George Wetherill to Speak on "The Peekskill Meteorite, October 9, 1992, Video Observations: an Orbit Determination" by Harold Williams

Total Page:16

File Type:pdf, Size:1020Kb

George Wetherill to Speak on SEP 2 4 1994 National Capital Astronomers, Inc. (703) 841-4765 Washington, DC (301) 320-3621 Volume LIII, Number 2 October, 1994 ISSN 0898-7548 George Wetherill to Speak on "The Peekskill Meteorite, October 9, 1992, Video Observations: An Orbit Determination" by Harold Williams The next meeting of the National find one, keep it and dispose of it as contains more than 165 entries. He is Capital Astronomers will be held on you wish; they are worth real money. a member of the National Academy Saturday October 1 at 7:30 P.M., in of Sciences and has won numerous the Lippsett Amphitheater, Room George heard of the video tapes. honors from many learned societies. lC114, of the Clinical Center CCN had one from Raleigh, North He is a member, and in fact a fellow, (Building 10) at the National Insti- Carolina. Washington Metro News in many societies including the tutes of Health (NIH). George 4 WRC had one from someone in American Geophysical Union, Me- Wetherill of the Department of Ter- Virginia near the Potomac who was teoritical Society, Geochemical So- restrial Magnetism (DTM) of the out partying with friends (one of the ciety, International Astronomical Carnegie Institution of Washington few nonfootball videos). The long- Union, American Astronomical So- (CIW) the oldest nonprofit research est duration track, around 30 sec- ciety. He has also been an officer in foundation in America, will speak onds, was from Johnstown Pennsyl- most of these societies at some time. on "The Peakskill Meteorite, Octo- vania. George said that he started to He has been associate editor or edi- ber9, 1992, Video Observations: An collect videos to compute the orbit tor of the Journal of Geophysical Orbit Determination." On October because he came to the conclusion Research, Annual Review of Earth 9, 1992 at 7:50 P.M., on a Friday that, ifhe didn't do it, perhaps no one and Planetary Science, Meteoritics, night when high school football else would. He collected fifteen vid- and Icarus. He has been an advisor to games were being video taped by eos with some of the fireballs of NASA, NSF, NAS, NRC, and other parents, coaching staffs, and local which seven videos proved to be numerous organizations on commit- television stations, a fireball ap- good for astrometric orbit determi- tees and panels. His employment peared over the United States visible nation. This is one of the few mete- and professional experience stretch from perhaps Texas to New Jersey orites that has struck the earth that from Radar Technician in the U.S. where it was cloudy. It struck a we now actually have an orbit back Navy during the Second World War women's carin Peekskill, New York out into space. It became visible at an to staff member at DTM several and the meteorite was recovered - altitude of 80 kilometers above the times and director ofDTM. He was 12.6 kilograms. Rumor has it that the earth. a faculty member and chairman of women sold the car to a museum for departments at UCLA. He was a around $7,000 dollars and the mete- George Wetherill is a geophysicist visiting professor at Cal Tech. All of orite for around $50,000. In America and planetary scientist whose publi- his higher education degrees are (home of the brave and chaotic), cation list, excluding abstracts, book from the University of Chicago in meteorites belong to the finder or reviews, and other minor publica- perhaps landowner or renter. If you tions, is itself 15 pages long and See WETHERILL, Page 6 October Calendar The Public is Welcome! Saturday, October 1, 1994, 5:30 PM - Dinner with McKinley Hall Basement. Information: Jerry Schnall, the speaker at the Athenian Plaka Restaraunt (7833 202/362-8872. Woodmont, Bethesda) before the monthly meeting. Friday, October 7, 1994, 11:30 PM - Earth Night Reservations are for 5:30PM sharp. 1994: "The Autumn Sky, Nocturnal Nature, and Fall Saturday, October 1,Night - October's best night for Foliage." Smithsonian Resident Associate Program for dark-sky observing and "absorbing" ("Moon- (SRAP), Overnight Studay Tour (SRAP Code: 525- dark" paractically all night long). So my firends, crawl 723), at Shennandoah National Park's Big Meadows out of thine cocooning hovels, flee the glowing fun- on Virginia's Skyline Drive. If postponed due to bad goid mass of urbania, and get thee to the night country, weather, alternative date is following Friday, October where thou can personally experience planet Earth for 14, same time. Information and cost: 202/357-3030. what she truly is: a precious ark of life, plying the (See article in Star Dust, 1993, September, p. 4.) wine-dark sea ofSpace. To encouraging you, several relatively light-pollution-free sities are available for Friday, October 7, 1994 - Open House at Hopewell NCA members's use. Information: Daniel Costanzo, Observatory. See the boxed item on page six for more details and directions. 703/841-4765. Saturday, October 8,19949:00 PM - "Exploring the Mondasys, October 3,10,17,24, and 31, at 7:30 PM Sky" telescope viewing at the open field in Rock Creek - Public nights at U.S. Naval Observatory (USNO), in Park nearest to the Nature Center. NCA members Northwest Washington, D.C. (off Massachusetts Av- please bring telescopes. For more information, call enue). Includes orientation program on USNO's mis- John Lohman, 703/820-4194 sion, viewing of operating atomic clocks, and glimpse through the finest optical telescopes in the Washing- Thursdays, October 13,20,27 and Nomber 3,1994, ton-Baltimore region. Information: USNO Public 7:00 PM - Daniel Costanzo (NCA), "Astronomy Affairs Office, 202/653-1541. O!O!O!: Life, The Universe & Everything (In Be- tween)." A four week adult education course at Ar- Tuesdays, October 4,11,18, and 25, at 7:30 PM- lington Planetarium. Information and cost: 703/358- Telescope making classes at Chevy Chase Commu- 7200. nity Center, Connecticut Avenue and McKinley Street, NW. Information: Jerry Schnall, 202/362- Saturday, October 14, 19949:00 PM - Open nights 8872. with NCA's Celestron 14-inch (0.36 meter) telescope at Ridgeview Observatory, south of Alexandria at Wedenesday, October 5 - "Sky Watch" column by 6007 Ridgeview Drive (off Franconia Road between Blaine P. Friedlander, Jr. appears in The Washington Telegraph Road and Rose Hill Drive). Information: Post "Style" section. It lists many other events for the Bob Bolster at 703/960-9126. month. Thursday, October 15, 1994 - Next deadline for all Thursday, Friday, and Saturday, October 6, 7, and submissions to November Star Dust. Send to Gary & 8, Early Evening Twighlight - Moon at her conve- Alisa Joaquin, Editors at 7821 Winona Ct., niently beautiful best asa thin waxing crescent, bathed Annandale, VA, 22003, or send an ASCII file via E- in Earthshine, gracing the early evening twighlight Mail at 71561.1747 @compuserve.comorfax to 703/ sky: "the old Moon in the young Moon's arms." You 658-2233. can enjoy this spectacle even from the light-polluted heart of urbania. So, go outside, take a look, and Saturday, October 29,1994, Night - October's sec- celebrate the beginning of a new "moonth" (a new ond best night for dark-sky observing and "absorbing" lunation). ("Moon-dark" until around Midnight). See October 1 listing. Fridays, October 6, 13,20, and 27, at 7:30 PM - Telescope making classes at American University, CALENDAR, continues on Page 3 Page 2 CALENDAR, from Page 2 Wednesday, November 2,1994 - "Sky Watch" col- Saturday, November 5, 1994 - November's best umn by Blaine P. Friedlander, Jr. appears in The night for dark-sky observing and "absorbing" Washington Post "Style" section. It lists many other ("Moon-dark" practically all night long). See October events for the month. 1 listing. Saturday, November 5, 1994, 11 :00 AM to 4:00 PM Saturday, Sunday, and Monday, November 5, 6, - The NCA and the Smithsonian Institution's National and 7,1994, Early Evening Twighlight - Moon at her Air and Space Museum (NASM) present "Binoculars! conveniently beautiful best. See October 6, 7, and 8 Telescopes! Astronomy!: A Free Consumer Presenta- listing. tion." NASM, Briefing Room (see accompanying article). Other events, objects, and phenomena too numerous to mention here are listed in the publications Sky & Saturday, November 5,1994- The November NCA Telescope, the Astronomical Calendar 1994, and the meeting will feature Carol Ann Grady speaking about Observer's Handbook 1994, plus numerous software "The Beta Pictoris Phenomenon in Herbig Ae/Be and packages. NCA members can purchase all these at a A-shell Stars." discount. To join NCA, use membership application on page seven: The Comet, Shoemaker-Levy 9, Strikes Jupiter Reviewed by Harold Alden Williams On Saturday September 10, 1994 at the view about half of the time. The of the entire campaign as well as the National Institutes of Health situation is further complicated by being one of the six principal inves- (NIH), Rob Landis of the Space the telescopes' not being able to look tigators, whom all also had many co- Telescope Science Institute (STScI) too near the Sun, Moon.aad Earth. investigators. Hal Weaver was also spoke on the Comet Shoemaker- The telescope is orbiting Earth every Rob's branch chief when he was Levy 9' s Striking Jupiter. Rob first 90 minutes, so not only is pointing with moving targets. With Hubble's told us a little about his Hubble complicated but so is the data path spherical aberration problem before Space Telescope (HST) work expe- that takes the information from the repair, bright moving targetlike rience. When hefirstarrived in 1992 telescope to STScI in Baltimore. planets needed fewer extensive at the STScI his primary responsi- Landis was recently transferred into spherical aberration deconvolutions bilities were in the Science Planning the newly created special projects of because of their high signal-to-noise Branch in the near-term planning the Public Outreach Office at STScI.
Recommended publications
  • Carnegie Institution of Washington Department of Terrestrial Magnetism Washington, DC 20015-1305
    43 Carnegie Institution of Washington Department of Terrestrial Magnetism Washington, DC 20015-1305 This report covers astronomical research carried out during protostellar outflows have this much momentum out to rela- the period July 1, 1994 – June 30, 1995. Astronomical tively large distances. Planetary nebulae do not, but with studies at the Department of Terrestrial Magnetism ~DTM! their characteristic high post-shock temperatures, collapse of the Carnegie Institution of Washington encompass again occurs. Hence all three outflows appear to be able to observational and theoretical fields of solar system and trigger the collapse of molecular clouds to form stars. planet formation and evolution, stars and star formation, Foster and Boss are continuing this work and examining galaxy kinematics and evolution, and various areas where the possibility of introducing 26Al into the early solar system these fields intersect. in a heterogeneous manner. Some meteoritical inclusions ~chondrules! show no evidence for live 26Al at the time of their formation. So either the chondrules formed after the 1. PERSONNEL aluminium had decayed away, or the solar nebula was not Staff Members: Sean C. Solomon ~Director!, Conel M. O’D. Alexander, Alan P. Boss, John A. Graham, Vera C. Rubin, uniformly populated with the isotope. Foster & Boss are ex- Franc¸ois Schweizer, George W. Wetherill ploring the injection of shock wave particles into the collaps- Postdoctoral Fellows: Harold M. Butner, John E. Chambers, ing solar system. Preliminary results are that ;40% of the Prudence N. Foster, Munir Humayun, Stacy S. McGaugh, incident shock particles are swallowed by the collapsing Bryan W. Miller, Elizabeth A. Myhill, David L.
    [Show full text]
  • Lecture 9—Is the Earth Rare?
    41st Saas-Fee Course From Planets to Life 3-9 April 2011 Lecture 9—Is the Earth Rare? List of Rare Earth arguments/ Nitrogen abundance/ Frequency of large impacts/ Chaotic obliquity fluctuations J. F. Kasting The Gaia hypothesis First presented in the 1970s by James Lovelock 1979 1988 • Life itself is what stabilizes planetary environments • Corollary: A planet might need to be inhabited in order to remain habitable The Medea and Rare Earth hypotheses Peter Ward 2009 2000 Medea hypothesis: Life is harmful to the Earth! Rare Earth hypothesis: Complex life (animals, including humans) is rare in the universe Additional support for the Rare Earth hypothesis • Lenton and Watson think that complex life (animal life) is rare because it requires a series of unlikely evolutionary events – the origin of life – the origin of the genetic code – the development of oxygenic photosynthesis) – the origin of eukaryotes – the origin of sexuality 2011 Rare Earth/Gaia arguments 1. Plate tectonics is rare --We have dealt with this already. Plate tectonics is not necessarily rare, but it requires liquid water. Thus, a planet needs to be within the habitable zone. 2. Other planets may lack magnetic fields and may therefore have harmful radiation environments and be subject to loss of atmosphere – We have talked about this one also. Venus has retained its atmosphere. The atmosphere itself provides protection against cosmic rays 3. The animal habitable zone (AHZ) is smaller than the habitable zone (HZ) o – AHZ definition: Ts = 0-50 C o – HZ definition: Ts = 0-100 C. But this is wrong! For a 1-bar atmosphere like Earth, o water loss begins when Ts reaches 60 C.
    [Show full text]
  • Chapter 9: the Origin and Evolution of the Moon and Planets
    Chapter 9 THE ORIGIN AND EVOLUTION OF THE MOON AND PLANETS 9.1 In the Beginning The age of the universe, as it is perceived at present, is perhaps as old as 20 aeons so that the formation of the solar system at about 4.5 aeons is a comparatively youthful event in this stupendous extent of time [I]. Thevisible portion of the universe consists principally of about 10" galaxies, which show local marked irregularities in distribution (e.g., Virgo cluster). The expansion rate (Hubble Constant) has values currently estimated to lie between 50 and 75 km/sec/MPC [2]. The reciprocal of the constant gives ages ranging between 13 and 20 aeons but there is uncertainty due to the local perturbing effects of the Virgo cluster of galaxies on our measurement of the Hubble parameter [I]. The age of the solar system (4.56 aeons), the ages of old star clusters (>10" years) and the production rates of elements all suggest ages for the galaxy and the observable universe well in excess of 10" years (10 aeons). The origin of the presently observable universe is usually ascribed, in current cosmologies, to a "big bang," and the 3OK background radiation is often accepted as proof of the correctness of the hypothesis. Nevertheless, there are some discrepancies. The observed ratio of hydrogen to helium which should be about 0.25 in a "big-bang" scenario may be too high. The distribution of galaxies shows much clumping, which would indicate an initial chaotic state [3], and there are variations in the spectrum of the 3OK radiation which are not predicted by the theory.
    [Show full text]
  • Dynamical Models of Terrestrial Planet Formation
    Dynamical Models of Terrestrial Planet Formation Jonathan I. Lunine, LPL, The University of Arizona, Tucson AZ USA, 85721. [email protected] David P. O’Brien, Planetary Science Institute, Tucson AZ USA 85719 Sean N. Raymond, CASA, University of Colorado, Boulder CO USA 80302 Alessandro Morbidelli, Obs. de la Coteˆ d’Azur, Nice, F-06304 France Thomas Quinn, Department of Astronomy, University of Washington, Seattle USA 98195 Amara L. Graps, SWRI, Boulder CO USA 80302 Revision submitted to Advanced Science Letters May 23, 2009 Abstract We review the problem of the formation of terrestrial planets, with particular emphasis on the interaction of dynamical and geochemical models. The lifetime of gas around stars in the process of formation is limited to a few million years based on astronomical observations, while isotopic dating of meteorites and the Earth-Moon system suggest that perhaps 50-100 million years were required for the assembly of the Earth. Therefore, much of the growth of the terrestrial planets in our own system is presumed to have taken place under largely gas-free conditions, and the physics of terrestrial planet formation is dominated by gravitational interactions and collisions. The ear- liest phase of terrestrial-planet formation involve the growth of km-sized or larger planetesimals from dust grains, followed by the accumulations of these planetesimals into ∼100 lunar- to Mars- mass bodies that are initially gravitationally isolated from one-another in a swarm of smaller plan- etesimals, but eventually grow to the point of significantly perturbing one-another. The mutual perturbations between the embryos, combined with gravitational stirring by Jupiter, lead to orbital crossings and collisions that drive the growth to Earth-sized planets on a timescale of 107 − 108 years.
    [Show full text]
  • The Iron Planet Sex and Skin Color
    PERIODICALS Yet, this is the key to the lesson, Kass says. necessary condition for national self- "God's dispersion of the nations is the PO- awareness and the possibility of a politics litical analog to the creation of woman: in- that will. hearken to the voice of what is stituting otherness and opposition, it is the eternal, true, and good." SCIENCE & TECHNOLOGY ''Mercu~'~Heart of Iron" by Clark R. Chapman, in Asfrononzy The Iron Planet (Nov. 19881, 1027 N. 7th St., Milwaukee, Wisc. 53233. More than a decade after America's un- plays a vita1 role in the two leading theo- manned Mariner 10 flew near the planet ries of the origins of the solar system. Ac- Mercury during 1974-75, scientists have fi- cording to one theory, formulated by cos- nally digested all of the data from the mochemist John Lewis during the 1970~~ flight. And they are starting to ask some the solar system was created in a more or big questions, reports Chapman, of Tuc- less orderly fashion. Lewis believes that son's Planetary Science Institute. the planets formed out of gases that cooled Located about midway between the and condensed. At some point, billions of Earth and the Sun, Mercury is a "truly bi- years ago, the sun flared up briefly, blast- zarre" planet. Its rock cmst is unusually ing away many gases. According to Lewis's thin; a "metallic iron core" accounts for theory, there should not be any sulfur, or 70 percent of the planet's weight. anything like it, on Mercury. The most surprising discovery made by A more recent theory, propounded by Mariner 10 was that the tiny planet has a George Wetherill of the Carnegie Institu- magnetic field, like Earth's but much tion, is that the solar system emerged from weaker.
    [Show full text]
  • Complex Life, by Jove!
    Complex Life, By Jove! By: Leslie Mullen The gas giants in our solar system. From left: Neptune, Uranus, Saturn, and Jupiter. Credit: NASA One of the tenets of astrology is that the positions of the planets affect us. For instance, the position of the planet Jupiter in your chart is supposed to indicate good luck for a certain aspect of your life. In an eerie echo of astrology, some scientists are now saying that the position of Jupiter in our solar system was very good luck for life on Earth. Jupiter is about 5 astronomical units (AU) away from the Sun − far enough away from Earth to not have interfered with the development of our planet, and yet close enough to gravitationally deflect asteroids and comets, limiting the number of dangerous impacts. Impacts by asteroids and comets can create cataclysmic events that destroy life − witness the demise of the dinosaurs 65 million years ago, widely believed to have been brought about by a "killer" asteroid impact. Without Jupiter, instead of being hit with a killer asteroid every hundred million years or so, we´d get one every 10,000 years. This reduction in impacts enabled the Earth to develop both simple and complex forms of life. But gas giant planets like Jupiter don´t always help in the development of complex life. Consider, for instance, that while Jupiter deflects many asteroids away from Earth, it also is responsible for most of the asteroids in the first place. When planetesimals were clumping together to form the terrestrial planets, the gravitational influence of Jupiter prevented a fifth planet from forming.
    [Show full text]
  • Deep Earth. (M)
    DOCUMENT RESUME ED 250 199 SE 045 178 TITLE The Earth's Core: How Does It Work? Perspectives in Science. Number 1. v INSTITUTION Carnegie Institution of Washington, Washington, DC.h PUB DATE 84 ; ,NOTE 35p. AVAILABLE FROMCarnegie Institution of Washington, 1530 P Street, NW, Washington, DC 20005 ($1.00). .PUB TIME Viewpoints, (120) EDRS PRICE MF01 Plus Postage. PC Not Available froniEDRS. DESCRIPTORS *College Science; *Geology; *Geophysics; Higher Education; High Schools;- Matter; Models; *Science Experiments; *Scientific Research; Secondary School Science; *Seismology IDENTIFIERS *Core (Earth Structure) ABSTRACT a Various research studies designed to enhance knowledge about the earth's core are discussed. Areas addressed includes (1) the discovery of the earth'score; (2) experimental approaches used .in studying the earth's core (including shock-wave everiments and experiments, at high static pressures), the search for the core's light elements, the possible presence of potassium in the core, and use of the diamond cell for investigating thecore;. (3) seismic explorations of the core; (4) inhomogeneities at the core-mantle boundary; (5) terrestrial magnetism and the outer core; and (6) theories of inner -earth structurk from the'perspective of solar system history. Studies of the earth's mantle which may provide additional information about the earth's core are also discussed. They include laboratory experiments with mantle materials and modeling of mantle structure at the Carnegie Institution's Department L_____of____Terreittrial Magnetism. It is poin04 out that althoughmany questions about the earth's core are still unanswered, the promise of new research tools is vast. Favored bfadvances in computer modeling and in techniques for experiments at Nary high presiure, today's scientists seem well-positioned to address these, questions but the deep earth.
    [Show full text]
  • Obituaries Prepared by the Historical Astronomy Division
    1274 Obituaries Prepared by the Historical Astronomy Division WULFF-DIETER HEINTZ, 1930-2006 also gained practical training in meridian circles and position Wulff Dieter Heintz, Professor Emeritus of Astronomy at micrometers, and learned to make binary star observations Swarthmore College, passed away at his home on 10 June with the old Fraunhofer refractor ͑1835͒ of the Munich Ob- 2006, following a two-year battle with lung cancer. He had servatory. It was here that his passion for binary stars was turned seventy-six just one week earlier. Wulff was a leading born. authority on visual double stars and also a chess master. A In 1953, Munich University awarded Wulff the degree of prominent educator, researcher, and scholar, Wulff was Doktor rerum naturalis in astronomy, which he completed noted for being both succinct and meticulous in everything under the direction of Felix Schmeidler. Wulff was almost he did. immediately recruited by the Munich University Observatory Wulff Heintz was born on 3 June 1930 in WXrzburg ͑Ba- to serve as the Scientific Assistant at the Southern Station in varia͒, Germany. Naturally left-handed, his elementary Mount Stromlo, Australia. He worked at Mount Stromlo school teachers forced him to learn to write ‘‘correctly’’ us- from 1954 to 1955, then returned to Munich to serve as ing his right hand, and so he became ambidextrous. During Research Officer from 1956-69, during which time he visited the 1930s, Wulff’s family saw the rise of Adolf Hitler and both the United Kingdom and the United States. Wulff was lived under the repressive Nazi regime.
    [Show full text]
  • 2006 Fall.Pdf
    THE NEWSLETTER OF THE CARNEGIE INSTITUTION [FALL 2006] [PAGE 3] [PAGE 10] [PAGE 11] Inside 3 Embryology Alumnus Andrew Z. Fire Shares Nobel Prize 4 Tipping the Mass Scales at the Edge of the Visible Universe 6 Small-scale Logging Blazes the Trail for Deforestation 7 Sugar Metabolism Tracked in Living Plant Tissues in Real Time 9 Minerals Go “Dark” Near Earth’s Core 10 More Awards: Two Other Carnegie Luminaries Honored 12 Mice Aid the Study of Human Eye Cancer 13 Carnegie’s George West Wetherill, Father of Earth-Formation Models, Dies at 80 14 Why Waves Go Wacky at Earth’s Center 14 Three New “Trojan” Asteroids Found Sharing Neptune’s Orbit 16 In Brief 20 David Greenewalt Building Dedicated at Broad Branch Road Ȝ Ȝ Ȝ Ȝ Ȝ Ȝ Ȝ DEPARTMENT GEOPHYSICAL DEPARTMENT THE DEPARTMENT DEPARTMENT CASE/ OF EMBRYOLOGY LABORATORY OF GLOBAL OBSERVATORIES OF PLANT OF TERRESTRIAL FIRST LIGHT ECOLOGY BIOLOGY MAGNETISM 2 As an institution founded with a mandate to conduct basic scientific research, Carnegie can often appear removed from the problems that dominate our headlines. Indeed, stories of violent crime, scandal, and complicated political problems can sometimes seem like dispatches from another frontier. The institution also seems distant from people who tackle issues of social gravity. One could easily conclude that Carnegie’s explorations of the nature of life, the Earth, and the cosmos have little to do with issues that are germane to our daily lives. Is this perceived gulf as wide as it seems? As a nonscientist, I am struck by how the passage of time can illuminate the value of basic research.
    [Show full text]
  • Uranus, Neptune, and the Mountains of the Moon
    PSRD: Uranus and Neptune: Late Bloomers http://www.psrd.hawaii.edu/Aug01/bombardment.html posted August 21, 2001 Uranus, Neptune, and the Mountains of the Moon --- The tardy formation of Uranus and Neptune might have caused the intense bombardment of the Moon 3.9 billion years ago. Written by G. Jeffrey Taylor Hawai'i Institute of Geophysics and Planetology Huge circular basins, marked by low regions surrounded by concentric mountain ranges, decorate the Moon. The giant holes may have formed during a short, violent period from about 3.9 to 3.8 billion years ago. Three hundred to 1000 kilometers in diameter, their sizes suggest that fast-moving objects with diameters of 20 to about 150 kilometers hit the Moon. Numerous smaller craters also formed. If most large lunar craters formed between 3.9 and 3.8 billion years ago, where were the impactors sequestered for over 600 million years after the Moon formed? One possibility has been studied with computer simulations by Harold Levison and colleagues from the Southwest Research Institute (Boulder, Colorado), Queen's University (Ontario, Canada), and NASA Ames Research Center in California. The idea, originally suggested in 1975 by George Wetherill (Carnegie Institution of Washington), is that a large population of icy objects inhabited the Solar System beyond Saturn. They were in stable orbits around the Sun for several hundred million years until, for some reason, Neptune and Uranus began to form. As the planets grew by capturing the smaller planetesimals, their growing gravitational attraction began to scatter the remaining planetesimals, catapulting millions of them into the inner Solar System.
    [Show full text]
  • The Origin of the Earth What's New?
    The Origin of the Earth What’s New? Alex N. Halliday1 rogress in understanding the origin of the Earth has been dramatic in been present. The relative propor- tions of aluminum-26 and iron-60 recent years, which is timely given the current search for other habitable are consistent with production in a Psolar systems. At the present time we do not know whether our solar supernova. system, with terrestrial planets located within a few astronomical units2 of a solar-mass star, is unusual or common. Neither do we understand where the DISKS AND PLANET FORMATION water that made Earth habitable came from, nor whether life in the Universe Immanuel Kant (1724–1804) and is rare or plentiful. Perhaps something unusual happened here on Earth. Pierre-Simon de Laplace (1749–1827) However, the timescales over which the Sun and solar system formed, as well both argued that the solar system as the detailed mechanisms involved, have been the subjects of extensive originated from a swirling disk of gas and dust (FIG. 1). In 1755, Kant recent studies. Discoveries have resulted mainly from improved mass spectro- proposed the idea that the planets metric measurements leading to a resolution of just 100,000 years accreted from circumstellar dust in some cases. This short review explains some of these developments. under gravity. Laplace presented a similar model in 1796 and KEYWORDS: early Earth, solar system, core formation, planets, explained mathematically the geochemistry, cosmochemistry, isotopes rotation of the disk and planets. This resulted from the increase in angular momentum associated THE BIRTH OF THE SUN with the contraction of the solar nebula as it collapsed to The solar system formed 4.5–4.6 billion years ago (Patterson form the Sun.
    [Show full text]
  • New Data, New Ideas, and Lively Debate About Mercury
    PSRD: 2001 Mercury Conference http://www.psrd.hawaii.edu/Oct01/MercuryMtg.html posted October 22, 2001 New Data, New Ideas, and Lively Debate about Mercury --- A hundred scientists gathered to share new data and ideas about the important little planet closest to the Sun. Written by G. Jeffrey Taylor Hawai'i Institute of Geophysics and Planetology Mercury is an important planet. It is closest to the Sun, so its chemical composition helps us test ideas for how the planets formed. In contrast to Venus and Mars, Mercury is generating a magnetic field today--useful in understanding Earth's magnetic field. It has a huge metallic core compared to the other rocky planets. Its cratered, lunar-like surface records a fascinating geologic history. A hundred scientists attended a conference about this important little planet. It was held at the Field Museum in Chicago, Illinois, and was sponsored by the Museum, the Lunar and Planetary Institute, and the National Aeronautics and Space Administration. Mariner 10, the only space mission to Mercury, flew by it three times in 1974 and 1975. Reworking the data in light of a better understanding of remote sensing and using new image analysis techniques is leading to amazing new insights about the planet's origin and geological evolution. And although we have had only one mission to the planet, there are a growing number of astronomical observations from Earth to study the tenuous and complicated mecurian atmosphere. Radar observations are providing dramatic new views of the surface and have revealed mysterious deposits (probably of water ice) in the polar regions.
    [Show full text]