^1,2Queenie H. S. Chan,¹Ian A. Franchi,¹Xuchao Zhao,¹Alice Stephant,¹Ian P. Wright,²Conel M. O’D. Alexander
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13414]
¹Planetary and Space Sciences, School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
²Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, District of Columbia, 20015 USA
Published by arrangement with John Wiley & Sons

The chondritic‐porous subset of interplanetary dust particles (CP‐IDPs) are thought to have a cometary origin. Since the CP‐IDPs are anhydrous and unaltered by aqueous processes that are common to chondritic organic matter (OM), they represent the most pristine material of the solar system. However, the study of IDP OM might be hindered by their further alteration by flash heating during atmospheric entry, and we have limited understanding on how short‐term heating influences their organic content. In order to investigate this problem, five CP‐IDPs were studied for their OM contents, distributions, and isotopic compositions at the submicro‐ to nanoscale levels. The OM contained in the IDPs in this study spans the spectrum from primitive OM to that which has been significantly processed by heat. Similarities in the Raman D bands of the meteoritic and IDP OMs indicate that the overall gain in the sizes of crystalline domains in response to heating is similar. However, the Raman Γ_G values of the OM in all of the five IDPs clearly deviate from those of chondritic OM that had been processed during a prolonged episode of parent body heating. Such disparity suggests that the nonaromatic contents of the OM are different. Short duration heating further increases the H/C ratio and reduces the δ¹³C and δD values of the IDP OM. Our findings suggest that IDP OM contains a significant proportion of disordered C with low H content, such as sp² olefinic C=C, sp³ C–C, and/or carbonyl contents as bridging material.

¹Heather B. Franz,²Nanping Wu,³James Farquhar,⁴Anthony J. Irving
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13404]
¹NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 USA
²Department of Geology, University of Maryland, College Park, Maryland, 20742 USA
³Department of Geology and ESSIC, University of Maryland, College Park, Maryland, 20742 USA
⁴Department of Earth and Space Sciences, University of Washington, Seattle, Washington, 98195 USA
Published by arrangement with John Wiley & Sons

The isotopic composition and abundance of sulfur in extraterrestrial materials are of interest for constraining models of both planetary and solar system evolution. A previous study that included phase‐specific extraction of sulfur from 27 shergottites found the sulfur isotopic composition of the Martian mantle to be similar to that of terrestrial mid‐ocean ridge basalts, the Moon, and nonmagmatic iron meteorites. However, the presence of positive Δ33S anomalies in igneous sulfides from several shergottites, indicating incorporation of atmospherically processed sulfur into the subsurface, complicated this interpretation. The current study expands upon the previous work through analyses of 20 additional shergottites, enabling tighter constraints on the isotopic composition of juvenile Martian sulfur. The updated composition (δ34S = −0.24 ± 0.05‰, Δ33S = 0.0015 ± 0.0016‰, and Δ36S = 0.039 ± 0.054‰, 2 s.e.m.), representing the weighted mean for all shergottites within the combined population of 47 without significant Δ33S anomalies, strengthens our earlier result. The presence of sulfur isotopic anomalies in igneous sulfides of some meteorites suggests that their parent magmas may have assimilated crustal material. We observed small negative Δ33S anomalies in sulfides from two meteorites, NWA 7635 and NWA 11300. Although negative Δ33S anomalies have been observed in nakhlites and ALH 84001, previous anomalies in shergottites have all shown positive values of Δ33S. Because NWA 7635 has formation age of 2.4 Ga and is much more ancient than shergottites analyzed previously, this finding expands our perspective on the continuity of Martian atmospheric sulfur photochemistry over geologic time.

¹Regina Rudawska,¹ Joe Zender,^1,2 Detlef Koschny,¹Hans Smit,³ Stefan Löhle,³Fabian Zander,³Martin Eberhart,³Arne Meindl,⁴Imanol Uriarte Latorre
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2019.104773]
¹Science Support Office European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ, Noordwijk, the Netherlands
²Lehrstuhl für Raumfahrttechnik, TU Munich, 85748, Garching, Germany
³Universitat Stuttgart, Institut für Raumfahrtsysteme, 70569, Stuttgart, Germany
⁴Technical University of Berlin, Berlin, Germany

We currently do not have a copyright agreement with this publisher and cannot display the abstract here