[meteorite-list] hot vs. cold meteorite falls

[Steinar Midtskogen]

A meteoroid could possibly travel in the Earth's shadow for several
hours before it reaches the atmosphere, and this could be enough to cool
down its interior if not a particularily large meteoroid.  But a core
temperature near 0° C sounds reasonable as a typical value.  Earth would
be -18° C without an atmosphere, but has a much higher albedo than the
typical meteoroid.  Obviously, 10 seconds or less of heating in the
atmosphere will not change the core temperature much.  And a couple of
minutes of falling in temperatures well below freezing will cool down
the melted crust.  In some cases the dark flight can be as low as one
minute or so, like the 2020-11-07 iron meteorite that fell in Sweden and
it wouldn't surprise me if the meteorite was pretty warm to touch just
after impact in that case.

Most people view meteorites as fireballs smashing into the ground
leaving a flaming crater, so the expectation is usually that they're
very hot.  I have received many reports of melt holes in icy lakes that
people are convinced must have been caused by red-hot meteorites.

-Steinar

Chris Peterson via Meteorite-list <meteorite-list at meteoritecentral.com>
writes:

> A meteoroid in space is nominally at or just above freezing (i.e. 0°
> C), but there is a fair range around that, especially toward the
> higher end, depending on its emissivity. It almost certainly will not
> be very cold. Space is not "cold". It is, of course, dominated by
> radiative heating and cooling. While it is radiating into something
> just barely above absolute zero, it is also absorbing the same amount
> of solar energy as a rock on the ground.
>
> In most cases, I would expect a meteorite to be on the cold side when
> it impacts. The heating that occurs during its brief ablative phase
> will have almost no effect on its internal temperature. But it will
> spend several minutes falling through air at one or two hundred meters
> per second, and for almost all of that time the air will be on the
> order of -40° C. That will result in significant cooling of typical
> meteorites of a few hundred grams to a few kilograms.
>
> I think that what can easily happen is that people who touch a freshly
> fallen meteorite actually experience cold as hot, due to their
> expectations. Whether we perceive something as hot or cold can be
> unrelated to the actual temperature. Remember that kids' game where
> you dare somebody to keep their back to you while you touch the back
> of their neck with a hot iron, and then actually touch them with an
> ice cube? Most people startle and believe you've burned them.
>
> Chris