Why HOT? (APOD 19 Nov 2006)

[mverber]

"... parts of it [a meteorite] are likely to be either very hot or very cold."

I can understand the Very Cold - as the rock has been in space for billions of years - but how can it be Very Hot? After all it only took a few seconds to traverse the atmosphere, how could it have heated significantly?

[Andy Wade]

"... parts of it [a meteorite] are likely to be either very hot or very cold."

I can understand the Very Cold - as the rock has been in space for billions of years - but how can it be Very Hot? After all it only took a few seconds to traverse the atmosphere, how could it have heated significantly?

Friction?
The atmosphere must be pretty thick if you're travelling fast enough.
The shuttle needs a heatshield of special tiles, and the Apollo landing pods look pretty burned after re-entry too.
I would have thought it depends on how quickly it cools down after entry into the atmosphere.

[orin stepanek]

When you consider most meteors burn up in the atmosphere; you know they get hot.
Orin

[linx]

Hi,
i would have thought that the bit of the meteorite would have been very hot after passing through the Earth's atmoshpere ..but i dont see evidence a severe scorch mark, such as i would expect, on the car in the APOD

Linx

[Andy Wade]

Hi,
i would have thought that the bit of the meteorite would have been very hot after passing through the Earth's atmoshpere ..but i dont see evidence a severe scorch mark, such as i would expect, on the car in the APOD

Linx

Hmmmm... define 'hot'.

Too hot to pick it up, or hot enough to burn the car paintwork?

The APOD description warns about not picking them up, so anything over about 40-50 deg C would feel too hot to pick up.

I was wondering about the ones that land on Antarctica, apparently they are really obvious as they are effectively 'rocks' just laid on top of the ice. But they're not hot enough to burn themselves into the ice, I expect that as it's very cold down there at the south pole I guess they would cool down pretty quickly.

[linx]

Hi Andy,

i presumed that any meteoerite fragment would be hot enough to burn the car paintwork & therefore too hot to handle as well

perhaps the heat that is generated whilst passing through the Earth's atmosphere does not penetrate to the core of the meterorite but is localised on the outer layers & surface ..which then cool more rapidly during their descent when meeting cooler air temperatures that surround them

just some thoughts
Linx

[iamlucky13]

Hi Andy,

i presumed that any meteoerite fragment would be hot enough to burn the car paintwork & therefore too hot to handle as well

perhaps the heat that is generated whilst passing through the Earth's atmosphere does not penetrate to the core of the meterorite but is localised on the outer layers & surface ..which then cool more rapidly during their descent when meeting cooler air temperatures that surround them

just some thoughts
Linx

That's pretty close to correct. As mverber mentioned, the meteors spend years in space before coming down, so they should be very cold before entry, possibly close to absolute zero depending how well they radiate heat compared to how well they absorb heat from the sun. As they pass through the atmosphere, the outer region heats up due to friction, but it usually sloughs off almost as fast as it heats up. The process is called ablation and it works somewhat similar to a person sweating to keep cool.

On the other hand, I suppose a small dense meteor might not ablate very well, and have little enough mass that the heat from re-entry penetrates all the way through, so it could potentially hit the ground hot.

[Wadsworth]

Either way, that is cool!
So I'm assuming the owner of the vehicle/property doesn't get to keep the meteorite?
I would definitely want at least a piece of it if it smashed into my car.

[Andy Wade]

Hi Andy,

i presumed that any meteoerite fragment would be hot enough to burn the car paintwork & therefore too hot to handle as well

perhaps the heat that is generated whilst passing through the Earth's atmosphere does not penetrate to the core of the meterorite but is localised on the outer layers & surface ..which then cool more rapidly during their descent when meeting cooler air temperatures that surround them

just some thoughts
Linx

Hi Linx.
I think you're right.
(I should say I know nothing about the subject but am just guessing based on an engineering background and some experience with stresses of different, mostly metallic materials) and a smattering of physics.
I guess they all start out very, very cold when in space. They will all be different sizes, physical makup, speed of travel, angle of entry into the atmosphere, length of 'burn' time. These are all variable factors which decide on whether or not the fragment gets to the ground in the first place.
Assuming they do, then some will be hot and others will be cold when they hit. You point about the core still being extremely cold is a good one. I imagine a 'metallic' meteorite would fare better than a rock/snowball.

I like the question about ownership of a meteorite. If it hit my car then I'd be wanting to auction it off to pay for the damage caused.
I suppose if it's on your land then it's yours isn't it? Is there an international law on the ownership of such unique space debris?

[BMAONE23]

If you look underneath the bumper, you can see where it went through the wood plank surface. follow that linear angle through the trunk and you can determine the angle of decent. If you look at the trunk lid at the "rip" point you will notice a discolored portion the approximate size of the meteorite. It does resemble burnt paint as it is discolored from the surrounding paint. http://antwrp.gsfc.nasa.gov/apod/image/ ... as_big.jpg

[linx]

Hi & thank you
iamlucky 13 & Andy for your replies, they were interesting to read & to think on

its so interesting to learn the information from knowledgeable people on this site

BMAONE23 ..its a shame we can't ask the owner of the car whether its a scorch mark or not ..to me it resembled battered, discoloured paintwork, but i couldnt see any blisters from the heat ..i'm only a distant observer tho & may well be wrong

Linx

[iamlucky13]

I think the discoloration is bare primer from the paint flaking off as the metal deforms/abrasion from the meteor. I doubt the meteor was in contact with that metal for nearly long enough to transfer sufficient heat to scorch the metal...although I admit friction could've done it. You'll see the same type of discoloration on auto bodies in fender benders.

Ownership would probably be a tricky issue. Normally ownership is granted to the owner of the land it is found on (famous example: willamette meteorite). Of course, if the owner was just parked in her own driveway, that certainly simplifies it. But if it's someone else's property and the property owner claims the meteor, should they not also be liable for damage caused by their posession? By the way, one of the links from the APOD says the car is now owned by "R.A. Langheinrich Meteorites."

Also, the first link has a really good analysis of the meteor. Based on eyewitness reports and several videos, they even produced a very confident orbit of the meteroid. They even have a chart comparing the orbit to several other falls where an orbit is known.

The most surprising part to me is they think the initial meteroid weighed as much as 20 tons! It fragmented on its way down, and the recovered portion was just the largest fragment.

[Martin]

Meteorites are finder’s keepers. There is no law that says you would have to give it to anyone if you find one. Unless it poses a health risk or was responsible for some international incident. But even then you would have property rights on it –to some extent.

There are individuals that make a living off these space rocks and some make a very good living at that. But if it’s on someone else’s property you may want to get their permission before searching. Although, if you’re talking about remote parts of a forest where the owner is of no consequence – then……….pick it up and run -run forest, run!!!!!!!!!!!!!!!!!

[Nereid]

I heard that the owner (of the car) bought it for ~$100, but sold it - because of its 'celebrity' status - for ~$thousands!

Don't know if this is just an urban legend though ...

[Galactic Groove]

If you look underneath the bumper, you can see where it went through the wood plank surface... ...If you look at the trunk lid at the "rip" point you will notice a discolored portion the approximate size of the meteorite. It does resemble burnt paint as it is discolored from the surrounding paint. http://antwrp.gsfc.nasa.gov/apod/image/ ... as_big.jpg

I think the part of the broken wood plank surface you're mentioning is actually the bottom part of the sheet metal of the trunk of the car.

Personally I believe that the missing paint from that ripped area is the cause of being hit from something moving so fast, it would have scraped that paint off, not scorched or discolored it.

[Andy Wade]

If you look underneath the bumper, you can see where it went through the wood plank surface... ...If you look at the trunk lid at the "rip" point you will notice a discolored portion the approximate size of the meteorite. It does resemble burnt paint as it is discolored from the surrounding paint. http://antwrp.gsfc.nasa.gov/apod/image/ ... as_big.jpg

I think the part of the broken wood plank surface you're mentioning is actually the bottom part of the sheet metal of the trunk of the car.

Personally I believe that the missing paint from that ripped area is the cause of being hit from something moving so fast, it would have scraped that paint off, not scorched or discolored it.

Yes I agree, it does look like a scrape mark.
And if this particular meteorite had been extremely hot I think it would have scorched the wooden floor, but there don't seem to be any signs of that.
I notice that the meteorite has got a couple of clean bits where the edges were knocked off during the impact.

[kovil]

Fascinating , hadn't really thought in depth about all that.

Time and force. How fast is the meteor moving, how much resistance does the atmosphere generate, how long does the descent take.

Can any heat generated have time in a 'heat flow diagram' approach to reach very far into the interior of the meteor ?

Will the atmospheric resistance force, vector into the meteor and cause structural fracture lines to develop and tear it apart in chunks ?

The composition of the meteor will affect these results, metallic or stoney or aggregate conglomerate; vastly different results to atmospheric interaction.

Yes, the meteor will be ambient temperature at arrival, plus the suns heating, minus its own ability to radiate.

My feeling is the descent, 3 to 13 seconds before impact is not enough for heat to penetrate much from its surface. Its surface could be 500 F up to 30 seconds after landing, even while its interior is -390 F. This is assuming a stoney meteorite 24" in diameter. (All a wild intuitive guess)

The blackened thin crust in the photo, suggests a very hot skin, with a cool interior. The intense heat of entry may cause spalling, like when an oxyacetylene torch is held close to concrete, and it boils the water out of hydration with the limestone, causing pops and flying chunks of concrete !

[Dr. Skeptic]

Hot or cold is dependent on angle of entry, the more obtuse the angle the more heat, structure density also plays a roll.