Cosmic ray spallation
Encyclopedia
Cosmic ray spallation is a form of naturally occurring nuclear fission
and nucleosynthesis
. It refers to the formation of elements
from the impact of cosmic rays on an object. Cosmic rays are highly energetic charged particles
from outside of Earth
ranging from proton
s, alpha particle
s, and nuclei of many heavier elements. About 1% of cosmic rays also consist of free electrons.
Cosmic rays cause spallation
when a ray particle (e.g. a proton
) impacts with matter
, including other cosmic rays. The result of the collision is the expulsion of large numbers of nucleons (protons and neutrons) from the object hit. This process goes on not only in deep space, but in Earth's upper atmosphere and crustal surface (typically the upper ten meters) due to the ongoing impact of cosmic rays.
Cosmic ray spallation after the Big Bang
is thought to be responsible for the abundance in the universe of some light elements such as lithium
, beryllium
, and boron
. This process (cosmogenic nucleosynthesis
) was discovered somewhat by accident during the 1970s: models of Big Bang nucleosynthesis
suggested that the amount of deuterium
was too large to be consistent with the expansion rate of the universe and there was therefore great interest in processes that could generate deuterium
after the Big Bang. Cosmic ray spallation was investigated as a possible process to generate deuterium. As it turned out, spallation could not generate much deuterium, nor could nucleosynthesis in stars . (The excess deuterium in the universe was finally explained by assuming the existence of non-baryonic dark matter
).
However, the new studies of spallation showed that this process could generate lithium, beryllium and boron, and indeed these isotopes are over-represented in cosmic ray nuclei, as compared with solar atmospheres (whereas H and He are present in about primordial ratios in cosmic rays).
In addition to the above light elements, isotopes of aluminium
, carbon
(carbon-14
), tritium, chlorine
, iodine
and neon
are formed within solar system materials through cosmic ray spallation, and are termed cosmogenic nuclide
s. Since they remain trapped in the atmosphere or rock in which they formed, some can be very useful in the dating of materials by cosmogenic radionuclide dating, particularly in the geological field. In formation of a cosmogenic nuclide, a cosmic ray
interacts with the nucleus
of an in situ
solar system atom
, causing cosmic ray spallation. These isotopes are produced within earth materials such as rock
s or soil
, in Earth's
atmosphere
, and in extraterrestrial items such as meteorite
s. By measuring cosmogenic isotopes, scientist
s are able to gain insight into a range of geological
and astronomical
processes. There are both radioactive and stable
cosmogenic isotopes. Some of the well-known naturally-occurring radioisotopes are tritium
, carbon
-14 and phosphorus
-32.
The timing of their formation determines which subset of nuclides formed by cosmic ray spallation, are termed primordial or cosmogenic (a nuclide cannot belong to both classes). By convention, certain stable nuclides of lithium, beryllium, and boron thought to have been produced by cosmic ray spallation in the period of time between the Big Bang
and the solar system's formation (thus making these primordial nuclide
s, by definition) are not termed "cosmogenic," even though they are were formed by the same process as the cosmogenic nuclides (although at an earlier time). In contrast, the radioactive nuclide beryllium-7 falls into this light element range, but this nuclide has a half-life too short for it to have been formed before the formation of the solar system, so that it cannot be a primordial nuclide. Since the cosmic ray spallation route is the most likely source of beryllium-7 in the environment, it is therefore cosmogenic.
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
and nucleosynthesis
Nucleosynthesis
Nucleosynthesis is the process of creating new atomic nuclei from pre-existing nucleons . It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma from the Big Bang as it cooled below two trillion degrees...
. It refers to the formation of elements
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
from the impact of cosmic rays on an object. Cosmic rays are highly energetic charged particles
Subatomic particle
In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...
from outside of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
ranging from 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, alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
s, and nuclei of many heavier elements. About 1% of cosmic rays also consist of free electrons.
Cosmic rays cause spallation
Spallation
In general, spallation is a process in which fragments of material are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection or vaporization of material from a target during impact by a projectile...
when a ray particle (e.g. a 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....
) impacts with matter
Matter
Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...
, including other cosmic rays. The result of the collision is the expulsion of large numbers of nucleons (protons and neutrons) from the object hit. This process goes on not only in deep space, but in Earth's upper atmosphere and crustal surface (typically the upper ten meters) due to the ongoing impact of cosmic rays.
Cosmic ray spallation after the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...
is thought to be responsible for the abundance in the universe of some light elements such as 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...
, beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
, and boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
. This process (cosmogenic nucleosynthesis
Nucleosynthesis
Nucleosynthesis is the process of creating new atomic nuclei from pre-existing nucleons . It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma from the Big Bang as it cooled below two trillion degrees...
) was discovered somewhat by accident during the 1970s: models of Big Bang nucleosynthesis
Big Bang nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis refers to the production of nuclei other than those of H-1 during the early phases of the universe...
suggested that the amount of 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 ...
was too large to be consistent with the expansion rate of the universe and there was therefore great interest in processes that could generate 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 ...
after the Big Bang. Cosmic ray spallation was investigated as a possible process to generate deuterium. As it turned out, spallation could not generate much deuterium, nor could nucleosynthesis in stars . (The excess deuterium in the universe was finally explained by assuming the existence of non-baryonic dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
).
However, the new studies of spallation showed that this process could generate lithium, beryllium and boron, and indeed these isotopes are over-represented in cosmic ray nuclei, as compared with solar atmospheres (whereas H and He are present in about primordial ratios in cosmic rays).
In addition to the above light elements, isotopes of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(carbon-14
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
), tritium, chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
and neon
Neon
Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
are formed within solar system materials through cosmic ray spallation, and are termed cosmogenic nuclide
Cosmogenic nuclide
See also Environmental radioactivity#NaturalCosmogenic nuclides are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ solar system atom, causing cosmic ray spallation...
s. Since they remain trapped in the atmosphere or rock in which they formed, some can be very useful in the dating of materials by cosmogenic radionuclide dating, particularly in the geological field. In formation of a cosmogenic nuclide, a cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
interacts with the nucleus
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...
of an in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
solar system atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
, causing cosmic ray spallation. These isotopes are produced within earth materials such as rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
s or soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
, in Earth's
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, and in extraterrestrial items such as meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s. By measuring cosmogenic isotopes, scientist
Scientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...
s are able to gain insight into a range of geological
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and astronomical
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
processes. There are both radioactive and stable
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...
cosmogenic isotopes. Some of the well-known naturally-occurring radioisotopes are tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
, carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
-14 and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
-32.
The timing of their formation determines which subset of nuclides formed by cosmic ray spallation, are termed primordial or cosmogenic (a nuclide cannot belong to both classes). By convention, certain stable nuclides of lithium, beryllium, and boron thought to have been produced by cosmic ray spallation in the period of time between the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...
and the solar system's formation (thus making these primordial nuclide
Primordial nuclide
In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known...
s, by definition) are not termed "cosmogenic," even though they are were formed by the same process as the cosmogenic nuclides (although at an earlier time). In contrast, the radioactive nuclide beryllium-7 falls into this light element range, but this nuclide has a half-life too short for it to have been formed before the formation of the solar system, so that it cannot be a primordial nuclide. Since the cosmic ray spallation route is the most likely source of beryllium-7 in the environment, it is therefore cosmogenic.
See also
- cosmogenic nuclideCosmogenic nuclideSee also Environmental radioactivity#NaturalCosmogenic nuclides are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ solar system atom, causing cosmic ray spallation...
for a list of cosmogenic nuclides used in material formation dating - Cosmic rays
- Nuclear fissionNuclear fissionIn nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
- NucleosynthesisNucleosynthesisNucleosynthesis is the process of creating new atomic nuclei from pre-existing nucleons . It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma from the Big Bang as it cooled below two trillion degrees...
- AstrophysicsAstrophysicsAstrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
- SpallSpallSpall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...
, or spalling - SpallationSpallationIn general, spallation is a process in which fragments of material are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection or vaporization of material from a target during impact by a projectile...
- Spallation Neutron SourceSpallation Neutron SourceThe Spallation Neutron Source is an accelerator-based neutron source facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development...
- ISIS neutron sourceISIS neutron sourceISIS is a pulsed neutron and muon source. It is situated at the Rutherford Appleton Laboratory on the Harwell Science and Innovation Campus in Oxfordshire, United Kingdom and is part of the Science and Technology Facilities Council...
- PSI Spallation Neutron Source (SINQ)
External links
- Ray Isotope Spectrometer
- University of Leeds paper, proceedings of the 26th ICRCInternational Cosmic Ray ConferenceThe International Cosmic Ray Conference, or ICRC, is a physics conference organized biennially by the International Union of Pure and Applied Physics since 1947, where physicists from the whole world present the results of the experiences about cosmic rays they are working on.Proceedings are...
.(Link down, Jan 2011) - Heavy Cosmic Ray propagation Using New Spallation Cross-Section Expressions, proceedings of the 26th ICRCInternational Cosmic Ray ConferenceThe International Cosmic Ray Conference, or ICRC, is a physics conference organized biennially by the International Union of Pure and Applied Physics since 1947, where physicists from the whole world present the results of the experiences about cosmic rays they are working on.Proceedings are...
.(Link down, Jan 2011) - Evidence for cosmic ray spallation production of helium and neon found in volcanoes