Advances in Geosciences

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The major evidence concerning Mercury's craters remains the imaging of Mariner 10 from over three decades ago. We are beginning to gain information about Mercury's unimaged side from Earth-based radar. The MESSENGER mission will start making major advances in a few years. Issues that have developed and remain to be resolved include the specific roles of the Late Heavy Bombardment and of hypothetical “vulcanoids” in cratering the planet, which affect calibration of the absolute chronology of Mercury's geological and geophysical evolution, and the role of secondary cratering, by ejecta from both the visible craters and from the numerous large basins.

Mariner-10 flybys of Mercury were the main sources of information on Mercury's exosphere up to the discovery of the exospheric sodium emission from ground based observatories (Potter and Morgan, Science 229 (1985) 651—653). These later observations were followed by the discovery of potassium (Potter and Morgan, Icarus 67 (1986) 336—340) and calcium emissions in Mercury's exosphere (Bida et al., Nature 404 (2000) 159—161). Several ground-based observations have underlined the significant spatial and temporal variations of Mercury's exosphere. Such observations lead to the suggestion of a large number of potential sources of ejection of volatiles from Mercury's surface, but also to the suggestions of strong relations between Mercury's exosphere and its magnetosphere as well as between Mercury's exosphere and upper surface.

We review some features of ion dynamics in Mercury's magnetosphere using single-particle simulations. Not unexpectedly, the small spatial and temporal scales of this magnetosphere lead to non-adiabatic transport features that have a variety of implications such as extreme sensitivity to initial conditions upon injection into the magnetosphere, formation of beamlets and of a thin current sheet in the magnetotail, or large scale filtering due to the finite width of the magnetosphere with respect to the ion Larmor radius. We show that ions are rapidly transported and energized within Mercury's magnetosphere, with possibly significant recycling of planetary material. The occurrence of reconnec-tion in the magnetotail however, may substantially alter the global convection pattern, and cause enhanced down-stream losses. We demonstrate that large non-adiabatic energization may be achieved for electrons as well, in particular during presumed expansion phases of substorms which lead to short-lived precipitation onto the planet surface and formation of bouncing electron clusters.

Many efforts are currently in progress to depict a realistic model of the Hermean magnetosphere, also in the frame of the researches that will be performed by the next space missions Messenger and BepiColombo. Although the magnetosphere of this planet can be roughly approximated by scaling the Earth's one (about 1:6.9), several differences are expected due to both the lack of an ionosphere, which rise questions concerning the closure of the magnetospheric currents, and the likely absence of a stable ring current. A remarkable feature, outlined by the models, is represented by the wide area accessible by the solar wind plasma on the Mercury's dayside, due to the broad footprint of the magnetospheric cusp regions. Moreover, the absence of a dense atmosphere/ionosphere implies that a large faction of the impinging plasma can reach the planet's surface. We present the results obtained by comparing two modelization of the Mercury's magnetosphere by means of ad hoc modified Tsyganenko and Toffoletto–Hill models. The analysis is focused on the dayside magnetospheric configurations and plasma entry patterns, derived by taking into account the effect of the magnetic reconnection with the interplanetary magnetic field. The role played by the radial IMF component (B_x) is also discussed.

Neutral Atom emission from Mercury Magnetosphere is discussed in this study. In particular, we consider those neutrals whose emission is directly related to the circulation of energetic ion of solar wind origin, via both charge-exchange and ion-sputtering. The environment of Mercury, in fact, is characterized by a weak magnetic field; thus, cusp regions are extremely large if compared to the Earth's ones, and intense ion fluxes are expected there. Spatial and energy distributions of ions and neutrals, and energy-integrated simulated ENA images, are obtained by means of a single-particle 3D simulation. The feasibility of neutral atom detection and imaging in the Hermean environment is also discussed here: simulated neutral atom images are investigated in the frame of the Neutral Particle Analyser-Ion Spectrometer (SERENA NPA-IS) experiment, on board the ESA mission BepiColombo/MPO.

The BepiColombo is an interdisciplinary mission to explore the planet Mercury through a partnership between ESA and Japan's Aerospace Exploration Agency (JAXA). From their dedicated orbits two spacecrafts, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), will be studying the planet and its environment. Both orbiter will be launched together on a single Soyuz—Fregat. The launch is foreseen for August 2013 with arrival in late summer 2019. Solar electric propulsion will be used for the journey to Mercury. The BepiColombo scientific payload has been selected in 2004. The MPO payload comprises eleven instruments/instrument packages; the MMO payload consists of five instruments/instrument packages. Together, both spacecraft and their scientific payload will provide the detailed information necessary to understand Mercury and its magnetospheric environment and to find clues to the origin and evolution of a planet close to its parent star. The MPO will focus on a global characterization of Mercury through the investigation of its interior, surface, exosphere, and magnetosphere. In addition, it will be testing Einstein's theory of general relativity. Major effort was put into optimizing the scientific return by defining the payload complement such that individual measurements can be interrelated and complement each other. A detailed overview of the status of BepiColombo will be given with special emphasis on the MPO and its payload complement.

The magnetosphere of Mercury is most intriguing because of its extreme nature, with scale sizes vastly different from the corresponding terrestrial ones, and a harsh environment at a comparatively small solar distance. The present brief paper summarizes some scientific topics where electric field measurements at low frequency will make a significant contribution to the understanding of the Mercury plasma environment, and discusses possible diagnostics.

The BepiColombo Mercury Magnetospheric Orbiter (MMO) spacecraft comprises the plasma and radio wave observation system called Plasma Wave Investigation (PWI). The PWI is designed and developed in collaboration between Japanese and European scientists. Since plasma/radio wave receivers were not installed in the former spacecraft, Mariner 10, which observed the planet Mercury, the PWI onboard the MMO spacecraft will provide the first plasma/radio wave data from Mercury orbit. It will give important information for studies of energy exchange processes in the unique magnetosphere of Mercury characterized by the interaction between the relatively large planet without ionosphere and the solar wind with high dynamic pressure. The PWI consists of three sets of receivers (EWO, SORBET, and AM²P), connected to two sets of electric field sensors (MEFISTO and WPT) and two kinds of magnetic field sensors (LF-SC and DB-SC). The PWI will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.1 Hz to 640 kHz for the magnetic field. In the present paper, we demonstrate the scientific objectives of plasma/radio wave observation around Mercury. Further, we introduce the PWI system, which is designed to meet the scientific objectives in the BepiColombo MMO mission.

According to the previous satellite observation (Mariner10 fly-by), Mercury has a magnetosphere with its own strong intrinsic magnetic field. In order to elucidate the detailed plasma structure and dynamics around Mercury, an orbiter BepiColombo Mercury magnetospheric orbiter (MMO) is planned to be launched in the timeframe between 2012 and 2013 as a joint mission between ESA and ISAS/JAXA. For measuring low energy ions, two sensors Mercury ion analyzer (MIA) and Mercury ion mass spectrum analyzer (MSA) will be onboard the MMO. MIA measures energy spectrum (5eV/q—30keV/q) of ions around Mercury as well as solar wind ions while MSA measures mass discriminated energy spectrum (5eV/q—40keV/q) of ions around Mercury. MIA is a toroidal top-hat type electrostatic analyzer with dynamic range as wide as 10⁶, while MSA consists of a similar electrostatic analyzer followed by a time-of-flight section for mass discrimination. In order to realize the wide dynamic range, electrical sensitivity control and attenuation grid are applied at the same time. The thermal environment around Mercury is so severe that the thermal design of the instrument is very important. Each sensor should have its own thermal shield in order to minimize the thermal input and to maintain the sensor temperature within an acceptable range.

Observational data suggest that the ice deposits in permanently shaded regions on the Moon are relatively impure, being highly mixed with the regolith. In contrast, the deposits on Mercury appear to be pure and covered by dry regolith. The differences in the deposits on the two bodies may be the result of differing weathering rates, their unique impact histories, or selection effects from the observation methods. We discuss the available data and results from modeling. We find that the most suitable explanation for the Mercury observations is that a comet deposited an ice layer at least 50 cm thick in the northern cold traps less than 50 Myr ago. The lunar model suggests that if a relatively pure ice layer exists, it is old and buried or was originally thin and is now impure.

The surface features of the Earth and Moon differ substantially. The detailed investigation of morphology is one of the foremost science goals of a Japanese lunar explorer Selenological and Engineering Explorer (SELENE) that will be launched in 2007. The Terrain Camera (TC), one of the mission instruments on SELENE, is a panchromatic stereo camera of 10 m spatial resolution from the SELENE nominal altitude of 100 km. Detailed lunar maps including digital terrain models (DTMs) will be produced from the TC data. These maps will be fundamental information for lunar morphology. In this paper, we describe the TC global high-resolution stereo mapping experiment.

Decades of research have sought to understand the similarities and differences between Venus and Earth. Yet, it is still not clear what chemical processes maintain the long-term stability of Venus' primarily CO₂ atmosphere because, until recently, the observed limit on O₂ was an order of magnitude smaller than predicted by photochemical model calculations. CO₂ dissociates into CO and O after absorbing photons at wavelengths <205 nm. These O atoms should combine to form O₂, and observations of intense airglow, produced as oxygen molecules in the O₂(a¹Δ) and O₂(c¹Σ) states decay radiatively to the ground state, confirm rapid production of O₂ on both day and night sides. Achieving an appropriate balance in numerical models between this rapid production of O₂ and the rapid destruction implied by the observational upper limits on O₂ has been a challenge for the past 25 years. Numerical modeling shows that recent proposals may resolve this gap between theory and observations, depending on the rates of poorly constrained reactions. The laboratory and observational studies needed to help resolve remaining questions regarding oxygen chemistry in the Venus middle atmosphere are outlined.

We present observations of energetic neutral atoms (ENAs) in the shadow of Mars by the neutral particle imager (NPI), part of the ASPERA-3 experiment on-board Mars Express. The observations are well into the umbra, where the count rates are low, and contamination by UV light minimal. We present statistics over all available observations, from the 2004 and the early 2005 eclipse seasons. We investigate skymaps of the observations, and their time dependence, and try infer the different origins of the observed fluxes: instrumental effects, ENAs from Mars and its interaction with the solar wind, and ENAs of possibly heliospheric origin. We also study the time evolution of the observed signals. It is found that most of the observed emissions are consistent with UV, but some are not, suggesting ENA fluxes — Mars related and non-Mars related. The NPI measure the integral ENA flux (0.1-60keV) with no mass or energy resolution, but with high angular resolution (5 × 11°). The sensor is also sensitive to UV light.

The behaviors of both the density and height of the peak of the primary Martian ionospheric layer have been intensively investigated. On the contrary, the study on the secondary layer is mainly focused qualitatively on the photochemistry processes leading to this layer. The observational behaviors of the secondary peak, i.e., that of the peak height and the peak density, are seldom emphasized. In this paper, the Martian ionospheric profiles obtained by the Mars Global Surveyor (MGS) Radio Science (RS) experiments during two continuous periods are investigated. For 1,678 of the available 3,377 ionospheric electron density profiles, the secondary peak can be easily distinguished. Both the solar zenith angle dependence and the solar activity dependence of the secondary peak are investigated. E10.7, the integrated extreme ultraviolet (EUV) energy flux at the top of the atmosphere reported in units of 10.7 cm radio flux, is used as the proxy of solar radiation in this study. However, the main pho-toionization source for the secondary layer is not mainly EUV but soft X-ray. This shortcoming should be improved by using X-ray flux measurements; however, this is beyond the scope of this study.

The Earth-orbiting submillimeter wave astronomy satellite (SWAS) observed the global mean surface and atmosphere temperature on Mars as a function of the altitude. Unlike for the infrared spectrometers, the temperature retrievals from submillimeter instruments can be performed in the presence of the atmospheric dust. During the 2001 global dust storm on Mars, SWAS measured the atmosphere and surface temperature for aerocentric longitudes from L_s = 166° to 233°, and observed the temperature inversion in the lower atmosphere. We use a recently developed general circulation model of the Martian atmosphere to simulate the temperature and other atmospheric fields under the conditions corresponding to those during the SWAS measurements. The model takes into account the radiative effects of the atmospheric dust. Simulations show an overall agreement with the SWAS measurements. In particular, the model reproduces the inversion of the global mean temperature and the surface cooling detected by SWAS. Time series of the globally averaged surface and atmospheric temperature at 0.05 hPa (∼49km) are also in a good agreement with the measurements. Without the dust, the model cannot reproduce these features. A brief discussion of the differences between the model and observations as well as their possible reasons is provided.

This paper reviews the current knowledge about bulk densities and porosities of cometary nuclei. Grain agglomeration and formation of small planetesimals in the Solar Nebula, as well as the subsequent collisional and thermal evolution of cometary nuclei are discussed, in order to provide a theoretical expectation on the range of bulk densities for the present comet population. Various methods for estimating cometary bulk densities, and corresponding results are reviewed, showing a reasonable agreement with the previously mentioned theoretical range. Current empirical estimates indicate that comets are bodies with rather low density and high porosity (typically ρ_bulk = 600 ± 400 kg/m³ and ψ = 0.6 ±0.3, respectively).

The Large angle and spectrometric coronagraphs aboard the Solar and helio-spheric observatory (SOHO) spacecraft observed a large (more than 1000) number of sungrazers. This led to many studies which tried to explain their origin and the peculiar shape of the observed cometary lightcurves. However, in the last years a few sungrazers have been observed also in the hydrogen Lyman-α spectral line by the UV coronagraph spectrometer on SOHO. This instrument allowed to perform UV spectroscopical observations of sungrazing comets on their final stage of life at projected heliocentric distances between 1.4 and 10 solar radii. Ultra violet coronagraph spectrometer (UVCS) detected in the sungrazer UV spectra mainly the Lyman-α spectral line. Typically, emission in this line originates in the hydrogen cloud produced by the water photodis-sociation, but, at these low heights, it is necessary to take into account also strong interaction processes (e.g., mass-loading and charge exchange) between the solar wind and the outgassed materials. From these observations, it has been possible to estimate cometary parameters such as the outgassing rates and the nucleus sizes, as well as parameters of the coronal plasma encountered by the comet. In this work we review the main results derived from the UVCS observations of sungrazing comets: the detection of a “hidden” mass below ∼6R_⊙, the indirect and direct evidences for the occurrence of fragmentation processes and a tentative estimate for the pyroxene dust grain number density. Moreover, we present here preliminary results on the UVCS data interpretation of a sungrazer observed in 2002.

The light curves of integrated visual brightness of the periodic comet 9P/Tempel during 1972, 1983, 1994, and 2005 appearances were constructed and studied. The values of photometrical parameters H₀, n, and H₁₀ were computed. A secular fading of this comet was studied. The photometrical peculiarities of comet and long-term evolution of comet's activity probably will change after impact. Therefore, the results, which are presented in this manuscript, are important.

A three-dimensional multi-fluid magnetohydronamic model of the interaction of a cometary coma with the solar wind has been applied to an active Halley-class gas source. The model includes both photo and electron impact ionization, ion recombination, elastic collisions, Coulomb ion/electron interactions, cooling of electrons by water vapor, and the coupling with the magnetic field. Heavy and light ions are treated separately, as necessary. An adaptive mesh refinement is employed to model both near-nucleus kilometer scale phenomena and the much larger structures of the bow shock and the coma tail. With 5.8 million computational cells and 25 levels of refinement, the structures in both the inner coma (within 20,000 km from the nucleus) and in the outer coma were satisfactorily resolved. The model output includes ion density, velocity, temperature, and pressure, electron and neutral temperatures, and magnetic fields. This model is compared to previous simulations and to the location of major plasma boundaries from the 1986 Halley flyby missions. There is satisfactory agreement from this model with the available mission data in features of the plasma structure such as the location of the bow shock, the inner shock, and the mass loading.

XMM-Newton observations of Jupiter show prominent soft X-ray emission from the auroral spots and, albeit at a lower intensity, from the equatorial regions. While the spectra of the auroral X-rays can be modeled with a superposition of unresolved emission lines, including most prominently those of highly ionized oxygen, Jupiter's equatorial ‘disk’ emission has a spectrum consistent with that of solar X-rays scattered in the planet's upper atmosphere. Remarkably, a large solar X-ray flare, which took place on the Sun's Jupiter-facing side in November 2003, is found to be associated with a corresponding feature in the Jovian disk X-ray lightcurve. This suggests that the non-auroral X-ray emission from Jupiter is directly controlled by the Sun. However, the XMM-Newton results support the view that Jupiter's auroral emissions originate from the capture and acceleration of heavy ions, followed by X-ray production by charge exchange. They presently favor a solar wind scenario, although a magnetospheric origin for some of the ions cannot be excluded.

Jupiter, Saturn, and Earth — the three planets having dense atmosphere and a well developed magnetosphere — are known to emit X-rays. Recently, Chandra X-ray observatory has observed X-rays from these planets, and XMM-Newton has observed them from Jupiter and Saturn. These observations have provided improved morphological, temporal, and spectral characteristics of X-rays from these planets. Both auroral and non-auroral (low-latitude) “disk” X-ray emissions have been observed on Earth and Jupiter. X-rays have been detected from Saturn's disk, but no convincing evidence for X-ray aurora on Saturn has been observed. The non-auroral disk X-ray emissions from Jupiter, Saturn, and Earth, are mostly produced due to scattering of solar X-rays. X-ray aurora on Earth is mainly generated via bremsstrahlung from precipitating electrons and on Jupiter via charge exchange of highly ionized energetic heavy ions precipitating into the polar atmosphere. Recent unpublished work suggests that at higher (>2keV) energies electron bremsstrahlung also plays a role in Jupiter's X-ray aurora. This paper summarizes the recent results of X-ray observations on Jupiter, Saturn, and Earth mainly in the soft energy (∼0.1—2.0keV) band and provides a comparative overview.

The X-ray spectrometer (XRS) onboard Hayabusa, a Japanese asteroid explorer, has been developed to determine major elemental composition of the surface of 25143 Itokawa through remote X-ray fluorescence spectrometry, which is planned during the asteroid rendezvous phase in 2005. During the cruising phase, the XRS observed cosmic X-rays. In addition, it also observed X-rays excited by the Sun off the surface of the Earth and the Moon just before the Earth swing-by conducted in May, 2004. We present the instrumentation of the XRS and discuss the recent results of observations from the viewpoint of design concept.

A possible scenario of future collaborative efforts among the Asian, European, and American space science communities is described with scientific objectives focused on the Saturnian system. The project tentatively named Saturn Atmosphere Probe and Phoebe Rover (SAPPORO) mission could probably be realized in around 2025 if organizational steps are taken now to facilitate dialogs and scientific exchanges among the scientists on a global scale.

In this paper, we review the possibility of space observations for the most important luminous transient phenomena occurring on planetary bodies. The construction of a breadboard of a CCD camera having a field of view of 120° and a sensitivity able to detect events of visual magnitude +6, together with the realization of the relative operation software, has been funded by the European Space Agency (ESA). This project has been developed by the firm Galileo Avionica S.p.A. (Campi Bisenzio, Italy). The estimated cost for such a space qualified camera is estimated between 3 and 4 million US$. It could fly as a piggy-back payload on a space platform and/or a constellation of satellites conceived for different space missions.

Certain techniques used in geophysical prospection to measure ground permittivity have been transposed to space plasmas. The principle is to measure the self impedance of a single electric antenna or the mutual impedance between two sets of Hertz dipoles. Since probe impedances depend on dielectric properties of the immersed medium, space plasma parameters such as the density and temperature of thermal electrons may be reliably and accurately deduced. Natural waves may also be investigated in a large frequency range including characteristic plasma frequencies. As any electrode immersed in a plasma acquires a charge, it perturbs the plasma in its immediate neighborhood. The way to get around this difficulty is to use four electrodes, two for transmitting and two for receiving. Transmitting electrodes are excited from a signal generator, while receiving electrodes are connected to a high input impedance voltmeter. The transmitted current I and the received voltage V being known, plasma properties may be deduced from both the imaginary and real parts of the mutual impedance Z = V/I. Such quadripole probes have been used on sounding rockets and spacecraft.

Here we report a infrared high-resolution spectroscopy of Pluto in the L band. The spectroscopic observation was performed by the Subaru telescope with the adaptive optics system. The spectrum is dominated by the strong and broad absorption features of methane, but includes some additional features. Comparing the spectrum with model calculations, we suggest that absorption features could be an indication of nonmethane hydrocarbons on Pluto's surface.

The Dawn mission is aimed at providing a wealth of fundamental information concerning the two giant asteroids (1) Ceres and (4) Vesta. According to current ground-based data, these two objects are thought to be radically different, and offer a nice example of the huge variety of physical properties characterizing the main belt asteroid population. In particular, (1) Ceres, the largest main belt asteroid, is thought to be a mostly primitive object, whereas (4) Vesta is the best example of a fully differentiated asteroid. A major goal of modern planetary science is to understand how and why these two objects, which are orbiting at fairly similar heliocentric distances, can be so different. In turn, this question is related to our understanding of the early phases in Solar Systems history, when planetary growth took place in the protoplanetary disk. In situ exploration of Ceres and Vesta by Dawn is expected to provide new fundamental data, and to possibly open new paths to theoretical investigations.

According to current plans of ESA, Gaia will be launched in 2011. With a systematic survey of the whole sky down to magnitude V = 20, Gaia will provide a fundamental contribution in practically all fields of modern Astrophysics. In particular, Gaia will be also a major milestone in the history of asteroid science. Based on its unprecedented astrometric performances, complemented by spectroscopic and photometric capabilities, Gaia will be able to measure the masses of about 100 asteroids. It will directly measure sizes of about 1,000 objects, will derive spin properties and overall shapes of about 10,000 objects, and will derive much improved orbits and taxonomic classification of hundreds of thousands asteroids. The post-Gaia era in asteroid science will be one in which we will know average densities of about 100 objects belonging to all the major taxonomic classes, we will have a much more precise knowledge of the inventory and size and spin distributions of the population, of the distribution of taxonomic classes as a function of heliocentric distance, and of the dynamical and physical properties of dynamical families.

We present the first results of a long-term campaign of photometric observations of the Karin family asteroids. This family is very compact, and is supposed to be extremely young, with an estimated age of about 5.8 Myrs. The purpose of our observations is to determine the rotational properties, the colors and hopefully the overall shapes of the largest possible number of family members, since this might provide important information about the physics of the original break-up event that quite recently produced this family. The lightcurves that we have already obtained for 12 objects are of a generally good quality. We have also obtained some indication that the largest member of the family, (832) Karin, might exhibit some color variation across its surface. This might be an interesting result, but it has to be confirmed by future observations.

We have carried out a near-infrared (J, H, and K bands) spectroscopy of the asteroid Karin with cooled infrared spectrograph and camera for OHS on the Subaru telescope. This asteroid is the brightest asteroid among the Karin cluster group, which is thought to be remnants of a collisional breakup only 5.8 million years ago. For different rotational phases of Karin, we derived different spectra such as a reddened spectrum like that of S-type asteroid and an un-reddened spectrum like that of ordinary chondrite. Our result supports the idea that S-type asteroids are parent bodies of ordinary chondrites.

Recent progress in asteroid surveys has revealed the fine structures down to sub-km in diameter of the size-frequency distributions (SFD) of main belt asteroids (MBAs), as well as near-Earth asteroids (NEAs). These SFDs can be compared with the SFD of lunar and planetary crater projectiles. The SFD of the projectiles that created the oldest craters on the lunar highlands, which are considered a fossil of the Late Heavy Bombardment (LHB) impactors of ∼4 Ga ago, shows a very good agreement with that of the current MBAs. This fact indicates that the LHB craters were created by the bombardment of ancient asteroids ejected from the main belt by a short-term, size-independent event, such as the radial movement of strong resonances due to the migration of giant jovian planets. On the other hand, the SFD of the projectiles that have created younger craters such as those on Mars is very different from that of the MBAs; instead, it is quite similar to the SFD of NEAs. This newer population of projectiles might be created by a long-term, size-dependent transportation mechanism of asteroids such as the Yarkovsky effect, which preferentially pushes smaller objects into strong resonances.

The majority of trans-Neptunian objects (TNOs) are probably small comets beyond the orbit of Neptune. A study of TNOs may enable a better understanding of the origin of short-period comets and of the process of planet formation and the early history of the solar system. An occultation survey is currently the only way to detect these objects down to a size of a few kilometers at such a distance. The status of the Taiwan—America Occultation Survey (TAOS) project is reported. In order to monitor thousands of stars on the order of a fraction of a second using CCD cameras, a novel CCD readout technique, the “shutter-less zipper mode,” is applied. Two predicted asteroid occultation events were successfully observed. Instead of a simple number count of occultation events, an interpretation of a TNO occultation survey result can be obtained by using the simulator described here. Through comparison of the results from an observation and from our simulator, a specific astronomical or astrophysical model can be constrained.

Chinese scientists have done many research works in this field of asteroid survey and related aspects. They found Asteroid 1125 — China at Yerkes Observatory in 1928 and found Asteroid Purple 1 at Purple Mountain Observatory (PMO) in 1955. Up to the middle period of 1980s, over 130 new numbered asteroids were found at PMO and among them two are Mars-crossing asteroids. The Schmidt CCD Asteroid Program (SCAP) of Beijing Astronomical Observatory (BAO) was put in practice in 1995. Two NEOs and a Mars-crossing asteroid were found in 1997. In 1990s, 575 asteroids were found by SCAP, which was the first place in the world at that time. The construction of NEO Search Telescope was started in 1999 and has been finished in principle. The telescope is a 1.0/1.2 m Schmidt telescope with 4 K × 4 K shift scanning CCD detector. It is to be expatiated in this paper. The telescope can also inspect space debris. In addition to ground base NEO Survey and investigation, we have tabled a proposal “auto-navigation for NEO exploration” and hope to have international cooperation.

Being the only article in this volume concerning energetic neutral atoms (ENA) coming from the heliospheric boundaries, this will be a mini-review, beginning with a brief introduction to the subject, and then highlighting the current status on observation and modeling in this field. We conclude with a view for future investigations.

The Habitable zones are usually believed to be appropriate environment for terrestrial planets that can provide the liquid-water, subtle temperature, atmosphere components of CO₂, H₂O, and N₂ [Kasting et al., Icarus 101 (1993) 108], supporting the development and biological evolution of life on their surfaces. In this work [see an accompanied paper, Ji et al., Astrophysical Journal 631 (2005) 1191 for details], we investigated the dynamical architecture of 47 UMa with the planetary configuration of the best-fit orbital solutions by Fischer et al. [Astrophysical Journal 586 (2003) 1394], to study the existence of the Earth-like planets in the region for 0.05 AU ≤ a ≤ 2.0 AU for 47 UMa by numerical simulations. In the study, we found that the “hot Earths” at 0.05 AU ≤ a ≤ 0.4 AU can dynamically survive at least for 1 Myr. The Earth-like planets can eventually remain in the system for 10 Myr at the areas involved in mean motion resonance (MMR) (e.g., 3:2 MMR and 9:5 MMR) with the inner companion. Moreover, we showed that the 2:1 and 3:1 resonances could be marginally stable, but the 5:2 MMR is unstable. In a dynamical sense, we point out that the most possible candidate habitable environment is that the Earth-like planets may bear the orbits of 0.8 AU ≤ a ≤ 1.0 AU and 1.0 AU ≤ a ≤ 1.30 AU (except 5:2 MMR) for relatively lower eccentricities. We also conducted similar studies in other multi-planet systems and found the potential existence of the Earth-like planets in habitable zones.

This paper reviews the proposal of future solar system sciences by JAXA and Japanese science communities, based on the discussion associated with the proposal for the future space programs, “JAXA Vision — JAXA 2025 —”, released in March 2005.