Helium is the chemical element with atomic number 2

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.Sony VAIO VPCS11J7E/B Battery

Helium is the second lightest element and is the second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in our own Sun and in Jupiter. Sony VAIO VPCS11M1E/W Battery

This is due to the very high binding energy (per nucleon) of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for its commonality as a product in both nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is believed to have been formed during the Big Bang. Sony VAIO VPCS11V9E Battery

Some new helium is being created currently as a result of the nuclear fusion of hydrogen in stars.

Helium is named for the Greek God of the Sun, Helios. It was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astronomer Jules Janssen.Sony VAIO VPCS11V9E/B Battery

Janssen is jointly credited with the discovery of the element with Norman Lockyer, who observed the same eclipse and was the first to propose that the line was due to a new element, which he named. In 1903, large reserves of helium were found in natural gas fields in parts of the United States, which is by far the largest supplier of the gas today.Sony VAIO VPCS11X9E/B Battery

Helium is used in cryogenics (its largest single use, absorbing about a quarter of production), particularly in the cooling of superconducting magnets, with the main commercial application being in MRI scanners. Helium's other industrial uses- as a pressurizing and purge gas, as a protective atmosphere for arc welding and in processes such as growing crystals to makesilicon wafers- account for half of the gas produced. Sony VAIO VPCS123FGB Battery

A well-known but minor use is as a lifting gas in balloons andairships. As with any gas with differing density from air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice. In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II), Sony VAIO VPCS125EC Battery

is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, that temperatures near absolute zero produce in matter.

On Earth, the lightness of helium has caused its evaporation from the gas and dust cloud from which the planet condensed, and it is thus relatively rare—0.00052% by volume in the atmosphere.Sony VAIO VPCS128EC Battery

Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenic helium is trapped with natural gas in concentrations up to 7% by volume, from which it is extracted commercially by a low-temperature separation process calledfractional distillation.Sony VAIO VPCS129GC Battery

Scientific discoveries

The first evidence of helium was observed on August 18, 1868 as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India.Sony VAIO VPCS12C7E/B Battery

This line was initially assumed to be sodium. On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D3 Fraunhofer line because it was near the known D1 and D2 lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Sony VAIO VPCS12L9E/B Battery

Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ????? (helios)."

In 1882, Italian physicist Luigi Palmieri detected helium on Earth, for the first time, through its D3 spectral line, when he analyzed the lava of Mount Vesuvius.Sony VAIO VPCS12V9E/B Battery

On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogenand oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun.Sony VAIO VPCW111XX/P Battery

These samples were identified as helium by Lockyer and British physicist William Crookes. It was independently isolated from cleveite in the same year by chemists Per Teodor Cleveand Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight.Sony VAIO VPCW111XX/PC Battery

Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen. His letter of congratulations to Ramsay offers an interesting case of discovery and near-discovery in science.Sony VAIO VPCW111XX/T Battery

In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube, then creating a discharge in the tube to study the spectra of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than onekelvin.Sony VAIO VPCW111XX/W Battery

He tried to solidify it by further reducing the temperature but failed because helium does not have a triple pointtemperature at which the solid, liquid, and gas phases are at equilibrium. Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure.Sony VAIO VPCW111XXP Battery

In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now calledsuperfluidity. This phenomenon is related to Bose-Einstein condensation. Sony VAIO VPCW111XXT Battery

In 1972, the same phenomenon was observed in helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson. The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity.Sony VAIO VPCW111XXW Battery

Extraction and use

After an oil drilling operation in 1903 in Dexter, Kansas, produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, Sony VAIO VPCW115XG Battery

with the help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas. With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium.Sony VAIO VPCW115XGP Battery

This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the American Great Plains, available for extraction as a byproduct of natural gas. The greatest reserves of helium were in the Hugoton and nearby gas fields in southwest Kansas and the panhandles of Texas and Oklahoma.Sony VAIO VPCW115XW/P Battery

This enabled the United States to become the world's leading supplier of helium. Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium plants during World War I. The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. Sony VAIO VPCW115XW/T Battery

A total of 5,700 m3(200,000 cubic feet) of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained. Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-7, which flew its maiden voyage from Hampton Roads, Virginia, to Bolling Field in Washington, D.C., on December 1, 1921.Sony VAIO VPCW115XW/W Battery

Although the extraction process, using low-temperature gas liquefaction, was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft. This use increased demand during World War II, as well as demands for shielded arc welding.Sony VAIO VPCW117XC/P Battery

The helium mass spectrometer was also vital in the atomic bomb Manhattan Project.

The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas, with the goal of supplying military airships in time of war and commercial airships in peacetime. Because of a US military embargo against Germany that restricted helium supplies, the Hindenburg, like all German Zeppelins, was forced to use hydrogen as the lift gas.Sony VAIO VPCW117XC/T Battery

Helium use following World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War. Helium use in the United States in 1965 was more than eight times the peak wartime consumption.Sony VAIO VPCW117XC/W Battery

After the "Helium Acts Amendments of 1960" (Public Law 86–777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas, to connect those plants with the government's partially depleted Cliffside gas field, near Amarillo, Texas.Sony VAIO VPCW119XJ Battery

This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, when it then was further purified.

By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to phase out the reserve.Sony VAIO VPCW119XJ/P Battery

The resulting "Helium Privatization Act of 1996" (Public Law 104–273) directed the United States Department of the Interior to start emptying the reserve by 2005.

Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available.Sony VAIO VPCW119XJ/W Battery

For many years the United States produced over 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in Arzew, Algeria, producing 17 million cubic meters (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Sony VAIO VPCW11AXJ Battery

Meanwhile, by 2000, the consumption of helium within the U.S. had risen to above 15 million kg per year. In 2004–2006, two additional plants, one in Ras Laffan, Qatar, and the other in Skikda, Algeria, were built, but as of early 2007, Ras Laffan is functioning at 50%, and Skikda has yet to start up. Algeria quickly became the second leading producer of helium.Sony VAIO VPCW11S1E/P Battery

Through this time, both helium consumption and the costs of producing helium increased. In the 2002 to 2007 period helium prices doubled, and during 2008 alone the major suppliers raised prices about 50%.

Helium in quantum mechanics

In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. Sony VAIO VPCW11S1E/T Battery

Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons along with some neutrons. As in Newtonian mechanics, no system consisting of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception.Sony VAIO VPCW11S1E/W Battery

Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons. Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps.Sony VAIO VPCW121AX Battery

In such models it is found that each electron in helium partly screens the nucleus from the other, so that the effective nuclear charge Z which each electron sees, is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus.

The related stability of the helium-4 nucleus and electron shell

The nucleus of the helium-4 atom is identical with an alpha particle. Sony VAIO VPCW126AG Battery

High energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud. This symmetry reflects similar underlying physics: the pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons Sony VAIO VPCW127JC/P Battery

(although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. Adding another of any of these particles would require angular momentum and would release substantially less energy (in fact, no nucleus with five nucleons is stable). Sony VAIO VPCW127JC/T Battery

This arrangement is thus energetically extremely stable for all these particles, and this stability accounts for many crucial facts regarding helium in nature.

For example, the stability and low energy of the electron cloud state in helium accounts for the element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements.Sony VAIO VPCW127JC/W Battery

In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions involving both heavy-particle emission, and fusion. Some stable helium-3 is produced in fusion reactions from hydrogen, but it is a very small fraction, compared with the highly favorable helium-4. Sony VAIO VPCW127JC/WZ Battery

The stability of helium-4 is the reason hydrogen is converted to helium-4 (not deuterium or helium-3 or heavier elements) in the Sun. It is also partly responsible for the fact that the alpha particle is by far the most common type of baryonic particle to be ejected from atomic nuclei; in other words, alpha decay is far more common than cluster decay.Sony VAIO VPCW12AAJ Battery

The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. Sony VAIO VPCW12AKJ Battery

So tight was helium-4 binding that helium-4 production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and also leaving few to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis andbinding energy) and thus no energetic drive was available, once helium had been formed, to make elements 3, 4 and 5. Sony VAIO VPCW12AVJ Battery

It was barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. However, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously (see triple alpha process). Sony VAIO VPCW12S1E/P Battery

There was thus no time for significant carbon to be formed in the few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.Sony VAIO VPCW12S1E/T Battery

All heavier elements (including those necessary for rocky planets like the Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Sony VAIO VPCW12S1E/W Battery

Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen.

Gas and plasma phases

Helium is the least reactive noble gas after neon and thus the second least reactive of all elements; it is inert and monatomic in all standard conditions.Sony VAIO VPCW213AG/L Battery

Because of helium's relatively low molar (atomic) mass, its thermal conductivity, specific heat, and sound speedin the gas phase are all greater than any other gas except hydrogen. For similar reasons, and also due to the small size of helium atoms, helium's diffusion rate through solids is three times that of air and around 65% that of hydrogen.Sony VAIO VPCW213AG/P Battery

Helium is the least water soluble monatomic gas, and one of the least water soluble of any gas (CF4, SF6, and C4F8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x2/10?5, respectively, versus helium's 0.70797 x2/10?5),[39] and helium's index of refraction is closer to unity than that of any other gas.Sony VAIO VPCW213AG/T Battery

Helium has a negative Joule-Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule-Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does it cool upon free expansion.[5] Once precooled below this temperature, helium can be liquefied through expansion cooling.Sony VAIO VPCW213AG/W Battery

Most extraterrestrial helium is found in a plasma state, with properties quite different from those of atomic helium. In a plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. Sony VAIO VPCW215AG/L Battery

The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth'smagnetosphere giving rise to Birkeland currents and the aurora.

Solid and liquid phases

Unlike any other element, helium will remain liquid down to absolute zero at normal pressures. Sony VAIO VPCW217JC Battery

This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Solid helium requires a temperature of 1–1.5 K (about ?272 °C or ?457 °F) and about 25 bar (2.5 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same.Sony VAIO VPCW217JC/L Battery

The solid has a sharp melting point and has acrystalline structure, but it is highly compressible; applying pressure in a laboratory can decrease its volume by more than 30%. With a bulk modulus on the order of 50 MPa it is 50 times more compressible than water.Sony VAIO VPCW217JC/P Battery

Solid helium has a density of 0.214 ± 0.006 g/cm3 at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa) is 0.187 ± 0.009 g/cm3.

Helium I state

Below its boiling point of 4.22 kelvins and above the lambda point of 2.1768 kelvins, the isotope helium-4 exists in a normal colorless liquid state, called helium I.Sony VAIO VPCW217JC/T Battery

Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further.

Helium I has a gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of styrofoam are often used to show where the surface is.Sony VAIO VPCW217JC/W Battery

This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K, respectively), which is only one-fourth the value expected from classical physics. Quantum mechanics is needed to explain this property and thus both types of liquid helium are called quantum fluids, meaning they display atomic properties on a macroscopic scale.Sony VAIO VPCW218JC Battery

This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion (thermal energy) from masking the atomic properties.

Helium II state

Liquid helium below its lambda point begins to exhibit very unusual characteristics, in a state called helium II. Sony VAIO VPCW218JC/L Battery

Boiling of helium II is not possible due to its high thermal conductivity; heat input instead causes evaporation of the liquid directly to gas. Helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, less is known about such properties in the isotope.Sony VAIO VPCW218JC/P Battery

Helium II is a superfluid, a quantum mechanical state of matter with strange properties. For example, when it flows through capillaries as thin as 10?7 to 10?8 m it has no measurable viscosity. However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed.Sony VAIO VPCW218JC/T Battery

Current theory explains this using the two-fluid model for helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.Sony VAIO VPCW218JC/W Battery

In the fountain effect, a chamber is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium.Sony VAIO VPCW219AJ/L Battery

In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases the pressure, causing liquid to fountain out of the container.

The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper.Sony VAIO VPCW219AJ/P Battery

This is because heat conduction occurs by an exceptional quantum mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat. Helium II has no such valence band but nevertheless conducts heat well.Sony VAIO VPCW219AJ/W Battery

The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound.Sony VAIO VPCW21AAJ Battery

Helium II also exhibits a creeping effect. When a surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. Sony VAIO VPCW21AKJ Battery

It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin. As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine liquid helium. Sony VAIO VPCW21AVJ Battery

Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the van der Waals force. These waves are known as third sound.Sony VAIO VPCY115FGS Battery

Isotopes

There are eight known isotopes of helium, but only helium-3 and helium-4 are stable. In the Earth's atmosphere, there is one 3He atom for every million 4He atoms. Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. Sony VAIO VPCY115FX/BI Battery

The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis.Sony VAIO VPCY115FXBI Battery

Helium-3 is present on Earth only in trace amounts; most of it since Earth's formation, though some falls to Earth trapped in cosmic dust. Trace amounts are also produced by the beta decay of tritium. Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle.Sony VAIO VPCY118EC Battery

3He is much more abundant in stars, as a product of nuclear fusion. Thus in theinterstellar medium, the proportion of 3He to 4He is around 100 times higher than on Earth. Extraplanetary material, such as lunar and asteroid regolith, have trace amounts of helium-3 from being bombarded by solar winds. Sony VAIO VPCY118GX/BI Battery

The Moon's surface contains helium-3 at concentrations on the order of 0.01 ppm, a lot higher than the ca. 5 ppt found in the Earth's atmosphere. A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the moon, mine lunar regolith and use the helium-3 for fusion.Sony VAIO VPCY119FJ/S Battery

Liquid helium-4 can be cooled to about 1 kelvin using evaporative cooling in a 1-K pot. Similar cooling of helium-3, which has a lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator. Equal mixtures of liquid 3He and 4He below 0.8 K separate into two immiscible phases due to their dissimilarity Sony VAIO VPCY11AFJ Battery

(they follow different quantum statistics: helium-4 atoms are bosons while helium-3 atoms are fermions).Dilution refrigerators use this immiscibility to achieve temperatures of a few millikelvins.

It is possible to produce exotic helium isotopes, which rapidly decay into other substances. Sony VAIO VPCY11AGJ Battery

The shortest-lived heavy helium isotope is helium-5 with a half-life of7.6×10?22 s. Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 also emits a beta particle as well as a gamma ray. Helium-7 and helium-8 are created in certain nuclear reactions.Sony VAIO VPCY11AHJ Battery

Helium-6 and helium-8 are known to exhibit a nuclear halo. Helium-2 (two protons, no neutrons) is aradioisotope that decays by proton emission into protium (hydrogen), with a half-life of 3×10?27 s.

Compounds

Helium has a valence of zero and is chemically unreactive under all normal conditions.Sony VAIO VPCY11AVJ Battery

It is an electrical insulator unless ionized. As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential. Helium can form unstable compounds, known as excimers, with tungsten, iodine, fluorine, sulfur and phosphorus when it is subjected to an electric glow discharge, to electron bombardment, or else is a plasma for another reason. Sony VAIO VPCY11M1E/S Battery

The molecular compounds HeNe, HgHe10, and WHe2, and the molecular ions He+2, He2+2, HeH+, and HeD+ have been created this way. This technique has also allowed the production of the neutral molecule He2, which has a large number of band systems, and HgHe, which is apparently held together only by polarization forces.Sony VAIO VPCY11S1E Battery

Theoretically, other true compounds may also be possible, such as helium fluorohydride (HHeF) which would be analogous to HArF, discovered in 2000. Calculations show that two new compounds containing a helium-oxygen bond could be stable. Two new molecular species, predicted using theory,Sony VAIO VPCY11V9E/S Battery

CsFHeO and N(CH3)4FHeO, are derivatives of a metastable [F– HeO] anion first theorized in 2005 by a group from Taiwan. If confirmed by experiment, such compounds will end helium's chemical inertness, and the only remaining inert element will be neon.Sony VAIO VPCY218EC/BI Battery

Helium has been put inside the hollow carbon cage molecules (the fullerenes) by heating under high pressure. The endohedral fullerene molecules formed are stable up to high temperatures. When chemical derivatives of these fullerenes are formed, the helium stays inside.Sony VAIO VPCY218EC/G Battery

If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy. Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds.Sony VAIO VPCY218EC/L Battery

Natural abundance

Helium is the second most abundant element in the known Universe (after hydrogen), constituting 23% of its baryonic mass. The vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang. Sony VAIO VPCY218EC/P Battery

As such, measurements of its abundance contribute to cosmological models. In stars, it is formed by the nuclear fusion of hydrogen in proton-proton chain reactions and the CNO cycle, part of stellar nucleosynthesis.

In the Earth's atmosphere, the concentration of helium by volume is only 5.2 parts per million.Sony VAIO VPCY21S1E/L Battery

The concentration is low and fairly constant despite the continuous production of new helium because most helium in the Earth's atmosphere escapes into space by several processes. In the Earth's heterosphere, a part of the upper atmosphere, helium and other lighter gases are the most abundant elements.Sony VAIO VPCY21S1E/P Battery

Nearly all helium on Earth is a result of radioactive decay, and thus an Earthly helium balloon is essentially a bag of retired alpha particles. Helium is found in large amounts in minerals of uranium and thorium, including cleveite, pitchblende, carnotite and monazite, because they emit alpha particles (helium nuclei, He2+) Sony VAIO VPCY21S1E/SI Battery

to which electrons immediately combine as soon as the particle is stopped by the rock. In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere.In the Earth's crust, the concentration of helium is 8 parts per billion. In seawater, the concentration is only 4 parts per trillion. Sony VAIO VPCZ110 Battery

There are also small amounts in mineral springs, volcanic gas, and meteoric iron. Because helium is trapped in the subsurface under conditions that also trap natural gas, the greatest natural concentrations of helium on the planet are found in natural gas, from which most commercial helium is extracted. Sony VAIO VPCZ110GB/BI Battery

The concentration varies in a broad range from a few ppm up to over 7% in a small gas field in San Juan County, New Mexico.

Modern extraction and distribution

For large-scale use, helium is extracted by fractional distillation from natural gas, which contains up to 7% helium.Sony VAIO VPCZ112GD/S Battery

Since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly nitrogen and methane). The resulting crude helium gas is purified by successive exposures to lowering temperatures, in which almost all of the remaining nitrogen and other gases are precipitated out of the gaseous mixture.Sony VAIO VPCZ112GX/S Battery

Activated charcoal is used as a final purification step, usually resulting in 99.995% pure Grade-A helium. The principal impurity in Grade-A helium is neon. In a final production step, most of the helium that is produced is liquefied via a cryogenic process. Sony VAIO VPCZ114GX/S Battery

This is necessary for applications requiring liquid helium and also allows helium suppliers to reduce the cost of long distance transportation, as the largest liquid helium containers have more than five times the capacity of the largest gaseous helium tube trailers.Sony VAIO VPCZ115 Battery

In 2008, approximately 169 million standard cubic meters (SCM) of helium were extracted from natural gas or withdrawn from helium reserves with approximately 78% from the United States, 10% from Algeria, and most of the remainder from Russia, Poland and Qatar.Sony VAIO VPCZ115FC/B Battery

In the United States, most helium is extracted from natural gas of the Hugoton and nearby gas fields in Kansas, Oklahoma, and Texas.Much of this gas was once sent by pipeline to the National Helium Reserve, but since 2005 this reserve is presently being depleted and sold off.Sony VAIO VPCZ115FC/S Battery

Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium. In 1996, the U.S. hadproven helium reserves, in such gas well complexes, of about 147 billion standard cubic feet (4.2 billion SCM).Sony VAIO VPCZ116 Battery

At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this is enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers. Sony VAIO VPCZ116GX/S Battery

It is estimated that the resource base for yet-unproven helium in natural gas in the U.S. is 31–53 trillion SCM, about 1000 times the proven reserves.

Helium must be extracted from natural gas because it is present in air at only a fraction of that of neon, yet the demand for it is far higher. Sony VAIO VPCZ117 Battery

It is estimated that if all neon production were retooled to save helium, that 0.1% of the world's helium demands would be satisfied. Similarly, only 1% of the world's helium demands could be satisfied by re-tooling all air distillation plants.Helium can be synthesized by bombardment of lithium or boron with high-velocity protons, but economically, this is a completely non-viable method of production. Sony VAIO VPCZ117FC/B Battery

Helium is commercially available in either liquid or gaseous form. As a liquid, it can be supplied in small containers called Dewars which hold up to 1,000 liters of helium, or in large ISO containers which have nominal capacities as large as 42 m3 (around 11,000 U.S. gallons). Sony VAIO VPCZ118 Battery

In gaseous form, small quantities of helium are supplied in high pressure cylinders holding up to 8 m3 (approx. 282 standard cubic feet), while large quantities of high pressure gas are supplied in tube trailers which have capacities of up to 4,860 m3 (approx. 172,000 standard cubic feet).Sony VAIO VPCZ118GC/B Battery

Conservation advocates

According to helium conservationists like Robert Coleman Richardson, the free market price of helium has contributed to "wasteful" usage (e.g. for helium balloons). Prices in the 2000s have been lowered by U.S. Congress' decision to sell off the country's large helium stockpile by 2015.Sony VAIO VPCZ118GX/S Battery

According to Richardson, the current price needs to be multiplied by 20 to eliminate the excessive wasting of helium.

Applications

Helium is used for many purposes that require some of its unique properties, such as its low boiling point, low density, low solubility, high thermal conductivity, or inertness. Sony VAIO VPCZ119 Battery

Of the 2008 world helium total production of about 32 million kg (193 million standard cubic meters) helium per year, the largest use (about 22% of the total in 2008) is in cryogenic applications, most of which involves cooling the superconducting magnets in medical MRI scanners.Sony VAIO VPCZ119FJ/S Battery

Other major uses (totalling to about 78% of use in 1996) were pressurizing and purging systems, maintenance of controlled atmospheres, and welding. Other uses by category were relatively minor fractions. Sony VAIO VPCZ119GC/X Battery

Controlled atmospheres

Helium is used as a protective gas in growing silicon and germanium crystals, intitanium and zirconium production, and in gas chromatography, because it is inert. Because of its inertness, thermally and calorically perfect nature, highspeed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels and impulse facilities. Sony VAIO VPCZ119L Battery

Gas tungsten arc welding

Helium is used as a shielding gas in arc welding processes on materials that at welding temperatures are contaminated and weakened by air or nitrogen. A number of inert shelding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminum or copper.Sony VAIO VPCZ119R/B Battery

Industrial leak detection

One industrial application for helium is leak detection. Because helium diffuses through solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers.Sony VAIO VPCZ119R/S Battery

The tested object is placed in a chamber, which is then evacuated and filled with helium. The helium that escapes through the leaks is detected by a sensitive device (helium mass spectrometer), even at the leak rates as small as 10?9 mbar·L/s (10?10 Pa·m3/s). The measurement procedure is normally automatic and is called helium integral test. Sony VAIO VPCZ11AFJ Battery

A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand-held device.

Helium leaks through cracks should not be confused with gas permeation through a bulk material. While helium has documented permeation constants (thus a calculable permeation rate) through glasses, ceramics, and synthetic materials, inert gases such as helium will not permeate most bulk metals. Sony VAIO VPCZ11AGJ Battery

Flight

Because it is lighter than air, airships and balloons are inflated with helium for lift. While hydrogen gas is approximately 7% more buoyant, helium has the advantage of being non-flammable (in addition to being fire retardant). While balloons are perhaps the most well-known use of helium, they are a minor part of all helium use.Sony VAIO VPCZ11AVJ Battery

Another minor use is in rocketry, where helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. Sony VAIO VPCZ11CGX/X Battery

For example, the Saturn V booster used in the Apollo program needed about 370,000 m3 (13 million cubic feet) of helium to launch.

Minor commercial and recreational uses

For its low solubility in nervous tissue, helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis.Sony VAIO VPCZ11DGX/SJ Battery

At depths below 150 metres (490 ft) small amounts of hydrogen are added to a helium-oxygen mixture to counter the effects of high pressure nervous syndrome.[95] At these depths the low density of helium is found to considerably reduce the effort of breathing.Sony VAIO VPCZ11FHX/XQ Battery

Helium-neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.Sony VAIO VPCZ11V9R/B Battery

For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.Sony VAIO VPCZ11X9E/B Battery

Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number. The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.Sony VAIO VPCZ11Z9E/B Battery

Scientific uses

The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to its extremely low index of refraction.[5] This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.Sony VAIO VPCZ125GX/S Battery

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.

Helium at low temperatures is used in cryogenics, and in certain crygenics applications. Sony VAIO VPCZ127FC Battery

As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERNuses 96 metric tons of liquid helium to maintain the temperature at 1.9 kelvin.Sony VAIO VPCZ128GC Battery

Safety

Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood. If enough helium is inhaled that oxygen needed for normal respiration is replaced, asphyxia is possible. Sony VAIO VPCZ12M9E/B Battery

The safety issues for cryogenic helium are similar to those of liquid nitrogen; its extremely low temperatures can result in cold burns and the liquid-to-gas expansion ratio can cause explosions if no pressure-relief devices are installed.

Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature.Sony VAIO VPCZ13M9E/B Battery

Biological effects

The speed of sound in helium is nearly three times the speed of sound in air. Because the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled there is a corresponding increase in the pitches of the resonant frequencies of the vocal tract.Sony VAIO VPCZ13V9E/X Battery

This causes a reedy, duck-like vocal quality. (The opposite effect, lowering frequencies, can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon.)

Inhaling helium can be dangerous if done to excess, since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration.Sony VAIO VPCZ13Z9E/X Battery

Breathing pure helium continuously causes death by asphyxiation within minutes. Inhaling helium directly from pressurized cylinders is extremely dangerous, as the high flow rate can result in barotrauma, fatally rupturing lung tissue.However, death caused by helium is rare, with only two fatalities reported between 2000 and 2004 in the United States.Sony VAIO VPCZZZHJ Battery

However, there were two cases in 2010, one in the USA in January and another in Northern Ireland in November.

At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high-pressure nervous syndrome, a sort of reverse-anesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.Sony VAIO VPZ117 Battery

A fusion rocket is a theoretical design for a rocket driven by fusion power which could provide efficient and long-term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power technology beyond current capabilities, and the construction of rockets much larger and more complex than any current spacecraft.Sony VAIO VPZ118 Battery

A smaller and lighter fusion reactor might be possible in the future when more sophisticated methods have been devised to control magnetic confinement and prevent plasma instabilities.

For space flight, the main advantage of fusion would be the very high specific impulse, the main disadvantage the (probable) large mass of the reactor. Sony VAIO VPZ119 Battery

In addition, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. The surest way of building a fusion rocket with current technology is to use hydrogen bombs as proposed in Project Orion, but such a spacecraft would also be massive.Sony VPCM11M1E/B Battery

Electricity generation vs. direct thrust

Many spacecraft propulsion methods such as ion thrusters require an input of electric power to run but are highly efficient. In some cases their maximum thrust is limited by the amount of power that can be generated (for example, a mass driver). Sony VPCM11M1E/W Battery

An electric generator that ran on fusion power could be installed purely to drive such a ship. One disadvantage is that conventional electricity production requires a low-temperature energy sink, which is difficult (i.e. heavy) in a spacecraft.Direct conversion of the kinetic energy of the fusion products into electricity is in principle possible and would mitigate this problem.Sony VPCM12M1E/L Battery

An attractive possibility is to simply direct the exhaust of fusion product out the back of the rocket to provide thrust without the intermediate production of electricity. This would be easier with some confinement schemes (e.g. magnetic mirrors) than with others (e.g. tokamaks). It is also more attractive for "advanced fuels" (see aneutronic fusion). Sony VPCM12M1E/P Battery

Helium-3 propulsion is a proposed method of spacecraft propulsion that uses the fusion of helium-3 atoms as a power source. Helium-3, an isotope of helium with two protons and one neutron, could be fused with deuterium in a reactor. The resulting energy release could be used to expel propellant out the back of the spacecraft. Sony VPCM12M1E/W Battery

Helium-3 is proposed as a power source for spacecraft mainly because of its abundance on the moon. Currently, scientists estimate that there are 1 million tons of helium-3 present on the moon, mainly due to solar wind colliding with the moon's surface and depositing it, among other elements, into the soil.Sony VPCM13M1E/L Battery

Only 20% of the power produced by the D-T reaction could be used this way; the other 80% is released in the form of neutrons which, because they cannot be directed by magnetic fields or solid walls, would be very difficult to use for thrust. Helium-3 is also produced via beta decay of tritium, which in turn can be produced from deuterium, lithium, or boron.Sony VPCM13M1E/P Battery

Even if a self-sustaining fusion reaction cannot be produced, it might be possible to use fusion to boost the efficiency of another propulsion system, such as aVASIMR engine.

Confinement concept

To sustain a fusion reaction, the plasma must be confined. The most widely studied configuration for terrestrial fusion is the tokamak, a form of magnetic confinement fusion.Sony VPCM13M1E/W Battery

Currently tokamaks weigh a great deal, so the thrust to weight ratio would seem unacceptable. NASA's Glenn Research Center has proposed a small aspect ratio spherical torus reactor for its "Discovery II" conceptual vehicle design. "Discovery II" could deliver a manned 172 000-kilogram payload to Jupiter in 118 days Sony VAIO VGN-Z11MN/B Battery

(or 212 days to Saturn) using 861 metric tons of hydrogen propellant, plus 11 metric tons of Helium-3-Deuterium (D-He3) fusion fuel.The hydrogen is heated by the fusion plasma debris to increase thrust, at a cost of reduced exhaust velocity (348–463 km/s) and hence increased propellant mass.Sony VAIO VGN-Z11VN/X Battery

The main alternative to magnetic confinement is inertial confinement fusion, such as that proposed by Project Daedalus. A small pellet of fusion fuel (with a diameter of a couple of millimeters) would be ignited by anelectron beam or a laser. To produce direct thrust, a magnetic field would form the pusher plate. Sony VAIO VGN-Z11WN/B Battery

In principle, the Helium-3 - Deuterium reaction or an aneutronic fusion reaction could be used to maximize the energy in charged particles and to minimize radiation, but it is highly questionable whether it is technically feasible to use these reactions. Both the detailed design studies in the 1970s, the Orion drive and Project Daedalus, used inertial confinement. Sony VAIO VGN-Z11XN/B Battery

In the 1980s, Lawrence Livermore National Laboratory and NASA studied an ICF-powered "Vehicle for Interplanetary Transport Applications" (VISTA). The conical VISTA spacecraft could deliver a 100-tonne payload to Mars orbit and return to Earth in 130 days, or to Jupiter orbit and back in 403 days. 41 tonnes of deuterium/tritium (D-T) fusion fuel would be required, plus 4124 tonnes of hydrogen expellant . The exhaust velocity would be 157km/s.Sony VAIO VGN-Z15 Battery

Magnetized target fusion (MTF) is a relatively new approach that combines the best features of the more widely studied magnetic confinement fusion (i.e. good energy confinement) and inertial confinement fusion (i.e. efficient compression heating and wall free containment of the fusing plasma) approaches.Sony VAIO VGN-Z15N Battery

Like the magnetic approach, the fusion fuel is confined at low density by magnetic fields while it is heated into a plasma, but like the inertial confinement approach, fusion is initiated by rapidly squeezing the target to dramatically increase fuel density, and thus temperature. MTF uses "plasma guns" Sony VAIO VGN-Z17 Battery

(i.e. electromagnetic acceleration techniques) instead of powerful lasers, leading to low cost and low weight compact reactors. The NASA/MSFC Human Outer Planets Exploration (HOPE) group has investigated a manned MTF propulsion spacecraft capable of delivering a 163 933-kilogram payload to Jupiter's moon Callisto using 106-165 metric tons of propellant (hydrogen plus either D-T or D-He3 fusion fuel) in 249–330 days.Sony VAIO VGN-Z17N Battery

This design would thus be considerably smaller and more fuel efficient due to its higher exhaust velocity (Isp=700 km/s) than the previously mentioned "Discovery II", "VISTA" concepts.

A popular confinement concept for fusion rockets is inertial electrostatic confinement, such as in the Farnsworth-Hirsch Fusor or the Polywell variation being researched by the Energy-Matter Conversion Corporation. Sony VAIO VGN-Z19 Battery

Dr. Robert Bussard published a series of technical articles discussing its application to spaceflight throughout the 1990s. His work was popularised by an article in the Analog Science Fiction and Fact publication, where Tom Ligon (who has also written severalscience fiction stories) described how the fusor would make for a highly effective fusion rocket.Sony VAIO VGN-Z19N Battery

It was also featured in this role in the science fiction novel The Wreck of the River of Stars, by Michael Flynn. However, there are theoretical difficulties with the concept, related to energy losses via bremsstrahlung radiation and maintaining a highly non-Maxwellian ion energy distribution.Sony VAIO VGN-Z21MN/B Battery

A still more speculative concept is antimatter catalyzed nuclear pulse propulsion, which would use tiny quantities of antimatter to catalyze a fission and fusion reaction, allowing much smaller fusion explosions to be created.Sony VAIO VGN-Z21VN/X Battery

Abiogenic petroleum origin is a largely abandoned hypothesis that was proposed as an alternative to theory of biological petroleum origin. It was relatively popular in the past, but it went largely forgotten at the end of the 20th century after it failed to predict the location of new wells.Sony VAIO VGN-Z21WN/B Battery

The abiogenic hypothesis argues that petroleum was formed from deep carbon deposits, perhaps dating to the formation of the Earth. Supporters of the abiogenic hypothesis suggest that a great deal more petroleum exists on Earth than commonly thought, and that petroleum may originate from carbon-bearing fluids that migrate upward from the mantle.Sony VAIO VGN-Z21XN Battery

The presence of methane on Saturn's moon Titan and in the atmospheres of Jupiter, Saturn, Uranus and Neptune is cited as evidence of the formation of hydrocarbons without biology.

The biogenic theory for petroleum was first proposed by Georg Agricola in the 16th century and various abiogenic hypotheses were proposed in the 19th century,Sony VAIO VGN-Z21ZN/X Battery

most notably by Alexander von Humboldt, the Russian chemist Dmitri Mendeleev and the French chemist Marcellin Berthelot. Abiogenic hypotheses were revived in the last half of the 20th century by Russian and Ukrainian scientists, who had little influence outside the Soviet Union because most of their research was published in their native languages. Sony VAIO VGN-Z25 Battery

The theory was re-defined and made popular in the West by Thomas Gold, who published all his research in English.

Although the abiogenic hypothesis was accepted by many geologists in the former Soviet Union, it allegedly fell out of favor because it never made any useful prediction for the discovery of oil deposits.Sony VAIO VGN-Z25/B Battery

Most geologists now consider the abiogenic formation of petroleum scientifically unsupported. The abiogenic origin of petroleum has also recently been reviewed in detail by Glasby, who raises a number of objections, including that there is no direct evidence to date of abiogenicpetroleum (liquid crude oil and long-chain hydrocarbon compounds).Sony VAIO VGN-Z25TN/B Battery

It has been recently discovered that thermophilic bacteria, in the sea bottom and in cooling magma, produce methane and hydrocarbon gases, but studies indicate they are not produced in commercially significant quantities (i.e. in extracted hydrocarbon gases, the median abiogenic hydrocarbon content is 0.02%).Sony VAIO VGN-Z26TN/B Battery

The abiogenic theory for the origin of petroleum is usually traced to the early part of the 19th century. The hypothesis was developed well before the field oforganic chemistry, much less that of biochemistry, was established so the chemical nature of the petroleum was not known. Sony VAIO VGN-Z27 Battery

Absent intellectual framework of organic and biological chemistry, abiologic theories were inevitable. In the early 19th century, Phlogiston theory was the dominant model for explaining chemical phenomena. Furthermore, the formal study of paleontology had only started in the early 19th century. Sony VAIO VGN-Z27/B Battery

It is within this scientifically primitive but changing environment that theories on the origin of petroleum originated.

Alexander von Humboldt was the first to propose an inorganic abiogenic hypothesis for petroleum formation after he observed petroleum springs in the Bay of Cumaux (Cumaná) on the northeast coast of Venezuela.Sony VAIO VGN-Z27TN/X Battery

In 1804 he is quoted as saying, "petroleum is the product of a distillation from great depth and issues from the primitive rocks beneath which the forces of all volcanic action lie." Abraham Gottlob Werner and the proponents of neptunism in the 18th century believed basalticsills to be solidified oils or bitumen. Sony VAIO VGN-Z29N Battery

While these notions have been proven unfounded, the basic idea that petroleum is associated with magmatism persisted. Other prominent proponents of what would become the abiogenic hypothesis included Mendeleev and Berthelot.

Russian geologist Nikolai Alexandrovitch Kudryavtsev proposed the modern abiotic hypothesis of petroleum in 1951.Sony VAIO VGN-Z29N/X Battery

On the basis of his analysis of the Athabasca Oil Sands in Alberta, Canada, he concluded that no "source rocks" could form the enormous volume of hydrocarbons, and that therefore the most plausible explanation is abiotic deep petroleum. However, humic coals have since been proposed for the source rocks.Sony VAIO VGN-Z31MN/B Battery

Kudryavtsev's work was continued by Petr N. Kropotkin, Vladimir B. Porfir'ev, Emmanuil B. Chekaliuk, Vladilen A. Krayushkin, Georgi E. Boyko, Georgi I. Voitov, Grygori N. Dolenko, Iona V. Greenberg, Nikolai S. Beskrovny, and Victor F. Linetsky.

Astronomer Thomas Gold was the most prominent proponent of the abiogenic hypothesis in the West until his death in 2004.Sony VAIO VGN-Z31VN/X Battery

Currently, Jack Kenney of Gas Resources Corporation is a prominent proponent in the West.

Little research is directed on establishing abiogenic petroleum or methane, although the Carnegie Institution for Science have found that ethane and heavier hydrocarbons can be synthesized under conditions of the upper mantle. Sony VAIO VGN-Z31WN/B Battery

Research mostly related to astrobiology and the deep microbial biosphere and serpentinite reactions, however, continue to provide insight into the contribution of abiogenic hydrocarbons into petroleum accumulations.

• rock porosity and migration pathways for abiogenic petroleum Sony VAIO VGN-Z31ZN/X Battery
• ocean floor hydrothermal vents as in the Lost City hydrothermal field;
• Mud volcanoes and the volatile contents of deep pelagic oozes and deep formation brines
• mantle peridotite serpentinization reactions and other natural Fischer-Tropsch analogs
• Primordial hydrocarbons in meteorites, comets, asteroids and the solid bodies of the solar system
  • Primordial or ancient sources of hydrocarbons or carbon in Earth Sony VAIO VGN-Z35 Battery
    • Primordial hydrocarbons formed from hydrolysis of metal carbides of the iron peak of cosmic elemental abundance (Cr, Fe, Ni, V, Mn, Co)
• isotopic studies of groundwater reservoirs, sedimentary cements, formation gases and the composition of the noble gases and nitrogen in many oil fields
• the geochemistry of petroleum and the presence of trace metals related to Earth's mantle (Ni, V, Cd, As, Pb, Zn, Hg and others)Sony VAIO VGN-Z35/B Battery

Similarly, research into the deep microbial hypothesis of hydrocarbon generation is advancing as part of the attempt to investigate the concept of panspermia andastrobiology, specifically using deep microbial life as an analog for life on Mars. Research applicable to deep microbial petroleum theories includes Sony VAIO VGN-Z35TN/B Battery

• Research into how to sample deep reservoirs and rocks without contamination
• Sampling deep rocks and measuring chemistry and biological activity
• Possible energy sources and metabolic pathways which may be used in a deep biosphere
• Investigations into the reworking primordial hydrocarbons by bacteria and their effects on carbon isotope fractionation Sony VAIO VGN-Z36GD Battery

A 2006 review article by Glasby presented arguments against the abiogenic origin of petroleum on a number of counts.

Foundations of the hypotheses

Within the mantle, carbon may exist as hydrocarbons, chiefly methane and as elemental carbon, carbon dioxide and carbonates.Sony VAIO VGN-Z36GD/B Battery

The abiotic hypothesis is that the full suite of hydrocarbons found in petroleum can be generated in the mantle by abiogenic processes, and these hydrocarbons can migrate out of the mantle into the crust until they escape to the surface or are trapped by impermeable strata, forming petroleum reservoirs. Sony VAIO VGN-Z36GD/J Battery

Abiogenic theories reject the supposition that certain molecules found within petroleum, known as biomarkers, are indicative of the biological origin of petroleum. They contend that these molecules mostly come from microbes feeding on petroleum in its upward migration through the crust, that some of them are found in meteorites, which have presumably never contacted living material, and that some can be generated abiogenically by plausible reactions in petroleum.

Most petroleum geologists prefer theories of oil formation, which holds that oil originated in shallow seas as vast quantities of marine plankton or plant materials died and sank into the mud. Under the resulting anaerobic conditions organic compounds remained in a reduced state where anaerobic bacteria converted the lipids(fats, oils and waxes) into a waxy substance called kerogen.Sony VAIO VGN-Z36TD/B Battery

As the source rock was buried deeper, overburden pressure raised temperatures into the oil window, between 80 and 180 °C. Most of the organic compounds degraded into the straight-chain hydrocarbons that comprise most of petroleum. This process is called the generation kitchen.Sony VAIO VGN-Z36TD/J Battery

Once crude oil formed, it became very fluid and migrated upward through the rock strata. This process is called oil expulsion. Eventually it was either trapped in an oil reservoir or oil escaped to the surface and was biodegraded by soil bacteria.Sony VAIO VGN-Z37D Battery

Oil buried deeper entered the "gas window" of more than 160 °C and was converted into natural gas by thermal cracking. Thus, theory predicts that no oil will be found below a certain depth, only unassociated gas. At greater depths, even natural gas would be pyrolyzed.Sony VAIO VGN-Z37D/B Battery

Primordial deposits

Thomas Gold's work was focused on hydrocarbon deposits of primordial origin. Meteorites are believed to represent the major composition of material from which the Earth was formed. Some meteorites, such as carbonaceous chondrites, contain carbonaceous material. Sony VAIO VGN-Z37GD Battery

If a large amount of this material is still within the Earth, it could have been leaking upward for billions of years. The thermodynamic conditions within the mantle would allow many hydrocarbon molecules to be at equilibrium under high pressure and high temperature. Sony VAIO VGN-Z37GD/X Battery

Although molecules in these conditions may disassociate, resulting fragments would be reformed due to the pressure. An average equilibrium of various molecules would exist depending upon conditions and the carbon-hydrogen ratio of the material.Sony VAIO VGN-Z39D Battery

Creation within the mantle

Russian researchers concluded that hydrocarbon mixes would be created within the mantle. Experiments under high temperatures and pressures produced many hydrocarbons, including n-alkanes through C10H22, from iron oxide, calcium carbonate, and water.Sony VAIO VGN-Z39D/X Battery

Because such materials are in the mantle and in subducted crust, there is no requirement that all hydrocarbons be produced from primordial deposits.

Hydrogen generation

Hydrogen gas and water have been found more than 6 kilometers deep in the upper crust, including in the Siljan Ring boreholes and the Kola Superdeep Borehole. Sony VAIO VGN-Z41MD/B Battery

Data from the western United States suggests that aquifers from near the surface may extend to depths of 10 to 20 km. Hydrogen gas can be created by water reacting withsilicates, quartz and feldspar, in temperatures in the 25° to 270°C range. These minerals are common in crustal rocks such as granite. Sony VAIO VGN-Z41WD/B Battery

Hydrogen may react with dissolved carbon compounds in water to form methane and higher carbon compounds.

One reaction not involving silicates which can create hydrogen is:

Ferrous oxide + Water ? Magnetite + hydrogen

The above reaction operates best at low pressures. At pressures greater than 5 GPa almost no hydrogen is created.Sony VAIO VGN-Z45GD/B Battery

Serpentinite mechanism

One proposed mechanism by which abiogenic petroleum is formed was first proposed by the Ukrainian scientist, Prof. Emmanuil B. Chekaliuk in 1967. He proposed that petroleum could be formed at high temperatures and pressures from inorganic carbon in the form of carbon dioxide, hydrogen and/or methane.Sony VAIO VGN-Z45TD/B Battery

This mechanism is supported by several lines of evidence which are accepted by modern scientific literature. This involves synthesis of oil within the crust via catalysis by chemically reductive rocks. A proposed mechanism for the formation of inorganic hydrocarbons is via natural analogs of the Fischer-Tropsch processknown as the serpentinite mechanism or the serpentinite process.Sony VAIO VGN-Z46GD/B Battery

Serpentinites are ideal rocks to host this process as they are formed from peridotites and dunites, rocks which contain greater than 80% olivine and usually a percentage of Fe-Ti spinel minerals. Most olivines also contain high nickel concentrations (up to several percent) and may also contain chromite or chromium as a contaminant in olivine, providing the needed transition metals.Sony VAIO VGN-Z46GD/U Battery

However, serpentinite synthesis and spinel cracking reactions require hydrothermal alteration of pristine peridotite-dunite, which is a finite process intrinsically related to metamorphism, and further, requires significant addition of water. Serpentinite is unstable at mantle temperatures and is readily dehydrated to granulite,amphibolite, talc–schist and even eclogite. Sony VAIO VGN-Z46MD/B Battery

This suggests that methanogenesis in the presence of serpentinites is restricted in space and time to mid-ocean ridges and upper levels of subduction zones. However, water has been found as deep as 12 km,so water-based reactions are dependent upon the local conditions. Oil being created by this process in intracratonic regions is limited by the materials and temperature.Sony VAIO VGN-Z46SD/B Battery

Serpentinite synthesis

A chemical basis for the abiotic petroleum process is the serpentinization of peridotite, beginning with methanogenesis via hydrolysis of olivine into serpentine in the presence of carbon dioxide. Sony VAIO VGN-Z46TD/B Battery

Olivine, composed of Forsterite and Fayalite metamorphoses into serpentine, magnetite and silica by the following reactions, with silica from fayalite decomposition (reaction 1a) feeding into the forsterite reaction (1b).

Evidence of abiogenic mechanisms

• Calculations by J.F. Kenney using scaled particle theory for a simplified perturbed hard-chain, Sony VAIO VGN-Z46TD/R Battery
• (a statistical mechanical model) predict that methane compressed to 30 or 40 kbar at 1000 °C (conditions in the mantle) is relatively unstable in relation to higher hydrocarbons. However, these calculations do not include methane pyrolisis yielding amorphous carbon and hydrogen, which is recognized as the prevalent reaction at high temperatures.Sony VAIO VGN-Z47GD/X Battery
• Experiments in diamond anvil high pressure cells have resulted in partial conversion of methane and inorganic carbonates into light hydrocarbons.

Biotic (microbial) hydrocarbons

The "deep biotic petroleum hypothesis", similar to the abiogenic petroleum origin hypothesis, holds that not all petroleum deposits within the Earth's rocks can be explained purely according to the orthodox view of petroleum geology. Sony VAIO VGN-Z48GD/X Battery

Thomas Gold used the term the deep hot biosphere to describe the microbes which live underground.

This hypothesis is different from biogenic oil in that the role of deep-dwelling microbes is a biological source for oil which is not of a sedimentary origin and is not sourced from surface carbon. Sony VAIO VGN-Z48TD/X Battery

Deep microbial life is only a contaminant of primordial hydrocarbons. Parts of microbes yield molecules as biomarkers.

Deep biotic oil is considered to be formed as a byproduct of the life cycle of deep microbes. Shallow biotic oil is considered to be formed as a byproduct of the life cycles of shallow microbes.Sony VAIO VGN-Z51WG/B Battery

Microbial biomarkers

Thomas Gold, in a 1999 book, cited the discovery of thermophile bacteria in the Earth's crust as new support for the postulate that these bacteria could explain the existence of certain biomarkers in extracted petroleum. Thorough rebuttal of biogenic origins based on biomarkers has been offered by Kenney, et al. (2001).Sony VAIO VGN-Z51XG/B Battery

Isotopic evidence

Methane is ubiquitous in crustal fluid and gas.Research continues to attempt to characterise crustal sources of methane as biogenic or abiogenic using carbon isotope fractionation of observed gases (Lollar & Sherwood 2006). Sony VAIO VGN-Z530N/B Battery

There are few clear examples of abiogenic methane-ethane-butane, as the same processes favor enrichment of light isotopes in all chemical reactions, whether organic or inorganic. ?13C of methane overlaps that of inorganic carbonate and graphite in the crust, which are heavily depleted in 12C, and attain this by isotopic fractionation during metamorphic reactions.Sony VAIO VGN-Z540EBB Battery

One argument for abiogenic oil cites the high carbon depletion of methane as stemming from the observed carbon isotope depletion with depth in the crust. However, diamonds, which are definitively of mantle origin, are not as depleted as methane, which implies that methane carbon isotope fractionation is not controlled by mantle values.Sony VAIO VGN-Z540NLB Battery

Commercially extractable concentrations of helium (greater than 0.3%) are present in natural gas from the Panhandle-Hugoton fields in the USA, as well as from some Algerian and Russian gas fields.

Helium trapped within most petroleum occurrences, such as the occurrence in Texas, is of a distinctly crustal character with an Raratio of less than 0.0001 that of the atmosphere.Sony VAIO VGN-Z540NMB Battery

The Chimaera gas seep, near Antalya (SW Turkey), new and thorough molecular and isotopic analyses including methane (~87% v/v; D13C1 from -7.9 to -12.3 ‰; D13D1 from -119 to -124 ‰), light alkanes (C2+C3+C4+C5 = 0.5%; C6+: 0.07%; D13C2 from -24.2 to -26.5 ‰; D13C3 from -25.5 to -27 ‰), hydrogen (7.5 to 11 %), carbon dioxide (0.01-0.07%; D13CCO2: -15 ‰), Sony VAIO VGN-Z550N/B Battery

helium (~80 ppmv; R/Ra: 0.41) and nitrogen (2-4.9%; D15N from -2 to -2.8 ‰) converge to indicate that the seep releases a mixture of organic thermogenic gas, related to mature Type III kerogen occurring in Paleozoic and Mesozoic organic rich sedimentary rocks, and abiogenic gas produced by low temperature serpentinization in the Tekirova ophiolitic unit.Sony VAIO VGN-Z55F Battery

Biomarker chemicals

Certain chemicals found in naturally occurring petroleum contain chemical and structural similarities to compounds found within many living organisms. These includeterpenoids, terpenes, pristane, phytane, cholestane, chlorins and porphyrins, which are large, chelating molecules in the same family as heme and chlorophyll.Sony VAIO VGN-Z55TG/B Battery

Materials which suggest certain biological processes include tetracyclic diterpane and oleanane.

The presence of these chemicals in crude oil is assumed to be as a result of the inclusion of biological material in the oil.Sony VAIO VGN-Z56GG/B Battery

This is predicated upon the theory that these chemicals are released by kerogen during the production of hydrocarbon oils, as these are chemicals highly resistant to degradation and plausible chemical paths have been studied. Abiotic defenders state that biomarkers get into oil during its way up as it gets in touch with ancient fossils.Sony VAIO VGN-Z56GG/E Battery

However a more plausible explanation is that biomarkers are traces of biological molecules from bacteria (archaea) that feed on primordial hydrocarbons and die in that environment. For example, hopanoids are just parts of the bacterial cell wall present in oil as contaminant.Sony VAIO VGN-Z56GGX Battery

Trace metals

Nickel (Ni), vanadium (V), lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg) and others metals frequently occur in oils. Some heavy crude oils, such as Venezuelan heavy crude have up to 45% vanadium pentoxide content in their ash, high enough that it is a commercial source for vanadium.Sony VAIO VGN-Z56TG/B Battery

Abiotic supporters argue that these metals are common in Earth's mantle, but relatively high contents of nickel, vanadium, lead and arsenic can be usually found in almost all marine sediments.

Analysis of 22 trace elements in oils correlate significantly better with chondrite, serpentinized fertile mantle peridotite, and the primitive mantle than with oceanic or continental crust, and shows no correlation with seawater.Sony VAIO VGN-Z56TG/E Battery

Reduced carbon

Sir Robert Robinson studied the chemical makeup of natural petroleum oils in great detail, and concluded that they were mostly far too hydrogen-rich to be a likely product of the decay of plant debris, assuming a dual origin for Earth hydrocarbons.Sony VAIO VGN-Z56TG/R Battery

However, several processes which generate hydrogen could supply kerogen hydrogenation which is compatible with conventional petroleum generation theories.

Olefins, the unsaturated hydrocarbons, would have been expected to predominate by far in any material that was derived in that way. He also wrote: "Petroleum ... [seems to be] a primordial hydrocarbon mixture into which bio-products have been added."Sony VAIO VGN-Z570N/B Battery

This has however been demonstrated later to be a misunderstanding by Robinson, related to the fact that only short duration experiments were available to him. Olefins are thermally very unstable (that is why natural petroleum normally does not contain such compounds) and in laboratory experiments that last more than a few hours, the olefins are no longer present.Sony VAIO VGN-Z57G Battery

The presence of low-oxygen and hydroxyl-poor hydrocarbons in natural living media is supported by the presence of natural waxes (n=30+), oils (n=20+) and lipids in both plant matter and animal matter, for instance fats in phytoplankton, zooplankton and so on.Sony VAIO VGN-Z57GG/X Battery

These oils and waxes, however, occur in quantities too small to significantly affect the overall hydrogen/carbon ratio of biological materials. However, after the discovery of highly aliphatic biopolymers in algae, and that oil generating kerogen essentially represent concentrates of such materials, no theoretical problem exists anymore.Sony VAIO VGN-Z57GGX Battery

Also, the millions of source rock samples that have been analyzed for petroleum yield by the petroleum industry have confirmed the large quantities of petroleum found in sedimentary basins.

Field observations

Field observations sometimes cited as commercial occurrence of abiotic petroleum, but disputed by critics, include the Siljan Ring, offshore Vietnam, Eugene Island block 330 oil field, and the Dnieper-Donets Basin.Sony VAIO VGN-Z57TG/X Battery

The Russian-Ukrainian school saw evidence of their theory in the fact that some oil reservoirs exist in non-sedimentary rocks such as granite, metamorphic or porous volcanic rocks. However, critics note that non-sedimentary rocks served as reservoirs for oil expelled from nearby sedimentary source rock through common migration or re-migration mechanisms.Sony VAIO VGN-Z58GG/X Battery

The following observations have been commonly been used to argue for the abiogenic hypothesis, however all of these petroleum occurrences can also be fully explained by conventional petroleum formation theories.

Lost City Hydrothermal Vent Field

The Lost City Hydrothermal Vent Field was determined to have abiogenic hydrocarbon production. Sony VAIO VGN-Z58GGX Battery

Proskurowski et al. wrote, "Radiocarbon evidence rules out seawater bicarbonate as the carbon source for FTT reactions, suggesting that a mantle-derived inorganic carbon source is leached from the host rocks. Our findings illustrate that the abiotic synthesis of hydrocarbons in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat."Sony VAIO VGN-Z590NJB Battery

Siljan Ring, Sweden

The Siljan Ring meteorite crater, Sweden, was proposed by Thomas Gold as the most likely place to test the hypothesis because it was one of the few places in the world where the granite basement was cracked sufficiently (by meteorite impact) to allow oil to seep up from the mantle;Sony VAIO VGN-Z590UAB Battery

furthermore it is infilled with a relatively thin veneer of sediment, which was sufficient to trap any abiogenic oil, but was modelled as not having been subjected to the heat and pressure conditions (known as the "oil window") normally required to create biogenic oil.Sony VAIO VGN-Z591U/B Battery

However, some geochemists concluded by geochemical analysis that the oil in the seeps came from the organic-rich Ordivician Tretaspis shale, where it was heated by the meteorite impact.

The Gravberg-1 borehole penetrated 7,500 m, through the deepest rock in the Siljan Ring in which proponents had hoped to find hydrocarbon reservoirs. Sony VAIO VGN-Z59G Battery

Some eight barrels of magnetite paste and hydrocarbon-bearing sludge were recovered from the well; Gold maintained that the hydrocarbons were chemically different from, and not derived from, those added to the borehole, but analyses showed that the hydrocarbons were derived from the diesel fuel-based drilling fluid used in the drilling.Sony VAIO VGN-Z620D Battery

This well also sampled over 13,000 feet (4,000 m) of methane-bearing inclusions.

A second borehole, Stenberg-1, was drilled a few miles away, finding similar results, This time no diesel fuel-based drilling fluid was found.Sony VAIO VGN-Z620N/B Battery

Bacterial mats

Direct observation of bacterial mats and fracture-fill carbonate and humin of bacterial origin in deep boreholes in Iran, Australia,Sweden and Canada are also taken as evidence for the abiogenic origin of petroleum .Sony VAIO VGN-Z650N/B Battery

Example proposed abiogenic methane deposits

Panhandle-Hugoton field (Anadarko Basin) in the south-central United States is the most important gas field with commercial helium content.

The B?ch H? oil field in Vietnam has been proposed as an example of abiogenic oil because it is 4,000 m of fractured basement granite, at a depth of 5,000 m.Sony VAIO VGN-Z670N/B Battery

However, others argue that it contains biogenic oil which leaked into the basement horst from conventional source rocks within the Cuu Long basin.

A major component of mantle-derived carbon is indicated in commercial gas reservoirs in the Pannonian and Vienna basins of Hungary and Austria.Sony VAIO VGN-Z690CTO Battery

Natural gas pools interpreted as being mantle-derived are the Shengli Field and Songliao Basin, northeastern China.

The Chimaera gas seep, near Ç?ral?, Antalya (southwest Turkey), has been continuously active for millennia and it is known to be the source of the first Olympic fire in the Hellenistic period. Sony VAIO VGN-Z690NAX Battery

On the basis of chemical composition and isotopic analysis, the Chimaera gas is said to be about half biogenic and half abiogenic gas, the largest emission of biogenic methane discovered; deep and pressurized gas accumulations necessary to sustain the gas flow for millennia, posited to be from an inorganic source, may be present.Sony VAIO VGN-Z690PAB Battery

Local geology of Chimaera flames, at exact position of flames, reveals contact between serpentinized ophiolite and carbonate rocks. Fischer-Tropsch process can be suitable reaction to form hydrocarbons gases.Sony VAIO VGN-Z690PCB Battery,Sony VAIO VGN-Z690PDB Battery,Sony VAIO VGN-Z690PEB Battery,Sony VAIO VGN-Z690PFB Battery,Sony VAIO VGN-Z690YAD Battery