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hu3

http://simulator.down2earth.eu/planet.html?lang=en

According to this calculator you get a 446km diameter crater if you input:

- 15km asteroid diameter

- 90º Angle

- 80km/s

- Dense Rock asteroid

- Hitting on Water at level 10m

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FYI these are the maximums you can input to get the largest possible crater using this simulator.

Yeah I had to max inputs on that calculator. Pretty wild.

We’re going to need a bigger calculator.

... not great, not terrible.

Hehe. That's a great scene. Meanwhile, I think it was big enough to do the job.

15kms at 80km/s

So, for a quarter of a second or less it was touching the ground and almost double the height of Everest (8.8kms).

I wonder if just the atmosphere would've caused it to explode already. At those speeds it'd go through the atmosphere within a second though.

It would be exploding for the duration, but at that size you just can’t get through much of the asteroid before it touches the ground.

That's why "dense rock" setting was used. Imagine if they had selected "solid iron". I don't know what settings are available for the calculator used, but "loose bunch of rocks" would probably fall apart in the atmo, dense rock would hold together until impact, and solid iron would just keep burrowing further

A 15km chunk of solid iron, now that's the kind of bunker buster you throw around in an interplanetary war.

Would it do more damage to the surface than a rocky asteriod of comparable mass, though? If it burrows deeper, it means it transfers more of its energy to the mantle and core of the Earth, and less to the crust. It will be like a full metal jacket bullet that goes straight through the target and transfers most of its energy to the wall on the other side, versus a regular bullet that tumbles and expands as soon as it hits the target.

Throwing Meteors as interplanetary weapons was a storyline from The Expanse books/TV series if I recall.

Deorbiting a multi-million dollar satellite as a weapon was the plot of of a Tom Clancy book. The bad guy was going to launch a nuke from his ship and the only thing that could get there in time was the super special satellite.

Was this an OpCenter plot? It's definitely not a Jack Ryan series plot. I never really picked up the post-divorce stuff he wrote.

Yeah. Bad guy mounted thrusters on large asteroids from the belts. Not technically meteors, but close enough.

Neat sci-fi.

At that speed I’m pretty sure that it would be vaporised on impact, so it wouldn’t matter.

For such a size impactor, atmosphere does nothing. Might as well be vacuum.

Sure, milliseconds before impact the atmosphere might be super-compressed (and super-heated). Perhaps even exert considerable force. But compared with kinetic energy of that size impactor, at such speed: negligable.

Small objects 'feel' the atmosphere much stronger. Surface area vs. volume.

Whatever parts of the atmosphere were involved in the direct vicinity of the impactor would be heated to plasma. It is just too much energy, you're talking about the equivalent of a massive number of H-Bombs all going off at roughly the same time.

It would probably punch a 15km wide hole in the atmosphere, no? Which would then rapidly collapse from the sides and collide with whatever was ejected... would be fun to watch while parked somewhere safe in orbit.

Better not be LEO... I wonder how high the ejecta would go and how far they would reach across the planet.

15 km diameter is about the size of "thick" atmosphere. The mass of the air in this volume is something about 0.000..% . At speed of 80 km/sec, well, atmosphere didn't slow it down much. And if there was only microbial life at that time it adapted and bounced back quickly.

I was thinking of it's 80km/s wake through the atmosphere. Coming straight in it wouldn't be long horizontally but the clap of 15kms of atmosphere being pushed aside and then coming together behind it...

Most likely 'behind' was filled by evaporated water and rocks. But that was quite a shock wave both in atmosphere and in the ground.

It's strange that in managed to get only 2x of its diameter into the crust. I though it could just get though into magma. That would make the biggest volcano ever.

Got me thinking, What happens, when and where.

A column of air weighs ~1kg/cm^2 (handy!), and the example has a 15km span of "Dense Rock" which I've seen mean "Dense Rock Equivalent" in the Volcanic Explosivity Index, where it has a density of 2,500 kg/m^3. Assuming that, a column of the asteroid is

2500kg/cm^2/(100cm/m * 100cm/m) = .25kg/m * 15km = 3,750kg

The kinetic energy per column of the impactor is 1/2mv^2, or 0.5 * 3750 * 80000m/s^2, or

1875 * 6.4e9m^2/s^2 = 1.2e13 Joules

Which is about 20 gallons of gasoline equivalent. As you say, that's absorbed in ~1s (space is 100km up, so 80km/s is just about right). If so that warms up and starts melting the surface of the asteroid, but not much more I guess.

Whoops, I carried down the wrong number to the gasoline conversion.. I left off the 1875

The whole impact is like 40000 gallons of gasoline per cm^2 of surface, or I think like 2kt TNT.

So then, not sure what the kinetics/kinematics is there. How much is released by the atmosphere impact vs then the surface stopping the asteroid.

Ok! ChatG4 is amazing!

https://chat.openai.com/share/25e4cef6-321a-43f7-8d13-40d1fd...

Summary: my initial math checks out for the total KE of the asteroid, and then we used that to look at the surface heating by the compressed atmosphere and then the Fourier heat analysis of conduction into the asteroid surface

Answer: Tho the atmosphere would be heated to 100k degrees and that's 1000x more than needed for vaporization of e.g. granite, the duration of ~1s means that only a few millimeters of surface would be vaporized by the time of impact.

does it give the same answer repeatedly? every time i've tried to solve problems like that with chatgpt i've been given beautifully worded garbage that doesn't commpute by hand, and won't be repeated if I retry the prompt.

That's my experience with ChatGPT 3.5. But with 4.. well, as far as I'm concerned, this is AGI.

I just did a compacted single-shot request in a new session and got the same answer!

It basically elided the simplifying analysis, went directly for the heat diffusion equation and based its conclusion on that. Impressive.

https://chat.openai.com/share/0c857ebd-779a-4f40-93a9-c35cd2...

Much too large for that. Under 50 meters or so you can get airbursts, after that it is direct impact.

It makes me wonder what an impactor like that would do if intercepted by the moon; that may be even enough mass to cause a temporary ring field just from the debris

If you wonder about things like that, you might want to read Seveneves by Neal Stephenson.

And it still only went down to about twice its diameter. Makes you really respect how tough the Earth's crust is.

The deepest borehole, about the size of a coffee can, is only 12km deep before the tooling started melting - can't drill with a liquid bit...

So 30km down it would be hitting liquid rock and a lot of heat.

Yes, the mantle is about that thick. And much thinner in some places even. Which makes me wonder how they detected this crater and what the crater is formed in. This is the relevant bit from the article:

"Between 1995 and 2000, Tony Yeates suggested magnetic patterns beneath the Murray Basin in New South Wales likely represented a massive, buried impact structure. An analysis of the region’s updated geophysical data between 2015 and 2020 confirmed the existence of a 520km diameter structure with a seismically defined dome at its centre.

The Deniliquin structure has all the features that would be expected from a large-scale impact structure. For instance, magnetic readings of the area reveal a symmetrical rippling pattern in the crust around the structure’s core. This was likely produced during the impact as extremely high temperatures created intense magnetic forces."

But they would not able to verify that at that depth without a lot of drilling and the end of the article suggests that they have yet to do so.

Would be wild if aliens had cameras on every planet and one day decides to show us what this looked like

Little grey dudes sitting us down in the slideshow room to show their holiday pictures from a few million years ago, lol. "And this is when ⌘⑩⌖⌦ nearly got eaten by a dinosaur!"

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