¹M. N. Rao, ²L. E. Nyquist, ^3,4D. K. Ross, ^5,6S. R. Sutton, ⁷P. Hoppe, ⁸C. Y. Shih, ⁹S. J. Wentworth, ¹⁰D. H. Garrison
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13177]
¹SCI, Johnson Space CenterHouston, Texas, USA
²XI/NASA Johnson Space CenterHouston, Texas, USA
³Jacob JETS, NASA Johnson Space CenterHouston, Texas, USA
⁴UTEP–CASSMAREl Paso, Texas, USA
⁵Department of Geophysical Sciences, University of ChicagoChicago, Illinois, USA
⁶CARS, Argonne National LaboratoryArgonne, Illinois, USA
⁷Max‐Planck Institute für Chemie, Mainz, Germany
⁸Jacobs, Johnson Space CenterHouston, Texas, USA
⁹HEPCO, Jacobs Engineering, Johnson Space CenterHouston, Texas, USA
¹⁰Barios Technology, NASA, Johnson Space CenterHouston, Texas, USA
Published by arrangement with John Wiley & Sons

Martian regolith components are found in some impact melts (IM) containing Martian atmospheric gases in the shergottites Elephant Moraine (EET) 79001, Tissint, Zagami, and Shergotty. Excess sulfur abundances provide strong indicators for the presence of an exogenous component. High sulfur abundances and the SO3‐SiO2 correlation in polished thin section (PTS) EET 79001,507 (here #507) are comparable to those in Martian soils. Correlations of SO3 with FeO in #507 from Lithology B and of CaO and Al2O3 in EET 79001,506 (here #506) from Lithology A suggest the possible occurrence of two varieties of sulfate‐bearing phases in impact‐melt precursors. Fe/S (atomic) ratios of 1.02–1.34 determined in several sulfide blebs in #507 differ from those determined in igneous sulfides (Fe/S = 0.92), and suggest that most sulfide blebs in #507 are not related to igneous sulfides. Fe/S (atomic) ratios in a Tissint glass range from ~0.5 (pyrite) to >1.1 suggesting a mixture of sulfur‐bearing phases. S K‐XANES spectra of the blebs in EET 79001 and Tissint glasses show that sulfur occurs as mixed amorphous sulfide and sulfite. The δ34S values and the 87Sr/86Sr (I) ratios determined in EET 79001 impact melts are consistent with the proposition that the sulfide blebs result from decomposition of secondary sulfates into sulfites during shock heating followed by reduction to sulfides by isentropic cooling. These results suggest the presence in some shergottites of extraneous regolith components containing oxidized S‐bearing species resembling sulfur species present in Martian soils.

¹A.P.Crósta, ^2,3W.U.Reimold,⁴M.A.R.Vasconcelos, ²N.Hauser, ¹G.J.G.Oliveira,¹M.V.Maziviero,⁵A.M.Góes
Chemie der Erde (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2018.06.001]
¹State University of Campinas, Brazil
²University of Brasília, Brazil
³Natural History Museum – Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
⁴Federal University of Bahia, Brazil
⁵University of São Paulo, Brazil
Copyright Elsevier

The Earth’s impact record is known to be rather limited in both time and space. There are ca. 190 impact structures currently known on Earth, representing a minor fraction of all the impact events that contributed to the initial formation of our protoplanet, and then to formation and modification of the surface of the planet. Moreover, the distribution of impact structures on Earth is manifestly uneven. One continent that stands out for its relatively small number of confirmed impact structures and impact ejecta occurrences is South America. The limited impact record for this large continent makes a robust case that there is a significant potential for further discoveries. Significant information on the impact record of South America is dispersed in different types of publications (journal articles, books, conferences abstracts, etc.), and in several languages, making it difficult to access and disseminate it among the geoscientific community. We aim to present a summary of the current knowledge of the impact record of this continent, encompassing the existing literature on the subject. It is published in two parts, with the first one covering an up-to-date introduction to impact cratering processes and to the criteria to identify/confirm an impact structure and related deposits. This is followed by a comprehensive analysis of the Brazilian impact structures. The Brazilian impact record accounts for the totality of the large structures of this kind currently confirmed in South America. The second part will examine the impact record of other countries in South America, provide information about a number of proposed impact structures, and review those that already have been discarded as not being formed by impact.