^1,2Peter Jenniskens,²Darrel Robertson,³Cyrena A. Goodrich,⁴Muawia H. Shaddad,⁴Ayman Kudoda,⁵Anna M. Fioretti,⁶Michael E. Zolensky
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13892]
¹SETI Institute, 339 Bernardo Avenue, Mountain View, California, 94043 USA
²NASA Ames Research Center, Moffett Field, California, 94035 USA
³Lunar and Planetary Institute, USRA, Houston, Texas, 77058 USA
⁴Department of Physics and Astronomy, University of Khartoum, Khartoum, 11115 Sudan
⁵CNR–Istituto di Geoscienze e Georisorse, I-35131 Padova, Italy
⁶Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas, 77058 USA
Published by arrangement with John Wiley & Sons

Asteroid 2008 TC3 impacted the Earth’s atmosphere with a known shape and orientation. Over 600 meteorites were recovered at recorded locations, including meteorites of nonureilite type. From where in the asteroid did these stones originate? Here, we reconstruct the meteor lightcurve and study the breakup dynamics of asteroid 2008 TC3 in 3-D hydrodynamic modeling. Two fragmentation regimes are found that explain the lightcurve and strewn field. As long as the asteroid created a wake vacuum, the fragments tended to move into that shadow, where they mixed with small relative velocities and surviving meteorites fell along a narrow strip on the ground. But when the surviving part of the backside and bottom of the asteroid finally collapsed at 33 km altitude, it created an end flare and dust cloud, while fragments were dispersed radially with much higher relative speed due to shock–shock interactions with a distorted shock front. Stones that originated in this final collapse tended to survive in a larger size and fell over a wider area at locations on the ground. Those locations to some extent still trace back to the fragment’s original position in the asteroid. We classified the stones from this “large mass” area and used this information to glean some insight into the relative location of recovered ureilites and ordinary and enstatite chondrites in 2008 TC3.

¹Taha Shisseh,¹Hasnaa Chennaoui Aoudjehane,²Carl B. Agee,³Omar Boudouma
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13899]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, km 8 Route d’El Jadida, 20150 Casablanca, Morocco
²Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87131 USA
³UPMC – Paris 06, UMR, 7193 Paris, France
Published by arrangement with John Wiley & Sons

Tirhert and Aouinet Legraa are the only documented unbrecciated eucrite falls in Africa. Aouinet Legraa fell in Algeria on July 17, 2013. Tirhert’s fall occurred about a year later in Morocco, on July 9, 2014. Both meteorites are covered by a black and glossy fusion crust as is typical of eucrites. Tirhert has a poikilitic texture with remnant subophitic pockets, and consists of millimeter-sized grains of plagioclase (An87-91), pigeonite (Mg# 42) with augite exsolution lamellae, and interstitial opaque minerals. Aouinet Legraa has a subophitic texture, and it is dominated by plagioclase laths (An82-89) enclosed by pigeonite (Mg# 37), with exsolution lamellae of augite. Remnant Ca zoning in pyroxene is observed in both rocks, although it is more abundant in Aouinet Legraa than Tirhert. The presence of exsolved pyroxenes suggests that these meteorites have undergone thermal metamorphism. Equilibration temperatures estimated from pigeonite and augite pairs using the QUILF program are ∼931 °C in Tirhert and ∼758 °C in Aouinet Legraa. This indicates that these rocks had distinct thermal histories. Aouinet Legraa has trace element abundances similar to the typical main group eucrite Juvinas, confirming its origin as a main group eucrite. The trace element abundances of Tirhert fall between those of cumulate and main group eucrites. Its rare earth element pattern is flat with a positive Eu anomaly. This likely suggests that Tirhert is a partial cumulate of plagioclase from a main group magma, or a flotation cumulate formed by flotation of plagioclase in a subvolcanic chamber or by scavenging crystals during eruption.