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Squink
2004-May-10, 02:37 AM
I've found myself wondering whether a martian blueberry, ejected from Meridiani Planum by a large meteor impact could survive passage through the earth's atmosphere. Pure hematite has a melting point of 1565 C, compared to 1535C for pure iron, and I've seen some tiny, intact iron-nickel meteorites. Does anyone happen to have some figures for the temperatures reached by micrometeors during earth entry?
I suppose the most likely scenario is that thermal stress would cause inhomogeneous blueberries to pop when heated, but still, is it possible that these things could be found on earth?

01101001
2004-May-10, 03:16 AM
I've found myself wondering whether a martian blueberry, ejected from Meridiani Planum by a large meteor impact could survive passage through the earth's atmosphere. Pure hematite has a melting point of 1565 C, compared to 1535C for pure iron, and I've seen some tiny, intact iron-nickel meteorites. Does anyone happen to have some figures for the temperatures reached by micrometeors during earth entry?

Well, if you're talking about the Meridiani spherules that are less than 5 mm in diamter, they lack the kilograms of mass needed to survive to the bottom of Earth's atmosphere.

Looking around the Web, I see that some meteorites are hematite, so if they start with enough mass they can reach the ground. Obviously the surface temperature must get pretty high, enough to make a meteor glow, surely above the melting point. I guess we can assume the interior starts out pretty cool, and must stay cool enough for a meteor to remain intact to the ground.

Irishman
2004-May-10, 08:18 PM
http://www.badastronomy.com/bad/misc/meteoric.html


Bad Addendum: many people think that a meteorite, after it hits the ground, is very hot and glows red. Actually, meteorites found shortly after impact tend to be warm, but not hot at all! It turns out that it certainly is hot enough to glow while it is in the part of the atmosphere that decelerates it the strongest, but any part that actually melts will be blown off ("ablated") by the wind of its passage. That leaves only the warm part.

Squink
2004-May-10, 09:33 PM
I'm sure that some astronomer somewhere has aimed his spectrograph at the skies during meteor showers and used the captured light curves to figure out the average surface temperature of the Leonids, Perseids or Aquarids. I just can't seem to find the numbers anywhere. Anyone?

beskeptical
2004-May-11, 03:51 AM
I have a few meteorites and tektites. The meteorites have a fusion crust. It is the remaining melted part and is much less than a millimeter thick.

The tektites are material that was blasted up from Earth during the impact and returned to Earth without reaching orbit or beyond. Tektites are homogeneous and look like glass or obsidian. They are not the same thing as meteorites.

beskeptical
2004-May-11, 03:58 AM
From, "Rocks From Space", O.R. Norton:

"more than 3,000 degrees"

It's a great source for meteorite affcionados.