Almahata Sitta (=asteroid 2008 TC₃) and the search for the ureilite parent body

Abstract

Abstract-This article explores what the recovery of 2008 TC 3 in the form of the Almahata Sitta meteorites may tell us about the source region of ureilites in the main asteroid belt. An investigation is made into what is known about asteroids with roughly the same spectroscopic signature as 2008 TC 3 . A population of low-inclination near-Earth asteroids is identified with spectra similar to 2008 TC 3 . Five asteroid families in the Main Belt, as well as a population of ungrouped asteroids scattered in the inner and central belts, are identified as possible source regions for this near-Earth population and 2008 TC 3 . Three of the families are ruled out on dynamical and spectroscopic grounds. New near-infrared spectra of 142 Polana and 1726 Hoffmeister, lead objects in the two other families, also show a poor match to Almahata Sitta. Thus, there are no Main Belt spectral analogs to Almahata Sitta currently known. Space weathering effects on ureilitic materials have not been investigated, so that it is unclear how the spectrum of the Main Belt progenitor may look different from the spectra of 2008 TC 3 and the Almahata Sitta meteorites. Dynamical arguments are discussed, as well as ureilite petrogenesis and parent body evolution models, but these considerations do not conclusively point to a source region either, other than that 2008 TC 3 probably originated in the inner asteroid belt.

Bidirectional visible‐NIR and biconical FT‐IR reflectance spectra of Almahata Sitta meteorite samples

“…The #25 chip is unique among all the chip samples measured in this study in that it shows very strong, well‐defined absorption bands very similar to those of H chondrites (Jenniskens et al. 2010) and this meteorite has been classified in fact as an H5 chondrite (Herrin et al.…”

“…These pieces of evidence suggest that this stone could have been a clast in the 2008 TC 3 asteroid (Sabbah et al. 2010; Jenniskens et al. 2010).…”

“…Almahata Sitta meteorite is the first observed fall from a tracked and spectrally observed asteroid 2008 TC 3 (Jenniskens et al. 2009, 2010), which gave a rare opportunity to compare the observational data of an asteroid with those of the meteorites derived from it.…”

Active Asteroids in the NEO Population

“…and high inclination of the orbit point to an origin in the 2 Pallas asteroid family (de León et al, 2010;Jenniskens et al, 2010). The meteoroids have higher density that most cometary meteoroids observed at Earth, but the meteoroid density and thermal properties may have been affected by heating due to the low perihelion distance of the stream.…”

Far from random: dynamical groupings among the NEO population

“…Meteoroid 2008 TC 3 caused the Almahata Sitta event (Jenniskens et al 2009;Oszkiewicz et al 2012). Mjolnir has an F-class spectrum similar to that of 2008 TC 3 (Jenniskens et al 2010), their orbits are akin. Objects in this dynamical group reach perihelion at 0.82-0.9 au in the region dominated by secular resonances.…”