Chondrules from high-velocity collisions: thermal histories and the agglomeration problem. Issue 3 (22nd February 2021)

• Record Type: Journal Article
• Authors: Choksi, Nick; Chiang, Eugene; Connolly, Harold C; Gainsforth, Zack; Westphal, Andrew J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 503:Issue 3(2021)
• Page Start: 3297
• Page End: 3308
• Publication Date: 2021-02-22
• Subjects: comets: general -- Kuiper belt: general -- meteorites, meteors, meteoroids -- minor planets, asteroids: general -- planets and satellites: formation -- protoplanetary discs; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab503
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We assess whether chondrules, once-molten mm-sized spheres filling the oldest meteorites, could have formed from super-km s −1 collisions between planetesimals in the solar nebula. High-velocity collisions release hot and dense clouds of silicate vapour which entrain and heat chondrule precursors. Thermal histories of CB chondrules are reproduced for colliding bodies ∼10–100 km in radius. The slower cooling rates of non-CB, porphyritic chondrules point to colliders with radii ≳ 500 km. How chondrules, collisionally dispersed into the nebula, agglomerated into meteorite parent bodies remains a mystery. The same orbital eccentricities and inclinations that enable energetic collisions prevent planetesimals from re-accreting chondrules efficiently and without damage; thus the sedimentary laminations of the CB/CH chondrite Isheyevo are hard to explain by direct fallback of collisional ejecta. At the same time, planetesimal surfaces may be littered with the shattered remains of chondrules. The micron-sized igneous particles recovered from comet 81P/Wild-2 may have originated from in-situ collisions and subsequent accretion in the proto-Kuiper belt, obviating the need to transport igneous solids across the nebula. Asteroid sample returns from Hayabusa2 and OSIRIS-REx may similarly contain chondrule fragments.