Tunguska Meteor That Blasted Millions of Trees in 1908 Might Have Returned To Space (space.com) 82
schwit1 quotes Space.com: A new explanation for a massive blast over a remote Siberian forest in 1908 is even stranger than the mysterious incident itself.
Known as the Tunguska event, the blast flattened more than 80 million trees in seconds, over an area spanning nearly 800 square miles (2,000 square kilometers) — but left no crater. A meteor that exploded before hitting the ground was thought by many to be the culprit. However, a comet or asteroid would likely have left behind rocky fragments after blowing up, and no "smoking gun" remnants of a cosmic visitor have ever been found.
Now, a team of researchers has proposed a solution to this long-standing puzzle: A large iron meteor hurtled toward Earth and came just close enough to generate a tremendous shock wave. But the meteor then curved away from our planet without breaking up, its mass and momentum carrying it onward in its journey through space.
Known as the Tunguska event, the blast flattened more than 80 million trees in seconds, over an area spanning nearly 800 square miles (2,000 square kilometers) — but left no crater. A meteor that exploded before hitting the ground was thought by many to be the culprit. However, a comet or asteroid would likely have left behind rocky fragments after blowing up, and no "smoking gun" remnants of a cosmic visitor have ever been found.
Now, a team of researchers has proposed a solution to this long-standing puzzle: A large iron meteor hurtled toward Earth and came just close enough to generate a tremendous shock wave. But the meteor then curved away from our planet without breaking up, its mass and momentum carrying it onward in its journey through space.
It was obviously a large spaceship (Score:5, Funny)
Ask Erich von Däniken.
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Yes, of course. What else could it be?
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So, the earth experienced a near miss? (Score:5, Insightful)
Am I interpreting this analysis correctly? They seem to be saying that the Tungsuka event was a near miss ! What would have happened in the event of an actual meteor impact? Did our planet just barely avoid a mass extinction event?
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Unlikely. Obviously such a meteoroid would lose some % of its kinetic energy during its pass through Earth's atmosphere. Say it was 10..20%. Then an impact would have released 5..10x 'Tunguska events' worth of energy. Spectacular, but not an extinction event. Say it was only 1% (really massive object that slowed down only slightly). Then an impact would have released ~100x that amount of energy. Catastrophic, but still not an extinction event. Say it was only 0.1%. Then it would have been such a massive, l
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Say it was 10..20%.
Sure, but we have no *basis* for saying that. It's just another "what if" scenario. It could just as have been 1%.
Re:So, the earth experienced a near miss? (Score:5, Informative)
Sure, but we have no *basis* for saying that. It's just another "what if" scenario. It could just as have been 1%.
It still wouldn't have been an ELE.
The Tunguska explosion released about 10MT of energy. That is about the same as Castle Bravo. If it was ten times bigger, it would be in the range of Tsar Bomba. Those events had a negligible effect on the climate.
Even if the impact was a full GT (10 to 20 Tsar Bombas) there is no reason to believe it would be an ELE, and most likely would barely have a measurable effect.
The 1815 "Year without a summer" was caused by the ~33 GT explosion of Mt Tambora. That was still nowhere near an ELE.
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GP mentioned Mt Tambora eruption/explosion which released huge amounts of ejecta, including between 10 and 120 million tonnes of sulfur.
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The Tunguska meteor is estimated to be about 100m in diameter. So that would be roughly 500,000 cubic meters.
Tambora ejected 175 billion cubic meters. About 350,000 times as much.
It is impossible for an airburst to be an ELE. If it is big enough to be an ELE, it is way too big to be an airburst.
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Being pedantic, an object of 100m in diameter is an asteroid and not a meteor. A meteoroid is an object of less than 1m in diameter. Typically, meteoroids burn up in the Earth's atmosphere to produce meteors or shooting stars. They can form meteor showers.
Therefore, the Tunguska event would likely be an asteroid entering the Earth's atmosphere.
Air blast for more damage (Score:2)
That's one theory. It's also possible that it simply blew up in a chain reaction, raining small fragments over a large area.
Bombs other than bunker-buster types are designed to explode above the ground in order to increase the damage compared to exploding at impact.
Here we're talking about a fairly large boom, so it can be compared to a nuclear bomb. A "smaller" 150-kiloton bomb would be detonated at one mile above ground for optimal damage. A much larger one such as a Mk-41/B-41 would destinated signifi
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blew up in a chain reaction, raining small fragments over a large area.
Or it was mostly ice and the explosion turned it into steam.
The problem with this new "deflection" theory is that the explosion pattern was nearly perfectly circular, with millions of trees flattened, all pointing away from the epicenter.
An object passing through the atmosphere would have left a linear pattern or an eccentric ellipse.
Also, what could cause a million-ton projectile to "curve"?
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An object passing through the atmosphere would have left a linear pattern or an eccentric ellipse.
. That’s what you might think, however the kinetic energy is extremely high and focused to a “small” area of origin, this resembles a bomb. It’s why all craters are circular and not ovals [scientificamerican.com], just look at the moon.
Hitting the atmosphere at something like 45,000 mph is like hitting a brick wall, the force felt is extreme, even enough to bounce meteors off that come in at an extremely low angle like a rock on a lake.
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It's awesome that just one single counter-example obliterates your claim. So here it is. https://www.lpi.usra.edu/publi... [usra.edu]
I'm kidding, there's more than one, https://www.sciencedirect.com/... [sciencedirect.com]
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He's not entirely wrong, just overly enthusiastic. Craters are circular much more than they should be, but not always. https://www.scientificamerican... [scientificamerican.com]
For a near miss though, you're not talking about an impactor exploding in the ground. You'd be looking at the impact of the shockwave. The article has a quote from somebody criticizing the idea based on the idea that the shockwave would be unlikely to be circular. Apparently the original authors published before actually simulating it. So... nothing to see h
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From your own 2nd reference URL:
"elliptical craters result from impact angles within 5 of horizontal and less than 1% of projectiles with isotropic impact trajectories create elliptical craters."
Indeed, in the interest of scientific rigor, he should have said "99% of all craters are circular", but in case of Earth, the atmosphere would bounce very shallow trajectories anyway.
Read your link (Score:2)
The first sentence from the first link you posted:
"The high velocities characteristic of objects striking a planet's surface result in impact craters that are circular even if the impact angle is not vertical"
So I wouldn't say that "obliterates" their claim that impact craters are circular even if the impact angle is not vertical. In fact, it states precisely the claim they made.
It also has a photo of a rare type of crater - a non-circular one, made by an object that was moving essentially parallel to the
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Also, what could cause a million-ton projectile to "curve"?
A Collision Avoidance System, nearly all FTL spacecraft have them now days
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A tachyon powered FTL spacecraft does not interact with subluminal matter. So no CAS would be needed.
Re: Air blast for more damage (Score:2)
If tachyons don't interact with normal matter, then how can you know anything about them? And how could a ship interact with them to become "tachyon powered"?
My hobby: blowing holes in sci-fi ideas that defy the laws of physics.
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And how could a ship interact with them to become "tachyon powered"?
The speed of light is a barrier in either direction. Tachyons can travel faster than light, but require infinite energy to slow down to c.
My hobby: blowing holes in sci-fi ideas that defy the laws of physics.
As long as they don't interact with subluminal matter, Tachyons don't violate the laws of physics.
You must have skipped school on the day when your high school physics teacher explained hyperdrives.
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Also, what could cause a million-ton projectile to "curve"?
Gravity.
They are claiming it curved AWAY from the earth. Can gravity do that?
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Atmosphere can.
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Re: Air blast for more damage (Score:1)
Circular ? I usually see a claim of butterfly
https://geology.mines.edu/wp-c... [mines.edu]
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The article doesn't go into detail on curvature. A fast-moving asteroid would curve slightly towards the Earth due to gravity, but the bouncing off the atmosphere would be in the opposite direction, tending to cancel out the effect of gravity (at the expense of some kinetic energy). We could thus picture the object's path as being linear, especially at higher rates of speed. If we graphed the object's height above the Earth's surface vs. time, initially there would be a steep decline as the object approa
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The models in the paper (I didn't waste time reading the linked article. The link to the paper is upthread.) acknowledge that the "SB" (their acronym, "Space Body") is decellerating through the whole of it's passage through the atmosphere. The rate of decelleration (jerk, third derivative of position w.r.t time) peaks at the densest atmosphere point, but the fastest point will be just after the object starts to feel atmosphere.
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I was waiting for someone to catch onto that (though TFA also mentions it, phrased differently).
Epicentres are the points on the surface of the earth directly above a focus solution for a seismic event. (If the velocity field around the focus is uniform, the two will be vertically above one another ; that's the normal assumption,
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Am I interpreting this analysis correctly? They seem to be saying that the Tungsuka event was a near miss ! What would have happened in the event of an actual meteor impact? Did our planet just barely avoid a mass extinction event?
Yes. If the miles wide and tens of miles long trail of fallen trees was just the shock-wave from it passing through the atmosphere, imagine what would have happened if it would have hit.
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They seem to be saying that the Tungsuka event was a near miss !
The theory is it went through the atmosphere, which would release huge amounts of energy, but was fast enough and was at the right angle to keep going and escape Earth's gravity. Not a miss but not an impact.
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No, they're not suggesting it was that large. They're talking about 100-200m diameter. An iron meteorite of that size would leave a huge crater and have some globally noticeable effects, but not cause an extinction event. For example, the one that killed off the dinosaurs is thought to have been about 100 times the diameter (that would be a million times the mass).
The idea is bunk though. Even the article points out that the pattern of fallen trees doesn't look at all like what you'd expect from a shockwave
Re:So, the earth experienced a near miss? (Score:4, Informative)
Not necessarily a mass extinction event.
The Chicxulub event, which extincted the dinosaurs ~ 65 million years ago, was a perfect storm. Both in the angle that it struck at (60 degrees), and where it struck. The ground there is gypsum, which is a sulfate. The angle caused a huge tsunami that hit as far away as the prairies in North America. The ejecta from the impact was super hot. The sky rained fire hail. Animals had to live in hell, literally when temperatures reached 50, then 70, then 90 degrees C. Then the vaporized sulfates crept across earth causing massive cooling on the long run (7 degrees C cooling).
If it had hit a bit east into the ocean, or a bit west into the other ocean, it would be very different.
This short video [youtube.com] summarizes the event, but being ~ 6 years old, it misses a bit of the more recent research (angle of the impactor, and soil make up).
Would Tunguska did the same? Depends on what angle and what geology it would have hit.
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Near miss my ass. More like a near hit!
Re: So, the earth experienced a near miss? (Score:1)
It's still out there! (Score:2)
Wouldn't that then leave it within earths orbit or plane around the sun? Keep your eyes on the sky! We may have a recurring nuclear event.
--
Shall I, that have destroyed my Preservers, return home? - Alexander the Great
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even if it still retained enough to escape Earths' gravity well; wouldn't that at least potentially put it somewhere in the near-Earth neighborhood?
No "ifs" about it. If it had lost too much energy to escape Earth, it would have come back down. Asteroids don't tend to do circularisation burns like a spacecraft.
So after grazing the Earth, it will be in a solar orbit that intersects Earths orbit. Countless objects are in such orbits, including Haley's comet.
But a 100m asteroid that could be billions of km away is still not easy to find.
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Re: It's still out there! (Score:1)
Could it have picked up organic material and possibly deposit it elsewhere? Not like that life might live elsewhere (maybe a few moons) but events like these could have spread life through the early solar system, and even between systems.
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Could it have picked up organic material and possibly deposit it elsewhere?
Nope, if you mean life.
The panspermia hypothesis requires a much larger meteorite, and a ground impact to throw large chunks of rock into space.
Bacteria might survive frozen for thousands of years for space travel, but would need to be deep inside the rocks to be protected from radiation.
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According to wikipedia, the time was 7:17 AM, about 9 days after the summer solstice. Tunguska is fairly far north. A grazing strike means the object's path was parallel to the Earth's surface, which limits the direction both coming and going.
I don't know the orbital mechanics, so I'm guessing here: if the object's path was in the ecliptic, it either was coming from inside the Earth's orbit or its orbit was retrograde. Passing by the Earth would likely have greatly changed its path, so its probably not in t
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Found it! Spotted by a probe. [hbr.org]
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Reducing orbital speed (kinetic energy) at apohelion will reduce perihelion on the next apparition, and it's previous perihelion would have been fairly close in to the Sun to have such an ang
Curved *away"? How did it do that? (Score:2)
I'm guessing that the statement that the meteor curved away from the Earth is something put in by the journalist writing the article who probably didn't realize that the meteor wasn't captured by Earth's gravitational field and drag caused by the atmosphere and curved toward the Earth on a hyperbola as it continued on into space.
Regardless, I thought that most of the material in the meteorite would have been vapourized and it's material distributed about the Earth. If the meteor was made of the same materi
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Also if it's outer layer vaporized during atmospheric transit then I think the operative word there is 'vaporized'; would be sufficiently distributed that you wouldn't necessarily find any remnants of it large enough to analyze.
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If it grazed the atmosphere but still had escape velocity then it must have been going gods-be-damned fast to begin with.
Why? Obviously any object arriving has greater than escape velocity, and all we know it that it lost some speed relative to Earth in the encounter.
But relative to the Sun, it may even have picked up some speed, like a gravity assist on a space probe. TFA does not give any details from the model.
Is a faster asteroid more, or less, likely to "bounce off" the atmosphere without surface impact, than a slow one?
TFA says "a very shallow angle — about 9 to 12 degrees tangential to the surface." huh? Is it
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Is it 9-12 degrees, or is it tangential?
Obviously 9Â - 12Â of from the tangent - or is that really not obvious for you?
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- or is that really not obvious for you?
It is of course an obvious possible interpretation, (missing "from" typo?) but still does not make much sense.
Or was it 9-12 degrees at first, and tangential near the surface?
If it really were tangential in the upper atmosphere, you would not need any strange physics to explain why it did not impact.
9-12 degrees is a very long way from that, and requires some mechanism to deflect it away.
I can imagine it bouncing like a skipping stone on a water surface, but the analogy does not stand up.
Being a "little bit
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There are two ways how to measure the angle.
Either using an angle versus the tangent or from perpendicular, they have chosen tangent. So it was 9 - 12 degrees off from the 180 degrees tangent.
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I didn't waste effort reading TFA, except to find the link to TFP, which I've posted upthread somewhere. Reading TFP didn't leave any uncertainties such as you're expressing.
They are talking about a trajectory which was 9-12 deg (most of the time they used 11.5 deg) below a trajectory which would have been tangential to the atmosphere at an altitude of 160km and several thousand km downrange of Tunguska. Lowest altitude of the trajectory at 11km. Deviation of the trajectoyy f
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I think you mean 40km/s. And "exit velocity". "Escape velocity" means something different.
Plain vanilla. Not even a cherry on the top.
No, it means the ablation is due to the interaction of a hypersonic (40-30 km/s) plasma of atmospheric gases on the iron. Or whatever else the o
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If it grazed the atmosphere but still had escape velocity then it must have been going gods-be-damned fast to begin with. Also if it's outer layer vaporized during atmospheric transit then I think the operative word there is 'vaporized'; would be sufficiently distributed that you wouldn't necessarily find any remnants of it large enough to analyze.
Err... No. If it was going goddamn fast to begin with it would have disintegrated. Air friction at those speeds is a b*tch. The slow knife and so on applies to meteorites too.
More likely something only a few km/s above escape velocity to begin with and skirting the Earth's atmosphere fairly high. Just a fairly substantial meteoritte - Extinction Level Event sized. one.
If that is the case, that is very bad news as it is:
1. Somewhere out there on a orbit which crosses Earth's Orbit
2. Not very far away
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Unless, of course, it was heading away from the Sun, in which case it could be a problem for the far distant future. And with a severe lack of information about the orbit, we've no real idea where or when it'll be coming from.
I'd say that probably means that the only protection we've got is the same as for any other impactor. But I think the osculating orbit in 1908 and the latitude of that osculation means that it is at a fairly high inclin
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Well within the normal range of meteors. Minimum speed at the top of the atmosphere is 11.8km/s, and the maximum common speeds are up around 70km/s. The upper limit is quite flexible without needing odd trajectories such as a sling-shot off Jupiter.
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It wasn't a meteor -- it was obviously a spaceship piloted by a teenage boy showing off for his friends!
Read somewhere that Tesla thought it was his doing (Score:4, Insightful)
I think this was in his autobiography, can't really remember where I read it, but Nikola Tesla was playing around with a "death ray" at this time and thought he'd blasted Tunguska himself.
I didn't know about the "no crater" bit.
Now I read this and think that we dodged a bullet there. We likely wouldn't be here if that thing would've been a hit.
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And I'm sure you're going to provide a reference for this claim.
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can't really remember where I read it, but Nikola Tesla was playing around with a "death ray" at this time and thought he'd blasted Tunguska himself.
It's a common science fiction theme.
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Meh. Tiny impactor.
Look at Canyon Diablo - same sort of size as that. Evan if it hit downtown Minneapolis, the suburban police could find living black people to kill the next day after blaming them for the impactor.
Here's what one looks like (Score:5, Informative)
More info and stats: http://fireball.meteorite.free... [meteorite.free.fr]
More Like A Notion Than An Actual Study (Score:4, Insightful)
From the article:
While the study authors didn't numerically calculate the impact of a shock wave that a "grazing" iron meteor of this size could produce...
And they quote Mark Boslough, a research professor at the University of New Mexico and physicist with Los Alamos National Laboratory:
"An object that survived such a transit through the atmosphere could not have descended close enough to the surface for a sonic boom to do the kind of damage that was observed at Tunguska," Boslough said.
The entire core of their notion is that this scenario could produce the observed blast pattern -- a symmetric circle yet they have not done the work to show that it could. This is quarter-baked at best.
And the "problem" they are seeking to solve, no rocky debris is not much of a problem given the current theory that it was a comet nucleus consisting of ice and dust. The Chelyabinsk meteor on the other hand was a LL5 chondrite stony meteor weighing about 12000 tonnes, but the largest fragment recovered was 654 kg, only 0.005% the mass of the parent body. A comet without any solid rocky body would not leave any fragment larger than dust.
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The entire core of their notion is that this scenario could produce the observed blast pattern -- a symmetric circle yet they have not done the work to show that it could.
Probably because the observed blast pattern WASN'T a symmetric circle, but rather more butterfly-shaped.
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There's a reason that I only read enough of TFA to find the link to the paper. Even if the journalists do a good job, you still need to read the paper itself. The link is upthread.
I AM KIROK!!! (Score:2)
Behold a god who bleeds!
Hasn't This Been Settled Yet? (Score:2)
Ha, hope it didn't say this, in departing... (Score:1)
"See you later, alligator"
"Hasta la vista, baby"
"I'll be back"
It was an attack (Score:1)