We present a theory of crystallization of a melt sphere of forsteriteand enstatite compositions taking account of nucleation and growth ofcrystalline nuclei and the release of latent heat due to thecrystallization. From comparison of the theory with the experimentusing a gas jet levitation system by Nagashima et al. (2006), weestimate the interfacial energy between melt and crystal and theactivation energy of self-diffusion. We disucss the conditions forthree states in the cooling of the melt, i.e. remelting, crystal growth,and glass formation, found in the experiment.

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We report NMR spectra and diffusion coefficient measurements of hydrogen clathrate hydrates. These were measured in situ at pressures to 300 bar using a sapphire tube filled with high pressure hydrogen gas. The guest hydrogen gives a liquid-like fast diffusion coefficient.

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High pressure and high temperature experiments of solid methane were performed in the pressure range of 10 to 81 GPa using diamond-anvil cell and Nd:YAG-laser. Solid methane melted under high temperature and wide pressure range. Three difference regions were distinguished depending on the temperature distribution. In the highest temperature region, difference in refractive index from surrounding solid methane was clearly observed during and after heating. The X-ray diffractmetry and Raman spectroscopy revealed formation of ethane molecules and a van der Waals compound consisting of methane and ethane molecules reported just recently. In the higher temperature region, the crystal structure was solid methane were almost broken but the methane molecules were kept. In the lower temperature region, the samples reverted to the solid methane in spite of melting during heating. According to theoretical studies, the pressure and temperature conditions of the most upper part of middle ice layer of Neptune and Uranus were calculated to be approximately 10GPa and 2000K.On the basis of the experimental results, the upper parts of the middle ice layer might be molten.

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Whether ferroelectric ice XI exists in the outer solar system attracts much interest, because long range electrostatic forces are caused by the ferroelectricity. Future plans for finding natural ice XI in space will be important issues in planetary science. We have been investigating how to make perfect ice XI by time-resolved neutron diffraction measurements. We report the detail of our recipe for the making ice XI in the laboratory. The results present useful information for infrared observation studies of ice objects in the solar system and the Galaxy.

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Jupiter's core mass is one approach to revealing formation scenario of the Solar System. Planetary models, which are consistent with observational properties obtained from in situ measurements made by telescopes and spacecraft missions, suggest a central core of Jupiter should range from zero to ten times mass of the Earth (Saumon & Guillot, 2004). This extensive limit keeps our solar system veiled. It results from uncertainties of equation of state (EOS) for hydrogen under strict conditions of the inside of a giant gaseous planet, at high pressure and temperature.
Assuming EOS to be polytrope models, we analyzed interior structures of Jupiter and Saturn numerically. At this meeting, we'll discuss the effect and dependency of rocky cores on EOS (polytrope index).

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Equation of state (EOS) for hydrogen under high pressure is a key quantity in un-derstanding the internal structures of gas giant planets like Jupiter. We just started laser experiments using the Gekko XII system in ILE, Osaka University to determine the EOS for hydrogen under high pressure around 2 Mbar. Our goal is to reveal the transition phase from the molecular form to metallic hydrogen. We will show the current status of our experiment, which will be able to give a constraint on the formation scenario of Jovian planets.

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Habitability of solid planets have been discussed mainly related to the distance from the central star, the size of the planet, and the obliquity of rotation axis. In addition to that the planet should be shielded from high-energy irradiation from the central star to cultivate lives on the surface of the planet. If the planet had intrinsic magnetic field, the surface would be saved from the high-energy irradiation as is the case for present Earth. Then the question is what is the condition to be satisfied to have intrinsic magnetic field.In this study we carried out numerical model on the thermal evolution of terrestrial planets with various sizes to discuss the condition to be satisfied to form intrinsic magnetic field.

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Several lines of evidence such as the reflection spectra of Mercury suggest that Mercury may consist of reduced materials. Therefore, we calculated the Mercury's thermal history assuming that the mantle and the core have the similar compositions to the silicate and metal-sulfide components of enstatite chondrite, respectively. We examined the possibility of the chemical convection in the liquid outer core, caused by the exclusion of light-alloying element associated with inner core growth. If the mantle convection occurs by dislocation creep, the inner core of Mercury does not grow. However, if the mantle convection occurs by diffusion creep and the grain size of mantle is smaller than 3 mm, the inner core grows during 4.5Gyr. In the latter case, the intrinsic magnetic field of Mercury may be explained.

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We performed mineralogical study of feldspathic phases in the Dhofar 378 Martian meteorite and found that Dhofar 378 contained recrystallizing fibrous plagioclase and K-rich feldspathic glass. We also performed heating experiment of the Zagami maskelynite at 900-1100 deg. C and found that heating at 1000 deg. C for 1-24 hours produced a similar plagioclase texture to Dhofar 378. This result combined with the crystallization experiment of Dhofar 378 suggests that Dhofar 378 was heated at up to 1000 deg. C and subsequently cooled at about 2.5 deg. C/hour after the shock.

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Oxygen isotopic compositions formed by non-mass dependent fractionation processes have been widely observed in calcium-aluminium rich inclusions (CAIs) and chondrules produced in the early solar nebula. So far, only photodissociation has been known to produce non-mass dependent oxygen isotopic fractionation. Therefore, the reason for the oxygen isotopic compositions of CAIs and chondrules has been discussed based on an ultraviolet photodissociation process of carbon monoxide in solar nebula. Recently, we found that electrical discharge can produce non-mass dependent oxygen isotopic fractionation in refractory oxide grains. Presolar silicate materials, which are an important reservoir of oxygen in the early solar nebula, are believed to have been produced in high-temperature regions prior to the formation of the solar nebula. Our results may provide another possible path, caused by the processing of presolar silicate materials and leading to the non-mass dependent oxygen isotopic fractionation of CAIs and chondrules.

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Yamamoto. et al theoretically proposed that the chemical reaction heat between an amorphous silicate dust and the surface layer diffuses into the center of the dust and the crystallization temperature falls, which is corresponding to the Greenberg model. By covering Mg-bearing silicate dust with carbon layer, we found that crystallization temperature falls 200 degrees for crystallization of carbon surface layer. Here we showed that crystallization of Mg-bearing silicate dust coved with carbon in methane gas atmosphere at 10-3 torr progresses at room temperature.

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We will discuss the properties of dust in the local interstellar medium.

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Observations of cometary jets showed that the degree of linear polarization is visibly higher than in the rest of the coma and it rapidly decreases with distance from the cometary nucleus. Simultaneously, the intensity of jets depends weakly on distance. We attribute the change in polarization to sublimation of ice from cometary dust particles and examine this idea with numerical simulation of light scattering by grains of irregular shape and ice-covered agglomerates consisting of these grains. We will show the disruption of agglomerated particles due to sublimation of ice could explain qualitatively the photo- and polarimetrical features observed in cometary jets.

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We conducted laser ablation experiments in model atmospheres to simulate chemical reactions between impact-generated CN radicals and an ambient atmosphere. We investigated the dependence of atmospheric composition on the yield of HCN.

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One of the features of Titan is dense atmosphere, mainly nitrogen and methane. Among various kinds of energy sources in Titan atmosphere, cosmic rays can penetrate deeply down to the surface, which could be most effective to produce organic compounds near the surface of Titan. We examined possible formation of bioorganic compounds in lower Titan atmosphere. A mixture of methane (5%) and nitrogen (95%) was irradiated with 3 MeV-protons from a van de Graaff accelerator. Solid product (CR tholin) was acid-hydrolyzed, and amino acids in the hydrolysate was quantified by HPLC and/or by GC/MS with a chiral column after derivatization by using chroloformate. MALDI-TOF-MS spctra implied that the CR tholin had -CH₂- structure. Various amino acids were detected in CR tholin after acid hydrolysis: Indigenousness of amino acids was checked with their D/L ratio and/or by using ¹³CH₄ as a carbon. Furthermore, recovering and hydrolyzing the synthesized CR tholin with H₂¹⁸O, amino acids that included ¹⁸O in the construction were identified by MALDI-TOF-MS. It was suggested that CR tholin could give amino acids after interaction with surface water ice and/or cometary water ice during meteoritic / cometary impacts.

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For the purpose of investigating the effects of condensation reactions on the circulation structures of Jovian atmosphere, we have developed a two-dimensional numerical model that incorporates condensation of water and ammonia and production reaction of ammonium hydrogensulfide. We have conducted numerical calculation for a fairly long period covering many life cycles of convective clouds.
The result shows that the vertical profile of stability has two peaks associated with condensation of water and ammonia. The stability of the layer associated with condensation of ammonia is not strong enough to prevent convective upward motion, because the upward motion ranging from the water condensation level to the tropopause appears intermittently.

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The scattering greenhouse effect of a CO₂ ice cloud layer has been proposed as a potential mechanism for keeping the Martian climate warm enough to support flowing water under a faint young Sun. Previous studies have shown that such warm climate is possibly achieved if a cloud layer with optimal ranges of particle size and optical depth is placed in the atmosphere. However, it has not been examined whether or not such an optimal cloud layer could be formed.
In this study, we construct a one dimensional, radiative-convective equilibrium model including cloud formation processes due to radiative cooling and estimate the parameters of cloud layer and the cloud-induced greenhouse effect. Our numerical analysis suggests that a CO₂ ice cloud layer which can cause strong greenhouse effect is formed with achieving both radiative and vapor pressure equilibria, and 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 10⁵ - 10⁷ kg^-1.

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Aiming for an atmospheric general circulation model (GCM) with a flexible and readable source code, a dynamical core is newly designed and its implementation tests are performed. In order to improve the flexibility and readability of the model, the source code is hierarchically structured by the use of modules and derived-type variables, array-valued functions are frequently used for operating array-valued variables, a set of naming rules are newly introduced for variables and functions, and a tool set for automatic generation of reference document (RDoc) are improved. The dynamical core developed here is named DCPAM, and is provided at http://www.gfd-dennou.org/ .

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73P/Schwassmann-Wachmann is one of the typical Jupiter Family Comets with the period of 5.4 years, and is a split comet which had split into 4 nuclei during 1995 appearance, and the recurrence of two or more fragment nuclei was observed in 2001. In this year, 2006, the both of main fragment C and fragment B were re-detected, additionally more than ten small fragments were detected. Moreover, the comet approached about 0.08AU to the earth in the middle of May this year so that it was a good chance to observe the inner coma of the splitting comet in detail.
The imaging polarimetry of 73P was performed by using "Polarimetric Imager for Comets (PICO)" attached to 50cm Telescope at Mitaka, NAOJ. We observed fragments B and C since the brightness of these reached to 8 mag. on late April. Especially, the fragment B has repeated outburst on early May, therefore, it was observed intensively.
We report the early results of the observations and make a comparison between fragments B and C, as well as discuss the difference of dust grains of these two fragments.

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The outburst of the Phoenicids observed in 1956 was investigated on the basis of the dust trail theory by using the newly linked orbit that was estimated from the asteroid 2003 WY25 and comet D/1819 W1(Blanpain). We find that a bundle of the trails formed from late 18th through early 19th centuries came close to the Earth's orbit at the epoch of the outburst in 1956. We introduce this as a brand new approach to explore the past history of cometary activities of dormant objects by inspecting the activity of related meteor showers, with a help of the dust trail theory.

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We are searching for extrasolar planets in binary systems to understand the planet formation in binary or multiple star systems by precise Doppler shift measurements, using HIgh Dispersion Echelle Spectrograph(HIDES) equipped on the Okayama Astrophysical Observatory's(OAO) 188cm telescope.Since 2003, we have monitored radial velocity variations about 10 pairs of visual binary systems every 1 or 2 month. We have reported about these stars in 2004 and 2005 autumn meeting.On last August, we have started a Doppler survey for SB1s(single-lined spectroscopic binary) with semi-major axis smaller than 10AU. The orbital elements of such binaries are well determined. We have selected target stars which orbital elements(period, eccentricity, amplitude) are already given. We can observationally investigate the distribution of binary's semi-major axis, which planets can stably exist, as a function of eccentricity.We will present the current status of the this survey and future works.

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It is suggested that organic compounds found in meteorites and comets had important roles in origins of life. In the Greenberg model, these organic compounds were originally formed in ice mantles of interstellar dusts in molecular clouds. There have been many works to evaluate this model. A frozen mixture of methanol, ammonia and water was irradiated with heavy ions to simulate the action of cosmic rays in molecular clouds. Amino acid precursors with large molecular weighs and complex structures were formed. Such organic compounds were altered with UV light in diffuse cloud, and with cosmic rays in small bodies in the solar system. Experiments to simulate such alteration processes of organic compounds are in progress to draw chemical evolution scenario to the generation of life on the Earth.

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25143 Itokawa is one of the smallest asteroids ever observed by spacecraft. Images taken by the HAYABUSA spacecraft reveal many unfamiliar morphologies relative to those found on previously explored asteroids. Because impact crater is an important feature on the surface of airless bodies, we investigate morphology of crater on Itokawa. We analyze images of Itokawa, and a detailed shape model of the asteroid that reconstructed from images. On Itokawa, there is no crater with a classical raised rim and bowl-shaped floor morphology, thus circular depressions are picked up as crater candidates at first. Finer material is ease to move to gravitational low regions.

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In November, 2005, the Hayabusa spacecraft successfully touch-downed at the smooth terrain of the asteroid, Itokawa, whose longest axis is as small as ~500m. At the decent phase for the touch down and its rehearsals, more than 30 unprecedentedly high-resolution images are obtained at different locations/areas of Itokawa. The widths of some of these images are too narrow, which required significant effort in estimating their exact locations. In this talk, we will report how we rectified these images into low-resolution images and briefly discuss geological characteristics apparent on these images.

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In HAYABUSA/XRS, X-ray CCD needs to be kept below -40 degree Celsius to achieve the energy resolution to analyze elemental composition of the asteroid surface. XRS has three different techniques cooling CCDs; 1.thermal filament between XRS and HAYABUSA, 2. Pertie cooler on CCDs, 3. passive radiation by the hood to remove the stray light. The thermometer attached on the hood is available to measure thermal emissivity from the asteroid. To construct a thermal model of Itokawa, we considered the thermal balance between XRS and other environments such as the solar flux, heat radiation of HAYABUSA and Itokawa, heat generation of inside instruments that affected the temperature observed by this thermometer. To estimate the heat generation of inside instruments we divided XRS into 26 elements and solved equations of thermal conduction between nodes. To reveal the radiation from Itokawa we constructed the thermal model considering the shape of Itokawa and tried to investigate the most suitable characteristic for the observation and compared our analysis with infrared and near infrared ground observations.

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XRS (x-ray spectrometer) onboard Hayabusa has observed x-ray fluorescence from near-Earth asteroid 25143 Itokawa to determine major elemental composition. Okada et al. (2006) reported average elemental mass ratios of Mg/Si = 0.78 + - 0.09 and Al/Si = 0.07 + - 0.03. In this study, we attempted to estimate upper limits of Ca and Fe. To discussion about abundance of Ca and Fe, we need to integrate data longer time, fallowing the result of numerical simulation. In this poster, we report a result and the method of the analyses.

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Our sub-group of SSP (Surface Science Package) has been set up in Minorbody exploration WG. Our goal is establishment of arrangement of surface science instruments for positioning, collecting geologic context, supporting selection of sampling sites, and calibrations of orbiter instruments. Scientific goal is to collect key evidence in sedimentology/stratigraphical geology under the micro-gravity environment. We will report the current status of this sub-group

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Before the rendezvous of Hayabusa spacecraft with the asteroid Itokawa, various ground-based observations of the asteroid had been performed and a lot of physical quantities about Itokawa were presumed. We summarize these results and verify how effective these results were for the Hayabusa mission. Furthermore, based on the verification result, it is considered how ground-based observation for the candidate asteroid of the next asteroid exploration mission should be advanced.

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As a post-Hayabusa mission in 2010's, our working group has been developing a new sampling system for C-type and other primitive asteroid surface and sub-surface materials, based upon technology and operation established and lessons learned by Hayabusa's touch-and-go sampling attempt at the S-type asteroid Itokawa in 2005. Both impact sampling with corer projectiles and a microgravity tether retraction system are under the development as well as shaped charge excavation on free asteroidal surface. This study summarizes results of those endeavors and future prospects of this challenge.

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This research proposes a stereoscopic system for opographic recognition for the next asteroid exploration. In this research procedures of software processing are as follows; (1) extract feature points from images, (2) searching corresponding points between stereo pair images using correlation coefficient with consideration of fisheye distortion, (3) computing three-dimensional locations of matched points from disparity. Progress in this research is demonstrated on the poster.

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The asteroid Itokawa is irregular in shape, so that we cannot adopt conventional GIS for the asteroid. The 3D map, which can be rotated with mouse operation, was required. The aim of this study is development of 3D GIS data visualization tool. The tool can display a polygon model of Itokawa with physical values, which are attributed to polygons.

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The plans of Post-Hayabusa missions have been discussed by the "Small Body Exploration WG" of ISAS/JAXA. In this paper, we report scientific objective of the exploration on surface feature and topology of asteroids. Specifications of payload instruments will be also presented.

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The Mercury Dust Monitor (MDM) will be onboard the BepiColombo MMO spacecraft which will be launched in 2013. The MDM is an array of lightweight and heat resistant piezoelectric (lead-zirconate-titanate; PZT) detector in order to measure momentum and incoming direction of hypervelocity micro-particles around Mercury. Two major scientific interests are flux and origin variations on interplanetary meteoroid complex inside 1 AU, and the in-situ investigation of the near-Mercury dust environment.The MDM consists of 4 flat PZT plates whose size is 4cm x 4cm and 1mm thick for each PZT. The calibration experiments of this system are made using micro-particle accelerators at HIT, Univ. Tokyo in Japan and at MPI-K in Germany. By analyzing impact signal, rough momentum and velocity of impact particles can be determined. Only the output signal within a few hundred nanoseconds immediately after impact is analyzed, which is free from interference with reflected waves and could contain an impact hysteresis. The following results are obtained; 1. Output amplitude is proportional to the momentum of particles below 6 km/s, 2. rise-time is related to the particle velocity above 10km/s, 3. there exists a transition region in between, and 4. the sensitivity is confirmed to be independent of the element thickness.

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Two types of imaging spectrometer had been developed and examined. One is Advanced Lunar Imaging Spectrometer (ALIS) and another is Liquid-Crystal Tunable Filter (LCTF) Telescope. ALIS is a Cassegrain telescope equipped with two PGP (Prism-Grating-Prism) type spectrometers; Visible (VIS) one and Near Infrared (NIR) one covering 380 – 1700 nm. LCTF is a multi-band refracting telescope using a tunable liquid-crystal filter covering 650 - 1100 nm. Ground-based observations of the moon were carried out by ALIS users group. The location of the observations was Science City at the peak of Mt. Haleakala, Maui, Hawaii, USA. The dates of ob-servation were August 15 – 26, 2005 and December 12 – 18, 2005. With ALIS we detected the shift of the wavelength of absorption band of ferrous iron at around 1000 nm. The data indicate the Mg/Fe heterogeneity in lunar mare basalts and suggest important sites for SELENE observation. LCTFT was used to gain a lunar absolute radiance and reflectance. The data are useful to arrange the exposure time of SELENE optical sensors.

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We report the observation and operation plans for lunar gravity field mapping using SELENE small satellites: Relay Satellite (Rstar) and VRAD Satellite (Vstar). Rstar and Vstar have been enlightened mass by the reduction of batteries, abolishment of altitude and active attitude control system, and newly developed release mechanism. We, therefore, estimate the status of batteries, satellite altitude, and electric power using ranging rate data and proto-flight test data to improve the accuracy of gravimetry.

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In this study, our goal is to accomplish the longer resonant period of the seismometer on-board penetrator, which have velocity transducer, and a resonant period of about 1 second at present state. From this improvement, we expect that the seismometer detect the moonquake signal, whose period is much longer than 1 sec, for example surface wave and free oscillation. To investigate the present dynamic response for long period range, we made the seismic observation with this short-period seismometer and broadband seismometer STS-2. In this presentation, we indicate the results from the comparison between the observed signals of these seismometers. Next, we examined the negative force feedback system as the method for lengthening the resonant period of the seismometer on-board penetrator. When we select a method using some feedback system, we will simulate and evaluate the accomplished characteristic. Here, we will indicate the results from the simulation and discuss the expected results from the seismic observation with this seismometer, which have simulated characteristic.

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Radar sounding instruments are onboard on some of recent planetarymissions including Mars Express and SELENE. Because the reflection signals detected by these instruments would include clutters from surface topography and complicated subsurface structures, which are hardto simulate even on numerical simulations, we are developing a laboratory platform, which can simulate reflection signals in a more realistic way. In this talk, we will present details of our experimental setup and future research plans.

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The Goal of this study is development of automatic extraction algorithm for craters, ridges, and grabens on DTM (Digital Terrain Model). Edge detection of topographic features is one of the most important parts of the extraction algorithm. The followings are candidates of methods for edges detections: (1) FFT (Fast Fourier Transform), (2) Hierarchical FFT, (3) Haar - Wavelet Transform. Their results will be reported.

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SELENE/MI will provide huge volumes of multi-band image data in the summer of 2007. The result of the trial application of existing methods to the images peculiar to the moon will be presented.

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Digital Terrain Model (DTM) of wide area of the moon will be provided by SELENE LISM TC (Terrain Camera) data.Development of automatic processing methods of this large DTM data set is important. We will demonstrate some indicators for mapping of topographic roughness in a few km scale, using DTM made from Apollo stereo images.

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In order to estimate bulk composition of the moon, crystallization sequence of lunar magma ocean (LMO) with several bulk compositions estimated by the previous studies was investigated to compare with crystallization sequence deduced from high P/T experiments for mare basalts. Based on the investigation, crystallization sequence of each LMO composition is not always in agreement with that deduced from mare basalt high P/T experiments. This evidence indicates estimation of bulk LMO composition should be carefully considered to consistent with the mare basalt petrogenesis.

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Lunar surface and subsurface temperature were measured in Apollo 15, 17 missions for lunar surface heat-flow value. Thermal diffusivity k of the lunar regolith was estimated to be 1.0E-8(m^2/s) by the analysis of annual temperature change (Langseth et al., 1976). From the analysis of the eclipse and lunar night time cooling-down curves, the existence of a thin layer (2cm, k=1.0E-9(m^2/s)) on the lunar surface was predicted. (Keihm et al., 1973).
Shorter periodic temperature change has better resolution to the thermal properties for its smaller thermal skin depth.
We analyzed the temperature history data in lunation and lunar eclipse which have shorter period compared to annual one. We could make the observed Lunation amplitude when we computed by 1-layered model whose thermal properties were uniform (k=1.0E-8). We should have postulated 2-layered model to explain the eclipse data (Takita et al., 2006). In the model calculations we set the k of the upper layer 1.0E-9(m^2/s) and the lower to be 1.0E-6(m^2/s), the eclipse-model amplitude matched the Apollo data when the thickness of the upper layer was about 2mm. Thus the value of k could be ten times bigger than the annual result.

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Alpha Ray Detector (ARD) will be on-board SELENE. The ARD investigates the gas emission on the lunar surface through alpha particle observations.We will discuss about estimation of the background due to cosmic ray to evaluate the spatial resolution and sensitivity.

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An investigation of the correlation of Lunar sodium (Na) distribution between its surface and atmosphere was made by a Monte-Carlo numerical model calculation.

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We have investigated the local-time (LT) dependence of distribution of Mercury's sodium exosphere, in order to understand production and loss processes of low release velocity component of the exosphere. As a method of the investigation, we compare a model sodium exosphere simulated by the Monte Carlo method with observation results [Sprague et al.,1997]. As an initial step of this investigation, we adopted the photon-stimulated desorption process as the released mechanism, and assumed that amount of sodium atoms supplied to Mercury's surface always exceeds that of released atoms from surface. As the results of the comparison the model could not meet with the observed LT dependence. It is suggested that, therefore, some additional mechanisms or effects, especially balance of supply and release for sodium atoms, should be considered. Following these results, we have investigated the LT dependence further by adopting new models considering non-uniformity of sodium atoms supplied to Mercury's surface and thermal desorption which is one of release mechanisms causes increase of sodium column density particularly at the dawn side region [Sprague et al.,1992; Hunten and Sprague,2002].

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The morphology and location of outflow channels on Mars indicate a subsurface origin of the water (e.g., [1]). However, the origin and processes that can provide the large inferred discharge, is not well understood. Following previous studies, we hypothesize that dike intrusion played a significant role [2]. We quantify, using numerical models the conditions, the conditions under which dikes may permit large discharges of water. We perform 2-D numerical simulations of the amount and distribution of meltwater adjacent to a cooling dike to test the hypothesis. We extend HYDROTHERM code developed by the USGS [3] and include the effects of the phase transition between ice and water. We thus account for both boiling and freezing. The interaction between magma and frozen ground is assumed to occur at depths between several kilometers and a few hundred meters depth. At the depths, boiling may occur without direct sublimation. We evaluate the melting process of the permafrost layer by estimating the following: (1) How much meltwater an be generated? (2) What is the pattern of hydrothermal circulation?, and (3) How fast does the dike cool? References.[1] Manga, M. (2004) [2] Ogawa, Y., Y. Yamagishi and K. Kurita (2003) [3] Hyba, D. O. and S. E. Ingebristen (1997).

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Secular variation of Martian true polar wander due to surface mass loading is calculated. The calculation here includes effect of not only remnant bulge but also polar tide on rotational stability. The true polar wander with the polar tide somewhat differs from that without the polar tide in the secular variation. This difference depends on Martian internal viscosity structure. It is because memory of visco-elastic deformation by the polar tide remains in the record of the moment of inertia tensor perturbation. The result in the present study suggests possible influence of polar tide on the true polar wander driven by Tharsis loading on Mars.

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Europan visco-elastic tidal deformation due to its non-synchronous rotation is calculated. The relationship between the geological settings, the rotation period, and the surface rheology is investigated on the basis of this calculation. This investigation infers that the surface viscosity ranges between 10¹⁹ and 10²⁰ Pa.s. The approach presented here suggests possibility of estimation for the surface viscosity on solid planets and satellites through its tectonic settings.

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Physical processes of planetary formation from dusts to planetesimals are not well understood. A previous experiment on collisional response of water ice spheres showed that the critical velocity, which was the onset velocity of fracturing depends on the size of the sphere (Higa et al.1998).
Since aggregate of dusts have high porosity, we performed low velocity collision experiments of gypsum spheres of about 50% in porosity. We found that compaction occurred at lower velocities than those where fracturing occurred. We will discuss on the influence of compaction on the critical velocity.

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