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Terrestrial helium consists almost exclusively (all but ~2ppm) [16] of 4 He. 4 He's boiling point of 4.2 K is the lowest of all known substances except 3 He. When cooled further to 2.17 K, it becomes a unique superfluid with zero viscosity. It solidifies only at pressures above 25 atmospheres, where it melts at 0.95 K.
The idea for the polar wind originated with the desire to solve the paradox of the terrestrial helium budget. This paradox consists of the fact that helium in the Earth's atmosphere seems to be produced (via radioactive decay of uranium and thorium) faster than it is lost by escaping from the upper atmosphere. The realization that some helium ...
Helium is a commonly used carrier gas for gas chromatography. The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating. [28] [30] Helium at low temperatures is used in cryogenics and in certain cryogenic applications.
A hycean planet is a hypothetical type of planet with liquid water oceans under a hydrogen atmosphere. [1] The presence of extraterrestrial liquid water makes hycean planets regarded as promising candidates for planetary habitability.
Terrestrial planets are substantially different from the giant planets, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets have a compact, rocky surfaces, and Venus, Earth, and Mars each also has an atmosphere. Their size, radius ...
Pure-play helium, also known as primary helium or green helium is helium that is extracted from the earth as the main product. Since the early 20th century, most of the world's helium supply has been extracted from natural gas as part of the nitrogen rejection process. The preference for primary helium is driven by the planned reduction in use ...
The composition of a primary atmosphere is primarily hydrogen and helium, with minor amounts of other volatiles like water vapor, methane, and ammonia, depending on the temperature and region of the protoplanetary disk. These atmopsheres are generally thick and extended, enveloping the young planet in a dense layer of gas. [2]
Jupiter's upper atmosphere is composed of about 75% hydrogen and 24% helium by mass, with the remaining 1% consisting of other elements. The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass.