George Wetherill (August 12, 1925-July 19, 2006) was the Director Emeritus, Department of Terrestrial Magnetism, Carnegie Institution of Washington, DC, USA. August 12 is the 224th day of the year (225th in leap years) in the Gregorian Calendar. ... 1925 (MCMXXV) was a common year starting on Thursday (link will display the full calendar). ... July 19 is the 200th day (201st in leap years) of the year in the Gregorian Calendar, with 165 days remaining. ... For the Manfred Mann album, see 2006 (album). ... The Carnegie Institution of Washington (CIW) is a foundation established by Andrew Carnegie in 1902 to support scientific research. ...

George Wetherill benefited from the GI Bill of Rights to receive four degrees, the Ph. B. (1948), S.B. (1949), S.M. (1951), and Ph. D., in physics (1953), all from the University of Chicago. He did his thesis research, on the spontaneous fission of uranium, as well as nuclear processes in nature, as an U.S. Atomic Energy Commission Predoctoral Fellow. Upon receiving his Ph. D., Wetherill became a staff member at Carnegie's Department of Terrestrial Magnetism (DTM) in Washington, D.C. There, he joined an interdepartmental group of Carnegie scientists who were working to date the Earth's rocks by geochemical methods involving natural radioactive decay. This involved determining the concentration and isotopic composition of inert gases such as argon, as well as the isotopes of strontium and lead. He originated the concept of the Concordia Diagram for the uranium-lead isotopic system; this diagram became the standard means for determining precise ages of rocks, and of detecting the possibility of metamorphism, and it forms the basis for all high-precision geochronology in rocks dating back to the early history of the Earth. He was also a member of the Carnegie group that accurately determined the decay constants of potassium and rubidium, an effort that has also become fundamental to the measurement of geological time. The G. I. Bill of Rights or Servicemens Readjustment Act of 1944 provided for college or vocational education for returning World War II veterans as well as one-year of unemployment compensation. ... The University of Chicago is a private university located principally in the Hyde Park neighborhood of Chicago. ... For the generation of electrical power by fission, see Nuclear power plant An induced nuclear fission event. ... General Name, Symbol, Number uranium, U, 92 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Atomic mass 238. ... Shield of the U.S. Atomic Energy Commission. ... Radioactive decay is the process in which unstable atoms lose energy by emitting radiation in the form of particles or electromagnetic waves. ... The word isotopic has a number of different meanings, including: In the physical sciences, to do with chemical isotopes; In mathematics, to do with a relation called isotopism. ... An inert gas is any gas that, in a given circumstance, is not reactive. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Atomic mass 87. ... General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish white Atomic mass 207. ... Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ... Geochronology is the science of determining the age of rocks, fossils, and sediments. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... General Name, Symbol, Number rubidium, Rb, 37 Chemical series alkali metals Group, Period, Block 1, 5, s Appearance grey white Atomic mass 85. ...

Wetherill left DTM in 1960 to become a professor of geophysics and geology at the University of California, Los Angeles. There, he served as chairman of the interdepartmental curriculum in geochemistry (1964-1968), and as chairman of the Department of Planetary and Space Sciences (1968-1972). At UCLA, his interests in age-dating techniques expanded to include extraterrestrial material, as he began applying his radiometric chronology techniques to meteorite and lunar samples. At the same time, he began theoretical explorations into the origin of meteorites. His studies concentrated on collisions between objects in the asteroid belt together with resonances between their motions and those of planets. He computed how these events could move material into Earth-crossing orbits to become meteorites or larger Earth-impacting bodies responsible for the devastating impacts that caused mass extinctions of the majority of living species, including the dinosaurs. Later, he, along with scientists elsewhere, proposed that a certain unusual class of meteorites was not asteroidal in origin but instead came from the planet Mars. This was later confirmed by laboratory work elsewhere and is now well accepted. The University of California, Los Angeles, generally known as UCLA, is a public university whose main campus is located in the affluent Westwood neighborhood of Los Angeles, California, United States. ... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... Apparent magnitude: up to -12. ... For details on the physical properties of bodies in the asteroid belt see Asteroid and Main-belt comet. ... Adjectives: Martian Atmosphere Surface pressure: 0. ...

In 1975, Wetherill returned to Carnegie's Department of Terrestrial Magnetism as director. He remained director until 1991, when he became a staff member. At DTM, he began extending his research efforts into questions concerning the origin of the terrestrial planets--Mercury, Venus, Earth, and Mars. He was stimulated by earlier studies by Victor Safronov (O. Yu SchmidtInstitute, Moscow), who showed that as a swarm of planetesimals coagulated into large bodies the swarm could evolve to produce a few terrestrial planets. Wetherill developed a technique to calculate numerically the orbital evolution and accumulation of planetesimal swarms, and he used the technique to reach specific predictions of the physical and orbital properties of terrestrial planets. His results agreed well with present observations. Note: This article contains special characters. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... In cosmogony, planetesimals are objects thought to exist within solar nebulae. ...

In addition to showing how the inner solar system formed, Wetherill's work provided the basis for a model of a giant-impact origin for the Moon and the core of Mercury. It also led to explanations for the isotopic abundances of present-day planetary atmospheres. Recently, Wetherill has shown that Jupiter plays an important role in the evolution of our solar system; by ejecting comets from the solar system, it offers a protective presence to the inner planets. Wetherill's theoretical work supports discussions on the origins of our solar system as well as on extrasolar planets. Apparent magnitude: up to -12. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ...

Wetherill has provided leadership in the scientific community by serving on advisory committees for NASA, the National Academy of Sciences, and the National Science Foundation. For 17 years, he was editor of the Annual Review of Earth and Planetary Sciences. He has served as president of the Meteoritical Society, the Geochemical Society, the Planetology Section of the American Geophysical Union, and the International Association of Geochemistry and Cosmochemistry. The National Aeronautics and Space Administration (NASA) is an agency of the United States Government, responsible for that nations public space program. ... President Harding and the National Academy of Sciences at the White House, Washington, DC, April 1921 The National Academy of Sciences (NAS) is a corporation in the United States whose members serve pro bono as advisers to the nation on science, engineering, and medicine. ... The logo of the National Science Foundation The National Science Foundation (NSF) is an independent United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. ... The Meteoritical Society is a non-profit scholarly organization founded in 1933 to promote research and education in planetary science with emphasis on studies of meteorites and other extraterrestrial materials that further our understanding of the origin and history of the solar system. ... The American Geophysical Union (or AGU) is a nonprofit organization of geophysicists, consisting (as of 2006) of over 49,000 members from over 140 countries. ...

His awards include election to the National Academy of Sciences in 1974, the 1981 Leonard Medal of the Meteoritical Society, the 1984 G. K. Gilbert Award of the Geological Society of America, the 1986 G. P. Kuiper Prize of the Division of Planetary Sciences of the American Astronomical Society, the 1991 Harry H. Hess Medal of the American Geophysical Union, the 1997 National Medal of Science awarded by President Clinton and the 2000 J. Lawrence Smith Medal (National Academy of Sciences) "for his unique contributions to the cosmochronology of the planets and meteorites and to the orbital dynamics and formation of solar system bodies." In 2003 Wetherill was awarded the Henry Norris Russell Lectureship, the highest honor bestowed by the American Astronomical Society. President Harding and the National Academy of Sciences at the White House, Washington, DC, April 1921 The National Academy of Sciences (NAS) is a corporation in the United States whose members serve pro bono as advisers to the nation on science, engineering, and medicine. ... The Leonard Medal honors outstanding contributions to the science of meteoritics and closely allied fields. ... The Meteoritical Society is a non-profit scholarly organization founded in 1933 to promote research and education in planetary science with emphasis on studies of meteorites and other extraterrestrial materials that further our understanding of the origin and history of the solar system. ... The G. K. Gilbert Award is presented annually by the Planetary Geology Division of the Geological Society of America for outstanding contributions to the solution of fundamental problems in planetary geology in the broadest sense, which includes geochemistry, mineralogy, petrology, geophysics, geologic mapping, and remote sensing. ... The Geological Society of America (or GSA) is a nonprofit organization dedicated to the advancement of the geosciences. ... The Gerard P. Kuiper Prize is awarded annually by the Division for Planetary Sciences of the American Astronomical Society for outstanding lifetime achievement in the field of planetary science. ... The American Astronomical Society (AAS) is a US society of professional astronomers and other interested individuals, headquartered in Washington, DC. The main aim of the AAS is provide a political voice for its members and organise their lobbying. ... The American Geophysical Union (or AGU) is a nonprofit organization of geophysicists, consisting (as of 2006) of over 49,000 members from over 140 countries. ... National Medal of Science The National Medal of Science, also called the Presidential Medal of Science, is an honor given by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral and social... J. Lawrence Smith Medal is awarded by the National Academy of Sciences for investigations of meteoric bodies. ... The Henry Norris Russell Lectureship is awarded each year by the American Astronomical Society in recognition of a lifetime of excellence in astronomical research. ...

Wetherill died [1] at his home in Washington, D.C Wednesday, July 19, 2006 after a long illness.

External links

• NASA
• Carnegie Institution Bio
• Publications
• International Center for Scientific research
• Obituary in Nature