¹A. J. King, ¹P. F. Schofield, ¹S. S. Russell
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12872]
¹Department of Earth Sciences, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The CM carbonaceous chondrite meteorites experienced aqueous alteration in the early solar system. They range from mildly altered type 2 to almost completely hydrated type 1 chondrites, and offer a record of geochemical conditions on water-rich asteroids. We show that CM1 chondrites contain abundant (84–91 vol%) phyllosilicate, plus olivine (4–8 vol%), magnetite (2–3 vol%), Fe-sulfide (120 °C), although higher water/rock ratios may also have played a role. The modal data provide constraints for interpreting the composition of asteroids and the mineralogy of samples returned from these bodies. We predict that “CM1-like” asteroids, as has been proposed for Bennu—target for the OSIRIS-REx mission—will have a high abundance of Mg-rich phyllosilicates and Fe-oxides, but be depleted in calcite.

¹Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12869]
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

This report presents bulk composition data for 10 lunar meteorite stones from Oman for which the names have been approved since June, 2012. On the basis of composition and reported find location, four new meteorites are represented among this group of stones. Data from neutron activation analysis of 371 subsamples of all lunar meteorites from Oman and Saudi Arabia analyzed in this laboratory are presented.

¹Mokkapati Shyam Prasad, ¹N. G. Rudraswami, ¹Agnelo A. De Araujo, ¹Vijay D. Khedekar
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12858]
¹CSIR-National Institute of Oceanography, Dona Paula, Goa, India
Published by arrangement with John Wiley & Sons

Fe-Ni metal is a common constituent of most meteorites and is an indicator of the thermal history of the respective meteorites, it is a diagnostic tool to distinguish between groups/subgroups of meteorites. In spite of over a million micrometeorites collected from various domains, reports of pure metallic particles among micrometeorites have been extremely rare. We report here the finding of a variety of cosmic metal particles such as kamacite, plessite, taenite, and Fe-Ni beads from deep-sea sediments of the Indian Ocean, a majority of which have entered the Earth unaffected by frictional heating during atmospheric entry. Such particles are known as components of meteorites but have never been found as individual entities. Their compositions suggest precursors from a variety of meteorite groups, thus providing an insight into the metal fluxes on the Earth. Some particles have undergone heating and oxidation to different levels during entry developing features similar to I-type cosmic spherules, suggesting atmospheric processing of individual kamacites/taenite grains as another hitherto unknown source for the I-type spherules. The particles have undergone postdepositional aqueous alteration transforming finally into the serpentine mineral cronstedtite. Aqueous alteration products of kamacite reflect the local microenvironment, therefore they have the potential to provide information on the composition of water in the solar nebula, on the parent bodies or on surfaces of planetary bodies. Our observations suggest it would take sustained burial in water for tens of thousands of years under cold conditions for kamacites to alter to cronstedtite.