Water in the Universe

The formation of an amorphous solid was first reported in 1935 [132,133]. These authors used the route of depositing warm water vapor on a cold substrate, which freezes in excess free energy by the rapid change in temperature. At substrate temperatures above 160K, the deposit was found to be crystalline ice I, whereas below this temperature, an amorphous solid was obtained. These deposits are referred to as ASW, which is a microporous material that can adsorb gases [134, 135]. In fact, ASW also condenses on interstellar dust particles and is likely the most abundant form of solid water in the universe. Therefore, studies on ASW bear an astrophysical relevance [134, 136]. The microporosity can be reduced greatly by sintering the sample to no more than 120 K. 

Water in its several forms is the substance most essential to life on earth. Some of its crystalline forms are stable in certain temperature-pressure ranges and others are metastable. Although the stable form of water at sufficiently low temperatures is crystalline, inside this stable phase, water can also exist in liquid form. When this occurs, water is said to be supercooled. Supercooled water occurs naturally in the form of small droplets in clouds. If liquid water is cooled quickly enough, the crystalline phase can be bypassed and a noncrystalline (amorphous) solid, that is, a glass, is the result. This amorphous glass phase of water is polymorphic, that is, it can exists in two different forms. Glassy water is undoubtedly the most common form of water in the universe. Scientists puzzle over the anomalous properties of glassy water when it is cooled it becomes more compressible, when compressed it is less viscous, and when cooled sufficiently, it expands. 

A. Hanslmeier, Water in the Universe, Astrophysics and Space Science Library 368, 1... 

The existence of water in the universe is therefore mainly based on the different nuclear burning phases that occur in the more massive stars. 

Hydrogen is the most abundant element in the universe and is found in a variety of compounds, including hydrocarbons (e.g., fossil fuels or biomass) and water. Since free hydrogen does not occur naturally on earth in large quantities, it must be produced from hydrogen-containing compounds. 

Hydrogen is the lightest known element. Although only found in the free state in trace amounts, it is the most abundant element in the universe and is present in a combined form with other elements. Water, natural gas, crude oils, hydrocarbons, and other organic fossil materials are major sources of hydrogen. 

Combustion has a very long history. From antiquity up to the middle ages, fire along with earth, water, and air was considered to be one of the four basic elements in the universe. However, with the work of Antoine Lavoisier, one of the initiators of the Chemical Revolution and discoverer of the Law of Conservation of Mass (1785), its importance was reduced. In 1775-1777, Lavoisier was the first to postulate that the key to combustion was oxygen. He realized that the newly isolated constituent of air (Joseph Priestley in England and Carl Scheele in Sweden, 1772-1774) was an element he then named it and formulated a new definition of combustion, as the process of chemical reactions with oxygen. In precise, quantitative experiments he laid the foundations for the new theory, which gained wide acceptance over a relatively short period. 

Liquid water is difficult to find in the universe. Scientists have found frozen ice in places such as Mars and gaseous water vapor in atmospheres such as that on Venus. However, no one has been able to find liquid water anywhere other than on Earth. Water is the only natural substance that is found in all three states of matter (solid, liquid, and gas) at the temperatures normally found on Earth. By exploring a few of the properties of water, you will discover what makes water unique. 

Water can be found, in all three aggregate states, almost everywhere in the universe as ice in the liquid phase on the satellites of the outer solar system, including Saturn s rings and in the gaseous state in the atmospheres of Venus, Mars and Jupiter and in comets (as can be shown, for example, from the IR spectra of Halley s comet). The OH radical has been known for many years as the photodissociation product of water. 

The second important source for the hydrosphere and the oceans are asteroids and comets. Estimating the amount of water which was brought to Earth from outer space is not easy. Until 20 years ago, it was believed that the only source of water for the hydrosphere was gas emission from volcanoes. The amount of water involved was, however, unknown (Rubey, 1964). First estimates of the enormous magnitude of the bombardment to which the Earth and the other planets were subjected caused researchers to look more closely at the comets and asteroids. New hypotheses on the possible sources of water in the hydrosphere now exist the astronomer A. H. Delsemme from the University of Toledo, Ohio, considers it likely that the primeval Earth was formed from material in a dust cloud containing anhydrous silicate. If this is correct, all the water in today s oceans must be of exogenic origin (Delsemme, 1992). 

There are new ideas and experiments on the rTCA cycle. A group from Harvard University studied some reaction steps in the rTCA cycle which were kept going by mineral photochemistry. The authors assumed that solar UV radiation can excite electrons in minerals, and that this energy is sufficient to initiate the corresponding reaction steps. In this photocatalytic process, semiconductor particles were suspended in water in the presence of a zinc sulphide colloid (sphalerite) the experiments were carried out in a 500 mL reaction vessel at 288 K. Irradiation involved a UV immersion lamp (200-410 nm) in the photoreactor. Five reactions out of a total of 11 in the rTCA cycle were chosen to check the hypothesis ... 

Welander, A. D. and Palumbo, R. F. (1963). Radionuclide Content of Oceanic Fish, Plankton, and Water in the Vicinity of Christmas Island, March Through August 1962, Report No. UWFL-88 (Laboratory of Radiation Biology, University of Washington, Seattle, Washington). 

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