelyabinsk, creating a fireball and a shock wave that shattered windows and injured more than 1,000 people.

In all of recorded human history, the number of people killed by asteroid impacts is zero.

“This is not something that should be keeping you up at night,” Brown said.

Boslough and Brown do not know if there is, in fact, an “enhanced” population of relatively large asteroids lurking in the Beta Taurids. It’s a conjecture.