ANTARCTIC MICROMETEORITES, CONSTRAINTS ON INTERPLANETARY ORGANICS FOR
HAYABUSA 2 AND OSIRIS-REX.
J. Duprat1, C. Engrand1, E. Dartois2, M. Godard1, G. Slodzian1.
1
CSNSM, CNRS/IN2P3-Univ. Paris Sud, Bât 104, 91405 Orsay Campus, France (Jean.Duprat@csnsm.in2p3.fr),
2
IAS CNRS/INSU-Univ. Paris-Sud, Bât. 121, 91405 Orsay Campus, France.
Within the coming years, both Hayabusa 2 and OSIRIS-REx space missions will open a new window on ourknowledge of the composition of carbonaceous asteroids. The comparison of samples from asteroids Ryugu andBennu to the known interplanetary material will provide crucial constraints on the origin and evolution of both
high and low temperature phases in the Solar System. A key issue will be the comparison of the organic
compound of these dark asteroids with that of carbonaceous chondrites, carbon-rich interplanetary dust particles
and cometary samples from 81P/Wild2 [1] or in-situ analyses of particles from comet 67P/ChuryumovGerasimenko [2, 3]. The comparison of Hayabusa 2 and OSIRIS-REx samples with carbon-rich interplanetary
dust will provide a unique tool to study the different kinds of asteroidal organic matter and their possible links
with cometary organics.
On short time scales, the extraterrestrial input on Earth is dominated by the mass provided by particles in the20-500 µm size range, (i.e. micrometeorites) [4]. Large collections of Antarctic MicroMeteorites (AMMs) havebeen extracted from blue ice fields of Adélie Land [5] and near Yamato mountains [6], in the South Pole Station
Water Well [7] and at Dome Fuji [8] or in the transantarctic mountains [9]. Thanks to the support of IPEV andPNRA, we achieved several AMM collections from snow at the vicinity of CONCORDIA Station located at
Dome C (73°S, 123°E) in the central regions of the Antarctic continent [10]. We recovered thousands of AMMs
from melting and filtering ultra-clean snow extracted from trenches. The AMMs from central Antarctic snow are
well preserved from terrestrial weathering and exhibit fragile particles [10, 11] resembling to the chondritic
porous IDPs from stratospheric collections [12, 13]. The cleanliness of such collections also allows identifying
rare particles with high carbon content, i.e. Ultra-Carbonaceous Antarctic Micrometeorites (UCAMMs) [14].
The UCAMM carbonaceous component consists in a highly disordered organic matter exhibiting extreme
deuterium excesses [15] and N/C ratios higher than those reported in IOM from carbonaceous chondrites [1618]. UCAMMs have no counterpart in meteorite collections and the identification of their potential parent bodyis challenging. The UCAMMs have similarities with the so-called CHON particles identified in comet 1P/Halleyby the Vega and Giotto space probes [19], and with C-rich IDPs identified in stratospheric collections [20]. The
isotopic compositions of light elements (H, C and N) were recently measured with the NanoSIMS using
polyatomic ions using a high mass resolution (HMR) protocol [21] and a dedicated series of standards to infer
the D/H instrumental mass fractionation [22]. STXM-XANES and TEM data reveal that UCAMMs contains
several components exhibiting different concentrations of minerals and a wide range of hydrogen and nitrogenisotopic compositions [23, 24]. The main carbonaceous component of UCAMM has large D/H ratio variations,while a minor component exhibit depletion in 15N and higher mineral content. Both the bulk elemental andisotopic compositions of UCAMMs indicate that these samples most probably originate from the solar systemouter regions, i.e. the cometary reservoir [15, 18]. Their high nitrogen concentration and high heterogeneous
isotopic composition can be accounted for by assuming that the precursors of their organic matter result from theirradiation by galactic cosmic rays of N-rich ices at the sub-surface of a parent body orbiting at large heliocentric
distances [18, 25].
The comparison of UCAMMs, and micrometeorites in general, with the future samples from Hayabusa 2 andOSIRIS-REx will provide new constraints on the association of primitive organic matter and minerals in theearly solar system. I will review these recent results and emphasize why both the experimental developmentsthat we used to analyze UCAMMs and ion irradiation experiments are of interest for a better understanding ofHayabusa 2 and OSIRIS-REx samples.
Acknowledgments: The study on micrometeorites was funded by the ANR project OGRESSE (11-BS56-026-01), theRégion Ile de France DIM-ACAV, Labex P2IO and CNES. The CONCORDIA station is a joint project of French and Italianpolar institute (IPEV and PNRA).
References: [1] Brownlee, D., An. Rev. of Earth and Planet. Sci., 2014. 42: p. 179-205. ; [2] Hilchenbach, M., et al.,ApJL, 2016. 816 ; [3] Fray, N., et al., Nature, 2016: p. in press. ; [4] Love, S.G., et al., Science, 1993. 262: p. 550-553. ; [5]Maurette, M., et al., Nature, 1987. 328: p. 699-702. ; [6] Noguchi, T., et al. # 117-119. Antarctic Meteorites XXV. 2000. ; [7]Taylor, S., et al., Nature, 1998. 392: p. 899-903. ; [8] Noguchi, T., et al., Ant. Met. Res., 2000. 13: p. 270. ; [9] Rochette, P.,
et al., PNAS, 2008. 105: p. 18206-18211. ; [10] Duprat, J., et al., Adv. Space Res., 2007. 39: p. 605-611. ; [11] Noguchi, T.,et al., EPSL, 2015. 410: p. 1-11. ; [12] Ishii, H.A., et al., Science, 2008. 319: p. 447. ; [13] Rietmeijer, F.J.M., in PlanetaryMaterials, 1998, p. 2/1-2/95. ; [14] Nakamura, T., et al., M&PS Suppl., 2005. 40: p. 5046. ; [15] Duprat, J., et al., Science,
2010. 328: p. 742-745 ; [16] Yabuta, H., et al. # 2239. LPSC. 2012. ; [17] Yabuta, H., et al., M&PS Suppl., 2012. 75: p.
5196. ; [18] Dartois, E., et al., Icarus, 2013. 224: p. 243-252. ; [19] Lawler, M.E., et al., Nature, 1992. 359: p. 810-812. ; [20]Thomas, K.L., et al., GCA, 1993. 57: p. 1551-1566. ; [21] Slodzian, G., et al., M&M, 2014. 20: p. 577-581. ; [22] Bardin, N.,et al., IJMS, 2015. 393: p. 17-24. ; [23] Bardin, N., et al. # 5275. 78th Met. Soc. Meeting. 2015. ; [24] Engrand, C., et al. #1902. LPSC. 2015. ; [25] Augé, B., et al., A&A, 2016. 592.