
The Hoba meteorite, estimated at 66 tons, left no crater when it fell to Earth - gus_massa
https://www.thevintagenews.com/2017/09/10/the-hoba-meteorite-estimated-at-66-tons-left-no-crater-when-it-fell-to-earth/
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tyingq
The explanation for why it didn't leave a crater is pretty unsatisfying.

I was expecting something about the flat shape and how it might have skipped
over the atmosphere and/or induced a lot of drag.

I did search a bit but didn't find an article that had both a plausible
explanation and some credible source.

~~~
comboy
I agree. Perhaps shape plus angle of fall and there could have been a thick
forest in that place or maybe a lake.

~~~
eloff
Those things matter at human terminal velocity (not much mind you) but not at
asteroid terminal velocity. Asteroids hit with so much speed that the kinetic
energy of impact mostly overcomes the binding energy between molecules and
even atoms and the impactor largely vaporizes. This is more true for comets
which are looser collections of ice and rock, and more true for larger
impactors.

~~~
russdill
Impactors like that have not slowed to their terminal velocity. They either
are small enough to be slowed by the atmosphere, bigger and explode in the
atmosphere, bigger still and they race all the way the ground.

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eloff
you're right

~~~
russdill
Completely off topic, but it really pisses me off that stuff like this gets
covered uncritically:

[https://blogs.wsj.com/indiarealtime/2016/02/08/meteorite-
kil...](https://blogs.wsj.com/indiarealtime/2016/02/08/meteorite-killed-man-
at-indian-college-says-chief-minister/)

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leeoniya
> Scientists have suggested that the massive rock apparently slowed down as it
> penetrated Earth’s atmosphere. It slowed so much that the Hoba reached a
> point of terminal velocity as it was about to impact the surface

i don't buy it.

why couldnt it be part of a bigger impactor, so if it was just a shard that
broke off after impact and flew mostly horizontally before settling?

maybe it struck the top of a thick glacier that has since melted?

maybe there were 200m of water in that location then?

terminal velocity for a meteor is 200-400mph. 66 tons at that speed would at
minimum leave it nowhere near the surface.

~~~
innagadadavida
No one seems to have proposed that it could have been magnetic and it
interacted with Earth's magnetic field.

~~~
vanattab
I don't think the earths magnetic field is anywhere near strong enough to
seriously effect a meteorites velocity.

~~~
dysan819
You don't have to guess, you can do the math.

While you're at it, watch this, it's fun (and related):
[https://www.youtube.com/watch?v=sENgdSF8ppA](https://www.youtube.com/watch?v=sENgdSF8ppA)

~~~
raverbashing
Yes, you can do the math. But "practical" intuition gives you a good sense of
possible orders of magnitude, though, sometimes fails.

A compass needle is easily moveable by hand. Even Lenz effect forces (when
only driven by magnets) are weaker than the attraction forces of the same
magnet (depending on the speed, of course) though going east->west the flux
doesn't change much.

So my conclusion is that, even though it might have had a small effect on it,
absolutely not enough to make it change velocity significantly.

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cronix
> The Hoba meteorite is an iron meteorite which is the only piece of iron on
> the Earth not made by men. Author: Digr. CC-BY 3.0

Hmm. The only one? I don't think so.

~~~
PhantomGremlin
Yeah, that verbiage also caught my eye. I think they might have been trying to
say something like

    
    
       iron meteorites are the only pieces
       of iron on the Earth not made by men
    

Which, depending on the definition of the words "on the Earth", isn't much
better. After all, iron is an element and, according to Wikipedia: _is by mass
the most common element on Earth, forming much of Earth 's outer and inner
core._

The USA has a very large iron meteorite on display. It was "stolen" from
native peoples in Oregon and eventually "stolen" again by New Yorkers and put
on display.

[https://en.wikipedia.org/wiki/Willamette_Meteorite](https://en.wikipedia.org/wiki/Willamette_Meteorite)

Despite my use of "stolen", I think NYC is a great place for something like
that. As a child I saw this meteorite in the American Museum of Natural
History.

Museums are great places. At least 1000x as many people have seen the
Willamette Meteorite than have seen the Hoba meteorite.

~~~
cronix
Yes, I actually live in West Linn, OR, and that's what caught my attention
since it's kind of famous around here. I had also recently been reading about
the dagger found buried with King Tut, which seems to have likely come from a
meteor.
[https://en.wikipedia.org/wiki/Tutankhamun%27s_meteoric_iron_...](https://en.wikipedia.org/wiki/Tutankhamun%27s_meteoric_iron_dagger)

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ballenf
A 66 ton chunk of iron falling on earth probably before any iron had been
smelted by humans.

Now think about the equivalent meteorite falling today: what substance could
it be comprised of that we haven't synthesized or seen yet? Maybe an exotic
isotope of an otherwise common element which demonstrates some exotic
properties. Superconducting at room temperature maybe.

Amazing to think about what asteroids could be out there headed our way (and
not big enough to destroy everything).

~~~
twic
There's a Stephen Baxter novel from a quarter of a century ago [1] in which an
antimatter meteorite falls to earth, and via undisclosed handwaving, ends up
as a deposit in the Antarctic, which is subsequently mined to provide a source
of power for various steampunk shenanigans:

[https://www.thebooksmugglers.com/2010/04/steampunk-week-
book...](https://www.thebooksmugglers.com/2010/04/steampunk-week-book-review-
anti-ice-by-stephen-baxter.html)

[1] yikes

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Nomentatus
With just the right spin, you might get a skipping-stone effect (given the
shape shown) on the atmosphere or ground or both.

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platz
for scale:

[http://triplicit.com/wp-
content/uploads/2016/09/DSC_7846-2.j...](http://triplicit.com/wp-
content/uploads/2016/09/DSC_7846-2.jpg)

thank you google

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iambateman
I have a serious question about the meteorite extinction case...

People talk about populating mars as insurance against a devastating meteor
attack wiping out the population.

Wouldn’t it also work to create a large shock-absorbing facility on earth? If
a meteorite is headed toward earth, you could simply enter the shelter, wait
for it to hit, and then come back out.

Of course then you’re dealing with interrupted ecosystems, but it’s hard for
me to believe that they would be worse than Mars.

P.s. I know populating Mars is considered diversification for other reasons,
but a mass extinction is certainly a reason given.

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jayalpha
"Wouldn’t it also work to create a large shock-absorbing facility on earth?"

Yeah, sure. would be possible. Simple physics.

The crater Chicxulub absorbed more Energy than a billion times the energy of
the atomic bombings of Hiroshima and Nagasaki.[1] So you basically would just
need a hell of an airbag. Hey, if you do it right and you can harvest the
energy then you can run the world electricity supply on it for a few years.

[1]
[http://doc.rero.ch/record/210367/files/PAL_E4389.pdf](http://doc.rero.ch/record/210367/files/PAL_E4389.pdf)

~~~
hanniabu
Not to mention we would need to survive the aftermath - possibility of debris
kicked up into the atmosphere blocking the sun for months or years, chain
reaction of volcanic eruptions with the same side effect plus lava, mass plant
and wildlife die-off leading to possible global ecosystem collapse, raised
global temperatures and water levels, and shifting tectonic that could
possibly shift elevations and flood wherever this 'facility' is located. I'm
sure there's many other issues I haven't thought of off the top of my head.

~~~
tejtm
well there is the glow from the returning ejecta turning the entire sky into a
broiler oven for a few days ... hate it when that happens, control of the
planet goes back to to the meek who were hiding deep underground at the time.

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nwatson
An interesting story about a meteorite, but what struck me was a sign of the
deification of Google ... a reader comment after the article reads: "Wonderful
description and High Quality Pictures. >>> Thanks Google<<< " \-- emphasis is
mine.

The source material, writing, comments system tied to the article all have
nothing to do with Google, yet the reader is attributing their joy in the
article to Google. I've seen Google deified in jest, but I don't think the
reader here is anything but serious.

Praise Google, Glory Be to Google, Google is Good, Google is Author of All
That Brings Us Joy. Google's Yoke is Easy and Their Burden is Light ... Google
only asks for your email and search/location/browsing history. We Are Google's
Image. Come to Google Just As You Are.

(Full Disclosure: I am happy to make the trade with Google ... for some reason
I trust Google and Amazon, don't think Apple has a clue outside their hardware
& associated software, and hate Facebook / Twitter.)

~~~
seandougall
Among its many other offerings, Google does still sport a quite serviceable
search engine. Perhaps the commenter simply meant to convey that that was how
they found the article?

