arXiv subjects

R. C. Ogliore

Publications and source records attributed to R. C. Ogliore.

5 recordsLinked to original sources

arXiv2025

Amides from the carbonaceous asteroid (162173) Ryugu: nanoscale spectral and isotopic characterizations

C-type asteroids, such as asteroid (162173) Ryugu, may have played a key role in delivering light elements to early Earth. Nitrogen (N)-bearing molecules have been chemically identified in some Ryugu grains, and based on the faint 3.06 um absorption band observed by the hyperspectral microscope MicrOmega, NH-bearing compounds appear to be globally distributed. However, the chemical forms of these NH-bearing compounds - whether organic molecules, ammonium (NH4+) salts, NH4+- or NH-organic-bearing phyllosilicates, or other forms - remain to be clarified. We report the characterization of two Ryugu particles (C0050 and C0052) using infrared spectroscopy at millimeter, micrometer, and nanometer scales, combined with NanoSIMS to constrain the nature and origin of NH-bearing components. Ryugu's C0052 particle contains rare (~1 vol.%) micrometer-sized NH-rich organic compounds with peaks at 1660 cm-1 (C=O stretching, amide I) and 1550 cm-1 (N-H bending, amide II), indicative of amides, absent in C0050. N isotopic analysis shows these amides are depleted in 15N (d15N ~ -200 permil), confirming their indigenous origin. The amides may have formed by hydrothermal alteration of carboxylic acids and amines on Ryugu's parent body or by irradiation of 15N-depleted N-bearing ice in the outer Solar System or interstellar medium. Such amides delivered by primitive small bodies may have contributed to prebiotic chemistry on early Earth.

astro-ph.EP↗

arXiv2017

The Future of Stardust Science

Recent observations indicate that >99% of the small bodies in the Solar System reside in its outer reaches --- in the Kuiper Belt and Oort Cloud. Kuiper Belt bodies are probably the best preserved representatives of the icy planetesimals that dominated the bulk of the solid mass in the early Solar System. They likely contain preserved materials inherited from the protosolar cloud, held in cryogenic storage since the formation of the Solar System. Despite their importance, they are relatively underrepresented in our extraterrestrial sample collections by many orders of magnitude ($\sim$10$^{13}$ by mass) as compared with the asteroids, represented by meteorites, which are composed of materials that have generally been strongly altered by thermal and aqueous processes. We have only begun to scratch the surface in understanding Kuiper Belt objects, but it is already clear that the very limited samples of them that we have in our laboratories hold the promise of dramatically expanding our understanding of the formation of the Solar System. Stardust returned the first samples from a known small solar-system body, the Jupiter-family comet 81P/Wild 2, and, in a separate collector, the first solid samples from the local interstellar medium. The first decade of Stardust research resulted in more than 142 peer-reviewed publications, including 15 papers in Science. Analyses of these amazing samples continue to yield unexpected discoveries and to raise new questions about the history of the early Solar System. We identify 9 high-priority scientific objectives for future Stardust analyses that address important unsolved problems in planetary science.

astro-ph.EP↗

arXiv2014

Ratio Estimation in SIMS Analysis

The determination of an isotope ratio by secondary ion mass spectrometry (SIMS) traditionally involves averaging a number of ratios collected over the course of a measurement. We show that this method leads to an additive positive bias in the expectation value of the estimated ratio that is approximately equal to the true ratio divided by the counts of the denominator isotope of an individual ratio. This bias does not decrease as the number of ratios used in the average increases. By summing all counts in the numerator isotope, then dividing by the sum of counts in the denominator isotope, the estimated ratio is less biased: the bias is approximately equal to the ratio divided by the summed counts of the denominator isotope over the entire measurement. We propose a third ratio estimator (Beale's estimator) that can be used when the bias from the summed counts is unacceptably large for the hypothesis being tested. We derive expressions for the variance of these ratio estimators as well as the conditions under which they are normally distributed. Finally, we investigate a SIMS dataset showing the effects of ratio bias, and discuss proper ratio estimation for SIMS analysis.

astro-ph.IM↗

arXiv2011

Incorporation of a Late-forming Chondrule into Comet Wild 2

We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct 26Al was found, with (26Al/ 27Al)0 < 3.0 x 10^-6. Assuming homogenous distribution of 26Al in the solar nebula, this particle crystallized at least 3 Myr after the earliest solar system objects--relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after calcium-aluminum-rich inclusionss.

astro-ph.EP↗

arXiv2010

Comparison of the Oxidation State of Fe in Comet 81P/Wild 2 and Chondritic-Porous Interplanetary Dust Particles

The fragile structure of chondritic-porous interplanetary dust particles (CP- IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alteration have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed ~300 nanograms of Wild 2 material - three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are >2σ different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.

astro-ph.EP↗