Amount Of Water Ice Research Articles

Compositional Study of Trans-Neptunian Objects at λ > 2.2 μm

Abstract Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 μm. These observations, collected with two broadband filters centered at 3.6 and 4.5 μm, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water, and we were able to distinguish between surfaces that are predominantly composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. Twenty-three percent of our sample may include other ices, such as carbon monoxide, carbon dioxide, methane, or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Furthermore, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population.

Исследование процесса теплообмена при охлаждении форели с применением диоксида углерода

There is a growing demand for rapid cooling in modern food industry. Traditional methods of fish cooling involve cold air, cold liquid, and ice. These methods have a number of disadvantages. For instance, they may have a negative effect on the appearance of the product, require a longer cooling time, or make fish absorb extra moisture. As a result, the quality of the product and its shelf life decrease, which results in demand contraction. Carbon dioxide is becoming increasingly popular in closed refrigeration systems. It is one of the most promising refrigerants, since traditional refrigeration technologies for fish cooling have a number of serious drawbacks. The paper introduces a utilization method for carbon dioxide obtained at alcohol processing plants. The authors analyzed the prospects of using carbon dioxide in combination with a binary mixture for cooling trout. A series of experiments proved the technological advantages of this technology. The paper features heat transfer in roundfish during cooling with water ice, a mixture of water ice and snow-like carbon dioxide, and snow-like CO2 in pure form. The obtained results show the effect of the concentration of snow-like carbon dioxide in water ice on the intensity of the cooling process. A higher intensity of the cooling process reduced the cooling time and the amount of water ice. The study of quality indicators of trout proved that the environment of water ice and carbon dioxide increased its shelf life by several times. The paper contains temperature graphs and duration curves at different concentrations of CO2.

Variations in the amount of water ice on Ceres' surface suggest a seasonal water cycle.

The dwarf planet Ceres is known to host a considerable amount of water in its interior, and areas of water ice were detected by the Dawn spacecraft on its surface. Moreover, sporadic water and hydroxyl emissions have been observed from space telescopes. We report the detection of water ice in a mid-latitude crater and its unexpected variation with time. The Dawn spectrometer data show a change of water ice signatures over a period of 6 months, which is well modeled as ~2-km2 increase of water ice. The observed increase, coupled with Ceres' orbital parameters, points to an ongoing process that seems correlated with solar flux. The reported variation on Ceres' surface indicates that this body is chemically and physically active at the present time.

VIS‐NIR reflectance of water ice/regolith analogue mixtures and implications for the detectability of ice mixed within planetary regoliths

AbstractPermanently shadowed regions at the poles of the Moon and Mercury have been pointed out as candidates for hosting water ice at their surface. We have measured in the laboratory the visible and near infrared spectral range (VIS‐NIR) bidirectional reflectance of intimate mixtures of water ice and the JSC‐1AF lunar simulant for different ice concentrations, particle sizes, and measurement geometries. The nonlinearity between the measured reflectance and the amount of ice in the mixture can be reproduced to some extent by the mixing formulas of standard reflectance models, in particular, those of Hapke and Hiroi, which are tested here. Estimating ice concentrations from reflectance data without knowledge of the mixing coefficients—strongly dependent on the size/shape of the grains—can result in large errors. According to our results, it is possible that considerable amounts of water ice might be intimately mixed in the regolith of the Moon and Mercury without producing noticeable photometric signatures.

NEAR-INFRARED OBSERVATIONS OF COMET-LIKE ASTEROID (596) SCHEILA

Asteroid (596) Scheila was reported to exhibit a cometary appearance and an increase in brightness on UT 2010 December 10.4. We used the IRCS spectrograph on the 8 m Subaru telescope to obtain medium-resolution spectra of Scheila in the HK band (1.4–2.5 μm) and low-resolution spectra in the KL band (2.0–4.0 μm) on UT 2010 December 13 and 14. In addition, we obtained low-resolution spectroscopy using the SpeX spectrograph on the 3 m NASA Infrared Telescope Facility on UT 2011 January 4 and 5. The spectrum of Scheila shows a consistent red slope from 0.8 to 4.0 μm with no apparent absorption features, resembling spectra of D-type asteroids. An intimate mixing model suggests that the amount of water ice that might be present on the surface of Scheila is no more than a few percent. The spectrum of the Tagish Lake chondrite matches the asteroid's spectrum at shorter wavelengths (λ < 2.5 μm), but no hydration features are observed at longer wavelengths on Scheila. Our analysis corroborates other studies suggesting that the comet-like activity of Scheila is likely not caused by the sublimation of water ice. The dust coma and tail may be results of a recent impact event.

Research Spotlight: Map of lunar hydrogen points to large amounts of water ice

In October 2009, NASA's Lunar Crater Observation and Sensing Satellite (LCROSS) mission smashed into a crater on the Moon and confirmed previous studies that suggested that water ice existed on the Moon. To learn more about lunar water, scientists are examining the abundance and distribution of hydrogen. Hydrogen has been detected near the lunar poles, but scientists have not been certain whether this hydrogen is the form of water ice or in other compounds such as molecular hydrogen. If hydrogen exists in a volatile compound such as water, it would remain stable only in cold, permanently shaded regions such as deep craters.

ESO-Large Program on TNOs: Near-infrared spectroscopy with SINFONI

We present in this work the observations performed with SINFONI in the framework of a new ESO-Large Program (2006–2008) on Trans-Neptunian Objects (TNOs) and Centaurs. We obtained 21 near-infrared (1.49 to 2.4 microns) spectra of high quality, including 4 spectra of objects never observed before. We search for the presence of features due to ices, particularly water ice. Eris is the only object showing deep methane ice absorption bands. The spectra of 4 objects are featureless, and 6 others show clearly the presence of water ice. For 7 objects, the detections are more ambiguous, but absorption bands could be embedded in the noise. The 3 remaining spectra are too noisy to draw any reliable conclusion. The possible amount of water ice on each object's surface has been computed. The analysis shows that some objects present strong compositional heterogeneities over the surface (e.g. Chariklo), while some others are completely homogeneous (e.g. Quaoar).

Spectroscopic Search for Water Ice on Jovian Trojan Asteroids

The Jovian Trojans likely formed beyond the snow line and so may contain considerable amounts of water ice. We seek near-infrared spectroscopic evidence for the 1.5 and 2.0 μm water ice bands in the Trojans. Our sample is focused on objects identified in previous measurements as being of special interest. The unusual Trojan (4709) Ennomos has a geometric albedo significantly above the mean Trojan albedo, perhaps because a recent impact has coated part of the surface with freshly excavated ice. Trojans (911) Agamemnon, (617) Patroclus, (1143) Odysseus, and (2797) Teucer were also observed. These objects have been independently reported to show possible weak absorptions at 1.7 and 2.3 μm, respectively. If real, the latter features may be due to organic materials present on the surfaces. However, all five targets appear spectrally featureless, even in our highest signal-to-noise ratio data. Simple models consisting of mixtures of water ice and a spectrally featureless material were used to quantify the limits to surface ice.

VLT-ISAAC 3–5 μm spectroscopy of embedded young low-mass stars

Aims.We study in this paper the ice composition in the envelope around intermediate-mass class I Young Stellar Objects (YSOs).Methods.We performed a spectroscopic survey toward five intermediate-mass class I YSOs located in the Southern Vela molecular cloud in the L (2.85–4.0 μm) and M (4.55–4.8 μm) bands at resolving powers –800 up to 10 000, using the Infrared Spectrometer and Array Camera mounted on the Very Large Telescope-ANTU. Lower mass companion objects were observed simultaneously in both bands.Results.Solid HO at 3 μm is detected in all sources, including the companion objects. CO ice at 4.67 μm is detected in a few main targets and one companion object. One object (LLN 19) shows little CO ice but strong gas-phase CO ro-vibrational lines in absorption. The CO ice profiles are different from source to source. The amount of water ice and CO ice trapped in a water-rich mantle may correlate with the flux ratio at 12 and 25 μm. The abundance of H2O-rich CO likely correlates with that of water ice. A weak feature at 3.54 μm attributed to solid CHOH and a broad feature near 4.62 μm are observed toward LLN 17, but not toward the other sources. The derived abundances of solid CHOH and OCN- are ~% and ~% of the HO ice abundance respectively. The HO optical depths do not show an increase with envelope mass, nor do they show lower values for the companion objects compared with the main protostar. The line-of-sight CO ice abundance does not correlate with the source bolometric luminosity.Conclusions.Comparison of the solid CO profile toward LLN 17, which shows an extremely broad CO ice feature, and that of its lower mass companion at a few thousand AU, which exhibits a narrow profile, together with the detection of OCN- toward LLN 17 provide direct evidences for local thermal processing of the ice.

Possible remnants of a frozen mud lake in southern Elysium, Mars

In this work we estimate the minimum persistence time of subsurface ice in water rich sediment layers remaining after sublimation of a martian lake. We simulate sublimation of ice from layers of different granulations and thicknesses. Presented results assume insolation and atmospheric conditions characteristic for the present day southern Elysium, where data from Mars Express have identified surface features possibly indicating the very recent presence of a frozen body of water [Murray et al., 2005. Nature 434, 352–356]. The age of these features is estimated to be several million years. On this time scale, we find that most of the water ice must have sublimated away, however remnant ice at a few percent level cannot be excluded. This amount of water ice is sufficient for chemical cementation of the observed features and explains their relatively pristine appearance, without significant signs of erosion.

PFS-MEX observation of ices in the residual south polar cap of Mars

The Mars Express spacecraft has a highly inclined orbit around Mars and so has been able to observe the south pole of Mars in illuminated conditions at the end of the southern summer ( L s = 330 ). Spectra from the planetary Fourier spectrometer (PFS) short wavelength (SW) channel were recorded over the permanent ice cap to study its composition in terms of CO 2 ice and H 2O ice. Models are fitted to the observed data, which include a spatial mixture of soil (not covered by ice) and CO 2 frost (with a specific grain size and a small amount of included dust and H 2O ice). Two different kinds of spectra were observed: those over the permanent polar cap with almost pure CO 2 ice, negligible water ice, no soil fraction required, and bright; and those over mixed terrain (at the edge of the cap or near troughs) containing a significant soil spatial fraction, more water ice and smaller CO 2 grain size. The amount of water ice given by fits to scaled albedo models is less than 10 ppm by weight. When using multi-stream reflectance models with the appropriate lighting geometry, the water amount must be 2–5 times greater than the albedo fit (less than 50 ppm). At the periphery of the residual polar cap, we found a region almost completely covered by water frost, modeled as a mixture of micron-sized and sub-mm sized grains. Our result using a granular mixture of micron-sized grains of water ice and dust with the CO 2 grains is different from the modeling of OMEGA polar cap observations using molecular mixtures.

Surface Composition of the Galilean Satellites from Galileo Near-Infrared Mapping Spectroscopy

AbstractThe Galileo Near Infrared Mapping Spectrometer (NIMS) is currently obtaining spectral maps of Jupiter’s moons to determine the composition and spatial distribution of minerals on the satellite surfaces. Sulfur dioxide, as a frost or ice, covers much of Io’s surface, except in hot volcanic areas. A weak spectral feature at 3.15 μm suggests the presence of an OH containing surface compound (hydroxide, hydrate, or water) and a broad absorption above 1 μm is reasonably attributed to iron-containing minerals, such as feldspars and pyrite. Water is the dominant molecule covering Europa’s surface, occurring as ice but also as a hydrate. The trailing side shows high concentrations of these hydrous minerals, whose identifications are not yet established. Ganymede’s surface exhibits water absorption bands, largely due to ice but hydrates are also present. A dark component is present, but with a smaller proportion compared to Callisto. Some of the non-ice features seen on Ganymede are similar to those found in Callisto’s spectra (see below). Among the icy Galilean satellites, Callisto shows the least amount of water ice, covering about 10% of the surface in patchy concentrations. Most of the surface is covered with unidentified (as yet) dark minerals. The exposed ice is often associated with impact craters, implying that the darker material exists as a blanket over more pure ice. Non-ice spectral features at 3.88, 4.03, 4.25, and 4.57 μm are present in Callisto’s spectra (and some of these appear in Ganymede’s spectra), each with different spatial distributions. Laboratory spectra suggest that the 4.25-μm feature is due to carbon dioxide which is trapped in the surface grains. The band at 4.03 μm may be due to sulfur dioxide, which probably originated from Io. Molecules containing CN, SH, SiH, and perhaps deuterated constituents are candidates for the other features, some of which could be derived from shock-heated and modified material from impacts, perhaps of carbonaceous composition. There is evidence for the presence of hydrated minerals on Callisto, based on water band shifts and shapes.