Farmington Meteorite: A fragment of an Apollo asteriod?

Abstract

We have attempted to reconstruct the orbit of the Farmington L5 chondrite which fell in Kansas in 1890. Because its radiation age is uniquely short (25 000 years), its orbit should still closely resemble that of its parent body. A search of 280 contemporary newspapers and other sources turned up more than 60 useable eyewitness reports from 32 localities, which led to the following estimate of the apparent radiant: height 60°, azimuth 20°, with an uncertainty of about 10°. Orbital elements were determined for this radiant for four plausible preatmospheric velocities: 13, 16, 19, and 22 km/sec. The results show quite definitely that Farmington had a small orbit of low inclination: semimajor axis 1–1.9 AU, perihelion ⩾ 0.4 AU, aphelion ⩽ 3.0 AU, inclination ⩽ 16°. Because of the short radiation age, the parent body of Farmington must already have been in an Earth-crossing orbit when the meteorite was ejected from it by an impact. Of the 11 known Earth-crossing asteroids with encounter velocities below 22 km/sec, 1862 Apollo, Hermes, and 1865 Cerberus are passable matches, while 1620 Geographos and 1685 Toro are more marginal possibilities. Apparently Earth-crossing asteroids are the immediate parent bodies of at least some meteorites. Their ultimate source must be the ultimate source of most stony meteorites.