A mass totaling 2,459 g was found on the Dar al Gani plateau in the eastern Sarir al Qattusah in central Libya, an area that covers ~12,000 km², of which ~8,000 km² are favorable for meteorite recovery (Schlüter et al., 2002). The area of meteorite recovery lies on Tertiary limestone marine sediments.
Dar al Gani 298 has a very fresh appearance with a weathering grade of W0, and it is rich in noble gases suggesting a very recent fall. The meteorite has been shocked to stage S3, with a 21Ne-based CRE age of 52.6 m.y. In contrast to many LL chondrites with Ar–Ar ages that reflect late impact resetting, such as ~1 b.y. determined by Weirich et al. (2009), the gas retention age of DaG 298 was calculated to be 4.48 b.y., which likely preserves its original crystallization age. The specimen of DaG 298 shown above is a 28.9 g partial slice.
It has been considered that the large Flora family of asteroids located near the ν6 resonance may be the source of LL chondrites (Bottke et al., 2009). In a study of LL6 chondrite orbits, Ustinova et al. (2008) propose that the ~7 km-diameter asteroid 3628 Božněmcová, which has a reflectance spectrum almost identical to the LL-group, is a good match to this chondrite group. In their study they determined a probable orbit for two 2002 LL6 falls, Bensour and Kilabo, which fell within five months of each other in northern Africa and which show striking similarities to each other. Based on their measured content of cosmogenic 26Al, the calculated orbits for these meteorites coincidentally intersect that of Božněmcová at the same point near the inner asteroid belt. They proposed that Bensour and Kilabo were ejected in a common event 19 m.y. ago, and that any differences in their CRE ages reflect differences in their shielding depth while on the parent asteroid.
In their near-IR spectrographic study of asteroids located near the 3:1 orbital resonance (Kirkwood gap of Jupiter), Fieber-Beyer et al. (2009) found that close similarities exist in the absorption spectra of the S(IV) asteroid 974 Lioba and that of LL chondrites. Importantly, the recent touchdown of the Hayabusa spacecraft onto the surface of the sub-km-sized S-type asteroid Itokawa has provided a wealth of knowledge about this most abundant type of asteroid. Itokawa's reflectance spectrum reveals an olivine and pyroxene composition very similar to that of known LL chondrite meteorites, such as DaG 298 (Abe et al., 2006).
The photo shown above is a view from the Hayabusa spacecraft of the southern hemisphere of Itokawa. It shows a surface largely strewn with angular boulders, many too large to have originated from impact craters present on Itokawa (e.g., Yoshinodai measures 50 × 30 × 20 m in size; Demura et al., 2006) (see top photo below). By contrast, the lowest topographic areas, such as the touchdown/sample collection location in Muses Sea, are smoothly surfaced with cm-sized gravel, probably produced by a grain-size sorting mechanism (see bottom photo below). The unusual double-lobed shape of Itokawa, which is characterized by a constricted neck 20 m deep and up to 120 m wide, demonstrates that Itokawa is a low-density (1.90 ±0.13 g/cm³) contact binary formed by gravitational coalescence of separate portions of an impact-disrupted parent body—its structure is a rubble-pile with a macro-porosity of ~40%.
All images are presented here courtesy of JAXA—Japan Aerospace Exploration Agency.
