Friday, November 8, 2013

Tunguska and Chelyabinsk Airbursts: Risk, Rocks, and Readiness

(Image © Don Davis; from PAINTINGS at

Stuff falls out of the sky every day. Most of it is tiny, some isn't, and on very rare occasions Earth's biosphere gets reset.

Now it looks like events like the Tunguska and Chelyabinsk airbursts aren't nearly as infrequent as we'd thought.
  1. Time for an Early Warning System
  2. Good News, Bad News, and Occam's Razor

Earth: A Nice Place to Live, But - - -

I like Earth, it's a nice place to live: but it isn't entirely safe. Between exploding mountains, cosmic debris falling out of the sky, intermittent ice ages and the occasional massive clusters of volcanoes pouring millions of cubic kilometers of lava over the landscape. That's not a typo.

The Ontong-Java_Plateau is the biggest one that we know about. It covers about 2,000,000 square kilometers and is up to 19 kilometers thick. The eruptions that formed it produced between 59,000,000 and 100,000,000 cubic kilometers of lava: and that's another topic.

Tunguska, Chelyabinsk, and Shanxi Province

(Copyright M. Ahmetvaleev, via NASA News, used w/o permission.)
"This image shows the flash above Chelyabinsk, Russia, from the fireball streaking through the sky on Feb. 15, 2013. The small asteroid was approximately 56 to 66 feet (17 to 20 meters) in diameter. The picture was taken by a local, M. Ahmetvaleev."

Conventional wisdom, Western style, says that nobody's ever been killed by meteorites. Meteorites may have killed livestock. Then again, maybe not.

Back in 1490 AD quite a few folks in Shanxi Province stopped living rather abruptly, when stones shot out of the sky. Western 'experts' say that the number of fatalities in Chinese records is too high. I'm pretty sure that survivors in Shanxi Province would have agreed, and that's yet another topic. Topics.

We're also supposed to believe that nobody died in the Tunguska event. That could be true. Very few folks were living near the Podkamennaya Tunguska River when something exploded, leveling 2,150 square kilometres of forest.

Just over a hundred years later, nobody died when a fireball lit up the sky over Chelyabinsk. The claim seems plausible, since Information Age tech makes disconnects between reality and 'official' reports hard to hide. Still more topics.

Damaged Buildings, Slashed and Seared People

The February 15, 2013, the Chelyabinsk object left a pretty vapor trail in the sky and did remarkably little property damage on the ground.

(Copyright M. Ahmetvaleev, via NASA News, used w/o permission.)
"This photograph of the meteor streaking through the sky above Chelyabinsk, Russia, on Feb. 15, 2013, was taken by a local, M. Ahmetvaleev. The small asteroid was about 56 to 66 feet (17 to 20 meters) wide."

(Reuters//Yevgeni Yemeldinov, used w/o permission.)
"Workers repair damage caused after a meteorite passed above the Urals city of Chelyabinsk February 15, 2013." (Reuters)

Granted, several thousand buildings needed repair afterward and more than 1,400 people needed medical attention: but it could have been worse.

Faith and Brains

I'm a Catholic, so I have to trust God. I'm also expected to use my brains, and plan for the future. (Catechism of the Catholic Church, 227, 2115)

Part of humanity's job is "subduing" this creation. From a Catholic point of view, this isn't the crazy Victorian-era notion that we can rip into natural resources like there's no tomorrow. We're expected to use our brains, plan ahead, and work toward building a world that future generations can use. (Catechism, 373, 1880, 2432, 2415, 2432)

We've seen streaks of light in the sky, probably ever since we've been around. About two centuries back, some scientists realized that meteors came from beyond Earth's atmosphere. Since then, we've learned quite a bit about meteors, asteroids, comets, and extinction events.

Today, we're very close to having the technology to move incoming asteroids and comets into less lethal orbits. If we're smart, we'll get a 'space patrol' organized before scientists notice something big headed our way.

More about being prepared:

Smarter than Cockroaches

America, China, India, Japan, Russia, or another space-faring nation could develop tech for moving asteroids and comets in the next few decades. Setting up a reliable system of observers and responders is another matter.

Even if America's Congress and every other nation's leadership decide that preventing a global catastrophe isn't important, I think humanity would survive a 'Chicxulub' event.

Quite a few species weren't wiped out 65,000,000, years back. We're not quite a resilient as cockroaches, but we're a whole lot smarter.

We live on every continent except Antarctica, maintain outposts there, and have a long track record of adapting to unpleasantness. I think some people would endure the radical climate changes and massive loss of wildlife. How much of anyone's civilization the survivors could hang on to: that's another question.

Again: I hope we have at least another few decades to get ready.

(Detlev van Ravenswaay, Science Source, via National Geographic News, used w/o permission.)
"An illustration of the Chicxulub impact crater in the Yucat√°n Peninsula."

1. Time for an Early Warning System

(Alexander Ivanov, via BBC News, used w/o permission.)
"Archive: Eyewitnesses and CCTV cameras captured the moment the meteor flew across the sky in Russia in February"
(BBC News)
"Chelyabinsk meteor: Space rock hit-rate 'underestimated' "
Rebecca Morelle, BBC News (November 6, 2013)

"The threat of another asteroid strike like the one that hit Russia earlier this year is much higher than was previously thought, a study suggests.

"Researchers have found that space rocks of a similar size to the one that exploded over Chelyabinsk are hurtling into the Earth's atmosphere with surprising frequency.

"Scientists say early warning systems need to be put in place.

"The study is published in the journal Nature...."
(Rebecca Morelle, BBC News)
"Much higher" in this case is about ten times what scientists assumed last year. The odds of a Chelyabinsk-size blast over Sauk Centre, Minnesota, this year is still very small. I'd probably have better odds for winning a lottery.

Quite a few folks don't live in Sauk Center, though. Sooner or later something will fall out of the sky, explode, and someone will get in the way of collapsing masonry.

The Chelyabinsk object only injured a thousand or so folks, with no known fatalities. for a 500 kiloton energy release, that's a remarkably low number. Some buildings in Chelyabinsk didn't stay intact, and that's yet again another topic.

Why Bother?

"Lead author Professor Peter Brown, from the University of Western Ontario, Canada, told the BBC World Service's Science in Action programme: 'Having some sort of system that scans the sky almost continuously and looks for these objects just before they hit the Earth, that probably is something worth doing.

" 'In the case of Chelyabinsk, a few days' to a week's warning would have been valuable.'


"The asteroid that exploded over Russia on 15 February this year was estimated to be about 19m-wide...."
(Rebecca Morelle, BBC News)
If astronomers tracked something as big as the Chelybinsk meteor a week before February 15, and were reasonably sure about where the it would hit, folks could prepare. Evacuating a city might not be possible, but letting everyone in the danger zone know could be done.

Old-school angst over agitating 'the masses' notwithstanding, I think most of us have enough sense to stay away from potentially dangerous areas, and take shelter. Here in Minnesota, we have tornado warnings every summer: and those only give us a few minutes to take cover.

I've lived here most of my life, and have yet to see 'the masses' panic over anything. Some of us did get a little crazy during the Cold War, and that's almost another topic.

The Next 'Big One'

For events like the Chicxulub impact, 65,000,000 years back, a week's warning wouldn't do much good. Not today.

I think we could do is let folks near ground zero know that they would die in about a week.

We don't have a rapid-response force ready that could move an object that size: not yet. Being on the same continent might be 'too close:' so evacuating folks would probably be impossible.

If something like that landed in an ocean again, the results would be a little different, but probably just as bad for people. Imagine a replay of the Merak incident, shortly after Krakatoa exploded: along the north Atlantic seaboard.

The good news is that events like that only happen every hundred million years or so: on average. We think. A key phrase there is "on average." These things don't happen on a fixed schedule. Another 'Chicxulub object' could be hit Earth in 35,000,000 years, or 70,000,000, or come in time for the Tokyo Olympics.

We just don't know.

2. Good News, Bad News, and Occam's Razor

(From Russian Emergency Ministry, via, used w/o permission.)
"Meteor Trail Over Russia: Feb. 15"
"Earth at Higher Risk of Asteroid Impact, Russian Meteor Explosion Reveals"
Charles Q. Choi, (November 6, 2013)

"The risk of asteroid impacts like the meteor explosion that devastated a Russian city earlier this year may be 10 times greater than previously thought, several new studies on the meteor's origin and power reveal.

"The meteor explosion over Chelyabinsk, Russia, on Feb. 15 was the first video-recorded meteor known to cause substantial damage and injuries. It was the largest airburst on the planet since the famed Tunguska event in 1908, also in Russia. Divers recovered a coffee-table-size chunk of the Chelyabinsk meteorite weighing about 1,430 pounds (650 kilograms), the largest fragment unearthed yet, from the bottom of Russia's Lake Chebarkul on Oct. 16. Satellites also watched it streak through the atmosphere...."
We're learning more about just about everything: including meteors and asteroids.

The good news is that damage from meteors isn't as bad as we'd thought. Calculations had been based on data from nuclear explosions, which release energy in a single burst. Meteors usually break up as they fall, releasing their energy over more time and distance.

Even so, I'd prefer to be elsewhere. The Chelyabinsk meteor was 30 times brighter than the sun for a short time, and apparently gave more that two dozen people sunburn.

The bad news is that these things may fall to Earth about 10 times as often as we thought.

Earlier estimates were based on what astronomers had noticed and tracked by telescope. Apparently Russian Academy of Sciences' Olga Popova and NASA Ames' Peter Jenniskens looked at records of airbursts and other data.

High-energy explosions have been happening in Earth's atmosphere that weren't connected with known nuclear bomb tests. Occam's Razor suggests that the airbursts happened when meteors exploded.

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