Kyoko Okudaira

Mineralogy and Petrology of Comet 81P/Wild 2 Nucleus Samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.

Development of silica aerogel with any density

New production methods of silica aerogel with high and low refractive indices have been developed. A very slow shrinkage of alcogel at room temperature has made possible producing aerogel with high refractive indices of up to 1.265 without cracks. Even higher refractive indices than 1.08, the transmission length of the aerogel obtained from this technique has been measured to be about 10 to 20 mm at 400 nm wave length. A mold made of alcogel which endures shrinkage in the supercritical drying process has provided aerogel with the extremely low density of 0.009 g/cm3, which corresponds to the refractive index of 1.002. We have succeeded producing aerogel with a wide range of densities

Design of a Silica-aerogel-based Cosmic Dust Collector for the Tanpopo Mission Aboard the International Space Station

We are developing a silica-aerogel-based cosmic dust collector for use in the Tanpopo experiment to be conducted on the International Space Station. The mass production of simple two-layer hydrophobic aerogels was undertaken in a contamination-controlled environment, yielding more than 100 undamaged products. The collector, comprising an aerogel tile and holder panel, was designed to resist launch vibration and to conform to an exposure attachment. To this end, a box-framing aerogel with inner and outer densities of 0.01 and 0.03 g/cm

Study of Hybrid Dust Sample Collection System Toward Mars Aeroflyby Sample Collection Mission

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Arcjet Testings of Silica Aerogel Toward Mars Aeroflyby Sample Collection Mission

, respectively, was fabricated. The aerogel mounted in the panel passed random vibration tests at the levels of the acceptance and qualification tests for launch. It also withstood the pressure changes expected in the airlock on the International Space Station.

Study of Micron-sized Martian Dust Sample Capture Using Aerogel

New sample collector system is proposed for the sample return mission on Mars under consideration in JAXA. The new sample collector consists of silica aerogels and carbon aerogels to compensate each other for their unique characteristics. In order to demonstrate the concept and verify the technical difficulties, several experiments are conducted in this study. Heating tests are carried out to see whether the sample collector can be applied to the aerodynamic heating environment. From the heating tests, no significant difference is observed in the sample collector between before and after heating. Unlike the silica aerogels, the surface alteration that makes the dust capturing difficult are not observed on the surface of carbon aerogels. The light gas gun experiments are also performed to simulate the dust particle capturing by using the sample collector. It is confirmed from the study that 10-30μm dust particles with the relative velocity of 4km/s could be successfully captured by using the present sample collector. After the light gas gun experiments, several particles are picked out from the sample collector by using a nano-manipulating system. The SEM and EDS analysis is successfully performed for particles picked out from the sample collectors. Consequently, it is concluded that the dust particles would be analyzed by the present analysis scheme, if the present sample collector would be applied to the MASC mission.

Thermal alteration of hydrated minerals during hypervelocity capture to silica aerogel at the flyby speed of Stardust

†† Heating tests of silica aerogel are carried out in an arcjet wind tunnel facility in order to examine whether it is suitable for the sample collector material used in the Mars Aeroflyby Sample Collection mission. After the heating tests, the surface of the aerogel test piece is visually inspected by using a digital microscope. Considerabel alterations are observed on the aerogel surface. The surface of aerogel has become black, and many crevices have developed along the aerogel surface. In addition, the surface seems to become hard due to a glassy material. In order to confirm that such damaged aerogel plays a role of the sample collector, preliminary simulation experiments are performed by using the two-stage light gas gun. In the experiments, 30µm-diameter spheres imitating the Martial dust particles are launched against aerogel target at the velocity of about 4.2km/s. A carrot-shaped tracks carved by the launched spheres are compared between the aerogel test pieces before and after heating test. It is found that the particle could be captured by the damaged aerogel without mechanical destruction if the particle has a diameter of the order of 10µm.

Petrographic, chemical and spectroscopic evidence for thermal metamorphism in carbonaceous chondrites I: CI and CM chondrites

A Mars Aero-flyby Sample Collection (MASC) mission has been proposed lately at Japan Aerospace Exploration Agency (JAXA). In order to improve the feasibility of this mission, the development of its sampling system during flying in the Martian dusty atmosphere to capture floating micron-sized dust particles is crucial. Since aerogel has been used as a capturing medium for micrometeoroids and space debris, it is also planned to be used for the MASC mission. In order to utilize aerogel as the capturing medium of hypervelocity micron-sized dust particles during the Martian atmospheric flight, several unknown effects, such as aerodynamic heating of aerogel, impact on heated aerogel, and thermal alteration of micron-sized particles inside aerogel, need to be clarified. This work attempts to evaluate these effects by carrying out three types of experiments, (1) heating tests of aerogel in an arcjet wind tunnel, (2) two-stage light gas gun dust capture simulations, and (3) Van de Graaff micron-particle capture simulations.