A few days back I posted about a very small asteroid orbiting on a very Earth-like orbit. At the time the nature of the object had not been determined. It was surmised that it could be a small natural asteroid or a returning piece of man-made space hardware.
NASA’s NEO Project Office at JPL is now reporting that 2010 KQ is probably not an asteroid. That determination is based on ground-based photometry and spectroscopy by 2 telescopes in Hawaii. Richard Miles used the British Faulkes North telescope to obtain visible wavelength colors and Bobby Bus used the NASA IRTF telescope to obtain near-infrared spectra. Both observers found the object to display colors that are not common among asteroids. A similar occurrence happened back in 2002 when a newly found “asteroid” was identified as the returning S-IVB upper stage from Apollo 12. At that time Rob Whiteley and I were the first to get visible color photometry on the object. Our data showed the object to much redder than any natural solar system object. Additional IRTF data identified spectral features corresponding to organic binders in paint.
“2010 KQ” is probably a rocket upper stage that was used to launch a satellite to very high Earth orbit, the Moon or interplanetary space. Though upper stages are metallic and may or may not be painted, exposure to the solar wind will quickly redden them (a process called space weathering). The orbit of “2010 KQ” suggests the last close approach with Earth was in April 1975. There were no interplanetary launches that month. It is still possible something launched into a high Earth orbit a few years before could have stayed in a loosely bound Earth orbit until it finally leaked into orbit around the Sun in April of ’75. Two possible candidates are the German-American solar probe Helios-1 (launched on Dec 10, 1974) and the Russian lunar sample return mission Luna 23 (launched on Oct 28, 1974). As observations are made over the next few months, we will have a better understanding of when this object left the Earth-Moon system. The best source for updates on the orbit and nature of KQ is Bill Gray’s pseudo-MPEC site.