Metallic hydrogen
Encyclopedia
Metallic hydrogen is a state
of hydrogen
which results when it is sufficiently compressed
and undergoes a phase transition
; it is an example of degenerate matter
. Solid metallic hydrogen is predicted to consist of a crystal lattice of hydrogen nuclei
(namely, proton
s), with a spacing which is significantly smaller than the Bohr radius
. Indeed, the spacing is more comparable with the de Broglie wavelength of the electron
. The electrons are unbound
and behave like the conduction electrons
in a metal
. In liquid metallic hydrogen, protons do not have lattice ordering; rather, it is a liquid system of protons and electrons.
column in the periodic table
, hydrogen is not, under ordinary conditions, an alkali metal. In 1935 however, physicists Eugene Wigner and Hillard Bell Huntington
predicted that under an immense pressure
of ~ ( or ), hydrogen atom
s would display metallic properties, losing hold over their electrons. Since then, metallic hydrogen has been described as "the holy grail of high-pressure physics".
The initial prediction about the amount of pressure needed was eventually proven to be too low. Since the first work by Wigner and Huntington the more modern theoretical calculations were pointing toward higher but nonetheless potentially accessible metallization pressures. Techniques are being developed for creating pressures of up to , higher than the pressure at the center of the Earth, in hopes of creating metallic hydrogen.
is a liquid
at normal pressure and temperatures near absolute zero
, a consequence of its high zero-point energy
(ZPE). The ZPE of protons in a dense state is also high, and a decline in the ordering energy (relative to the ZPE) is expected at high pressures. Arguments have been advanced by Neil Ashcroft and others that there is a melting point maximum in compressed hydrogen
, but also that there may be a range of densities (at pressures around ) where hydrogen may be a liquid metal, even at low temperatures.
, up to room temperature
(~), far higher than any other known candidate material. This stems from its extremely high speed of sound
and the expected strong coupling
between the conduction electrons and the lattice vibrations.
liquids and gases, and supersolid
s. Egor Babaev predicted that if hydrogen and deuterium
have liquid metallic states, they may have ordered states in quantum domains which cannot be classified as superconducting or superfluid in the usual sense. Instead, they may represent two possible novel types of quantum fluids: "superconducting superfluids" and "metallic superfluids". Such fluids were predicted to have highly unusual reactions to external magnetic fields and rotations, which might provide a means for experimental verification of Babaev's predictions. It has also been suggested that, under the influence of magnetic field, hydrogen may exhibit phase transition
s from superconductivity to superfluidity and vice-versa.
LiH6 would be a stable metal at only of the pressure required to metallize hydrogen, and that similar effects should hold for alloys of type LiHn and possibly other alloys of type ?Lin.
reported that they had serendipitously
produced, for about a microsecond
and at temperature
s of thousands of kelvin
s and pressures of over a million atmospheres (>100 GPa), the first identifiably metallic hydrogen. The team did not expect to produce metallic hydrogen, as it was not using solid hydrogen
, thought to be necessary, and was working at temperatures above those specified by metallization theory. Previous studies in which solid hydrogen was compressed inside diamond anvils to pressures of up to 2500000 atm (253.3 GPa), did not confirm detectable metallization. The team had sought simply to measure the less extreme electrical conductivity changes which were expected to occur. The researchers used a 1960s-era
light gas gun
, originally employed in guided missile
studies, to shoot an impactor plate into a sealed container containing a half-millimeter thick sample of liquid hydrogen
. The liquid hydrogen was in contact with wires leading to a device measuring electrical resistance. The scientists found that, as pressure rose to 1400000 atm (141.9 GPa), the electronic energy band gap
, a measure of electrical resistance
, fell to almost zero. The band-gap of hydrogen in its uncompressed state is about , making it an insulator but, as the pressure increases significantly, the band-gap gradually fell to . Because the thermal energy
of the fluid (the temperature became about due to compression of the sample) was above , the hydrogen might be considered metallic.
in 1998, and later Paul Loubeyre and René LeToullec from Commissariat à l'Énergie Atomique
, France
in 2002, have shown that at pressures close to those at the center of the Earth
(3.2 to 3.4 million atmospheres or 324 to 345 GPa) and temperatures of 100–300 K, hydrogen is still not a true alkali metal, because of the non-zero band gap. The quest to see metallic hydrogen in laboratory at low temperature and static compression continues. Studies are also undergoing on deuterium
. Shahriar Badiei and Leif Holmlid from the University of Gothenburg have shown in 2004 that condensed metallic states made of excited hydrogen atoms (Rydberg matter
) are effective promoters to metallic hydrogen.
was metalized and found to be superconducting
by M.I. Eremets et al., confirming earlier theoretical prediction by Ashcroft. In this hydrogen rich alloy, even at moderate pressures (because of chemical precompression) the hydrogen forms a sub-lattice with density corresponding to metallic hydrogen.
However, the claimed high-pressure metallic and superconducting phase of SiH4 was later identified as platinum hydride, that formed after the decomposition of SiH4.
, Saturn
, and some of the newly discovered extrasolar planet
s. Because previous predictions of the nature of those interiors had taken for granted metallization at a higher pressure than the one at which we now know it to happen, those predictions must now be adjusted. The new data
indicate much more metallic hydrogen must exist inside Jupiter than previously thought, that it comes closer to the surface, and that therefore, Jupiter's tremendous magnetic field
, the strongest of any planet in the solar system
is, in turn, produced closer to the surface.
forms a metal alloy. It is well known that hydrogen can permeate to a remarkable extent various ordinary metals under conditions of ordinary pressure. In some metals (e.g., lithium
) a chemical reaction occurs that produces an ordinary non-metallic chemical compound (lithium hydride). In other cases it is possible that the hydrogen literally alloys itself with the metal (somewhat analogous to mercury
amalgam
formation). Certainly it is known that many metals remain metallic (e.g., palladium
) after absorbing hydrogen—most become brittle
, but many ordinary alloys are brittle, too.
, called inertial confinement fusion
, involves aiming laser
beams at pellets of hydrogen isotope
s. The increased understanding of the behavior of hydrogen in extreme conditions could help to increase energy yields.
Metallic Hydrogen" (MSMH), which would not immediately revert to ordinary hydrogen upon release of pressure.
In addition, MSMH would make an efficient fuel
and also a clean one, with only water
as an end product (if burned in pure oxygen). Nine times as dense as standard hydrogen, it would give off considerable energy when reverting to standard hydrogen. Burned more quickly, it could be a propellant
with up to five times the efficiency of liquid H2/O2, the current Space Shuttle
fuel. Unfortunately, the above-mentioned Lawrence Livermore experiments produced metallic hydrogen too briefly to determine whether metastability is possible.
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...
of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
which results when it is sufficiently compressed
Hydrogen compressor
A hydrogen compressor is a device that increases the pressure of hydrogen by reducing its volume. Compression of hydrogen gas naturally increases its temperature, due to Charles' Law....
and undergoes a phase transition
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....
; it is an example of degenerate matter
Degenerate matter
Degenerate matter is matter that has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle...
. Solid metallic hydrogen is predicted to consist of a crystal lattice of hydrogen nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
(namely, proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s), with a spacing which is significantly smaller than the Bohr radius
Bohr radius
The Bohr radius is a physical constant, approximately equal to the most probable distance between the proton and electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom...
. Indeed, the spacing is more comparable with the de Broglie wavelength of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
. The electrons are unbound
Bound state
In physics, a bound state describes a system where a particle is subject to a potential such that the particle has a tendency to remain localised in one or more regions of space...
and behave like the conduction electrons
Conduction band
In the solid-state physics field of semiconductors and insulators, the conduction band is the range of electron energies, higher than that of the valence band, sufficient to free an electron from binding with its individual atom and allow it to move freely within the atomic lattice of the material...
in a metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
. In liquid metallic hydrogen, protons do not have lattice ordering; rather, it is a liquid system of protons and electrons.
Metallization of hydrogen under pressure
Though at the top of the alkali metalAlkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
column in the periodic table
Periodic table
The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...
, hydrogen is not, under ordinary conditions, an alkali metal. In 1935 however, physicists Eugene Wigner and Hillard Bell Huntington
Hillard Bell Huntington
Dr. Hillard Bell Huntington was a physicist who first proposed, in 1935, that hydrogen could occur in a metallic state...
predicted that under an immense pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
of ~ ( or ), hydrogen atom
Hydrogen atom
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively-charged proton and a single negatively-charged electron bound to the nucleus by the Coulomb force...
s would display metallic properties, losing hold over their electrons. Since then, metallic hydrogen has been described as "the holy grail of high-pressure physics".
The initial prediction about the amount of pressure needed was eventually proven to be too low. Since the first work by Wigner and Huntington the more modern theoretical calculations were pointing toward higher but nonetheless potentially accessible metallization pressures. Techniques are being developed for creating pressures of up to , higher than the pressure at the center of the Earth, in hopes of creating metallic hydrogen.
Liquid metallic hydrogen
Helium-4Helium-4
Helium-4 is a non-radioactive isotope of helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on earth. Its nucleus is the same as an alpha particle, consisting of two protons and two neutrons. Alpha decay of heavy...
is a liquid
Liquid helium
Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...
at normal pressure and temperatures near absolute zero
Absolute zero
Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....
, a consequence of its high zero-point energy
Zero-point energy
Zero-point energy is the lowest possible energy that a quantum mechanical physical system may have; it is the energy of its ground state. All quantum mechanical systems undergo fluctuations even in their ground state and have an associated zero-point energy, a consequence of their wave-like nature...
(ZPE). The ZPE of protons in a dense state is also high, and a decline in the ordering energy (relative to the ZPE) is expected at high pressures. Arguments have been advanced by Neil Ashcroft and others that there is a melting point maximum in compressed hydrogen
Compressed hydrogen
Compressed hydrogen is the gaseous state of the element hydrogen kept under pressure. Compressed hydrogen in hydrogen tanks at 350 bar and 700 bar is used for mobile hydrogen storage in hydrogen vehicles...
, but also that there may be a range of densities (at pressures around ) where hydrogen may be a liquid metal, even at low temperatures.
Superconductivity
In 1968, Ashcroft put forward that metallic hydrogen may be a superconductorSuperconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
, up to room temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...
(~), far higher than any other known candidate material. This stems from its extremely high speed of sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....
and the expected strong coupling
Coupling (physics)
In physics, two systems are coupled if they are interacting with each other. Of special interest is the coupling of two vibratory systems by means of springs or magnetic fields, etc...
between the conduction electrons and the lattice vibrations.
Possibility of novel types of quantum fluid
Presently known "super" states of matter are superconductors, superfluidSuperfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...
liquids and gases, and supersolid
Supersolid
A supersolid is a spatially ordered material with superfluid properties. Superfluidity is a special quantum state of matter in which a substance flows with zero viscosity.-Background:...
s. Egor Babaev predicted that if hydrogen and deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
have liquid metallic states, they may have ordered states in quantum domains which cannot be classified as superconducting or superfluid in the usual sense. Instead, they may represent two possible novel types of quantum fluids: "superconducting superfluids" and "metallic superfluids". Such fluids were predicted to have highly unusual reactions to external magnetic fields and rotations, which might provide a means for experimental verification of Babaev's predictions. It has also been suggested that, under the influence of magnetic field, hydrogen may exhibit phase transition
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....
s from superconductivity to superfluidity and vice-versa.
Lithium doping reduces requisite pressure
In 2009, Zurek et al. predicted that the alloyAlloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
LiH6 would be a stable metal at only of the pressure required to metallize hydrogen, and that similar effects should hold for alloys of type LiHn and possibly other alloys of type ?Lin.
Metallization of hydrogen in shock-wave compression
In March 1996, a group of scientists at Lawrence Livermore National LaboratoryLawrence Livermore National Laboratory
The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...
reported that they had serendipitously
Serendipity
Serendipity means a "happy accident" or "pleasant surprise"; specifically, the accident of finding something good or useful without looking for it. The word has been voted as one of the ten English words hardest to translate in June 2004 by a British translation company. However, due to its...
produced, for about a microsecond
Microsecond
A microsecond is an SI unit of time equal to one millionth of a second. Its symbol is µs.A microsecond is equal to 1000 nanoseconds or 1/1000 millisecond...
and at temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s of thousands of kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s and pressures of over a million atmospheres (>100 GPa), the first identifiably metallic hydrogen. The team did not expect to produce metallic hydrogen, as it was not using solid hydrogen
Solid hydrogen
Solid hydrogen is the solid state of the element hydrogen, achieved by decreasing the temperature below hydrogen's melting point of 14.01 K . It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" in the Annales de Chimie et...
, thought to be necessary, and was working at temperatures above those specified by metallization theory. Previous studies in which solid hydrogen was compressed inside diamond anvils to pressures of up to 2500000 atm (253.3 GPa), did not confirm detectable metallization. The team had sought simply to measure the less extreme electrical conductivity changes which were expected to occur. The researchers used a 1960s-era
1960 in science
The year 1960 in science and technology involved some significant events, listed below.-Astronomy and space exploration:* March 14 - Jodrell Bank Observatory in England makes radio contact with the U.S...
light gas gun
Light gas gun
The light-gas gun is an apparatus for physics experiments, a highly specialized gun designed to generate very high velocities. It is usually used to study high speed impact phenomena , such as the formation of impact craters by meteorites or the erosion of materials by micrometeoroids...
, originally employed in guided missile
Guided Missile
Guided Missile is a London based independent record label set up by Paul Kearney in 1994.Guided Missile has always focused on 'the underground', preferring to put out a steady flow of releases and developing the numerous GM events around London and beyond....
studies, to shoot an impactor plate into a sealed container containing a half-millimeter thick sample of liquid hydrogen
Liquid hydrogen
Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...
. The liquid hydrogen was in contact with wires leading to a device measuring electrical resistance. The scientists found that, as pressure rose to 1400000 atm (141.9 GPa), the electronic energy band gap
Band gap
In solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the...
, a measure of electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
, fell to almost zero. The band-gap of hydrogen in its uncompressed state is about , making it an insulator but, as the pressure increases significantly, the band-gap gradually fell to . Because the thermal energy
Thermal energy
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature....
of the fluid (the temperature became about due to compression of the sample) was above , the hydrogen might be considered metallic.
Other experimental research since 1996
Many experiments are continuing in the production of metallic hydrogen in laboratory conditions at static compression and low temperature. Arthur Ruoff and Chandrabhas Narayana from Cornell UniversityCornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
in 1998, and later Paul Loubeyre and René LeToullec from Commissariat à l'Énergie Atomique
Commissariat à l'Énergie Atomique
The Commissariat à l'énergie atomique et aux énergies alternatives or CEA, is a French “public establishment related to industrial and commercial activities” whose mission is to develop all applications of nuclear power, both civilian and military...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
in 2002, have shown that at pressures close to those at the center of the Earth
Planetary core
The planetary core consists of the innermost layer of a planet.The core may be composed of solid and liquid layers, while the cores of Mars and Venus are thought to be completely solid as they lack an internally generated magnetic field. In our solar system, core size can range from about 20% to...
(3.2 to 3.4 million atmospheres or 324 to 345 GPa) and temperatures of 100–300 K, hydrogen is still not a true alkali metal, because of the non-zero band gap. The quest to see metallic hydrogen in laboratory at low temperature and static compression continues. Studies are also undergoing on deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
. Shahriar Badiei and Leif Holmlid from the University of Gothenburg have shown in 2004 that condensed metallic states made of excited hydrogen atoms (Rydberg matter
Rydberg matter
Rydberg matter is a phase of matter formed by Rydberg atoms; it was predicted around 1980 by É. A. Manykin, M. I. Ozhovan and P. P. Poluéktov. It has been formed from various elements like caesium, potassium, hydrogen and nitrogen; studies have been conducted on theoretical possibilities like...
) are effective promoters to metallic hydrogen.
Experimental results in 2008
The theoretically predicted maximum of the melting curve (the prerequisite for the liquid metallic hydrogen) was discovered by Shanti Deemyad and Isaac F. Silvera by using pulsed laser heating. Hydrogen-rich alloy SiH4Silane
Silane is a toxic, extremely flammable chemical compound with chemical formula SiH4. In 1857, the German chemists and Friedrich Woehler discovered silane among the products formed by the action of hydrochloric acid on aluminum silicide, which they had previously prepared...
was metalized and found to be superconducting
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
by M.I. Eremets et al., confirming earlier theoretical prediction by Ashcroft. In this hydrogen rich alloy, even at moderate pressures (because of chemical precompression) the hydrogen forms a sub-lattice with density corresponding to metallic hydrogen.
However, the claimed high-pressure metallic and superconducting phase of SiH4 was later identified as platinum hydride, that formed after the decomposition of SiH4.
Metallization of hydrogen in 2011
In 2011 Eremets and Tojan reported observing the liquid metallic state of hydrogen and deuterium at static pressures.Astrophysics
Metallic hydrogen is thought to be present in large amounts in the gravitationally compressed interiors of JupiterJupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
, and some of the newly discovered extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
s. Because previous predictions of the nature of those interiors had taken for granted metallization at a higher pressure than the one at which we now know it to happen, those predictions must now be adjusted. The new data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
indicate much more metallic hydrogen must exist inside Jupiter than previously thought, that it comes closer to the surface, and that therefore, Jupiter's tremendous magnetic field
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
, the strongest of any planet in the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
is, in turn, produced closer to the surface.
Hydrogen permeation of metals
As mentioned earlier, pressurized SiH4Silane
Silane is a toxic, extremely flammable chemical compound with chemical formula SiH4. In 1857, the German chemists and Friedrich Woehler discovered silane among the products formed by the action of hydrochloric acid on aluminum silicide, which they had previously prepared...
forms a metal alloy. It is well known that hydrogen can permeate to a remarkable extent various ordinary metals under conditions of ordinary pressure. In some metals (e.g., lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
) a chemical reaction occurs that produces an ordinary non-metallic chemical compound (lithium hydride). In other cases it is possible that the hydrogen literally alloys itself with the metal (somewhat analogous to mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
amalgam
Amalgam (chemistry)
An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore.The...
formation). Certainly it is known that many metals remain metallic (e.g., palladium
Palladium
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...
) after absorbing hydrogen—most become brittle
Hydrogen embrittlement
Hydrogen embrittlement is the process by which various metals, most importantly high-strength steel, become brittle and fracture following exposure to hydrogen...
, but many ordinary alloys are brittle, too.
Nuclear power
One method of producing nuclear fusionNuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
, called inertial confinement fusion
Inertial confinement fusion
Inertial confinement fusion is a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that most often contains a mixture of deuterium and tritium....
, involves aiming laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
beams at pellets of hydrogen isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s. The increased understanding of the behavior of hydrogen in extreme conditions could help to increase energy yields.
Fuel
It may be possible to produce substantial quantities of metallic hydrogen for practical purposes. The existence has been theorized of a form called "MetastableMetastability
Metastability describes the extended duration of certain equilibria acquired by complex systems when leaving their most stable state after an external action....
Metallic Hydrogen" (MSMH), which would not immediately revert to ordinary hydrogen upon release of pressure.
In addition, MSMH would make an efficient fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
and also a clean one, with only water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
as an end product (if burned in pure oxygen). Nine times as dense as standard hydrogen, it would give off considerable energy when reverting to standard hydrogen. Burned more quickly, it could be a propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
with up to five times the efficiency of liquid H2/O2, the current Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
fuel. Unfortunately, the above-mentioned Lawrence Livermore experiments produced metallic hydrogen too briefly to determine whether metastability is possible.