The Vissannapeta eucrite

A wholly encrusted single stone that fell in Vissannapeta, Andhra Pradesh, India has been identified as a cumulate eucrite based on its primary textur e and mineral composition: anorthite(An(92.4-94.6)), orthopyroxene(En(49.1- 51.8)Fs(44.2-49.7)Wo(1.2-4.0)), and clinopyroxene (En(38.8-46.8)Fs(14.8-33. 6)Wo(19.6-46.4)). The stone is pyramidal in shape, and the crust shows rib- like flow features indicating that it had an oriented passage through the a tmosphere towards the terminal stage of its flight. Conditions of its fall, mineralogical characteristics, and results of measurements of cosmogenic r adioactivity (Al-26, Na-22, and Mn-54) and track density are described. Alu minum-26 and Na-22 in Vissannapeta are similar to 75% of the expected value s and also lower by a similar factor compared to the activities measured in Piplia Kalan, another eucrite, which fell similar to 18 months before Viss annapeta. Because higher activity of 22Na and 54Mn would be expected from s olar cycle modulation of galactic cosmic rays, these results, as well as th e track density gradient, indicate that Vissannapeta was a small body (less than or equal to 120 kg) in the interplanetary space wherein the nuclear c ascade due to galactic cosmic rays did not develop fully. Tracks, surface m orphology, and crustal features indicate at least two fragmentation events in the atmosphere.