Close up of granular structure of meteorite rock
The formation of the large grains of low-Ca pyroxene found in meteorite NWA 11004 probably involve high-temperature metamorphism with minor to moderate partial melting, preceding the impact that gave this grain its mosaic texture. Credit: Li et al. [2020], Figure 2b
Source: Journal of Geophysical Research: Planets

The early solar system was a violent place dominated by collisions of newly formed bodies. These newly formed bodies were heated by powerful but short-lived radioactive decay of now-extinct isotopes like 26Al. Insight about these early times comes mainly from the study of primitive ancient meteorites. However, few of them have survived to the present day without some amount of modifications (on the parent body or later), making detailed petrological analyses necessary to unravel the history of these complex meteorites.

Li et al. [2020] describe the history of one of these meteorites, NWA11004, which presents evidence for both melting and impacts, one of which took place about 4546 million years ago. Remarkably, an even earlier heating event, strong enough to induce melting is suggested from several petrological and geochemical indicators. This implies that the parent body of NWA11004 was hot before the impact. The early age of this event provides up-to-now elusive evidence for heating by short-lived isotopes, especially 26Al and can change the view of thermal state of early planetesimals.

Citation: Li, Y., Rubin, A. E., Hsu, W., & Ziegler, K. [2020]. Early impact events on chondritic parent bodies: Insights from NWA 11004, reclassified as an LL7 breccia. Journal of Geophysical Research: Planets, 125, e2019JE006360.

—Laurent G. J. Montési, Editor in Chief, and Justin Filiberto, Associate Editor, JGR: Planets

Text © 2020. The authors. CC BY-NC-ND 3.0
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