In Situ Dating Experiments of Igneous Rocks Using the KArLE Instrument: A Case Study for Approximately 380 Ma Basaltic Rocks

We report new K-Ar isochron data for two approximately 380 Ma basaltic rocks, using an updated version of the Potassium-Argon Laser Experiment (KArLE). These basalts have K contents comparable to lunar KREEP basalts or igneous lithologies found by Mars rovers, whereas previous proof-of-concept studies focused primarily on more K-rich rocks. We continue to measure these analogue samples to show the advancing capability of in situ K-Ar geochronology. KArLE is applicable to other bodies including the Moon or asteroids

Dating Igneous Rocks Using the Potassium-Argon Laser Experiment (KArLE) Instrument: A Case Study for ~380 Ma Basaltic Rocks

We report new K-Ar isochron data for two approximately 380 million-years-old basaltic rocks, using an updated version of the Potassium-Argon Laser Experiment (KArLE), which is being developed for future in situ dating of planetary materials. These basalts have K contents comparable with those of lunar KREEP basalts or igneous lithologies found by Mars rovers, whereas previous proof-of-concept studies focused primarily on more K-rich rocks. We aim to measure these analogous samples to show the advancing capability of in situ K-Ar geochronology

月・火星着陸機用その場K-Arアイソクロン年代計測法の開発

学位の種別:課程博士University of Tokyo(東京大学

Control-Data Separation and Logical Condition Propagation for Efficient Inference on Probabilistic Programs

We introduce a novel sampling algorithm for Bayesian inference on imperative probabilistic programs. It features a hierarchical architecture that separates control flows from data: the top-level samples a control flow, and the bottom level samples data values along the control flow picked by the top level. This separation allows us to plug various language-based analysis techniques in probabilistic program sampling; specifically, we use logical backward propagation of observations for sampling efficiency. We implemented our algorithm on top of Anglican. The experimental results demonstrate our algorithm's efficiency, especially for programs with while loops and rare observations.Comment: 11 pages with appendice

In Situ Geochronology on Mars and the Development of Future Instrumentation

We review the in situ geochronology experiments conducted by the Mars Science Laboratory mission's Curiosity rover to understand when the Gale Crater rocks formed, underwent alteration, and became exposed to cosmogenic radiation. These experiments determined that the detrital minerals in the sedimentary rocks of Gale are ∼4 Ga, consistent with their origin in the basalts surrounding the crater. The sedimentary rocks underwent fluid-moderated alteration 2 Gyr later, which may mark the closure of aqueous activity at Gale Crater. Over the past several million years, wind-driven processes have dominated, denuding the surfaces by scarp retreat. The Curiosity measurements validate radiometric dating techniques on Mars and guide the way for future instrumentation to make more precise measurements that will further our understanding of the geological and astrobiological history of the planet

More on Large Q2Q^2 Events with Polarized Beams

We discuss polarized proton-positron scattering in the context of the excess of large $Q^2$ events at HERA. We define and estimate a polarized asymmetry to examine two scenarios, the contact interaction and the stop scenario with broken R-parity. This asymmetry exhibits a characteristic behavior depending on the scenarios. Thus the polarized experiment at HERA will provide with a good test for these models.Comment: 6 pages, 3 figures, PTPTe

Characterization of the MASCOT landing area by Hayabusa2

Context. After landing on C-type asteroid Ryugu, MASCOT imaged brightly colored, submillimeter-sized inclusions in a small rock. Hayabusa2 successfully returned a sample of small particles from the surface of Ryugu, but none of these appear to harbor such inclusions. The samples are considered representative of Ryugu. Aims. To understand the apparent discrepancy between MASCOT observations and Ryugu samples, we assess whether the MASCOT landing site, and the rock by implication, is perhaps atypical for Ryugu. Methods. We analyzed observations of the MASCOT landing area acquired by three instruments on board Hayabusa2: a camera (ONC), a near-infrared spectrometer (NIRS3), and a thermal infrared imager. We compared the landing area properties thus retrieved with those of the average Ryugu surface. Results. We selected several areas and landforms in the landing area for analysis: a small crater, a collection of smooth rocks, and the landing site itself. The crater is relatively blue and the rocks are relatively red. The spectral and thermophysical properties of the landing site are very close to those of the average Ryugu surface. The spectral properties of the MASCOT rock are probably close to average, but its thermal inertia may be somewhat higher. Conclusions. The MASCOT rock can also be considered representative of Ryugu. Some of the submillimeter-sized particles in the returned samples stand out because of their atypical spectral properties. Such particles may be present as inclusions in the MASCOT rock

Boulder size and shape distributions on asteroid Ryugu

In 2018, the Japanese spacecraft Hayabusa2, arrived at the small asteroid Ryugu. The surface of this C-type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study. Using a few hundred Optical Navigation Camera (ONC) images with a pixel scale of approximately 0.65 m, we focus on boulders greater than 5m in diameter. Smaller boulders are also considered using five arbitrarily chosen ONC close-up images with pixel scales ranging from 0.7 to 6 cm. Across the entire surface area (~2.7 km2) of Ryugu, nearly 4400 boulders larger than 5m were identified. Boulders appear to be uniformly distributed across the entire surface, with some slight differences in latitude and longitude. At ~50 km−2, the number density of boulders larger than 20m is twice as large as on asteroid Itokawa (or Bennu). The apparent shapes of Ryugu's boulders resemble laboratory impact fragments, with larger boulders being more elongated. The ratio of the total volume of boulders larger than 5m to the total excavated volume of craters larger than 20m on Ryugu can be estimated to be ~94%, which is comparatively high. These observations strongly support the hypothesis that most boulders found on Ryugu resulted from the catastrophic disruption of Ryugu's larger parent body, as described in previous papers (Watanabe et al., 2019; Sugita et al.,2019). The cumulative size distribution of boulders larger than 5 m has a power-index of −2.65 ± 0.05, which is comparatively shallow compared with other asteroids visited by spacecraft. For boulders smaller than 4 m, the power-index is even shallower and ranges from −1.65 ± 0.05 to −2.01 ± 0.06. This particularly shallow power-index implies that some boulders are buried in Ryugu's regolith. Based on our observations, we suggest that boulders near the equator might have been buried by the migration of finer material and, as a result, the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes

In vitroNeo-Genesis of Tendon/Ligament-Like Tissue by Combination of Mohawk and a Three-Dimensional Cyclic Mechanical Stretch Culture System

Tendons and ligaments are pivotal connective tissues that tightly connect muscle and bone. In this study, we developed a novel approach to generate tendon/ligament-like tissues with a hierarchical structure, by introducing the tendon/ligament-specific transcription factor Mohawk (MKX) into the mesenchymal stem cell (MSC) line C3H10T1/2 cells, and by applying an improved three-dimensional (3D) cyclic mechanical stretch culture system. In our developed protocol, a combination of stableMkxexpression and cyclic mechanical stretch synergistically affects the structural tendon/ligament-like tissue generation and tendon related gene expression. In a histological analysis of these tendon/ligament-like tissues, an organized extracellular matrix (ECM), containing collagen type III and elastin, was observed. Moreover, we confirmed thatMkxexpression and cyclic mechanical stretch, induced the alignment of structural collagen fibril bundles that were deposited in a fibripositor-like manner during the generation of our tendon/ligament-like tissues. Our findings provide new insights for the tendon/ligament biomaterial fields

Characterization of coatings for straylight and photoluminescence suppression in the Raman Spectrometer for MMX (RAX)

The Martian Moons eXploration (MMX) mission led by JAXA to Mars moons Phobos and Deimos involves a small rover developed by DLR/CNES that will be operating on Phobos’ surface. Aboard it is the Raman Spectrometer for MMX (RAX), whose main scientific objectives address Phobos surface mineralogy, its heterogeneity and relation to the Mars mineralogy. Raman spectrometers require strong suppression of straylight, since this technique operates with few nano-Watt signals that should have significant contrast to all other sources of light inside the instrument. The mission requirements involving RAX call for a compact and sophisticated optical design, precluding space for straylight suppressive elements. To optimize straylight suppression in RAX, Raman scattering, Photoluminescence and reflection were characterized for candidate coatings representing different absorbing materials and fabrication technologies over spectral ranges between 530 nm and 680 nm. This was complimented by mechanical testing to aid selection of the coatings for parts inside the RAX flight model