The Ardon L6 ordinary chondrite: A long-hidden Spanish meteorite fall

Abstract

We report and describe an L6 ordinary chondrite fall that occurred in Ardon, Leon province, Spain (longitude 5.5605 degrees W, latitude 42.4364 degrees N) on July 9th, 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa Gonzalez Perez, at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports, the event was widely observed in Northern Spain. Ardon is a very well-preserved, fresh, strongly metamorphosed (petrologic type 6), and weakly shocked (S3) ordinary chondrite with well-equilibrated and recrystallized minerals. The mineral compositions (olivine Fa(23.7 +/- 0.3), low-Ca pyroxene Fs(20.4 +/- 0.2)Wo(1.5 +/- 0.2), plagioclase An(10.3 +/- 0.5)Ab(84.3 +/- 1.2)), magnetic susceptibility (log chi = 4.95 +/- 0.05 x10(-9) m(3) kg(-1)), bulk density (3.49 +/- 0.05 g cm(-3)), grain density (3.58 +/- 0.05 g cm(-3)), and porosity (2.5 vol%) are typical for L6 chondrites. Short-lived radionuclides confirm that the meteorite constitutes a recent fall. The Ne-21 and Ar-38 cosmic ray exposure ages are both about 20-30 Ma, similar to values for many other L chondrites. The cosmogenic Ne-22/Ne-21 ratio indicates that preatmospheric Ardon was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate, thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.