Diamonds in meteorites and impact shock

Researchers report characteristics of diamond-containing meteorites that raise the possibility of a small-planetesimal origin. Ureilite meteorites are known to contain diamonds. One hypothesis holds that diamonds in ureilites formed similar to those on Earth; the latter are formed deep in the mantle where overlying rock creates sufficiently high pressures. If diamonds in ureilites formed in this manner, their parent body would have been a large protoplanet, similar in size to Mars or Mercury, which would support the existence of such bodies in the early Solar System. Fabrizio Nestola, Cyrena Goodrich, and colleagues investigated diamonds in three samples of ureilites via electron microscopy and micro X-ray diffraction, finding no evidence requiring formation under the high static pressures or long growth times of a planet’s interior. The authors found coexisting micrometer-sized and nanometer-sized diamonds, along with metallic iron and graphite. Additionally, the authors report that this mineral assemblage is consistent with formation of diamonds by rapid shock transformation of graphite, in a process similar to that used in catalyzed production of diamonds in industry. Such a mechanism is suggested by shock features in the silicate minerals. According to the authors, the finding suggests that the formation of diamonds in ureilites does not require a Mars-sized parent body, with significant implications for planetary formation models.

Article #19-19067: “Impact shock origin of diamonds in ureilite meteorites,” by Fabrizio Nestola et al.

MEDIA CONTACTS: Fabrizio Nestola, University of Padova, ITALY; e-mail:

[email protected]

; Cyrena Goodrich, Lunar and Planetary Institute, Houston, TX; e-mail:

[email protected]

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