Polar caps

The oceans hold about 97% of the earth s water. More than 2% of the total water and over 75% of the freshwater of the world is locked up as ice ia the polar caps. Of the remaining 1% of total water that is both Hquid and fresh, some is groundwater at depths of > 300 m and therefore impractical to obtain, and only the very small difference, possibly 0.06% of the total water of this planet, is available for human use as it cycles from sea to atmosphere to land to sea. Only recently have humans been able to regulate that cycle to their advantage, and even now (ca 1997), only infinitesimally, ia some few isolated places. 

FIGURE 6.24 The polar ice caps on Mars extend and recede with the seasons. They are mostly solid carbon dioxide and form by direct conversion of the gas into a solid. They disappear by sublimation. Although some water ice is also present in the polar caps, the temperature on Mars never becomes high enough to melt it. On Mars, ice is just another rock. 

Most of the stars of our sample have been selected from the H K BPS survey ( Beers, Preston Shectman [1], First, stars were selected from the weakness of their H H lines for the Balmer lines intensity on prism-objective Schmidt telescope plates. Then, the candidate stars were observed with a slit spectrograph in order to have a quantitative estimate of their metallicity. The survey has operated on about 7000 square degrees of the sky, mostly on the polar caps. It has supply a vast amount of metal-poor stars, with hundreds of them more metal-poor than the most metal-poor globular clusters. We selected from this sample stars with metallicities estimated to have [Fe/H] < -2.7. The actual metallicity histogram is given for the sample on fig. 1. 

By definition, the atom fraction of 16Q frozen in polar caps is... 

Spacecraft images of icy moons, (a) Voyager 2 image of Triton, showing complex "cantaloupe" terrain and a polar cap of nitrogen ice smooth areas near the equator may be frozen lakes. 

Spore relatively large polar caps visible in vivo. ... 

Ross RG, Kargel JS (1998) Thermal conductivity of solar system ices, with special reference to Martian polar caps. In de Bergh C, Festou M, Schmitt B (eds) Solar system Ices, Kluwer, Dordrecht, pp 33-62... 

It was suggested by Megill and Hasted [169] in relation to polar-cap absorption events, and by Kummler and Bortner [170] with respect to... 

More than any other planet. Mars has captured our attention and fueled our speculations. Much of this interest relates to the possibility of martian hfe, as championed by Percival Lowell in the last century and subsequently in scientihc papers and science fiction. Lowell s argument for life on Mars was based partly on geochemistry, in that his assessment of the planet s hospitable climate was dependent on the identification of H2O ice rather than frozen CO2 in the polar caps. Although this reasoning was refuted by Alfred Wallace in 1907, widespread belief in extant... 

Polar caps—The deposits of frozen carbon dioxide at Mars s poles. The ice caps advance and recede with the changing Martian seasons, and bear a strong resemblance to Earth s polar regions. 

Treatment of Pr1Sn(OH)2Cl. 3/4 H2O in DMF under the same conditions gives the compounds [(PriSn)12Oi4(OH)6]2+ CF2. 3 H20 and [(PriSn)i2Oi4(OH)6]2+ CF2.2 DMF, in which the structure of the cation (12-39) can be viewed as a sphere with an equatorial ring of six square-pyramidal RSn04 units, with polar caps each of three RS11O5 units the presence of the familiar 4-4-4 motif is indicated.118 124... 

It should be mentioned, that soft X-ray emission of PSR 1929+10 can be due to polar caps or due to non-thermal mechanism. 

Icy satellites have an icy crust and mantle and are composed of mixtures of ice and silicates. Stripe patterns showing layered structures with different sand contents have been discovered on the polar cap on Mars. There could be a wide range of temperature conditions from the melting point of ice to below 100 K in icy satellites and on Mars. Therefore, it is important to study the rheological properties of ice-silicate mixtures at wide temperatures to elucidate the tectonics of icy satellites and the flow dynamics of ice sheets on Mars. 

Kargel, J.S. Tanaka, K.L. Baker, G. Komatsu, G. MacAyeal, D.R. Formation and dissociation of clathrate hydrates on mars polar caps, northern plains and highlands. Lunar Planet. Sci. 2002, XXXI. www.lpi.usra.edu/meetings/lpsc2000/pdf/ 1981.pdf... 

Kaplan and later researchers also found that the abundance of water in the Martian atmosphere is a function both of location on the planet and season. The highest concentrations of water vapor measured for the planet s atmosphere are just less than 500 pm ppt H20 during the planet s winter and less than 10 pm ppt HzO during its summer. Water concentrations tend to he highest over the polar caps and lowest at the planet s equator, where it may reach such low values as to be unmeasurable. 

The solution circular dichroism spectra also reveals R(AO, giving the sum, R(T.) = R(E) + R(A ). A comparison of the single crystal and the solution CD spectra indicates that R(E) has minor rotatory strength of -0.16 Dp and R(A2) +0.32 DP (72). This result supports the observed relation between the relative magnitudes of R(E) and R(A2) and the arrangement of non-ligating atoms in tris-bidentate complexes (Table VII). The polar capping of A -(+). g -... 

Decreasing levels of stratospheric ozone (O3) over the polar caps have lead to the speculation that a reduction in high-atmospheric (stratospheric) ozone levels will lead to increased skin cancers rates (caused by excessive, nonhistorical UV-band radiation exposure). 

In higher fullerenes the surface curvature decisively influences the sites for reactions to occur. The strain at individual carbon atoms is by far higher around the molecular poles than in the so-called belt region, and so any addition reaction will preferably take place at the outer polar caps. Nevertheless, the regiochemistry of a specific addition is governed by the aspects discussed above. Accordingly, also here (5,6)-double bonds are unfavorable from an energetic point of view and will be avoided wherever possible. 

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