Space Exploration News From Around the Internet, Updated Every Weekday. June 23, 2000 - Issue #262
ASTRONOMERS ESTIMATE THERE ARE 900 EARTH CROSSING ASTEROIDS
A new report being prepared for Science Magazine estimates that there are 900 asteroids at least a kilometer in size buzzing around near the Earth - and we've only found 40% of them. The lead researcher, William Bottke from Cornell University, has developed a method to statistically project the number of near-Earth asteroids based on data from Spacewatch, an asteroid tracking program.
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
January 12, 2000
ASTEROID POPULATION COUNT SLASHED
NASA scientists taking a census of large asteroids in our solar system neighborhood have cut their estimate in half.The revised calculation comes from data gathered by NASA's Near-Earth Asteroid Tracking System (NEAT) and published in the January 13 issue of the journal Nature.
"Until now, scientists thought the population of large, near-Earth asteroids was between 1,000 and 2,000, but we've downgraded that figure significantly," said Dr. David Rabinowitz, of Yale University, New Haven, CT, lead author of the article and NEAT co-investigator. "We now believe there are between 500 and 1,000 near-Earth asteroids larger than one kilometer (about 0.6 miles) in diameter.
"This newer estimate was made possible by the computerized technology of the NEAT camera," Rabinowitz said. The NASA-funded system began tracking near Earth asteroids and comets in 1995 with a charge-coupled device camera mounted on a 1-meter (39- inch) Air Force telescope atop Mount Haleakala on Maui, HI.
The new figures may represent good news in the quest to achieve NASA's stated goal of finding 90-percent of all large, near-Earth asteroids by 2010, according to Pravdo. "Right now we know of 322 large, near-Earth asteroids," he said. "That was a fairly small fraction of the 2,000 asteroids in our previous estimate. With our new calculations of between 500 and 1,000 such objects, this 322 figure represents a large chunk."
While stressing that we must learn more about potential hazards from asteroids, Rabinowitz said, "None of the asteroids we've observed will hit Earth anytime in the near future."
"This new analysis reduces by half the estimated number of these potential hazards to Earth," Pravdo said.
"In the past, we relied on humans poring over photographic plates of the nighttime sky," Rabinowitz said. "The problem was, they didn't know how many asteroids they were missing, because they couldn't see faint objects. People's eyes also became tired and teary and they overlooked some objects. Machines don't get tired."
"With this computerized technology, we can find asteroids more easily and count them more accurately," said NEAT project manager Dr. Steven Pravdo of NASA's Jet Propulsion Laboratory, Pasadena, CA, a co-author of the Nature article. "It's important to know your observational limits, and with that information, we can develop models for what we are not able to see. This makes our estimates even more accurate."
Additional co-authors on the Nature article are Eleanor Helin of JPL, NEAT principal investigator, and Kenneth Lawrence, also of JPL. Helin was also principal investigator of the Palomar Planet-Crossing Asteroid Survey, a photographic search program, conducted for almost 25 years until it was discontinued and replaced by NEAT, the electronic detection program, in 1995. Her efforts were key to the organization of the NEAT program.
Data gathered by the asteroid tracking system are processed at Haleakala, and then undergo post-processing and analysis at JPL. This latest asteroid estimate is based on data collected between 1995 and 1998.
The asteroid tracking system has been on hiatus for the past year, but plans are in the works to re-activate the system in February using an upgraded 1.2 meter (48 inch) Air Force telescope on Haleakala. In addition, later this year, NEAT scientists will begin using the 1.2 meter (48 inch) Oschin telescope at Palomar Observatory near San Diego, CA.
Additional information on the NEAT project is available at http://neat.jpl.nasa.gov. Information on near-Earth objects is available at http://neo.jpl.nasa.gov.
The Near Earth Asteroid Tracking System is managed for NASA's Office of Space Science, Washington, D.C. by JPL, a division of the California Institute of Technology, Pasadena, CA.
Yale University
January 12, 2000
Yale Researcher Finds Number of "Near-Earth Asteroids" Are Fewer than Believed
New Haven, Conn. -- The number of "near-Earth asteroids" that have a chance, though miniscule, of colliding with Earth this century is half what was originally estimated, a Yale researcher says."They are the kind of asteroids you hear about in movies that are about two-thirds of a mile in diameter and could easily obliterate a city because they are coming in at cosmic velocities," said Research Associate David Rabinowitz. "The main thing we want to stress is that none of the known asteroids are in imminent danger of falling to earth and no impacts are predicted in the near future."
It was previously estimated that there are 1,000 to 2,000 such asteroids in chaotic orbits. Rabinowitz and his fellow researchers estimate that these asteroids actually total half that, or 500 to 1,000. Each has a 0.5 percent chance of colliding with Earth in the next million years, he said in the article published this week in the journal "Nature."
"The reduced number doesn't make us feel that much safer, but it does allow us to plan more accurately," Rabinowitz said. "The goal is to find the asteroids hundreds to thousands of years before they even come close."
The other researchers were Eleanor Helin, Kenneth Lawrence, and Steven Pravdo, all of the Jet Propulsion Laboratory at the California Institute of Technology. They made their observations through a U.S. Air Force telescope in Hawaii that was designed to look for artificial satellites.
Rabinowitz said smaller asteroids the size of a large house or hotel generally burn up or blow up before they hit the ground.
"But an asteroid the size of a city block is more dangerous because it could punch through the atmosphere and raise a lot of dust, which would change the climate of the Earth," he said. "It would be like a nuclear bomb coming in."
Efforts are underway around the world to survey this asteroid population because most of the threatening bodies remain undiscovered and their number is uncertain, the researchers said.
The observations were made using a large-format, charge-coupled device and a one meter aperture telescope based on the summit of Haleakala Crater on the island of Maui. Earlier photographic methods required a trained observer to identify asteroids by visual inspection and the accuracy varied according to the skill of the observer. The automated method is more consistent and provides a record of every detectable asteroid.
The researchers said that, at the current rate of discovery, about 90 percent of the asteroids probably will be identified in the next 20 years. The goal, however, is to double the current worldwide detection rate to complete the program in 10 years.
"If we can find the asteroids in 10 years, that's plenty of time," Rabinowitz said. "If you wait 100 or 1,000 years, that's too much time."
Rabinowitz is currently working with Professor Charles Baltay, chairman of the Yale Physics Department, to develop one of the world's largest electronic cameras. It will be used by Yale astronomers and physicists to study the properties of distant galaxies and supernova, and to study the expansion of the universe. The new camera also will be used in cooperation with astronomers at the Jet Propulsion Lab to continue the survey for near-Earth asteroids.
BBC News: Taskforce tackles asteroid threat
January 3, 2000
GOVERNMENT TASK FORCE TO INVESTIGATE IMPACT THREAT
On Tuesday 4th January the British National Space centre will announce the establishment of a government task force to investigate the threat posed to the Earth by asteroids and comets.The distinguished members of the Task Force, Dr. Harry Atkinson (Chairman), Sir Crispin Tickell and Professor David Williams will consider the threat posed by asteroids and comets, the action that Britain is currently taking to evaluate and reduce the risk, and will make recommendations as to what should be done in the future. Their recommendations will be submitted to Dr David Cope, the Director General of the British national Space Centre, who will report to Lord Sainsbury by 31st May 2000.
There has already been substantial press interest in this announcement, so keep your eyes on the media. Lord Sainsbury will be on BBC1 between 0800 and 0830 with Austin Atkinson.
Here we go!
Jay Tate
Spaceguard UK
Department of Trade and Industry
London, England
30 December 1999
SCIENCE MINISTER ANNOUNCES TASK FORCE ON POTENTIALLY HAZARDOUS NEAR EARTH OBJECTS
A Task Force to look at the potential for risk posed by Near Earth Objects (NEOs) has been announced by Science Minister, Lord Sainsbury.The three-strong team will make proposals to the British National Space Centre on the nature of the hazard and the potential levels of risk. It will also consider how the United Kingdom should best contribute to international effort on NEOs.
The Task Force will be chaired by Dr Harry Atkinson, formerly of the Science and Engineering Research Council (SERC) and past Chairman of the European Space Agency's Council. Two other appointees, Sir Crispin Tickell and Professor David Williams join Dr Atkinson.
Lord Sainsbury said: "The risk of an asteroid or comet causing substantial damage is extremely remote. This is not something that people should lie awake at night worrying about. But we cannot ignore the risk, however remote, and a case can be made for monitoring the situation on an international basis.
"I hope that the setting up of this Task Force will help the UK play a full and prominent role in international discussions on this important issue. I am delighted to be able to announce such a well-qualified team of experts and I look forward to receiving their report by the middle of 2000."
Notes:
- 1. Near Earth Objects are either asteroids or comets. Many NEOs have been
identified and their orbits determined using ground-based telescopes,
including some of NASA's, in a number of countries, although many remain
to be surveyed.
- 2. Of the known NEOs, none is believed to pose a significant risk to the
Earth in the foreseeable future. However, on a time-scale of many millions
of years, the Earth has been hit by objects of sufficient size to cause
serious damage, including the object which is thought to have impacted
the Earth about 65 million years ago, with global consequences including
the extinction of the dinosaurs.
- 3. The British National Space Centre has responsibility for co-ordination
with the work of other agencies on the threat to the Earth from space
debris and NEOs.
- 4. Dr Harry Atkinson, a New Zealander by birth, has had many years of
experience in dealing with science and technology internationally. This
has involved both intergovernmental organisations (such as the ESA) and
the co-ordination of activities between national agencies (including
NASA). He was attached to the Cabinet Office in the early 1970s, on the
staff of the Chief Scientific Advisor, where his tasks included reviewing
all governmental activities in environmental pollution.
Subsequently, in the Science Research Council his responsibilities included astronomy and space. This involved UK co-operation with other countries in many space science missions, and in ground-based astronomical facilities in Australia, South Africa, Hawaii and La Palma.
He helped to set up the European Synchrotron Radiation Facility at Grenoble and the EISCA facility in the Arctic Circle; and was concerned with the high-flux Beam Reactor (ILL), also at Grenoble. Until a year ago, he was Chief Scientist of the British insurance industry's Loss Prevention Council.
- 5. Sir Crispin Tickell has been Chancellor of the University of Kent since
1996 and has a distinguished diplomatic career. He was Permanent
Secretary of the Overseas Development Agency, 1984-87, British
Permanent Representative to UN, 1987-90, and Warden of Green College,
Oxford, 1990-97.
Sir Crispin has played a prominent role in presiding, chairing and advising committees and associations on environmental issues. These include Chairmanship of the International Institute for Environment and development; the Climate Institute of Washington; Earth Watch (Europe) and the Advisory Committee on the Darwin Initiative for the Survival of Species since 1992. He is author of a wide range of environmental publications.
- 6. Professor David Williams holds the Perren Chair of Astronomy at
University College London and is President of the Royal Astronomical
Society. He was previously Reader in Mathematics and Professor of
Theoretical Astrophysics at the University of Manchester Institute of
Science and Technology, UMIST, and has worked at NASA's Goddard Space
Flight Centre. He is co-author of titles on interstellar chemistry and
astrophysics, and has published over 200 articles in learned journals.
July 22, 1999: New Torino Scale Measures Asteroid Threat
National Research Council
Washington, D.C.
May 13, 1998
Policies Needed for Reporting Potential Hazards Of Asteroid Collisions with Earth
Recent news of a possible asteroid collision with Earth in 2028 sparked intense scientific and popular interest worldwide. When further data revealed that the asteroid had virtually no chance of hitting this planet, the episode prompted the astronomy community to re-evaluate how they communicate such information to the public.NASA and astronomers should develop protocols for reporting information about asteroids that appear to pose a potential hazard to Earth, says a new report from a National Research Council committee, which began its work before the recent episode. These protocols will be important because several telescope facilities and new instruments now coming into operation will dramatically increase the rate by which scientists are able to discover asteroids and comets whose orbits approach Earth. With the flood of discoveries expected within the next decade also will come the risk of false alarms.
Some 400 Earth-approaching asteroids and comets larger than one kilometer in diameter have been discovered so far, but only an estimated 10 percent of the objects this size have been identified. Of the thousands that may be discovered, some initially -- for a few days, weeks, or even years -- may seem likely to collide with Earth, until enough data have been collected to determine accurate orbits and interpreted to show otherwise. Policies for handling such potentially important information will be needed. International scientific organizations, such as the International Astronomical Union, could play a role in this task, the report says.
Most asteroids orbit the sun in a belt between Jupiter and Mars, but thousands have orbits that sometimes take them uncomfortably close to Earth. Geological processes such as erosion tend to erase scars left when asteroids and comets occasionally hit Earth, but there are some notable exceptions, such as Arizona's Meteor Crater. Moreover, there is evidence that an asteroid or comet some five to 10 kilometers in diameter created an enormous crater in Yucatan, Mexico, some 65 million years ago. That event has been implicated in the extinction of dinosaurs and other living organisms. This information, coupled with recent evidence of the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994, has led to increased scientific and public interest in assessing the likelihood that a large object might hit Earth again.
Although asteroids and comets are potential hazards to Earth, these tiny worlds offer a trove of clues to the solar system's birth and early history, the report says. Exploration of asteroids also may be used as stepping stones toward manned missions to Mars. Comets are frozen chunks of ice and dust thought to be left from the formation of the planets in the solar system. Asteroids are minor planets, some made from almost pure mixtures of nickel and iron like those at the Earth's core or from minerals similar to those found in the Earth's crust, and others from exotic combinations of carbon compounds.
To better understand the scientific opportunities posed by asteroids and comets, the report recommends that priorities be given to the following areas:
Telescopic studies. NASA, other government agencies, and private research organizations should further coordinate their programs using ground-based telescopes to search for and study asteroids and comets. Because a typical asteroid or comet is very faint and travels by Earth so quickly, the opportunity to view it may last no more than a few days or a week at most. To conduct the detailed observations that these fleeting objects require, routine or priority access to existing infrared and optical telescopes is needed. Otherwise, telescopes dedicated to characterizing the asteroids and comets discovered by ongoing search programs should be developed.
Laboratory investigations. More research is needed to increase understanding of extraterrestrial materials, such as meteorites, which are believed to come from asteroids. Laboratory studies can address, for example, the puzzle of how the environment in space changes the surfaces of asteroids to such an extent that the physical characteristics of the most common varieties of asteroids and meteorites do not match. NASA, other government agencies, and private research organizations should support additional laboratory investigations of samples of these space-borne objects. New analytical instruments, such as those necessary to study very small samples of meteorites, also are needed.
Robotic and manned spacecraft missions. Spacecraft that pass by, rendezvous with, or obtain samples from asteroids orbiting near Earth provide important information on the detailed physical characteristics, composition, and geologic histories of planetary bodies that is otherwise unobtainable. Moreover, Earth-approaching asteroids or comets are among the most accessible objects in the solar system. Indeed, some are easier to reach than the moon. NASA's Galileo missions, for example, provided a wealth of information about asteroids Ida and Gaspra orbiting between Mars and Jupiter. Last year, a NASA spacecraft made detailed observations of another asteroid, Mathilde. The spacecraft is currently en route to a February 1999 rendezvous with Eros, one of the largest Earth-approaching asteroids. NASA should continue such missions and improve spacecraft technology, such as propulsion and navigation systems, to allow additional low-cost rendezvous and sample-return missions.
Should the United States choose to undertake further manned exploration beyond Earth, a strong case can be made for beginning with missions to Earth-approaching asteroids, the report says. Because missions to these asteroids represent deep-space exploration with moderate technical challenges, they would be the least-expensive next step in human exploration of space and could provide the experience and technology needed for fruitful missions to Mars and beyond. Five percent of Earth-approaching asteroids are readily accessible by relatively short space flights.
A primary concern would be keeping the length of the mission as short as possible to minimize hazards and risks to which astronauts are exposed, including weightlessness, radiation, meteoroid impact, and equipment failure. Further research should be conducted to study specific technical requirements necessary for a six- to 12-month round-trip expedition. With the anticipated increase in discoveries of Earth-approaching asteroids, there likely will be opportunities for missions to one or more asteroids each year.
The study was funded by the NASA. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. It is a private, non-profit institution that provides science advice under a congressional charter. A committee roster follows.
Copies of The Exploration of Near-Earth Objects are available from the National Academy Press for $10.00 (prepaid) plus shipping charges of $4.00 for the first copy and $.50 for each additional copy; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).
NATIONAL RESEARCH COUNCIL Commission on Physical Sciences, Mathematics, and Applications Space Studies Board Committee on Planetary and Lunar Exploration Ronald Greeley (chair) Professor of Geology Department of Geology Arizona State University Tempe Jeffrey R. Barnes Associate Professor College of Oceanic and Atmospheric Sciences Oregon State University Corvallis Richard P. Binzel Professor Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology Cambridge Wendy Calvin Geophysicist Astrogeology Team U.S. Geological Survey Flagstaff, Ariz. Russell F. Doolittle* Research Professor of Biochemistry Center for Molecular Genetics University of California San Diego Heidi Hammel Principal Research Scientist Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology Cambridge Larry A. Haskin Professor of Chemistry and Earth and Planetary Sciences Department of Earth and Planetary Sciences Washington University St. Louis Bruce Jakosky Associate Professor, Atmospheric and Space Physics Laboratory for Atmospheric and Space Physics University of Colorado Boulder Kenneth Jezek Director, Byrd Polar Research Center, and Professor, Department of Geological Sciences Ohio State University Columbus George E. McGill Professor Emeritus Department of Geosciences University of Massachusetts Amherst Harry Y. McSween Jr. Professor Department of Geological Sciences University of Tennessee Knoxville Michael Mendillo Professor, Department of Astronomy, and Professor, Department of Electrical and Computer Engineering Boston University Boston Gerald Schubert Professor of Geophysics and Planetary Physics Department of Earth and Space Science University of California Los Angeles Everett Shock Associate Professor Department of Earth and Planetary Sciences Washington University St. Louis RESEARCH COUNCIL STAFF David H. Smith Senior Program Officer _________________________________________ (*) Member, National Academy of Sciences
The report cited in this release is available online
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