A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

Abstract

Micrometeorites with diameter Ϸ100 -200 m dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.asteroids ͉ cosmic dust ͉ differentiation

Trace element geochemistry of K-rich impact spherules from howardites

“…-it is now well established that basaltic achondrites derived from a number of parent bodies (Yamaguchi et al, 2001;Scott et al, 2008;Gounelle et al, 2009) -the Fe/Mn ratios of the spherules are consistent with a link to the HEDs; moreover, the occurrence of an unmelted diogenitic remnant in a high K-spherule strongly strengthens this conclusion (Barrat et al, 2009a).…”

Short-Lived Radionuclides and Early Solar System Chronology

“…The latter age is earlier than the differentiation age inferred by Goodrich et al (2010) for ureilites and may imply that feldspathic clasts date later crustal processing rather than parent-body differentiation. Gounelle et al (2009) reported that a basaltic micrometeorite has no excess 26 Mg in plagioclase with high Al/Mg ratios, giving an upper limit for the 26 Al/ 27 Al at the time of formation of <2.8 Â 10 À7 , implying formation more that 7.9 Ma after CAI formation.…”

Evaluating Changes in the Elemental Composition of Micrometeorites During Entry Into the Earth’s Atmosphere

“…The size of most of the dust ranges from a few μm to a few mm. A significant aspect of micrometeorite studies is that some of these particles may have sampled unfamiliar asteroids that are not represented in our meteorite collection (Yada et al 2005;Gounelle et al 2009). The dust particles are anticipated to originate predominantly in the asteroid belt anddrift further-into the inner solar system with a large probability of getting trapped in orbital resonance with Earth due to their smaller orbital eccentricities compared to cometary particles (Dermott et al 1994;Reach et al 1997;Brownlee 2001, pp.…”