Presolar Stardust in Asteroid Ryugu

Medientyp: E-Artikel
Titel: Presolar Stardust in Asteroid Ryugu
Beteiligte: Barosch, Jens; Nittler, Larry R.; Wang, Jianhua; O’D. Alexander, Conel M.; De Gregorio, Bradley T.; Engrand, Cécile; Kebukawa, Yoko; Nagashima, Kazuhide; Stroud, Rhonda M.; Yabuta, Hikaru; Abe, Yoshinari; Aléon, Jérôme; Amari, Sachiko; Amelin, Yuri; Bajo, Ken-ichi; Bejach, Laure; Bizzarro, Martin; Bonal, Lydie; Bouvier, Audrey; Carlson, Richard W.; Chaussidon, Marc; Choi, Byeon-Gak; Cody, George D.; Dartois, Emmanuel; [...]
Erschienen: American Astronomical Society, 2022
Erschienen in: The Astrophysical Journal Letters
Sprache: Nicht zu entscheiden
DOI: 10.3847/2041-8213/ac83bd
ISSN: 2041-8205; 2041-8213
Schlagwörter: Space and Planetary Science ; Astronomy and Astrophysics
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Beschreibung: <jats:title>Abstract</jats:title> <jats:p>We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are <jats:inline-formula> <jats:tex-math> <?CDATA ${4.8}_{-2.6}^{+4.7}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>4.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac83bdieqn1.gif" xlink:type="simple" /> </jats:inline-formula> ppm for O-anomalous grains, <jats:inline-formula> <jats:tex-math> <?CDATA ${25}_{-5}^{+6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>25</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac83bdieqn2.gif" xlink:type="simple" /> </jats:inline-formula> ppm for SiC grains, and <jats:inline-formula> <jats:tex-math> <?CDATA ${11}_{-3}^{+5}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac83bdieqn3.gif" xlink:type="simple" /> </jats:inline-formula> ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: <jats:inline-formula> <jats:tex-math> <?CDATA ${23}_{-6}^{+7}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac83bdieqn4.gif" xlink:type="simple" /> </jats:inline-formula> ppm SiC and <jats:inline-formula> <jats:tex-math> <?CDATA ${9.0}_{-3.6}^{+5.4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>9.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac83bdieqn5.gif" xlink:type="simple" /> </jats:inline-formula> ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu–CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.</jats:p>
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