Patrick N. Peplowski¹, David Bazell¹, Larry G. Evans², John O. Goldsten¹, David J. Lawrence¹ and Larry R. Nittler³

¹The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
²Computer Sciences Corporation, Lanham-Seabrook, Maryland, USA
³Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA

A reanalysis of NEAR X-ray/gamma-ray spectrometer (XGRS) data provides robust evidence that the elemental composition of the near-Earth asteroid 433 Eros is consistent with the L and LL ordinary chondrites. These results facilitated the use of the gamma-ray measurements to produce the first in situ measurement of hydrogen concentrations on an asteroid. The measured value, inline image ppm, is consistent with hydrogen concentrations measured in L and LL chondrite meteorite falls. Gamma-ray derived abundances of hydrogen and potassium show no evidence for depletion of volatiles relative to ordinary chondrites, suggesting that the sulfur depletion observed in X-ray data is a surficial effect, consistent with a space-weathering origin. The newfound agreement between the X-ray, gamma-ray, and spectral data suggests that the NEAR landing site, a ponded regolith deposit, has an elemental composition that is indistinguishable from the mean surface. This observation argues against a pond formation process that segregates metals from silicates, and instead suggests that the differences observed in reflectance spectra between the ponds and bulk Eros are due to grain size differences resulting from granular sorting of ponded material.

Reference
Peplowski PN, Bazell D, Evans LG, Goldsten JO, Lawrence DJ and Nittler LR (2015) Hydrogen and major element concentrations on 433 Eros: Evidence for an L- or LL-chondrite-like surface composition. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12434]

Published by arrangement with John Wiley & Sons

Aaron S. Burton^1,†, Hannah McLain³, Daniel P. Glavin¹, Jamie E. Elsila¹, Jemma Davidson⁴, Kelly E. Miller⁵, Alexander V. Andronikov⁵, Dante Lauretta⁵ and Jason P. Dworkin¹

¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
³Catholic University of America, Washington, District of Columbia, USA
⁴Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
^†Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA

Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon-rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino-terminal (n-ω-amino) acids β-alanine, and γ-amino-n-butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n-ω-amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch-type reactions, although this hypothesis needs further testing.

Reference
Burton AS, McLain H, Glavin DP, Elsila JE, Davidson J, Miller KE, Andronikov AV, Lauretta D and Dworkin JP
(2015) Amino acid analyses of R and CK chondrites. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12433]

Published by arrangement with John Wiley & Sons

William K. Hartmann

Planetary Science Institute, Tucson, Arizona, USA

The well-recorded Chelyabinsk event, the Tunguska event, and the re-entry of the Zond IV vehicle offer opportunities to compare reactions of modern eyewitnesses to eyewitness accounts of possible ancient fireball events. The first-century book, Acts of the Apostles, gives three separate descriptions of a bright light “from heaven,” which occurred probably in the 30s (C.E.) near Damascus, Syria. The details offer a strikingly good match to a Chelyabinsk-class or Tunguska-class fireball. Among the most impressive, unexpected consistencies with modern knowledge is the first-century description of symptoms of temporary blindness caused by exposure to intense radiation, matching a condition now known as photokeratitis. An analysis of the re-entry of debris from the Russian Zond IV over the eastern United States in 1968 shows how actual perceived phenomena in an unfamiliar natural celestial apparition are often conceived by the observer in terms of current cultural conceptions, and it is suggested that this happened also in the first-century case.

Reference
Hartmann WK (2015) Chelyabinsk, Zond IV, and a possible first-century fireball of historical importance. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12428]

Published by arrangement with John Wiley & Sons