Description of a very dense meteorite collection area in western Atacama: Insight into the long‐term composition of the meteorite flux to Earth

Abstract

International audience–We describe the geological, morphological, and climatic settings of two new meteorite collections from Atacama (Chile). The " El M edano collection " was recovered by systematic on-foot search in El M edano and Caleta el Cobre dense collection areas and is composed of 213 meteorites before pairing, 142 after pairing. The " private collection " has been recovered by car by three private hunters and consists of 213 meteorites. Similar to other hot desert finds, and contrary to the falls and Antarctica finds, both collections show an overabundance of H chondrites. A recovery density can be calculated only for the El M edano collection and gives 251 and 168 meteorites larger than 10 g km À2 , before and after pairing, respectively. It is by far the densest collection area described in hot deserts. The Atacama Desert is known to have been hyperarid for a long period of time and, based on cosmic-ray exposure ages on the order of 1–10 Ma, to have been stable over a period of time of several million years. Such a high meteorite concentration might be explained invoking either a yet unclear concentration mechanism (possibly related to downslope creeping) or a previously underestimated meteorite flux in previous studies or an average terrestrial age over 2 Myr. This last hypothesis is supported by the high weathering grade of meteorites and by the common terrestrial fragmentation (with fragments scattered over a few meters) of recovered meteorites

Meteorites from the Lut Desert (Iran)

“…Besides Antarctica (Harvey 2003), hot deserts are suitable places for the preservation, the accumulation, and the subsequent recovery of meteorites. High numbers of meteorites have been collected and studied from arid regions such as Atacama (Muñoz et al 2007;Gattacceca et al 2011;Hutzler et al 2016), Sahara (Bischoff and Geiger 1995;Schl€ uter et al 2002;Ouazaa et al 2009), Australian deserts (Bevan and Binns 1989;Bevan 1992;Benedix et al 1999), Arabian Peninsula (Al-Kathiri et al 2005;Gnos et al 2009;Hezel et al 2011;Hofmann et al 2018), central (Rubin and Read 1984;Merriam and Harbaugh 2007) and southwestern United States (Zolensky et al 1990;Rubin et al 2000;Kring et al 2001;Hutson et al 2013), and Xinjiang Province in China (Li et al 2017;Zeng et al 2018). Finding new meteorite dense collection areas (DCAs) is important for (1) discovering new types of meteorites (e.g., Bischoff 2001;Kent et al 2017;Pourkhorsandi et al 2017a), (2) providing more samples for statistical works on the meteorite flux (e.g., Bland et al 1996), (3) studying meteorite fall process by mapping strewnfields resulting from meteorite showers (e.g., Kring et al 2001;Gnos et al 2009), and (4) studying the alteration of extraterrestrial material in the terrestrial environment (Bland et al 2006;Saunier et al 2010;Uehara et al 2012;Zurfluh et al 2016;Pourkhorsandi et al 2017b) also in relation with paleoclimate (Bland et al 1998;…”

Characteristics of the Sahara as a meteorite recovery surface

“…(), and Hutzler et al. () was very successful and allowed us to provide precise and high densities of meteorites in Oman and Chile. This led us to consider field missions in the desert of Morocco and Tunisia.…”

“…), except in the Atacama where values above 100 met km −2 are reported in Hutzler et al. (), 86 met km −2 after pairing correction, on a 0.5 km 2 surface. Hutzler et al.…”

“…; Hutzler et al. ). In these areas, there is little precipitation, with an average of 170 mm y −1 in Antarctica (Van de Berg et al.…”

“…Hutzler et al. () also tried to estimate the recovery bias (the number of meteorites present but not collected) leading to a corrected pre‐pairing density of 150 met km −2 . By contrast, little information is available for the Sahara, thus motivating the present work.…”