Motopi Pan / asteroid 2018 LA

A new meteorite with associated orbit has been added to the table: Motopi Pan. Although officially classified as a howardite (in the MetBull database), it is a complex HED breccia with howardite, cumulate and basaltic eucrites, as well as diogenite lithologies, as the authors write in an article published online today in MAPS (Jenniskens et al., 2021). This is only the second time (the first was Almahata Sitta in 2008) that a meter-scale asteroid was found to be on a collision course with Earth only a few hours prior to impact (the asteroid was named 2018 LA), observed as a meteor when it entered the Earth’s atmosphere, and meteorites recovered afterwards, this time in Botswana. Because of the longer observation arc, the orbit is much better constrained compared to a typical “meteorite-with-orbit” fall. The orbit strongly suggests the meteoroid was delivered via the nu-6 resonance from the large asteroid Vesta. From the combination of ejection age (= cosmic-ray exposure age, ca. 22 Ma) and shock-reset age in phosphates, Jennsikens et al. (2021) even suggest that the source crater of the impact might be Rubria, in the Venenaia impact basin on Vesta.

Full disclosure: I am a co-author on the paper. /m4

New paper accepted: Flensburg (C1-ungr.) in MAPS

A paper describing the trajectory and orbit of the Flensburg (carbonaceous, C1 ungrouped) meteorite, which fell on September 12th, 2019 in northernmost Germany, has been accepted for publication into MAPS, and the corresponding preprint uploaded on arxiv.org. The meteoroid delivering the single known piece of the Flensburg meteorite (of only 24.5 g) originates from a quite elongated orbit with a large semi-major axis (ca. 2.8 AU), which puts it right on the 5:2 orbital resonance with Jupiter, as well as in the Jupiter Family Comets field (2 < Tisserand parameter <3). It had a mass in the range of 10-20 metric tons and correspondingly, a radius of 2-3 meters. The authors suggest that based on the orbit and the very short cosmic-ray exposure age of only 7 ka (Bischoff et al., 2021), the meteoroid probably originated on a carbonaceous asteroid close to the edge of the 5:2 resonance.

Flensburg is only the fourth carbonaceous meteorite with an orbit (the others being Tagish Lake, Maribo, and Sutter’s Mill). Its interesting to note that carbonaceous meteorites are now slightly over-represented (ca. 11%) among meteorites with orbits compared to their abundance among “normal” finds (ca. 4%), perhaps because, once landed on the surface, they decay quickly and are thus less likely to be found without the “prompt” provided by the fireball observation. /m4

New paper out: Cavezzo, an anomalous L-chondrite

A new paper by Gardiol et al. in MNRAS (available online) summarizes the results from the initial investigation of the Cavezzo chondrite, which fell in Italy on the evening of January 1st, 2020. The meteorite, of which two fragments have been found, is an anomalous L5 chondrite, the 9th L-chondrite out of 34 meteorites with orbits. The semi-major axis and eccentricity of its parent meteoroid plot along the characteristic trend, and as is often observed, the perihelion is just inside Earth’s orbit, while the aphelion is in the asteroid belt. /m4

New paper out: Dishchii’bikoh in MAPS

A new meteorite with an orbit has been published in Meteoritics & Planetary Science (MAPS): Dishchii’bikoh. It is a rare LL7 chondrite which fell near the city of Cibecue in Arizona / USA, and takes its name as pronounced in the language of the local White Mountain Apache tribe. Several fragments of almost 80 g total mass were recovered using the weather radar footprint of the fall. The orbit of the meteorite is remarkable for being relatively short (1.13 AU semi-major axis) and steeply inclined (ca. 21° to the ecliptic). Radionuclides suggest it was a relatively large meteoroid, at R = 60-100 cm. The cosmic-ray exposure age is quite typical for an ordinary chondrite, at 11 Ma. It seems likely the meteorite derived from the Flora family of asteroids in the inner asteroid belt, similar to other recent LL chondrite falls, like Stubenberg (2016) and Chelyabinsk (2013).

Full disclosure: I am a co-author on the paper. /m4

Novo Mesto* – a new meteorite linked to a bright fireball

novo mesto meteorite
The Novo Mesto* meteorite. (Photo: Bojan Ambrožič / bojanambrozic.com)

In the morning of February 28th, a bright daytime fireball was observed over Slovenia. Now, a fresh, fusion-encrusted meteorite (ca. 200 g), looking like an equilibrated chondrite, has been found in the region where the fragments from the fireball were expected to drop. On March 7th, it was found and reported by Gregor Kos in the driveway of his house, and later confirmed to be a meteorite by Bojan Ambrozic. Later that same day, the meteorite was handed over to the Natural History Museum of Slovenia. The prospective name of the meteorite (not yet approved by the Meteoritical Society, which is why I provide the name with an asterisk) is Novo Mesto*.

Obviously, this is an excellent candidate for a meteorite which will have an associated orbit. /m4