- Volatiles
In
planetary science , volatiles, are that group of elements and compounds with low boiling points (see volatile) that are associated with a planet's or moon's crust and/or atmosphere. Examples includenitrogen ,water ,carbon dioxide ,ammonia ,hydrogen andmethane , all compounds of C, H, O and/or N, as well assulfur dioxide . In astrogeology, these compounds, in their solid state, often comprise large proportions of the crusts ofmoons anddwarf planet s. In terrestrial geology, the term more specifically refers to components ofmagma (mostlywater vapor and carbon dioxide) that affect the appearance and strength ofvolcanoes . Volatiles affect the viscosity of the magma, and the tendency to explosive eruptions.Planetary scientists often class volatiles with exceptionally low melting points, such as
hydrogen andhelium , as gases (as ingas giant ), while those volatiles with melting points above about 100 K are referred to as ices. The terms "gas" and "ice" in this context can apply to compounds that may be solids, liquids or gases. Thus,Jupiter andSaturn are referred to as "gas giants" even though the vast majority of the "gas" in their interiors is liquid, andUranus andNeptune are called "ice giant s" despite the fact that neither planet contains more than trace amounts of solid ice.The Earth's
Moon is considered very low in volatiles: its crust contains oxygen chemically bound into the rocks (as egsilicates ), but negligible amounts of hydrogen, nitrogen or carbon.In contrast, those elements with high boiling points are known as "
refractory elements". [cite web | url= http://www.psrd.hawaii.edu/PSRDglossary.html#refractory | title=Glossary | work=Planetary Science Research Discoveries | date=Updated January 2008 | accessdate=2008-08-28]References
External links
* [http://yesserver.space.swri.edu/yes2000/glossary.html Glossary] of planetary astronomy terms
* [http://sio.ucsd.edu/volcano/about/volatiles.html Volatiles] of Costa Rican volcanoes.
* [http://www.psrd.hawaii.edu/PSRDglossary.html#volatile Volatile] Planetary Science Research Discoveries
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