News flash! Aurigids Observed in Hawaii, Observations of Oort Cloud Dusts ejected from a Long-period Comet

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Observation Plan of short-duration meteor trains

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After the successful observations of persistent meteor trains in this decade, many train images and movies are archived as the METRO campaign archives. Here we show the recent aproaches for meteor train studies as well as the future observation plan for meteor physics studies in Kochi University of Technology.

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We introduce the observation results of Itokawa with XRS onboard Hayabusa.

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We found that the CCDs onbord Hayabusa XRS has degradated more or less by the radiation. This has caused not achiving the energy resolution of prelaunch.
So we have to develop onbord processing method for future X-ray fluorescence spectrometer.
In this presentation, we evaluated how the Hotpixel had worsen the energy resolution in Hayabusa by using 'CCD-image' data taken in cruising phase and in laboratory.
We present the results of another processing method for future asteroids exploration.

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The spin states of the small solar system objects can be altered by a net torque arising from the anisotropic thermal re-emission of sunlight on the surface, the so-called YORP effect. We present the results of ground-based observations of the near-Earth asteroid Itokawa, which is the target asteroid of the Hayabusa spacec, and its comparison with the theoretical model of Itokawa's YORP.

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The Hayabusa spacecraft, which was launched in May 2003, arrived at Asteroid Ito-kawa in September 2005, and it made observations of Itokawa and tried touch down in about three months.Hayabusa has four scientific instruments, that is Multi-Spectral Telescopic Imager (AMICA), Laser Altimeter (LIDAR), Near-Infrared Spectrometer (NIRS), and X-ray Fluorescence Spectrometer (XRS). The data obtained by these instruments were firstly analyzed by Hayabusa Science Team and some of the results have been pub-lished as scientific papers. At the same time, the science team was preparing to open them to the public and this work has almost been done. Therefore the science team release the data archives to public from April 24, 2007. All the scientific data that Hayabusa obtained are open to the public.The Hayabusa data archives can be accessed from the following web site:(URL) http://hayabusa.sci.isas.jaxa.jp/

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In the Primitive Body Exploration Program of Japan, we are aiming for sample return missions, by following the Hayabusa's heritage, from surfaces and potentially sub-surfaces of C-type asteroids and CAT objects or D-type asteroids within the next decade. Thus we are currently developing new sampling systems suitable for such targets. In particular, the impact sampling system with corer projectiles and a microgravity tether retraction system as well as tape tether mechanism are evaluated in the microgravity condition. This study summarizes results of those endeavors and future prospects of this challenge.

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The evolution of the Earth has been much affected by asteroid and comet impacts. As known in the Tunguska impact in 1908, the impacts are also threat for the human civilization. In order to avoid such threat, the discovery and follow-up observations of asteroids and comets, especially near-earth objects (NEO), are necessity. We have been carrying out the observations of NEO in Bisei Spaceguard Center since 2000. We have discovered more than 100 asteroids, and one of which was asteroid 20826, the second largest Apollo-type asteroid. We have also contributed to derivations of accurate orbital elements of known asteroids by follow-up observations. In addition to these discoveries and follow-up observations, the observations for physical properties are also important. For example, we have started light curve observations to determine the rotational period of asteroids. In this paper, we introduce the activities of Bisei Spaceguard Center.

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We started observation of members of young asteroid families at Maidanak observatory in Uzbekistan from 2005 June.The young family asteroids may still preserve properties of the original collision of their break-up event because of less orbital/collisional evolutions.A part of colligional properties seems to appear in their lightcurves.The surface spectrum of young family asteroids whose age is known is a good index of time scale of space weathering.Based on above motivations, we started multi bands photometric observations of young family asteroids at Maidanak Observatory, Uzbekistan.We will report here our observations from 2006 January to 2006 May.

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We have begun a numerical investigation on the orbital evolution of small asteroids originally located in the main belt. Our framework of work consists of three parts: (1) Carrying out numerical integrations of particles injected into some resonances in the main belt. (2) Estimate of the impact ratio of the fragments on the Moon. (3) Creating a synthetic crater record assuming a size distribution of the asteroids, and comparing it with the real lunar crater record.

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Titan is the sole satellite has dense atmosphere. It is of interest to know the possible formation mechanism of amino acids on Titan since it will give us suggestions on possible chemical evolution pathways to the primitive Earth. For the simulation of chemical reactions in upper and lower atmospheres of Titan, we synthesized tholin by plasma discharge and by proton irradiation from a gas mixture of nitrogen and methane. The product tholins were characterized. The Py-GC/MS results showed tholins contain aromatic and N-containing heterocyclic compounds. MALDI-Mass spectra of the tholins showed that both tholins gave peaks at m/z = 100-400, and had -CH2- units in them. Thus tholins formed by plasma discharge (PD) and those by proton irradiation (CR) might have similar structures each other. We hydrolyzed tholins and analyzed amino acids by HPLC. A number of amino acids were detected from both tholins. CR-tholins are superior to PD-tholins in energy yield. It is suggested that more tholins containing amino acid precursors are produced in the lower atmosphere of Titan than in the upper atmosphere.

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Trans-Neptunian objects (TNOs) orbit beyond Neptune and offer important clues on the origin and evolution of the solar system. We investigated the dynamical properties of 622 TNOs by performing computer simulations of their orbits plus several clones. We identified 196 TNOs locked in resonance with Neptune in the Edgeworth-Kuiper belt. Occupied resonances sorted by distance from the Sun are: 1:1, 5:4, 4:3, 11:8, 3:2, 18:11, 5:3, 12:7, 19:11, 7:4, 9:5, 11:6, 2:1, 9:4, 16:7, 7:3, 12:5, 5:2, 8:3, 3:1, 4:1, 11:2, and 27:4. Beyond 50AU, we examined the long-term evolution of 27 resonant TNOs by integrating their orbits over 4Gyr. The origin of 4Gyr-resident 9:4, 5:2, and 8:3 resonant TNOs was investigated using static and planetary migration dynamical models. We found that the long-term stable populations of 9:4, 5:2, and 8:3 resonant TNOs are well explained through adiabatic resonance capture by a migrating Neptune over a dynamically excited ancient trans-Neptunian belt. Therefore, this suggests that the primordial planetesimal disk had at least 47-50AU in radius, and suffered a dynamical perturbation leading to 0.1-0.3 or greater eccentricities and a range of inclinations up to ~20 degrees during early stages of the solar system's existence, before planetary migration.

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Existence of an intrinsic magnetic field is one of the most important key factors for terrestrial planets to be habitable. Strong and stable magnetic field is formed by dynamo action which requires a vigorous convection within molten metallic core, and the vigorous convection within molten metallic core is driven when the mantle transports the heat from core to surface effectively. In this sense, whether a planet is habitable or not depends on its thermal evolution.
In this study, we constructed a new numerical model on the thermal evolution of terrestrial planets to investigate the duration of intrinsic magnetic field as a function of the planet's size. According to our numerical results, the planet can have its magnetic field for more than 2 billion years if its mass is less than 1.4 Earth-mass.

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It is thought that the interplanetary dust is mainly produced by collision between asteroids. According to the infrared spectra, many of the asteroids in the outer half of the main belt are hydrous. On the other hand, most of the fine-grained Antarctic micrometeorites (~80%) are similar in chemistry and mineralogy to hydrated, porous meteorites. In order to elucidate the origin of interplanetary dust, it is important to understand the impact disruption events of hydrous targets.
For elucidating the effects of dehydration of hydrous minerals in the dust production, we performed impact disruption experiments onto two gypsum targets and anhydrite, hemihydrate target, and determine the mass frequency distribution of the debris from the disruption of the targets.

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Sintering of dust aggregates is one of the important changes of material properties in formation process of planetesimals. Poppe (2003) studied the temperature and time dependence of sintering process of highly porous aggregates consisting of 1.5um diameter silica spheres.
In this work, we investigate the temperature and time dependence of sintering of lower porosity aggregates consisting of 10um diameter silica spheres and study the changes of the compressive strength of the aggregates due to sintering. We report the results including the preliminary results of aggregates which have a size distribution peaked at 1um in diameter.

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Porous structure is common in the asteroids and satellites of the outer planets. It is important to study the relationship between the structure of small bodies and their thermal and collisional evolution. Our previous study showed that high velocity impacts need higher specific energy than low velocity impacts for catastrophic disruption when the targets have same compressive strength (Setoh et al. 2006). This is probably due to the difference in the degree of attenuation of the stress wave in the tar-gets. In order to investigate the attenuation rate of the stress wave in the porous targets, we measured the fragment velocities of each targets.

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M-class asteroids were originally considered to be metallic, but, nowadays, owing to the progress of spectroscopic studies, most of them are considered to be rocky bodies. However, at least one asteroid 16 Psyche is likely to be metallic based on the high radar albedo.There are only limited studies on collisional evolution of metallic asteroids. We therefore performed impact experiments of iron projectiles into mainly silicate powders and investigated the degree of fragmentation and deformation of the projectile due to impact. We will discuss on the collisional and dynamical evolution of metallic asteroids according to the results of the laboratory experiments.

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Lunar Impact Flash has been detected mainly in meteor stream season. Recent years, Lunar Impact Flash by sporadic meteor was reported. So, we attempted to detect sporadic Lunar Impact Flash. The observation was 25h in total. We are going to analyze the observed data, and check the event like flash.

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Time variation of a pole location is calculated regarding a case of large-scale true polar wander due to surface mass loading on Mars. In this calculation, both cases with and without effect of pole tide are investigated. Through comparison between them, the effect of the pole tide on the time variation of the pole location is discussed. As a conclusion, this calculation quantitatively indicates that the pole tide stabilizes the pole location over much longer time scale than that of relaxation. On the other hand, it also implies that the effect of the pole tide is negligibly small in a case of longer term variation than the delay by this stabilization.

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Cross-sectional morphologies of channels and valleys on Venus are of special importance in discussing their formation processes both qualitatively and quantitatively. We have already reconstructed cross-sectional and depth profiles of some canali and sinuous rilles, which are both representative channel types on Venus, using a new radar clinometric method. And we reported that the sinuous rilles and canali may have formed by mechanical and thermal erosion, respectively. This time, we reconstruct cross-sectional and depth profiles of some valley networks, and examine the relationship between the flow direction and the surrounding terrain. Valley networks often occur in the vicinity of or in connection to sinuous rilles. In addition, transitional morphology between sinuous rilles and valley networks is observed in both landforms. Therefore formation of the valley networks seems to be related to that of the sinuous rilles. As a result of our analyses, the valley networks likely have formed under a strong structural control compared with sinuous rilles and have originated with diverse formation mechanisms.

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We have studies the conditions required for the formation of ice XI. We measured diffraction profiles of ice with many kinds of dopants using the High Resolution Powder diffractometer (HRPD). We carefully created samples of ice that contained impurities, which assisted the ice XI conversion process as a catalyst. The results indicate that ice with an ionized defect OH- transforms to an enough ice XI after several hundred hours. We studied an irradiated ice. The gamma- and UV-irradiation also creates OH-. The detail is underway.

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We have analyzed moonquake events detected by Apollo seismometers at each Apollo station and derived S/N of their events for our penetrator seismometer. From these analyses, it has been found that moonquake events had particular spectrum for each station. It means that the S/N of moonquake events is affected mainly by the observation site. It is supposed to be caused from the differences of the local structure on the lunar surface. In this presentation, we discuss the relation between the observed signal by the penetrator seismometer and the local structure of the observation site.

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The apparent brightness of the moon depends on viewing geometry, which is defined by the incident angle, the emission angle and the phase angle of the sunlight. A photometric correction function to estimate the exact reflectance of the moon is necessary for each wavelength. However the lunar surface photometric correction function for the two bands (1250 nm and 1550 nm) of Multi-band Imager onboard SELENE (KAGUYA) has not been optimized. A near-infrared (NIR) telescope has been developed to obtain the NIR moon image at various phase angles and to estimate the photometric functions of the moon for these bands. We observed the moon with a CMOS camera (XEVA-FPA320, XenICs) mounted on a telescope through the bandpass filters of 1250 nm and 1550 nm central wavelength (125FS10-25 and 155FS10-25, Andover Co.). The telescope is a refracting-type telescope (ED102SWT, Vixen) and its aperture size is 102 mm and its focal length is 920 mm. Tracking with a motor-drive equatorial mounting, we observed some fixed stars, Vega, and the moon. This time, we discuss the method of estimating lunar surface photometric functions at 1250 nm and 1550 nm and preliminary ones within the obtained data to date.

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Lunar craters, ranging in diameter from 40 to 180 km, are believed to have exhumed material from 5-30 km beneath the surface to the peaks. We analyzed the central peaks of craters, which located three major lunar crustal terranes and classified lithologies of central peaks using Clementine UVVIS five-color spectra. We estimated crustal structure and geological settings based on the results.As a similar study, Tompkins and Pieters investigated the central peaks of 109 impact craters across the Moon and classified lithologies of central peaks using Clementine UVVIS five-color spectra. Although our method is basically same as theirs, we analyzed not only central peaks but also their surroundings. The obtained map suggests that, within Feldspathic Highland Terrane, the materials at higher latitude tend to show colors indicating more mafic lithology. We postulate two hypotheses. One is that the color change is caused by the change of lithology itself. Another is that the color change is caused by the change of phase angle of sunlight. We present two crustal structure models based on these two hypotheses.

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Origin of the lunar crustal structure will be discussed.

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Dating of geological units of planetary surfaces is one of the most important subjects of planetary science for understanding a origin and evolution of the planet. Based on the simple idea that older surfaces accumulate more craters, we can infer ages of units by measuring the crater frequencies with remote-sensing image data. In this study, we evaluate the statistical fluctuation of the crater frequency and its effect on age determination using a Monte Carlo simulation prior to the SELENE (KAGUYA) / Terrain Camera acquiring extensive high-resolution images over the entire Moon.

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Spectral Profiler (SP) is a visible and near infrared spectrometer onboard SELENE (KAGUYA) spacecraft and observes the Moon for about 1 year. SP covers 500-2600nm in wavelength with high spectral resolutions of 6-8nm and SNRs of ~2300@810-860nm and could identify the mineralogical compositions of the lunar surface and contributes to the completion of the global map of the mineral distribution. We present our data processing plans of SP, including radiometric calibration and further analyses. We also discuss the method how we could retrieve the mineralogical information correctly from the continuous reflectance data of optical remote sensing, focusing the case of the Moon. We introduce the necessary procedures of data processing of SP to make a very initial mineralogical map with low resolution, to identify cryptomare deposits, to detect the material of mantle-origin, and to clarify the vertical distribution of minerals at the walls of large craters.

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Goal of this study is a proposal of algorithm to help geologic mapping on the basis of massive data derived from the above-stated SELENE mission. A classification technique by clustering which takes band luminance as feature quantity has been adopted for a geological classification in the past; however proper results have not been presented because band luminance is affected by the topographical effects and capturing timing. Therefore various texture features extracted from band images are also provided as the feature quantity, and the result of study if these bring a better result will be presented.

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Quantifying surface roughness may contribute significantly in the stratigraphic study of the Moon. It is urgent that we develop automatic processing methods to facilitate a large DTM (Digital Terrain Model) dataset which will be obtained by KAGUYA Terrain Camera. We demonstrate Median Differential Slope method as an indicator of topographic roughness on a kilometer scale, using DTM made from Apollo Mapping Camera images.

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A miniaturized x-ray tube specialized for in-situ x-ray fluorescence and diffraction analyses of rocks and powder samples is being developed. Our primary motivation for the miniaturization is to mount tubes on spacecraft for a future Japanese lunar lander/rover mission, which is the next Japanese lunar exploration program to the SELENE lunar orbiter, and perform remote controlled x-ray generators. Possible x-ray instruments for the mission would be: the x-ray fluorescence/diffraction analyzer on the lander, and the x-ray fluorescence spectrometer mounted on the arm of the rover. For the miniaturization and the future operations on the lunar surface, carbon nanotube based field-emission-type (CNT-FE) x-ray tube was adopted. Due to FE's high electron current density and no need to heat itself up, the downsized x-ray tube is attainable with simple cathode dimension. In this presentation, we show the first test model of the CNT-FE miniaturized x-ray tube and results of its initial successful experiments.

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To investigate the major elemental composition of lunar and planetary surface, we are developing gamma-ray detector, which can be used in a rover on a planet. We utilize CdTe semiconductor detectors which have high detection efficiency for gamma-rays. To achieve the efficiency necessary for the observation, 1mm thick CdTe detectors are stacked. In this presentation, we show development status of CdTe detectors and simulation results about the stacked detector resonse to MeV gamma-rays.

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Analytical procedure and method is under development for the X-Ray Spectrometer onboard SELENE(Kaguya). We present the system in detail. Furterhmore, we investigate the datainterpretation for XRF, including the surface microscopic and macroscopic roughness as well as mineral mixing effects. For a daily automatic analysis for huge amount of data, correction equations for ther effects are necessary to be defined. We also present the currect status of the correction method.

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Science experiment on the Moon with the small intelligent lander is under study. Despite of small mass badget for science instrument, short mission life without long-lived survivability, and limitation of landing site on the lunar near side, small mission can provide an opportunity for landing at the most desirable site for its objective. It will be also a good testbed of technology demonstlation for future lunar and planetary missions. We present here the small lunar lander mission and its science payload proposed.

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The SELENE-2, a lunar landing mission to clarify the lunar origin and evolution, has been studied in Japan Aerospace Exploration Agency (JAXA). And our group proposes to develop Science Instrument Package (SIP), it can conduct detailed analyses of the lunar rock samples collected by the rover with an X-ray spectrometer/diffractometer, a multi-band microscope. The SIP also controls the sample surface condition with grinding and brushing, avoiding it from contamination by surface bearing dusts and weathering processes. This study bring out the influence on analytical precision by contamination on the sample surface with an X-ray spectrometer.

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According to infrared astronomical observation, the silicates of circumstellar dust are an amorphous material and a crystal of olivine and pyroxene while the silicate of interstellar dust is amorphous material. And the crystal hardly contains iron. We synthesized an amorphous silicate with the solar composition by the sol-gel method, and did the heating experiments. Each sample was analyzed by Infrared absorption spectroscopy and X-ray diffraction. We found that the olivine takes magnesium in preference to iron in the process of crystallization from an amorphous silicate.

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Organic matter alteration on carbonaceous chondrite parent body was simulated under micro FT-IR with a heating stage. Leonardite (IHSS standard humic acid) and synthetic saponite were used as the macromolecular organics and the matrix mineral. These powdered samples were dispersed by MilliQ water then dropped on an CaF2 plate and dried. They were heated in the heating stage at room temperature to 600C by 10C/min in air, Ar gas and H2+CO2 gas mixture. IR spectra were collected at every 20C under the micro FT-IR. Aliphatic C-H increased from room temperature to approximately 250C then decreased. Aromatic C-H increased from room temperature to around 400-450C then decreased. Aliphatic C-H decreased faster and Aromatic C-H increased faster in Air than in Ar or H2+CO2. The decrease in aliphatic C-H of leonardite and the increase in aromatic C-H were slower with the presence of saponite than those of leonardite only.

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Ion microprone analyses of rare earth elements (REEs) have been performed for fine-grained refractory inclusions in Efremovka meteorite (CV3-reduced type), because they are most likely of condensation origin from the hot solar nebula. The results show various REE patterns, suggesting fractionation of REEs, i.e. separation of gas and refractory dust, under variable conditions. Condensation calculation has been performed for REEs using simple assumptions and the results were compared with the observed REE patterns trying to understand formation conditions of refractory inclusions, especially those of fine-grained ones.

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Dust from comet 81P/Wild2 has been successfully recovered in the Stardust mission. We obtained three-dimensional structures of 16 particles in a few tens of mm in size, which were extracted from impact tracks in aerogel collectors by using SR imaging microtomography.Imaging experiments were performed at BL47XU of Spring-8 at 7.13 keV with the voxel size of 76.5nm, which gives the effective spatial resolution of a few hundreds nm. The cosmic dust particles are largely classified into three types; (1) crystalline, (2) amorphous-rich and (3) others. We will report the features of the individual captured particles by considering their mineral compositions by XRD too.

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We produced sub-micron silicate particles as cosmic dust simulants to examine changes in infrared absorption spectra by particle size, shape, and distortion. Quartz from Andhra Pradesh, India and olivine from San Carlos, USA were used as samples. The crystals were crushed in a WC mortar first, and then powdered in an alumina mortar. Sub-micron particles were formed successfully by using a planetary ball mill with zirconia balls in the final step. The sizes and shapes of the particles were observed under an SEM and latticed distortion by crushing was evaluated by XRD. Infrared absorption spectra of the particles were changed by the particle size, shape and lattice distortion compared with result of samples without crushing by the ball mill. Sub-micron powder of olivine crystals obtained in the present experiments will be used as samples in reproduction experiments for Stardust sample recovery in aerogel collectors.

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Since the unidentified infrared (UIR) bands were observed from wide variety of objects in the Galaxy and in the extragalactic regions, the carriers of these bands could be the clue to understand the evolution of interstellar matters. Polycyclic aromatic hydrocarbons (PAHs) have been considered most plausible candidates of the UIR bands. During the formation and growth of PAH clusters, PAHs may be undergone plasma environments. Since the effects of plasma on the formation of PAH clusters have never been elucidated, we tried to produce PAH clusters in a plasma field and measure their infrared spectra for understanding the plasma effects on the PAHs. We discuss the effects of plasma and the carrier of the UIR bands by comparing the spectroscopic data and the UIR bands.

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The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft has observed energetic particles in Saturn's magnetosphere. In order to clarify energetic particle distribution, we have investigated pitch angle distributions of 20 keV – a few MeV electrons in the inner magnetosphere (<15 Rs). In this presentation, we will discuss the effect of absorption by the E-ring and the possibility of wave-particle interactions based on the Radio and Plasma Wave Science (RPWS) data.

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The scattering greenhouse effect of a CO₂ ice cloud layer may expand the outer edge of the habitable zone in which a terrestrial planet have warm and wet climate. This study explores how the scattering greenhouse effect depends on the planetary mass or surface gravity by using a CO₂-H₂O atmosphere model taking into account the radiative adjustment processes for CO₂2 ice cloud profile. For a planet with the surface gravity and solar flux equivalent to those of paleo-Mars at 3.8Ga, a CO₂ ice cloud layer which can cause strong greenhouse effect is possibly formed. In this case, the global mean surface temperature rises above the melting point of H₂O when the surface pressure is larger than 3 bar and the mixing ratio of cloud condensation nuclei is kept within the range 10⁶ - 10⁷ kg^-1. As the surface gravity increases, the atmospheric pressure required for such warm climate tends to increase.

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Characteristics of the seasonal variation of meridional circulation of the Martian atmosphere are investigated by using a Mars general circulation model. Numerical results show that a summer/winter-type cross-equatorial one-cell circulation prevails most of the period of year, while a spring/fall-type two-cell circulation appears during only short periods around equinoxes. A similar tendency can beobserved also in the seasonal transition of meridional circulation in the Earth's atmosphere. This tendency is consistent with the theory that the latitudinal location of the upward branch of the Hadley circulation is quite sensitive to the off-equatorial latitudinal shift of heat source.

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