^1,2Laura Flagg,²Alycia J. Weinberger,³Keith Matthews
¹Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ 86011-6010, USA
²Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015, USA
³Caltech Optical Observatories, California Institute of Technology, MC 301-17, Pasadena, CA 91125, USA

The detectability of planetesimal impacts on imaged exoplanets can be measured using Jupiter during the 1994 comet Shoemaker-Levy 9 events as a proxy. By integrating the whole planet flux with and without impact spots, the effect of the impacts at wavelengths from 2 – 4 μμm is revealed. Jupiter’s reflected light spectrum in the near-infrared is dominated by its methane opacity including a deep band at 2.3 μμm. After the impact, sunlight that would have normally been absorbed by the large amount of methane in Jupiter’s atmosphere was instead reflected by the cometary material from the impacts. As a result, at 2.3 μμm, where the planet would normally have low reflectivity, it brightened substantially and stayed brighter for at least a month.

Reference
Flagg L, Weinberger AJ, Matthews K (2015) Detectability of Planetesimal Impacts on Giant Exoplanets. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.08.024]
Copyright Elsevier

^1,2Marina A. Ivanova, ¹Cyril A. Lorenz, ³Alexander N. Krot,²Glenn J. MacPherson
¹Vernadsky Institute of Geochemistry and Analytical Chemistry of Russian Academy of Sciences, Moscow, Russia
²National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA
³Hawaiʻi Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu, Hawaiʻi, USA

A calcium-aluminum-rich inclusion 3N from the Northwest Africa (NWA) 3118 CV3 carbonaceous chondrite is a unique cm-sized compound object, primarily a forsterite-bearing type B (FoB) CAI, that encloses at least 26 smaller CAIs of different types, including compact type A (CTA), B, C, and an ultra-refractory inclusion. Relative to typical type A and B CAIs found elsewhere, the bulk compositions of the types A and B CAIs within 3N more closely match the bulk compositions predicted by equilibrium condensation of a gas of solar composition. Being trapped within the FoB melt may have protected them from melt evaporation that affected most “stand-alone” CAIs. 3N originated either as an aggregate of many smaller (mostly types A, B, C) CAIs plus accreted Fo-bearing material (like an amoeboid olivine aggregate) which experienced partial melting of the whole, or else as a FoB melt droplet that collided with and trapped many smaller solid CAIs. In the former case, 3N recorded the earliest accretion of pebble-sized bodies known. In the latter case, the presence of a large number of individual refractory inclusions within 3N suggests a very high local density of refractory solids in the immediate region of the host CAI during the brief time while it was melted. Collisions would have occurred on time scales of hours at most, assuming a melt solidification interval for the host CAI of 300–400 °C (maximum) and a cooling rate of ~10 °C/h.

Reference
Ivanov MA, Lorenz CA, Krot AN, MacPherson GJ (2015) A compound Ca-, Al-rich inclusion from CV3 chondrite Northwest Africa 3118: Implications for understanding processes during CAI Formation. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12489]
Published by Arrangement with John Wiley&Sons