RESUMO
Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu's parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu's parent body formed ~2 million years after the beginning of Solar System formation.
RESUMO
It is of great significance to experiment with a simulator for remote sensing to confirm the properties and meaning of remote-sensed information and to forecast certain phenomena. This paper describes a simulator for remote sensing. The simulator, suitable for the measurement of soil moisture, consists of an optical source, a polarimeter, orbital guides for them, and a sample stage. SiC and MgO were used as soil models. The moisture in beach sand was also estimated. The degree of polarization increases with the moisture content and particle size of the sample. The field capacity point of each sample is determined by means of the polarimeter.
RESUMO
The components of an object and the moisture in it can be estimated by measuring the degree of spectral polarization of scattered light from that object. In this paper the degree of spectral polarization of scattered light from CuSO(4), CuCl(2), Fe(2)O(3), SiC, S, NiCl(2), and CoCl(2) as models of soil was measured and compared with that of volcanic ash and natural soil. From these results it is estimated that Fe appears in natural soil and Si appears in volcanic ash. The field capacity point of soil was obtained from measurements of the degree of spectral polarization, and it was detected more clearly in a shorter wavelength region (about 400 nm).
RESUMO
A field-averaging spectrograph camera utilizing a continuous interference filter and a step tablet has been investigated and its characteristics measured. Using color patches, the values obtained with the camera are compared with those obtained by a spectroradiometer and a self-spectrophotometer. The results obtained with the photographic method show slightly higher values than those of the other methods in the measured wavelength region. In the measurement of spectral reflectances of two-color patches with different ratios of area within a field of view angle, the same reversal point of the relative reflectance curves is observed with this camera as the spectroradiometer. Therefore, the function of a field-averaging spectrograph camera is the same as a spectroradiometer, which is widely used for remote sensing applications at the present time. Moreover, it is more compact, portable, and lower priced than conventional instruments. The spectral reflectances of scenes were measured by photographic and spectroradiometer methods in field experiments. The spectral image of soil photographed by a beam split camera used with the field-averaging spectrograph camera is displayed in false color.
