Chris Peterson wrote:
I've never really seen anything formal. I've done the calculations, and I've seen others do them as well. It's one of those things that comes up from time to time.
There are quite a few papers on the temperature of meteoroids in space.
Wylie in 1934 confronts the notion that meteors are fireballs - hence meteorites should be hot. He cites reports that stone meteorites were cold to the touch, or barely warm - but he acknowledges some stone and iron meteorites were reported as warm or hot. He states the expected temperature of a meteoroid in space as 39F.
Butler in the 1963 calculated the temperature of iron meteoroids at varying distances from the sun and concluded a rough value of 90C for one entering the earth's atmosphere. Later in 1966 he reported experimental measurements under simulated space conditions for various meteoroid materials. The focus of that paper was to determine the expected temperature of a meteoroid that approached the orbit of mercury, since if it is high enough to anneal the crystal structure, any meteoroid without this annealing would be unlikely to have come that close to the sun in its past.
Staley in 1966 has a more comprehensive paper on theoretical estimates of meteoroid temperature and specifically addresses the idea they could be cold. One subtlety is that during any period where the meteoroid is in the shadow of the earth, it will be cooling due to radiative loss not balanced by absorption from the sun. Another subtlety is that for large objects that are headed toward the sun from a distant origin, they may be traveling fast enough that they are not in thermal equilibrium with the sun and could have cold internal temperatures.
In 1998 Lyne reports on models of atmospheric entry of large meteors, applied to the Tunguska event. He points out in the abstract that 'The atmospheric entry of a meteor is quite complex..." This is quite different from saying it is all well understood and easily modeled.
In 2004 Popova reports on meteoroid ablation models. Like many papers, this focuses on small objects that don't reach the ground. Even so he points out the complexity of the models and their inadequacies, and the lack of observational data for validation.
I don't know of a detailed simulation of the entry of an object that results in, say, a 1-100 kg iron meteorite. I imagine it would be quite a task to simulate with any confidence.
As far as space being "cold" - there is an anthropomorphic view that temperature only has importance in terms of heat transfer by direct contact, while even for humans on earth, radiation plays a big role. Pre-1960's writings may say you need atoms in space in order to have temperature, but nowadays it's more common just to regard space as being bathed in cosmic background radiation that amounts to photon gas with a Maxwell-Boltzmann distribution corresponding to around 2.7K - which I consider cold. When it comes to a meteroid in space, it sees that 2.7K radiation in all directions except a tiny part of the sky containing the sun, which is at much higher temperature. The equilibrium temperature it reaches is due to the balance between its energy radiatively received from, and lost to, both the sun and the "coldness of space."
There are high velocity atoms and ions in the solar system, but they are not in equilibrium with the background radiation and would have minimal contribution to a meteoroid's temperature in comparison to the sun and background radiation.
I personally find it unlikely a freshly fallen meteorite would be cold, but I have no problem with the idea it might be quite hot, particularly if it is iron and especially if it fragmented explosively, or hit with high velocity.
zloq