L. P. Keller
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View article: The variety and origin of materials accreted by Bennu’s parent asteroid
The variety and origin of materials accreted by Bennu’s parent asteroid Open
The first bodies to form in the Solar System acquired their materials from stars, the presolar molecular cloud and the protoplanetary disk. Asteroids that have not undergone planetary differentiation retain evidence of these primary accret…
View article: Mineralogical evidence for hydrothermal alteration of Bennu samples
Mineralogical evidence for hydrothermal alteration of Bennu samples Open
View article: Space weathering effects in Bennu asteroid samples
Space weathering effects in Bennu asteroid samples Open
The OSIRIS-REx mission deployed contact pad samplers to collect regolith from the uppermost surface of the asteroid Bennu that was exposed to the space environment. Space weathering processes, dominated by micrometeoroid impacts and solar …
View article: Space Weathering Effects on Mercurian Surface Analogs: Insights from Coordinated Spectral, Microstructural, and Chemical Analyses
Space Weathering Effects on Mercurian Surface Analogs: Insights from Coordinated Spectral, Microstructural, and Chemical Analyses Open
Introduction: Nanophase iron (npFe) is known to be the cause of increasing optical maturity (spectral reddening, an overall darkening, and decreasing prominence of spectral features) on the Moon and S-type asteroids [e.g., 1, 2], but what …
View article: Revealing the Moon's Taurus‐Littrow Landslide via Integrated Analysis of Pristine Apollo 17 Soil Core 73001/2
Revealing the Moon's Taurus‐Littrow Landslide via Integrated Analysis of Pristine Apollo 17 Soil Core 73001/2 Open
The “light mantle” deposit at the base of South Massif in the Moon's Taurus‐Littrow Valley was a primary science target for the Apollo 17 exploration. The possibility that it was a landslide triggered by ejecta from Tycho Crater is critica…
View article: An overview of the petrography and petrology of particles from aggregate sample from asteroid Bennu
An overview of the petrography and petrology of particles from aggregate sample from asteroid Bennu Open
The OSIRIS‐REx mission returned a sample of regolith from the carbonaceous asteroid Bennu in September 2023. We present preliminary in situ investigations of the petrology and petrography of selected particles ranging in size from 0.5 to 3…
View article: An evaporite sequence from ancient brine recorded in Bennu samples
An evaporite sequence from ancient brine recorded in Bennu samples Open
View article: Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu
Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu Open
View article: Analyzing the Mineralogy and Space Weathering Characteristics of the Finest Fraction in Apollo Core Sample 73002
Analyzing the Mineralogy and Space Weathering Characteristics of the Finest Fraction in Apollo Core Sample 73002 Open
Apollo 17 core sample 73001/2 was recently made available to researchers for analysis using state‐of‐the‐art techniques in the framework of a modern understanding of lunar surface processes. In this work, we employ transmission electron mi…
View article: Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by <scp>OSIRIS</scp>‐<scp>REx</scp>
Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by <span>OSIRIS</span>‐<span>REx</span> Open
On September 24, 2023, NASA's OSIRIS‐REx mission dropped a capsule to Earth containing ~120 g of pristine carbonaceous regolith from Bennu. We describe the delivery and initial allocation of this asteroid sample and introduce its bulk phys…
View article: Petrographic and chemical characterization and carbon and nitrogen isotopic compositions of cometary IDPs and their GEMS amorphous silicates
Petrographic and chemical characterization and carbon and nitrogen isotopic compositions of cometary IDPs and their GEMS amorphous silicates Open
GEMS (glass with embedded metal and sulfides) are the dominant carrier of amorphous silicates in anhydrous interplanetary dust particles (IDPs) and one of the most suitable materials to study early solar system processes. Amorphous silicat…
View article: Asteroid (101955) Bennu in the Laboratory: Properties of the Sample Collected by OSIRIS-REx
Asteroid (101955) Bennu in the Laboratory: Properties of the Sample Collected by OSIRIS-REx Open
On 24 September 2023, the NASA OSIRIS-REx mission dropped a capsule to Earth containing approximately 120 g of pristine carbonaceous regolith from Bennu. We describe the delivery and initial allocation of this asteroid sample and introduce…
View article: Understanding the Dust Environment at Mercury: From Surface to Exosphere
Understanding the Dust Environment at Mercury: From Surface to Exosphere Open
We provide an overview of our understanding of the dust environment at Mercury and the role that dust plays in shaping the planet's surface and exosphere. Our understanding of the role that dust impacts play in the generation of Mercury's …
View article: Boulder Diversity in the Nightingale Region of Asteroid (101955) Bennu and Predictions for Physical Properties of the OSIRIS‐REx Sample
Boulder Diversity in the Nightingale Region of Asteroid (101955) Bennu and Predictions for Physical Properties of the OSIRIS‐REx Sample Open
The sample of asteroid (101955) Bennu was collected from the Nightingale sample site by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer spacecraft and arrived on Earth on 24 September 2023. To …
View article: Solar Energetic Particle Track-production Rates at 1 au: Comparing In Situ Particle Fluxes with Lunar Sample-derived Track Densities
Solar Energetic Particle Track-production Rates at 1 au: Comparing In Situ Particle Fluxes with Lunar Sample-derived Track Densities Open
Heavy ( Z > 26) solar energetic particles (SEPs) with energies ∼1 MeV nucleon −1 are known to leave visible damage tracks in meteoritic materials. The density of such “solar flare tracks” in lunar and asteroidal samples has been used as a …
View article: Solar-Energetic-Particle Track-Production Rates at 1 au: Comparing In-situ Particle Fluxes with Lunar Sample-Derived Track Densities
Solar-Energetic-Particle Track-Production Rates at 1 au: Comparing In-situ Particle Fluxes with Lunar Sample-Derived Track Densities Open
Heavy (Z>26) solar energetic particles (SEPs) with energies ~1 MeV/nucleon are known to leave visible damage tracks in meteoritic materials. The density of such solar flare tracks in lunar and asteroidal samples has been used as a measure …
View article: Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu
Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu Open
Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preser…
View article: Space Weathering of Genesis Mission Solar-wind Collectors with Inferences for Weathering on Airless Bodies
Space Weathering of Genesis Mission Solar-wind Collectors with Inferences for Weathering on Airless Bodies Open
Samples from the Genesis Solar Wind Sample Return (NASA Discovery 5) are a unique opportunity to study the initial stages of space weathering, i.e., the physical and chemical effects of solar-wind irradiation. Arrays of collectors containi…
View article: Overview of the search for signs of space weathering on the low-albedo asteroid (101955) Bennu
Overview of the search for signs of space weathering on the low-albedo asteroid (101955) Bennu Open
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View article: Short-Term Biochar Impacts on Crop Performance and Soil Quality in Arid Sandy Loam Soil
Short-Term Biochar Impacts on Crop Performance and Soil Quality in Arid Sandy Loam Soil Open
A two-year field study was conducted in sandy loam soil to evaluate the impacts of biochar on soil quality and the growth and yields of pinto bean (Phaseolus vulgaris) and sorghum–Sudan (Sorghum × drummondii). A wood-derived commercial bio…
View article: A New Coordinated NanoSIMS, Transmission Electron Microscopy and Atom Probe Tomography Approach for the Characterization of Primitive Astromaterials
A New Coordinated NanoSIMS, Transmission Electron Microscopy and Atom Probe Tomography Approach for the Characterization of Primitive Astromaterials Open
View article: Diverse assemblage of presolar and solar system materials in anhydrous interplanetary dust particles: Coordinated NanoSIMS and TEM analyses
Diverse assemblage of presolar and solar system materials in anhydrous interplanetary dust particles: Coordinated NanoSIMS and TEM analyses Open
A coordinated TEM and NanoSIMS isotopic imaging study of microtome sections of three anhydrous interplanetary dust particles (IDPs) revealed a diverse collection of primitive materials having disparate origins and histories. Presolar silic…
View article: Aqueous Alteration Processes Recorded in Kuiper Belt Dust
Aqueous Alteration Processes Recorded in Kuiper Belt Dust Open
Interplanetary dust particles (IDPs) are samples of dustproducing solar system objects including many primitive and organic-rich bodies not sampled by known meteorites.Many of these IDPs contain high densities >10 10 /cm 2 of solar energet…
View article: Solar wind contributions to Earth’s oceans
Solar wind contributions to Earth’s oceans Open
View article: Solar energetic particle tracks in lunar samples: A transmission electron microscope calibration and implications for lunar space weathering
Solar energetic particle tracks in lunar samples: A transmission electron microscope calibration and implications for lunar space weathering Open
Transmission electron microscope (TEM) imaging techniques combined with focused ion beam sample preparation were used to calibrate the solar energetic particle track production rate in lunar samples. Track density measurements by TEM as a …
View article: Investigating Space Weathering Effects on Carbonaceous Asteroids Using High-flux and Low-flux Ion Irradiation of the Murchison Meteorite
Investigating Space Weathering Effects on Carbonaceous Asteroids Using High-flux and Low-flux Ion Irradiation of the Murchison Meteorite Open
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View article: Characterizing the spectral, microstructural, and chemical effects of solar wind irradiation on the Murchison carbonaceous chondrite through coordinated analyses
Characterizing the spectral, microstructural, and chemical effects of solar wind irradiation on the Murchison carbonaceous chondrite through coordinated analyses Open
We performed H+ and He+ irradiation experiments on slabs of the Murchison CM2 meteorite to simulate solar wind irradiation of carbonaceous asteroids. Two separate 6 mm × 6 mm regions were irradiated with 1 keV H+ and 4 keV He+, respectivel…
View article: The Role of Hydrated Minerals and Space Weathering Products in the Bluing of Carbonaceous Asteroids
The Role of Hydrated Minerals and Space Weathering Products in the Bluing of Carbonaceous Asteroids Open
The surfaces of airless bodies such as lunar and S-type asteroids typically become spectrally redder in visible to near-infrared reflectance with longer exposures to space weathering. However, some carbonaceous asteroids instead become spe…
View article: Jarosite in Antarctic deep ice supports the ice-weathering model for jarosite formation on Mars
Jarosite in Antarctic deep ice supports the ice-weathering model for jarosite formation on Mars Open
<p>On Earth, jarosite is a weathering product forming in acidic-oxidative environments from the alteration of iron-bearing minerals in presence of liquid water. Typical settings where this iron-potassium hydrated sulphate is found, a…
View article: Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars
Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars Open