One of the eye-witnesses to Barwell, Joseph Grewcock - https://www.bbc.com/news/av/magazine-35054625
described the meteorite as being 'red-hot'. He originally thought it had fallen off a lorry, so had no reason to be 'psychologically tricked'. The number of similar reports connected to other falls, makes me believe you are correct. Regards, Finbarr. On Mon, Mar 22, 2021 at 9:30 PM Eric Christensen via Meteorite-list < meteorite-list@meteoritecentral.com> wrote: > There was a recent discussion on a social media forum about a stone from > the recent Punggur fall being warm enough on impact to melt a synthetic > bedsheet. I followed the discussion with interest but don't have an > account on that platform - so wanted to post here. The original poster > also referenced the other recent Indonesian fall (Kolang), where a finder > reported the stone felt as if it had been "cooked with sunlight". There > are many other references to freshly fallen meteorites being warm or hot to > the touch, or sometimes cold to the touch. The oft-repeated rebuttal is > that meteoroids come from the icy void of space where they must be > extremely cold, and that any brief heating experienced during the luminous > ablative phase will dissipate during the few minutes of dark flight through > the atmosphere. Also, that the human brain will trick surprised finders > into misinterpreting "very cold" for "very hot". It seems to me that > there's an obvious error in this argument - the initial condition of a > meteoroid being very cold is not (necessarily) true. In fact the opposite > can be true - meteoroids (or asteroids) can actually be very hot prior to > Earth impact. "Cooked with sunlight" is an extremely good description. > > Consider figure 1 from Delbo and Harris "Physical properties of near-Earth > asteroids from thermal infrared observations and thermal modeling", > published in 2002 in MAPS: > > https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2002.tb01174.x > > The sunlight side of a model asteroid at 1 AU has a temperature of about > 400 Kelvin = 127 C = 260 F. The side facing away from the sun will be > cooler; how much cooler will depend on the thermal inertia of the body, > pole orientation, rotation speed, etc. There may be steep temperature > gradients across an asteroid at impact time, or it may be relatively > equilibrated. Most meteorite droppers should fall into the latter > category, being small (sub-meter), fast rotators, and regolith free. > > How much heat is gained during ablation, and retained during dark flight, > ought to depend on the thermal inertia of the meteorite. Metal-rich > meteorites or those with low porosity ought to retain more heat, and be > less efficiently cooled during dark flight. > > So - are fresh meteorites hot or cold on impact? I think the answer is, > "it depends!". One could even contrive a set of circumstances where an > asteroid with a large thermal gradient drops two meteorites of equal sizes > right next to each other, coming from different parts of the asteroid, > where one lands hot and the other lands cold. Tarp-melting hot? I don't > see why not. Cold enough to form frost? Sure. Hot enough to ignite a > grass fire? No. > > Regards, > > Eric Christensen > > > ______________________________________________ > > Visit our Facebook page https://www.facebook.com/meteoritecentral and the > Archives at http://www.meteorite-list-archives.com > ______________________________________________ > > Meteorite-list mailing list > Meteorite-list@meteoritecentral.com > https://pairlist3.pair.net/mailman/listinfo/meteorite-list >
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