April 20, 2005. NASA's Spitzer Telescope Sees Signs of Alien Asteroid Belt. Spitzer Press Release. NASA's Spitzer Space Telescope has spotted what may be the dusty spray of asteroids banging together in a belt that orbits a star like our Sun. The discovery offers astronomers a rare glimpse at a distant star system that resembles our home, and may represent a significant step toward learning if and where other Earths form. ... Dr. Charles Beichman of the California Institute of Technology, Pasadena, Calif... "We can't directly see other terrestrial planets, but now we can study their dusty fossils." Asteroid belts are the junkyards of planetary systems. They are littered with the rocky scraps of failed planets, which occasionally crash into each other, kicking up plumes of dust. In our own solar system, asteroids have collided with Earth, the moon and other planets. If confirmed, the new asteroid belt would be the first detected around a star about the same age and size as our Sun. The star, called HD69830, is located 41 light-years away from Earth. There are two other known distant asteroid belts, but they circle younger, more massive stars. ...Beichman and colleagues used Spitzer's infrared spectrograph to observe 85 Sun-like stars. Only HD 69830 was found to possibly host an asteroid belt. They did not see the asteroids themselves, but detected a thick disk of warm dust confined to the inner portion of the star system. The dust most likely came from an asteroid belt in which dusty smash-ups occur relatively frequently, about every 1,000 years. "Because this belt has more asteroids than ours, collisions are larger and more frequent, which is why Spitzer could detect the belt," said Dr. George Rieke, University of Arizona, Tucson, co-author of the paper. "Our present-day solar system is a quieter place, with impacts of the scale that killed the dinosaurs occurring only every 100 million years or so."....
Feb 2005. The Sloan Digital Sky Survey. By Michael A. Strauss and Gillian R. Knapp. Sky & Telescope magazine. This is a fascinating article with sections on "The Origins of Asteroid Families", "Neither Stars nor Planets", "Cannibalism and the Milky Way", "Cosmological Mirages." Lots of interesting techniques for using filters. Excerpt (in the asteroid section): Mounted at the survey telescope's focal plane, the SDSS imaging camera simultaneously scans the sky through five rows of color filters: u (for ultraviolet), g (for green), r (for red), i (infrared), and z (a longer wavelength infrared band). Well not exactly simultaneously; the five are observed sequentially (r, i, u, z, and g), with roughly a five minute of time separating each. In the five minutes between the r and g exposures of a given patch of sky, Earth advances 9,000 km along its orbit, creating a parallax of several arcseconds in the apparent position of a main-belt asteroid (the effect of the asteroid's own orbital motion is several times smaller). ...The SDSS software recognizes this characteristic motion and can thus distinguish asteroids from much more numerous images of stars. The SDSS has precisely measured the colores of some 100,000 asteroids to date -- more than 100 times the number for which colors had been available beforehand.... An asteroid's orbit around the Sun is characterized by three numbers: its semimajor axis, its eccentricity; and its inclination. Plotting these quantities for all known asteroids shows clumps with similar orbits, termed "families." It has long been suggested that the members of a particular family are shards of a larger single body that was broken up in a collision some time ago. If this were the case, one would expect that a given family's asteroids would share the same composition and age and therefore would have similar colors. The SDSS data confirm this hypothesis dramatically. Collisions aren't the only processes that alter asteroids. Planetary scientists have predicted that asteroid colors should evolve as the rocky objects' surfaces are altered by the solar wind and by micrometeoroid impacts. The Sloan asteroids' colors and orbital parameters support this "space weathering" hypothesis (S&T: October 2004, page 26). They also solve a long-standing mystery: why the interiors of meteorites that have fallen to Earth have colors that differ from those of the commonest asteroids. [SDSS website is http://www.sdss.org/]
Experiencing the Great Oklahoma Fireball of 1920
Dec. 2002 Did a Comet Swarm Kill the Dinosaurs? by DAVID TYTELL, Sky & Telescope magazine, p. 24. IN 1991 A MODERN SCIENTIFIC "WHODUNIT" WAS SOLVED WHEN geologists identified a deeply buried, 180-kilometer-Wide crater in the Yucatan peninsula. Now known as Chicxulub, the scar resulted from the impact of a 10-km asteroid or comet nucleus 65 million years ago. Geologic evidence indicates that the impact triggered global tidal waves, worldwide firestorms, and massive earthquakes. It also left a worldwide layer of extraterrestrial dust. When Earth finally returned to normal, the dinosaurs and the majority of all then-living species had gone extinct, opening the way for mammals to diversify and dominate Earth.
Height of meteors measured: "…pinpoint glow occurred at an altitude of 115 kilometers. Only 300 milliseconds later, at 107 km, the tiny meteoroid had developed a luminous bow shock about 600 meters (2,000 feet) wide."
September 3, 2003. Make a note: 21 March 2014 might just be Asteroid D-day. By Charles Arthur, Technology Editor of http://www.independent.co.uk -- "The Earth is imperilled by an asteroid again, which will strike the planet on 21 March 2014 if our luck turns out to be truly bad, astronomers say."
September 3, 2003. Pointless Asteroid Scare by David Morrison
July 21, 2003 Search for Large Asteroids Nears Completion, Experts Ponder Gaps in Program, By Michael Paine. SYDNEY, Australia -- A stated goal of finding 90 percent of all large Near Earth Asteroids (NEAs) by 2008 is more or less on target, .... The goal, originally outlined by NASA and mandated by the U.S. Congress, is designed to insure that space rocks in the vicinity of Earth's orbit, and larger than 1 kilometer (0.62 miles), are found and tracked. An object of this size could cause global destruction if one were to hit Earth. .... The global experts gathered here reiterated a common concern among asteroid scientists: When the current goal is reached, there will still be many unfound smaller objects that are easily capable of destroying a large city. Full story.
COMETS
Spaceguard http://cfa-www.harvard.edu/~marsden/SGF/
ESA Near Earth Objects Space Mission Preparation http://www.esa.int/gsp/completed/neo/index.htm
Asteroid Flash Animation
http://www.jpl.nasa.gov/templates/flash/neo/neo.htm
06/11/2003 Evidence for meteor in early mass extinction found ... LSU geophysicist Brooks Ellwood is plumbing the geologic record, trying to correlate known mass extinctions to meteor strikes.... Ellwood and four other researchers have just published an article in the journal Science in which they tie an early mass extinction to a meteor strike. This extinction happened 380 million years ago in what is called the middle Devonian. It was a time when only small plants, wingless insects and spiders inhabited the land and everything else lived in the sea. About 40 percent of all species disappeared from the fossil record at this time.ÊThe extinction has been known to geologists for a long time but this is the first time it has been tied to a meteor strike. This is also the oldest known impact that has been tied to a mass extinction.... What is unique about Ellwood's work, however, is the means he uses to identify the different layers in the geologic record: induced magnetism.Ê... "The magnetic pattern associated with an impact layer is often distinctive, making it easier to find in a thick sequence of strata," he said.ÊÊÊÊ..."We know that meteors have struck the Earth hundreds of times," Ellwood said. "If I had to guess, I would say that once every 5 million years a meteor big enough to cause a mass extinction hits the Earth. See full article.
March 26, 2003 ESA Press Release N¡Ê19-2003:ÊÊESA Studies Missions to Safeguard the Earth. http://www.esa.int/export/esaCP/Pr_19_2003_p_EN.html. The six missions under study were: Don Quijote: This proposal involves the launch of two spacecraft to test technologies required to deflect an asteroid heading towards Earth. Earthguard 1: A proposal to mount a ÒhitchhikerÓ telescope on a spacecraft en route to the inner Solar System,... EUNEOS: A medium-sized telescope mounted on a dedicated spacecraft platform that would search for the most dangerous NEOs from inside the orbit of Venus. ISHTAR: In addition to measuring the mass, density and surface properties of an NEO, this spacecraft would probe the interior of an NEO in order to study its structure and internal strength. SIMONE: A fleet of five low-cost microsatellites that would each fly by and/or rendezvous with a different type of NEO. Remote observation of NEOs from Space: A space-based observatory to carry out remote sensing and detect physical characteristics of NEOs, such as size, composition and surface properties.
March 17, 2003 -- WORRIED ABOUT ASTEROID-OCEAN IMPACTS? DON'T SWEAT THE SMALL STUFF. From Lori Stiles, UA News Services, 520-621-1877. The idea that even small asteroids can create hazardous tsunamis may at last be pretty well washed up. Small asteroids do not make great ocean waves that will devastate coastal areas for miles inland, according to both a recently released 1968 U.S. Naval Research report on explosion-generated tsunamis and terrestrial evidence. Full Article
March 6, 2003. NASA's Newest Maps Reveal a Continent's Grandeur and a Secret. The existence of the impact crater known as Chicxulub (Chik-sah-loob) was first proposed in 1980. In the 1990s, satellite data and ground studies allowed it to gain prominence among many scientists as the long sought-after "smoking gun" responsible for the demise of the dinosaurs and more than 70 percent of Earth's living species 65 million years ago. Now, the Shuttle Radar Topography Mission has provided the most telling visible evidence to date of a 180-kilometer (112-mile) wide, 900-meter (3,000-foot) deep impact crater, the result of a collision with a giant comet or asteroid on one of Earth's all-time worst days. Full article at http://www.jpl.nasa.gov/releases/2003/30.cfm
February 4, 2003 RELEASE NO: NOAO 03-03 NASA Should Lead More Focused Program to Reduce Threat from Hazardous Asteroids; http://www.noao.edu/outreach/press/pr03/pr0303.html, National Optical Astronomy Observatory
January 2, 2003, Earth and Asteroid Play Orbital Cat and Mouse Game--http://www.jpl.nasa.gov/releases/2003/1.cfm--The first asteroid discovered to orbit the Sun in nearly the same path as Earth will make its closest approach to our planet this month before scurrying away for 95 years. The space rock, measuring about 60 meters (approximately 200 feet) across, is like a mouse teasing a cat. The asteroid approaches the Earth, first on one side and then on the other. Animation: http://neo.jpl.nasa.gov/2002aa29.html
25 July 2002 (AP) Astronomers: Asteroid Hit Unlikely
By Andrew Bridges -- http://www.space.com/spacewatch/asteroid_threat_020725.html -- Astronomers said Wednesday that they are keeping close watch on a newly discovered 1.2 mile-wide asteroid (2002 NT7) to determine whether it will collide with Earth Feb. 1, 2019.
June 20, 2002. Paris (AFP) See Asteroid Gives Earth Closest Shave In Years -- A football-pitch-sized asteroid capable of razing a major city came within a whisker of hitting the Earth on June 14, but was only spotted three days later, ....
March 21, 2002, Close-call Asteroid Causes More Worries By Stuart J. Goldman -- http://SkyandTelescope.com/news/current/article_545_1.aspÊ Excerpt: Billed as the "blind-spot" asteroid, a building-size space rock passed the Earth unnoticed two weeks ago. An automated sky survey detected minor planet 2002 EM7 on March 12th. Subsequent orbital calculations determined that the asteroid had come closest to the Earth four days earlier at a distance of about 464,000 kilometers (288,000 miles), slightly more than the distance from the Earth to the Moon. Prior to the flyby, 2002 EM7 was too close to the Sun, hence the "blind-spot" moniker.
February 25, 2002 New Probe of Yucat‡n Crater Ends by J. Kelly Beatty http://SkyandTelescope.com/news/current/article_503_1.asp
Jan 28, 2002, The Great Dying--http://science.nasa.gov/headlines/y2002/28jan_extinction.htm?list617264 -- Excerpt: Somehow, most of the life on Earth perished in a brief moment of geologic time roughly 250 million years ago. Scientists call it the Permian-Triassic extinction or "the Great Dying" -- not to be confused with the better-known Cretaceous-Tertiary extinction that signaled the end of the dinosaurs 65 million years ago. Whatever happened during the Permian-Triassic period was much worse: No class of life was spared from the devastation. Trees, plants, lizards, proto-mammals, insects, fish, mollusks, and microbes -- all were nearly wiped out. Roughly 9 in 10 marine species and 7 in 10 land species vanished. Life on our planet almost came to an end. Science@NASA.
December 17, 2001 -- Earth May Have Had Several Generations Of Life Evolution -- http://www.cosmiverse.com/space12170103.html -- Earth may have survived several early impacts from large asteroids, causing life to disappear and reappear several times according to a theory put forth recently. The early Earth, in other words, may have been an interrupted Eden - a planet where life repeatedly evolved and diversified, only to be sent back to square one by asteroids 10 or 20 times wider than the one that hastened the dinosaurs' demise. When the surface of the Earth finally became inhabitable again, thousands of years after each asteroid impact, the survivors would have emerged from their hiding places and spread across the planet - until another asteroid struck and the whole cycle was repeated. [Cosmiverse.]
Sunlight Could Push Asteroids into Killer Orbits--Scientists have long been puzzled about why there are asteroids in orbits outside of the belt between Mars and Jupiter, but a new culprit might have been uncovered: sunlight. U.S.-Czech research indicates that the gradual force from sunlight could slowly push asteroids into gravitational interaction with Jupiter, which could then swing them into wild orbits, including those which cross the Earth's orbit. For more information, go to http://www.swri.org/9what/releases/asteroid.htm
Nov 2001 Leonids Put on a Spectacular Show--It was one of the most anticipated meteor showers in recent years, and to the delight of skywatchers around the world, the Leonid Meteor Storm of 2001 was a night to remember. Viewers in North America saw up to 2,600 meteors an hour during perfect viewing conditions, making it the best storm since 1966 (when skywatchers saw more than 150,000 meteors an hour). Even though the peak of the storm is over, you can expect to continue seeing Leonid meteors until November 21st, when the Earth leaves the dust clouds left by Comet Tempel-Tuttle. For more information, go to http://spaceweather.com/meteors/gallery_18nov01.html
Nov 7, 2001 Fewer Earth Crossing Asteroids Than Previously Thought--Some good news: the Earth is less likely to be struck by an asteroid than scientists previously calculated. The odds are only 1 in 5,000 that an asteroid big enough to wipe out civilization will hit the Earth within the next 100 years (much lower than the 1 in 1,500 of earlier estimates). Astronomers from Princeton University used data from the Sloan Digital Sky Survey to calculate that there are 700,000 asteroids in the solar system larger than 1 kilometre; but only a fraction of those will ever cross the Earth's orbit. For more information, go to http://www.sdss.org/news/releases/20011108.asteroid.html
Binzel, Richard P., A New Century for Asteroids, Sky & Telescope magazine, July 2001, p. 44 (hard copy).
NEAR Falls for Eros (hard copy article in Sky & Telescope) by J. Kelly Beatty, May 2001 issue.
March 10, 2000 The Ups and Downs of Impacts -- A team of scientists led by Timothy S. Culler (University of California, Berkeley) concludes that the rate of impacts on the Moon -- and therefore Earth -- has taken some dramatic downs and ups over the past 4 billion years.
March 14 Tagish Lake: Mystery Meteorite At last year's Lunar and Planetary Science Conference, held each March in Houston, Texas, meteorite specialists were salivating over the Tagish Lake meteorite, which had dropped as a hail of fragments onto the Yukon's winter wilderness just two months before. A year later, the Tagish Lake fall is still causing a scientific buzz because its unique composition, forged at the very beginning of the solar system, defies easy explanation. "We were hoping to find all these amino acids," laments Iain Gilmour (Open University), "and they're just not there." What Gilmour and others have identified are puzzling clues to the meteorite's origin. (Sky & Telescope magazine online)
February 22, 2001 ASTEROID OR COMET TRIGGERED LARGEST MASS EXTINCTION IN EARTH'S HISTORY, FORESHADOWING FATE OF DINOSAURS ftp://ftp.hq.nasa.gov/pub/pao/pressrel/2001/01-023.txt
February 14, 2001 ASTEROID MISSION NOT YET "NEAR" AN END ftp://ftp.hq.nasa.gov/pub/pao/pressrel/2001/01-020.txt
MOVIE OF ASTEROID LANDING (February 12, 2001) http://near.jhuapl.edu/iod/20010731/index.html
January 31, 2001, NEAR MISSION COMPLETES MAIN TASK, NOW WILL GO WHERE NO SPACECRAFT HAS GONE BEF0RE, ftp://ftp.hq.nasa.gov/pub/pao/pressrel/2001/01-013.txt -- ...NEAR spacecraft, the first to orbit an asteroid, ... will now attempt another first: a controlled descent to the surface of the asteroid on Feb. 12. -- NEAR Renamed for Shoemaker. January 02, 2001, Asteroid Landing Draws Near By Leonard David
December 18, 2000 Impact crater examined for clues to dinosaurs' demise -- The rock and dust kicked up by an asteroid impact 65 million years ago were not enough to kill the dinosaurs, according to researchers -- but the debris may have sparked a deadly global chemical reaction in the atmosphere.
December 11, 2000 The Baffling Geminid Meteors http://science.nasa.gov/headlines/y2000/ast08dec_1.htm -- Most meteor showers are caused by comets, but the Geminids, which peak on December 13th, seem to come from a curious near-Earth asteroid.
Sept. 28, 2000 -- 56-mile-wide Crater in Virginia -- NASA Press Release ftp://ftp.hq.nasa.gov/pub/pao/pressrel/2000/00-152.txt
January 22, 1997-- Very early on the morning of January 22, 1997, Lottie Williams, a resident of Tulsa, Oklahoma, was walking for exercise in a park near her home. She saw a "big bright light, like a fire" in the sky. "It was coming over the park and as it approached us it got bigger. All the colors that you see that come from fire, all those colors were there." A few minutes later, Williams felt a gentle tap on her shoulder. On the ground, she found a light piece of charred metal, about the size of her hand. After some investigation, Williams confirmed that the metal fragment came from a rocket that had been used to put a satellite into orbit for the U.S. Air Force in 1996. After nine months in space, a fuel tank from the rocket crashed into an empty field in Texas. A metal splinter from that tank hit Williams on the shoulder... See full article on January 22, 2002: The Center for the Study of Technology and Society. See also The Aerospace Corporation.
Hardcopy Articles
Chandler, David L., Asteroid for the Millennium, Astronomy magazine, Dec 2002. p. 43. Asteroid 1950DA might collide with Earth 900 years from now.
Phillips, Jim, Meteorite Field Guide, Mercury Magazine, Nov-Dec 2001. p.
Kress, Monica, Collecting Cosmic Dust, Mercury Magazine, Nov-Dec 2001. p. 24.
Jenniskens, Peter, Ready for the Storm, (on Leonid meteor storms). Mercury Magazine, Nov-Dec 2001. p. 14.
Freedman, David H., Policing the Universe, (on Brian marsden and the IAU Minor Planet Center), Astronomy Magazine, Sept. 1998, p. 59.
Morrison, David, Target Earth, Astronomy Magazine, Feb 2002, p. 46. Chances of an asteroid or large meteoroid impacting Earth are low, but the results could be disastrous.
Sawyer, Kathy, Seeing Spots, Astronomy Magazine, Oct 1998, p. 44. On Louis Frank's theory that 25,000 comets enter Earth's upper atmosphere every day.
Verschuur, Gerrit L., Impact Hazards: Truth and Consequences, Sky & Telescope Magazine, June 1998. p. 26.
--------------------------------------------------------------------------------
Subject: Target Earth info
Date: Wed, 10 Jan 2001 07:45:15 -0800
From: Seth Teitler satelite@uclink.berkeley.edu [from] a talk by Walter Alvarez on the impact theory, ...
... about half of the genera (plural of genus), animal and plant, died off.
... the asteroid was about 10 km across, moving 30 km/sec, while the oceans are at most about 5 km deep.
The explosion released energy equivalent to 100 million megatons of TNT, more than 10,000 times the yield of all the nuclear weapons of the Cold War. Nearby rock would have been heated to ~20,000 K--a few times the surface temp. of the Sun! This would have been enough to vaporize the rock, but not enough to initiate fusion (someone asked him about this).
Walter had several of the same slides that we use in our show. In particular he had a map of the USA and Mexico with some blue and red dots on it. The blue dots mark spots where the K-T boundary layer has been found; also there was a spot on the Brazos River (I think in Texas) where sandstones were found that were interpreted by Jody Bourgeious as tsunami deposits. The tsunami generated by the impact would have been about 1 km high.
Current thinking is that the ash and dust and whatnot would have darkened the sky for only a few months--still enough to kill lots of plants and animals, but not a year or more, as the old script says. Also, the material thrown up would have generated 3 kinds of acid rain; Walter seemed to be saying that the acid rain would have been more important in killing things off than the lack of sunlight.
Finally, an exciting recent find is that geologists have found outcrops of the ejecta blanket in Belize.
--------------------------------------------------------------------------------
Small Telescope Science Program's Homepage for the Deep Impact Mission -- http://deepimpact.umd.edu/stsp/ -- a joint effort between technically-proficient amateur astronomers, professional astronomers with discretionary telescope time, and private observatories to gather valuable ground-based optical data on Comet Tempel 1, the target of the Deep Impact Mission. Provide observations of Tempel 1 to supplement the professional data taken by the mission's science team.
--------------------------------------------------------------------------------
ASTEROIDS
Asteroid and Comet Impact hazards -- http://impact.arc.nasa.gov/
Asteroid 1997 XF11 (Earth Close-Approach 2028) -- http://ssd.jpl.nasa.gov/ca_97xf11.html
The Continuing Story Of Asteroid 1999 AN10: http://neo.jpl.nasa.gov/news/news017.html
Guide to minor body astrometry http://cfa-www.harvard.edu/cfa/ps/info/Astrometry.html
How Dangerous are Earth-Crossing Objects? -- http://www.pibburns.com/catastro/impacts.htm
IAU: List of Predicted Close Approaches http://cfa-www.harvard.edu/iau/lists/CloseApp.html
IAU: Minor Planet Center http://cfa-www.harvard.edu/cfa/ps/mpc.html
IAU Minor Planet Names: http://cfa-www.harvard.edu/iau/lists/MPNames.html
The Minor Planet Observer--http://www.minorplanetobserver.com/-- Palmer Divide Observatory
Near Earth Asteroid Tracking Program http://neat.jpl.nasa.gov/
Near Earth Objects http://www.nearearthobjects.co.uk/
Near Earth Object Program (JPL) http://neo.jpl.nasa.gov/
Planetary Defense: Catastrophic Health Insurance for Planet Earth -- http://www.fas.org/spp/military/docops/usaf/2025/v3c16/v3c16-1.htm
Spaceguard Foundation http://cfa-www.harvard.edu/~marsden/SGF/ program for detecting near-Earth asteroids
Toutatis http://echo.jpl.nasa.gov/asteroids/4179_Toutatis/toutatis.html an odd-shaped, weirdly spinning asteroid
METEORITES
Mrs. E. Hulitt Hodge was struck by a 8.5 pound meteorite at 1:00 P.M. on November 30, 1954. After it penetrated the ceiling of her living room and ricocheted off of the radio, it struck her in the hip while she slept on the couch. She was seriously bruised, even though she was covered by two heavy quilts. This is the only record of a human being struck by a meteorite. The meteorite is in the permanent collection at the Smithsonian. [Info from "Rocks From Space," by O. Richard Norton, Copyright 1994, Mountain Press Publishing Company, Missoula, Montana]
A boy was reported hit on the head in Mbale, Uganda on August 14, 1992 by a 3 gram meteor fragment that passed through some banana tree leaves. See http://home.planet.nl/~terkuile/meteorites/mbale/mbale.html
Meteor near-misses and strikes -- http://astro.wsu.edu/worthey/astro/html/im-meteor/strikes.html
Article dealing with the misconception that "Meteors are heated by friction as they pass through the atmosphere": http://www.space.com/scienceastronomy/top5_myths_020903-4.html
--------------------------------------------------------------------------------
Other Resources
Earth Impact Effects Program. Fill in the blanks describing an incoming meteor and determine the likelihood of your event and the resulting impact damage. http://www.lpl.arizona.edu/impacteffects/
--------------------------------------------------------------------------------