The impact and recovery of asteroid 2008 TC3

Abstract

In the absence of a firm link between individual meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554-995 nm wavelength range, and designated 2008 TC(3) (refs 4-6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.

Density of asteroids

“…Therefore, in addition to albedo and reflectance spectra that point toward different surface properties/composition, density suggests that there are fundamental differences in the composition and internal structures of B-types. The recent recovery of the Almahata Sitta meteorite, originating from the impact of asteroid 2008 TC 3 on Earth in October 2008, indeed indicated that B-type could be associated with unusual Ureilite achondrites (Jenniskens et al 2009). Based on a comparison of the densities of (1) Ceres and (2) Pallas (used as archetypes for the definition of C and B taxonomic classes), Carry et al (2010a) had suggested that B-types were less hydrated than C-types; a hypothesis supported by the lack of signature of organic or icy material in their spectra (Jones et al 1990).…”

Survival of the impactor during hypervelocity collisions – I. An analogue for low porosity targets

“…Such phenomena, which have been observed only relatively recently, are the source of the olivine and dark material deposits observed on Vesta (McCord et al 2012;Reddy et al 2012) and probably of the "Black Boulder" on (25143) Itokawa (Hirata & Ishiguro 2011). Mixing of asteroid material with different lithology through impacts is also necessary to explain the nature of the Near-Earth asteroid 2008 TC3, a multi-lithology body whose formation mechanism is still not completely understood (Jenniskens et al 2009;Bischoff et al 2010). 2008 TC3 impacted Earth's atmosphere on October 7, 2008 and it is estimated that it exploded approximately 37 km above the Nubian Desert in Sudan.…”

MarcoPolo-R: Near-Earth Asteroid sample return mission selected for the assessment study phase of the ESA program cosmic vision

“…This fall is the first instance where an object was observed astronomically as an asteroid and then was recovered as meteorite samples. It was identified as an F-class object, similar to C-class (bluer in the visible), but the meteorites are unexpectedly friable breccias of mostly ureilite and enstatite chondrite clasts [12,13]. The recovered meteorites represent only 0.005% of the initial mass [12], which demonstrates that mechanically weak material does exist in significant quantities within the inner Solar System and that the existing meteorite collection is significantly biased towards heavily processed material.…”

“…The already mentioned spectral observations of asteroid 2008 TC3 and the analysis of fragments recovered on Earth provide evidence that there is a discrepancy between the expected composition of a small body based solely on its spectral properties and the actual one from recovered fragments [12]. Moreover, in-situ measurements that can be made by a lander are interesting but severely limited by the resources available.…”