Michelle S. Thompson

Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

Here we report microchemical and microstructural features indicative of space weathering in a particle returned from the surface of asteroid Itokawa by the Hayabusa mission. Space weathering features include partially and completely amorphous rims, chemically and structurally heterogeneous multilayer rims, amorphous surface islands, vesiculated rim textures, and nanophase iron particles. Solar-wind irradiation is likely responsible for the amorphization as well as the associated vesiculation of grain rims. The multilayer rims contain a nanocrystalline outer layer that is underlain by an amorphous inner layer, and both have compositions that are distinct from the underlying, crystalline orthopyroxene grain. The multilayer rim features could be derived from either radiation-induced sputter deposition or vapor deposition from micrometeorite impact events. The amorphous islands on grain surfaces have a distinctive morphology and composition suggesting that they represent surface deposits of melt derived from micrometeorite impact events. These observations indicate that both irradiation damage and micrometeorite impacts play a role in surface modification and space weathering on asteroid Itokawa.

The cystine/glutamate antiporter system xc− drives breast tumor cell glutamate release and cancer-induced bone pain

Abstract Bone is one of the leading sites of metastasis for frequently diagnosed malignancies, including those arising in the breast, prostate and lung. Although these cancers develop unnoticed and are painless in their primary sites, bone metastases result in debilitating pain. Deeper investigation of this pain may reveal etiology and lead to early cancer detection. Cancer-induced bone pain (CIBP) is inadequately managed with current standard-of-care analgesics and dramatically diminishes patient quality of life. While CIBP etiology is multifaceted, elevated levels of glutamate, an excitatory neurotransmitter, in the bone-tumor microenvironment may drive maladaptive nociceptive signaling. Here, we establish a relationship between the reactive nitrogen species peroxynitrite, tumor-derived glutamate, and CIBP. In vitro and in a syngeneic in vivo model of breast CIBP, murine mammary adenocarcinoma cells significantly elevated glutamate via the cystine/glutamate antiporter system xc−. The well-known system xc− inhibitor sulfasalazine significantly reduced levels of glutamate and attenuated CIBP-associated flinching and guarding behaviors. Peroxynitrite, a highly reactive species produced in tumors, significantly increased system xc− functional expression and tumor cell glutamate release. Scavenging peroxynitrite with the iron and mangano-based porphyrins, FeTMPyP and SRI10, significantly diminished tumor cell system xc− functional expression, reduced femur glutamate levels and mitigated CIBP. In sum, we demonstrate how breast cancer bone metastases upregulate a cystine/glutamate co-transporter to elevate extracellular glutamate. Pharmacological manipulation of peroxynitrite or system xc− attenuates CIBP, supporting a role for tumor-derived glutamate in CIBP and validating the targeting of system xc− as a novel therapeutic strategy for the management of metastatic bone pain.

In situ Thermal Shock of Lunar and Planetary Materials Using A Newly Developed MEMS Heating Holder in A STEM/SEM

The US Department of Energy’s Basic Energy Sciences Office published a report entitled, “Future Electron Scattering and Diffraction” in 2014. In the report, it listed the “Lab-in-gap” dynamic microscope as one of the major instrumentation needs for enabling breakthrough scientific opportunities. Specifically, it called for sample stage and holder designs that would allow advanced in situ analyses [1]. We have recently manufactured a MEMS-based heating and electric bias holder that fits into the sample stage of the newly developed 200-kV Hitachi HF5000 transmission electron microscope. The new sample stage enables a wider, jewel-less sample holder design, providing a larger platform which is advantageous for laying out electric contacts and transportation of stimuli. As shown in Fig. 1a, the Hitachi “Blaze” Heating Holder comes with the MEMS-based heating chips, which are SiN membranes sandwiching a heating element, manufactured by Norcada Inc. The contact pad to the heating chip is a replaceable. Simulated temperature profiles at 850 and 1100 C indicated the central 160 μm-diameter is isothermal (Figs.1b and 1c). At the center of the isothermal region, there are 19 sample wells in 5 arrays. These sample wells have a 30 nm-thick SiN support film, providing electron transparency and exceptional chemical, thermal and mechanical stability.

The Oxidation State of Nanophase Fe Particles Produced by Space Weathering as Revealed Through Aberration-Corrected Transmission Electron Microscopy

Mineral grains on the surfaces of planetary bodies such as the Moon and near-Earth asteroids are continuously modified by collisional processes such as micrometeorite impacts and radiation processing from solar energetic ions. These processes are collectively known as space-weathering and they alter the microstructural and microchemical characteristics of minerals on planetary surfaces [1]. These features were first identified in lunar soils returned by the Apollo missions e.g., [2].

Transmission Electron Microscopy Studies of Carbonaceous Chondrites which Experienced Experimentally Simulated Space Weathering Effects

Introduction: Mineral grains on the surfaces of airless bodies such as the Moon and asteroids are continually modified due to their exposure to interplanetary space. Radiation processing via solar energetic ions from the solar wind and micrometeorite impacts collectively alter the microstructure, chemical composition, and optical properties of soils grains on airless planetary surfaces [1]. This phenomenon is known as space weathering, and understanding the nanoscale effects that result from this processing is essential for interpreting spectroscopic data collected by remote sensing spacecraft.

In Situ Heating of Lunar Soil in the Transmission Electron Microscope: Simulating Micrometeorite Impacts.

Mineral grains on the surfaces of airless bodies are continually modified due to their exposure to interplanetary space. They experience radiation processing from solar energetic ions and collisional processes such as micrometeorite impacts. These processes are collectively known as space weathering and together they alter the microstructural, chemical, and optical characteristics of minerals on planetary surfaces [1]. These features were first identified in lunar soils returned by the Apollo missions, e.g., [2]. Understanding the modification of crystal structure and chemistry as a result of space weathering provides insight into the evolution of planetary surfaces throughout the history of the solar system, and is important for determining the mineralogy of those surfaces from spectroscopic remote sensing spacecraft data.

Electron energy-loss spectroscopy of iron nanoparticles in lunar soil using an aberration-corrected scanning transmission electron microscope

Introduction and Motivation: Mineral grains on the surfaces of airless planetary bodies like the Moon are subjected to continuous radiation processing from solar energetic ions and also experience micrometeorite impact events. Together these processes alter the morphology, chemistry, and microstructure of surface particles and are collectively known as space weathering [1]. The optical properties of material on airless body surfaces are altered by space weathering, making it difficult to understand the chemical composition or mineralogy of that planetary body from remote sensing data [2]. Space-weathering features were first recognized in lunar soil samples returned by the Apollo missions e.g., [3]. These features primarily develop in the outer 100 nm of mineral grains exposed to interplanetary space, making transmission electron microscopy (TEM) uniquely suited for studying this surface process [3].