A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydro-chemical, and isotopic features found in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions).
[4] Scientific studies show that their composition matches normal tropospheric rainwater for the areas in which they fall.
In addition, megacryometeors also display textural variations of the ice surface and hydro-chemical and isotopic heterogeneity in its composition, which gives potential evidence to a complex formation process in the lower atmosphere.
[5] A detailed micro-Raman spectroscopic study made it possible to place the formation of the megacryometeors within a particular range of temperatures: −10 to −20 °C (14 to −4 °F).
[10] They are sometimes confused with meteors because they can leave small impact craters, though they form in the atmosphere and not from outer space.