* Astronomy

Title: The Vissannapeta eucrite
Author: Ghosh, S., Pant, N. C., Rao, T. K., Rama Mohana, C., Ghosh, J. B., Shome, S

A wholly crusted single stone which fell in Vissannapeta, Andhra Pradesh, India has been identified as a cumulate eucrite based on its primary texture and mineral composition: anorthite(An92.4-94.6), orthopyroxene(En49.1-51.8Fs44.2-49.7Wo1.2-4.0) and clinopyroxene (En38.8-46.8 Fs14.8-33.6Wo19.6-46.4). The stone is pyramidal in shape and the crust shows rib-like flow features indicating that it had an oriented passage through the atmosphere towards the terminal stage of its flight. Conditions of its fall, mineralogical characteristics and results of measurements of cosmogenic radioactivity (26Al, 22Na and 54Mn) and track density are described. Compared to Piplia Kalan, another eucrite, which fell about 18 months before Vissannapeta, the observed activity levels of these nuclides are approximately 75% whereas higher activity of 22Na and 54Mn would be expected from solar cycle modulation of galactic cosmic rays. These results, as well as the track density gradient indicate that Vissannapeta was a small body ((120kg) in the interplanetary space wherein the nuclear cascade due to galactic cosmic rays did not develop fully. Tracks, surface morphology and crustal features indicate at least two fragmentation events in the atmosphere.

Read more