Publications by authors named "D E Brownlee"

Micrometeorites are estimated to represent the main part of the present flux of extraterrestrial matter found on the Earth's surface and provide valuable samples to probe the interplanetary medium. Here, we describe large and representative collections of micrometeorites currently available to the scientific community. These include Antarctic collections from surface ice and snow, as well as glacial sediments from the eroded top of nunataks-summits outcropping from the icesheet-and moraines.

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Humans display remarkable interindividual variation in their immune response to identical challenges. Yet, our understanding of the genetic and epigenetic factors contributing to such variation remains limited. Here we performed in-depth genetic, epigenetic and transcriptional profiling on primary macrophages derived from individuals of European and African ancestry before and after infection with influenza A virus.

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Article Synopsis
  • Samples from the carbonaceous asteroid Ryugu, collected by the Hayabusa2 spacecraft, show evidence of carbon dioxide-bearing water inclusions in a pyrrhotite crystal, suggesting its parent asteroid formed in the outer Solar System.
  • The analyzed samples contain few high-temperature materials like chondrules, yet are abundant in low-temperature formation products like phyllosilicates and carbonates, indicating aqueous alteration in a low temperature, high pH environment.
  • Numerical simulations reveal that Ryugu's parent body likely formed about 2 million years after the Solar System began to develop, based on the mineralogical and physical properties of the samples.
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Magnesium stable isotope ratios and minor element abundances of five olivine particles from comet 81P/Wild 2 were examined by secondary ion mass spectrometry (SIMS). Wild 2 olivine particles exhibit only small variations in δMg values from -1.0 / ‰ to 0.

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Filamentary enstatite crystals are found in interplanetary dust particles (IDPs) of likely cometary origin but are very rare or absent in meteorites. Crystallographic characteristics of filamentary enstatites indicate that they condensed directly from vapor. We measured the O isotopic composition of an enstatite ribbon from a giant cluster IDP to be δO = 25 ± 55, δO = -19 ± 129, ΔO = -32 ± 134 (2σ errors), which is inconsistent at the 2σ level with the composition of the Sun inferred from the Genesis solar wind measurements.

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