[meteorite-list] Re: Impact Structures - Simple vs Complex?
Jeff: A general rule of thumb RE: crater characteristics: TRANSITION BETWEEN SIMPLE - COMPLEX Moon - 15 km Mercury and Mars - 7 km Earth - 3 to 5 km but the correct answer is it depends. I tried to answer this question at: http://www.ottawa.rasc.ca/astronomy/earth_craters/intro.html Charles O'Dale Meeting Chair Ottawa RASC http://www.ottawa.rasc.ca/astronomy/earth_craters/index.html Date: Wed, 15 Mar 2006 23:01:29 +1100 From: Jeff Kuyken [EMAIL PROTECTED] Subject: [meteorite-list] Impact Structures - Simple vs Complex? To: Meteorite List meteorite-list@meteoritecentral.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=Windows-1252 Here's a question for those of you more familiar with impact structures on Earth. I believe I saw somewhere that craters fall into 2 main categories? simple and Complex with the later having a central uplift, concentric rings, etc among other things. My question is: How small can a complex crater be? Is there a definitive size restraint or does it completely depend on a multitude of variables such as the make-up of the impacting body, velocity, impact angle, target rock, etc? Any help is appreciated, Jeff Kuyken Meteorites Australia www.meteorites.com.au __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] From the Admin - Please Read
Good Evening; Due to a family emergency I have put the List in moderated mode. I will approve emails once or twice daily until things get back to normal. Sorry for the inconvenience. Regards, Art __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] The longest name (was Muonionalusta meteorite)
In a message dated 3/16/2006 6:53:10 P.M. Mountain Standard Time, [EMAIL PROTECTED] writes: It's a mouthful? not edible though is it? Yes Jerry, it is certainly a mouthful. And not at all edible. But it is not the longest meteorite name in A to Z. Should we have a little game, and see if anybody can find the longest name? (And, no, Mike and Bill, you can't play!!!) Anne M. Black www.IMPACTIKA.com [EMAIL PROTECTED] President, I.M.C.A. Inc. www.IMCA.cc __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] New Theory: Global Warming Caused byTunguska Event / climate change
Mark suggested: On the same note, I invite as many people as possible to install this screen saver application: http://bbc.cpdn.org/ it has been produced by the BBC and is using distributed computing (i.e our own domestic computers) to accurately model the earths climate hopefully they will get a better insight into what really is going to happen when the climate gets worse. I was in agreement with you up until those last five words... Worse than what? Or more specifically, worse by what metric and what timescale? For example, I would consider an ice age worse than the present (as far as the earth's current life forms are concerned), but I don't think anyone is too concerned about it happening in the next century. --Rob __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Mystery of Saturn's Vanishing 'Spokes' Illuminated
http://www.newscientistspace.com/article/dn8860-mystery-of-saturns-vanishing-spokes-illuminated.html Mystery of Saturn's vanishing 'spokes' illuminated Kimm Groshong New Scientist 16 March 2006 The mystery of the disappearing spokes in Saturn's rings may not be because they are hard to see. New research suggests they may not be there at all when the Sun is at a certain angle. NASA's Voyager missions in 1980 and 1981 captured detailed images of the peculiar radial structures, some of which stretched as far as 20,000 kilometres across Saturn's B ring. The Hubble Space Telescope has also imaged the spokes. But the features disappeared in October 1998 and were still nowhere to be seen when NASA's Cassini probe arrived at Saturn in 2004. Some researchers argued the reason was that the viewing conditions were not good enough and that Cassini would not see the spokes again until 2007, when Saturn's rings will lie nearly edge-on to the Sun. But in September 2005, Cassini captured a series of images of the rings on the dark side of the planet, featuring smaller, fainter spokes. Scientists believe spokes are produced when micron-sized dust grains on the surface of boulders in the main ring become charged and float above the ring plane. But they do not agree about how the dust particles become charged. Background plasma The most popular model says meteorites bombard the rings, producing a transient cloud of dense plasma that charges the grains. Another possible explanation is that high-energy electron beams from aurora on Saturn create the temporary plasma cloud. We don't really know which model is correct, says Mihály Horányi, at the University of Colorado, Boulder, US. But he and his colleagues, including spokes expert Carolyn Porco of the Space Science Institute also in Boulder, say once they are triggered, the background plasma environment above the rings plays an important role in determining how long the grains will stay aloft. And the plasma density above the rings is linked to the angle between the Sun and the rings. If that angle is too high, the particles will quickly fall back to the ring and we won't have a chance to see a whole group of them as a spoke, Horányi told New Scientist. Spoke cycles The group argues that when the background plasma density is low, the grains kicked up above the ring plane continue to be repelled by the ring and can therefore create spokes. Such a low plasma density can be produced when the Sun is at a low angle relative to the ring plane and fewer photons shine down on the rings. If the plasma density is high, the levitated grains will fall back down to the ring, the researchers say. They suggest that, when the plasma density is relatively low, spoke activity switches off when the angle between the rings and the Sun exceeds 20°. In that case, they say, we expect spoke activity for about 8 years at a time, followed by a period without spokes that lasts 6 to 7 years. And although Cassini is too close to the ring plane to look for spokes, the team expects that the spokes will have returned by July 2006, when Cassini has a better opportunity for viewing. Journal Reference: Science (vol 311, p 1587) __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Impact Structures - Simple vs Complex?
Hi, Jeff, List, The crater categories are: 1. simple 2. complex-immature 3. complex-mature 4. central peaked crater 5. peak ring basin (two ring crater) 6. multi-ring basin The factors determining which crater results from an impact are, in order of importance: 1. gravity at the surface 2. strength of the materials of the surface 3. total energy of the impact On Earth the transition from simple to complex occurs between a one mile crater and a three mile crater. On Mars the transition from simple to complex occurs between a 2-1/2 mile crater and a 6 mile crater. On the Moon the transition from simple to complex occurs between a 8 mile crater and a 20 mile crater. When there is a significant impact, at first there is just a huge blown out hole, called the transient crater cavity. In the right materials, on the right body, the crater might just fill back in, leaving only a circular wrinkle on the surface. If the center of the impact re-bounds strongly, there is a central peak. In most craters the original steep walls slump, shallowing the crater. The Moon's original crust (the highlands) was struck with impacts that produced giant basins, both multi-ringed and flooded. The lunar crust was probably only 40 to 60 miles thick at that time. Yet, despite producing basins 1,000 kilometers or more across, no sample from the Moon has any mantle rock in it, so it seems that even the biggest impacts don't dig deeply into the planet. Instead, they heat and melt vast areas of surface. The Earth's impact with the Moon's parent body, and the subsequent in-fall of debris, probably re-melted the Earth's crust to a depth of ten miles or more, perhaps re-melting the entire crust right down to the mantle. (Just when it had gotten all solid and settled, too.) Yet, there is a NASA pic of a so-called zap pit on a glass spherule from the Apollo 11 soil samples, a tiny BB of glass that got hit with something even smaller, which left a little bitty crater. The zap pit is a ring basin and it's only 30 microns across! So, the true answer to your question as to how big a crater has to get to become a complex crater is: Well, that all depends... Sterling K. Webb - - Original Message - From: Jeff Kuyken [EMAIL PROTECTED] To: Meteorite List meteorite-list@meteoritecentral.com Sent: Wednesday, March 15, 2006 6:01 AM Subject: [meteorite-list] Impact Structures - Simple vs Complex? Here's a question for those of you more familiar with impact structures on Earth. I believe I saw somewhere that craters fall into 2 main categories? simple and Complex with the later having a central uplift, concentric rings, etc among other things. My question is: How small can a complex crater be? Is there a definitive size restraint or does it completely depend on a multitude of variables such as the make-up of the impacting body, velocity, impact angle, target rock, etc? Any help is appreciated, Jeff Kuyken Meteorites Australia www.meteorites.com.au __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] ANSMET
Hello Everyone, Kids asking questions of ANSMET members: http://humanedgetech.com/expedition/ansmet/showDispatch.php?id=23092exp=258 Be sure to click on the great photos and explore the URLs at the bottom of the page, which lead to more great photos. I, for one, am jealous. I would really like to be on an ANSMET team (or at least have one of their cool patches). -Walter Branch __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
AW: AW: AW: [meteorite-list] Empty quarter expedition
Hi Stan and list, I couldn't see my reply on the list - there were some problems obviously... I copy it again. Martin ... My compliments too, that you answered to my email. In my eyes you are missing some essential points. In the metioned article your assertion was made concerning solely the Oman. May I quote again? Drawing on his experience with meteor fragments in Oman where he set up a program to recover fragments from the desert, he (Pfof.Matter) said that the program had recovered meteorite fragments from the moon and even one from Mars. Collectors though, he said, had robbed the desert of its heritage simply for money and not for scientific research. With this statement and this word choice (robbed) you are not only implying that those collectors acted unethically, but also that they acted illegally. I have here right on my desk a paper issued by the ministry of industry and commerce, Muscat, giving the permit for export of the stones, which were presented and inspected there before. I simply won't accept, that you spuriously accuse the finder of those meteorites, who cared for the legal export, to be a criminal. That is completely unbearable. Your specialization in sedimentology and geochemistry, the fact, that you never took part in a meteorite expedition in Oman and your response now is a portent for me, that you supposedly don't have the insight, what exactly was taking place in Oman concerning meteorites. But I gladly will contribute some explanations for you. Until 2 years ago export permits were issued for the finds of the collectors by the authorities of Oman. So you might not be surprised anylonger, that meteorites from Oman were available on the collectors market, if I remember right e.g. Dhofar 001 was found in 1999 by a Russian expedition. This partially explains your point (1) You may not approve to the fact, that the Omani didn't percieve their meteorites to be a natural heritage worthy of protection, but to deduce from this lack of awareness, that the hunters or collectors, call them like you want, would be criminals is inadmissible. That meteorites are no subject to national laws (e.g. to mining laws etc) is the normal case, as meteorites are a so exceedingly rare, that in general they didn't attract interest at all, nor was cared for a special legal reglementation for them, most probably because of the small volume of the finds (we are talking about a few tons worldwide in the last 10 years) and the monetary neglibility of that, what you may imagine to be the private meteorite market. (Remember e.g. the discussions risen about the legal status of the recent Neuschwanstein fall). Funny enough it were the activities of the private hunters, mainly in the Mahgreb countries and the appearance of the NWA meteorites on the market during the last 4 years, which rose the awareness in several nations, that meteorites do exist at all and that they have to be protected by corresponding laws. Exceptions here were Australia and Canada, Namibia (because of Gibeon too, I guess, since 2001 the export is forbidden). I ask myself, why the Suisse universities with there good cooperations with Oman since 30 years, failed through this long period to advise the authorities of Oman to protect their meteorites from being brought out from the country. So again. Call the teams which are collecting nowadays not respecting the new situation or those individuals, who never cared before for export permits, looters, but avoid such polemic simplifications. Secondly: We have a fundamentally different situation with the meteorites from Oman compared to the NWA-meteorites. The Omani meteorites are collected by persons, who perform an excellent field work. Each stone is photographed in situ, the coordinates are taken by GPS, the number of the fragments is noted (some note also details about the geology around the find site), the date of find is recorded as well as the exact weight of all stones, and a provisional field number for further processing is conferred. Thus exactly the modus operandi which the Swiss-Omani teams are applying and, if you want, which are analoguos to the proceeding of the Antarctic teams. A huge volume of data was consequently assembled and was made accessible to research. Strewnfields could be reconstructed, leading to further finds (like e.g. the Martian of the Suisse team). All in all an effort, which the Suisse team alone couln't have accomplished. By the way the most successful team in Oman ever, was lead by skilled geologists, employed by the Vernadsky institute, one of the leading institutions in meteoritics. Furthermore by no means are the finds from Oman lost for research. It is of vital concern for the commercial oriented teams, that they get there stones classified, as it increases the value of the material remarkably. So you'll find, that grosso modo all Omani finds were properly classified (or are under classification), even the most weathered ordinary
Re: [meteorite-list] My first martian meteorite
Color me green with envy. Gary On 16 Mar 2006 at 6:46, M come Meteorite Meteorites wrote: Hello I have buy my first martian meteorite from a moroccan dealer days ago. Its little, at 16 grams, but its a martian meteorite. When arrive I put some photos of the mass, and after I cut for the analysis. Matteo M come Meteorite - Matteo Chinellato Via Triestina 126/A - 30030 - TESSERA, VENEZIA, ITALY Email: [EMAIL PROTECTED] Sale Site: http://www.mcomemeteorite.it Collection Site: http://www.mcomemeteorite.info MSN Messanger: spacerocks at hotmail.com EBAY.COM:http://members.ebay.com/aboutme/mcomemeteorite/ ___ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Impact Structures - Simple vs Complex?
Hi all: I know that I am responding to my own message, but now have hard numbers (spoke to someone who actually knows what is happening). 1. The size of the transition from simple to complex craters goes as 1/g (gravity), with a little having to do with the material. Therefore: 2. The transitions: Earth: 3 km Mars: 7 km Mercury: 10 km Moon: 17 km Larry Quoting Larry Lebofsky [EMAIL PROTECTED]: Hi Jeff: It has been some time since I studied this (will ask around here at the Lunar and Planetary Science Conference), but I think that it is basically: size matters! How big of a hole can you maintain in a bowl shape before gravity and the strength of the material take over? Larry Quoting Jeff Kuyken [EMAIL PROTECTED]: Here's a question for those of you more familiar with impact structures on Earth. I believe I saw somewhere that craters fall into 2 main categories? simple and Complex with the later having a central uplift, concentric rings, etc among other things. My question is: How small can a complex crater be? Is there a definitive size restraint or does it completely depend on a multitude of variables such as the make-up of the impacting body, velocity, impact angle, target rock, etc? Any help is appreciated, Jeff Kuyken Meteorites Australia www.meteorites.com.au __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list -- Dr. Larry A. Lebofsky Senior Research Scientist Co-editor, Meteorite __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Mars Odyssey THEMIS Images: March 13-17, 2006
MARS ODYSSEY THEMIS IMAGES March 13-17, 2006 o Feature of the Week: Valles Marineris http://themis.asu.edu/feature o Surface Drainage (Released 13 March 2006) http://themis.asu.edu/zoom-20060313a o Gali Gullies (Released 14 March 2006) http://themis.asu.edu/zoom-20060314a o Double Vent (Released 16 March 2006) http://themis.asu.edu/zoom-20060316a o Crater Floor (Released 17 March 2006) http://themis.asu.edu/zoom-20060317a All of the THEMIS images are archived here: http://themis.asu.edu/latest.html NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in co.oration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] New Theory: Global Warming Caused byTunguskaEvent / climate change - ~ot
Hi Rob, Well, 'Worse' meaning, the entire world's landmass that is currently at 5 meters or below, above sea level, most probably won't be I'd say that would be a start :) Of course you might argue it won't effect 'us', but then why do we bother having kids? They key at the moment is 'they' just have no idea what will happen and when, the theories seem to range from 'global cooling' to 'complete catastrophe' unless they can model it in enough detail, there are just too many factors to get answers. The earth is warmer now than it has been for many million of years, and the rate of warming is accelerating. - will it be a problem?, who knows. Can we do anything about it? Probably not, but unless we have some idea about what is going on we will never know if there is something we should be doing. Countires need to start thinking about planning for sea level rise and especially air stream changes, since it often takes many decades to change country wide infrastructure, - for example people still seem intent on building on flood plains. Whilst I don't attribute it to global warming, Here in Southern Britain we are currently facing the worst drought for 80 years, rainfall is way way below average, and we have a hosepipe ban in place (and yes it is still winter!), I can imagine what could happen if global warming really did happen... Best, Mark -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Thursday, March 16, 2006 11:55 PM To: mark ford; meteorite-list@meteoritecentral.com Subject: RE: [meteorite-list] New Theory: Global Warming Caused byTunguskaEvent / climate change Mark suggested: On the same note, I invite as many people as possible to install this screen saver application: http://bbc.cpdn.org/ it has been produced by the BBC and is using distributed computing (i.e our own domestic computers) to accurately model the earths climate hopefully they will get a better insight into what really is going to happen when the climate gets worse. I was in agreement with you up until those last five words... Worse than what? Or more specifically, worse by what metric and what timescale? For example, I would consider an ice age worse than the present (as far as the earth's current life forms are concerned), but I don't think anyone is too concerned about it happening in the next century. --Rob __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Dawn Asteroid Mission Could Rise Again
http://www.newscientistspace.com/article/dn8861-dawn-asteroid-mission-could-rise-again.html Dawn asteroid mission could rise again Kimm Groshong New Scientist 17 March 2006 NASA has pried up what appeared to be the final nail in the coffin of its Dawn mission to visit the two largest main-belt asteroids, Ceres and Vesta. According to an official NASA statement, associate administrator Rex Geveden will be conducting a review of the decision to cancel the mission in light of additional information provided by NASA's Jet Propulsion Laboratory. Mary Cleave, associate administrator for NASA's science mission directorate axed the mission on 2 March, having reviewed the findings of an independent review board. NASA ordered the Dawn mission to stand down in October 2005 to allow the board to assess its progress, after technical problems and funding issues became apparent. NASA has never been critical of the mission's science objectives. When the mission was cancelled, Andrew Dantzler, director of NASA's planetary science division, said the review board had found 29 major issues that would have to be resolved before Dawn could proceed. He said the mission was behind schedule and estimated to come in about 20% over-budget. NASA is granting no interviews with Geveden until the new review is complete. The statement, dated 9 March, says: The review is expected to conclude within the next two weeks. Planet forming Lucy McFadden, a co-investigator for the Dawn mission based at the University of Maryland in College Park, US, says she does not know what the new information from JPL is. But the fact that NASA is willing to listen to our case is important, she told New Scientist. She emphasises the importance of the mission's timing to achieve its scientific goals. The opportunity to visit, by spacecraft, both Vesta and Ceres is limited to launching within the next year, she says. There is urgency to do this now for the sake of space science exploration in the next decade. A new mission to both asteroids would not be feasible again for 15 years, she says. Furthermore, she says, findings from Hubble and ground-based telescopes have made Ceres and Vesta more scientifically interesting in recent years: They're not just fragments of rocks. They're bodies that were growing into planets and they have some characteristics of planets. Water ice It has long been known that Vesta has been heated in its history, but recent spectroscopic results suggest there may also be small amounts of water on the asteroid's surface. In the case of Ceres, which scientists had always believed to be uniform in composition, Hubble has found the asteroid may actually have a water ice mantle that expands, inflating its shape. That changes our whole view of Ceres, she says. So, McFadden concludes, it is compelling to go both Ceres and Vesta not only because so little is known about the main asteroid belt, but also because they are precursors to our planets and they may contain clues about the formation of the solar system's inner planets. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Semi-Ad: Opinion asked
Hola list, what do you think about that kind of auction, my friend Dr.Brinker set up? Item number: 6612147920 http://cgi.ebay.com/BA-s-Meteorites-Consultation-Hour_W0QQitemZ6612147920QQc ategoryZ3239QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Thanks! Martin __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Astronomers Watch the Skies for Threat of Deadly Impact (99942 Apophis)
http://www.paramuspost.com/article.php/20060316230330846 Astronomers watch the skies for threat of deadly impact By Bruce Lieberman The Paramus Post March 17 2006 Shortly after sunset Friday, April 13, 2029, if the sky is clear enough, people across Europe and North Africa will see an asteroid appear as a bright point of light flying 19,400 miles overhead before it disappears silently below the western horizon. A short time later, if astronomers' worst fears are realized, the asteroid will pass through a region of space less than 2,000 feet across. At that place, the gravitational pull of Earth will yank the asteroid into a new orbit around the sun - and on a collision course with Earth seven years later. It all sounds like the premise of Armageddon, Deep Impact or some other blockbuster Hollywood film. But the asteroid, named 99942 Apophis, is science fact, not science fiction. In December 2004, astronomers caused a brief stir when their calculations estimated that the newly discovered asteroid - named after the ancient Egyptian god, Apep, the Destroyer - might collide with Earth in 2029. Additional tracking data quickly ruled out the possibility of a 2029 collision. But the potential for a strike in 2036, should the asteroid enter that crucial gravitational space, places it at the top of NASA's list of 3,800 near-Earth asteroids the agency has identified. Based on the latest information, the asteroid, which is nearly twice the size of a typical football stadium, has a 1-in-6,250 chance of colliding with Earth on April 13, 2036. We're very concerned that people put this in perspective, said Russell Schweickart, a former Apollo astronaut and head of a foundation that focuses public attention on the threat from asteroids and comets. This is not something to lose sleep over, (but) it is something the government needs to attend to. Right now, NASA is doing little more than looking for asteroids and keeping track of them, Schweickart said. Plans to deflect Apophis, if it becomes necessary, exist only in the pages of a few academic papers. Last year, Schweickart's group, the B612 Foundation - named for the asteroid in the book, The Little Prince - corresponded with NASA officials about the threat of Apophis. It would have devastating consequences if it hit, Schweickart wrote. There is the serious question of whether, if it is headed toward impact, we will know enough to make a timely decision. Schweickart and other scientists urged NASA to place a data-tracking radio transponder on the asteroid's surface by 2014. A transponder would help nail down orbital alterations caused by a phenomenon called the Yarkovsky effect. This is produced when an asteroid absorbs energy from the sun and re-radiates it back into space as heat. With one side of the asteroid lit and the other in darkness, the imbalance in thermal radiation produces a tiny acceleration. A transponder would help scientists understand how the Yarkovsky effect is influencing the asteroid's orbit. NASA responded to the urging with a wait-and-see proposal. We conclude a space mission based solely on any perceived collision hazard is not warranted at this time, wrote Mary L. Cleave, associate administrator for NASA's science mission directorate. The agency believes continued optical and radio telescope observations will rule out Apophis as a threat. If not, NASA would launch a mission to the asteroid by 2018. A radio transponder, placed either in orbit or on its surface, would determine the asteroid's position in 2029 down to a few hundred feet, according to NASA. If an impact seems probable, a rocket would be launched to deflect the asteroid. The design phase would have to be completed by 2020 in order to launch by 2024, NASA noted. Schweickart said he doesn't necessarily disagree with NASA's analysis, as long as the agency can design, build, launch and successfully complete such a mission before 2029. The danger is being overly optimistic about how long it takes to do that. If a deflection mission becomes necessary, scientists agree, it will need to be completed before 2029 when Apophis would commit itself to a future collision course. Due to the physics of gravity and orbital mechanics, delaying action would require much, much more energy to move the asteroid. That (will be) an impossible task, I'll tell you right now, Schweickart said. COSMIC PINBALL The threat of an asteroid strike has always been with us. More than 4 billion years ago, a lot of debris was left over after the ring of gas and dust swirling around a young sun coalesced into planets and moons. In their lonely roundabouts through the void, these leftovers - asteroids and comets - sometimes pass close to a planet, like two race cars converging as they circle a track. During a close encounter, the larger object - a planet, for example - can yank the smaller one - an asteroid - out of its orbit. As the two part ways, there is a slight chance that the asteroid will pass
[meteorite-list] Mars Exploration Rover Update - March 16, 2006
http://marsrovers.jpl.nasa.gov/mission/status.html SPIRIT UPDATE: Spirit Continues Driving on Five Wheels - sol 778-783, Mar 16, 2006: Spirit continued to make progress toward McCool Hill despite a reduction in solar energy and problems with the right front wheel. The team plans to have the rover spend the winter on the hill's north-facing slopes, where the tilt toward the sun would help maximize daily output by the solar panels. On Spirit's 779th sol, or Martian day (March 13, 2006), the drive actuator on the right front wheel stalled during a turn to adjust the position of the rover's antennas. The stall ended the day's drive, which brought Spirit 29 meters (95 feet) closer to McCool, still approximately 120 meters (390 feet) away. Engineers conducted tests on sols 781 and 782 (March 15 and 16, 2006) on a testbed at the Jet Propulsion Laboratory as well as remotely on Spirit. Further analysis is needed to determine what caused the right front actuator to stop working. Meanwhile, the operations team has successfully commanded Spirit to drive using only 5 wheels. Engineers plan to have Spirit continue driving backward with five healthy wheels while dragging the right front wheel. Sol-by-sol summaries: Sol 778 (March 12, 2006): Spirit spent the day conducting remote atmospheric sensing. Sol 779: Spirit drove about 29 meters (95 feet) and acquired post-drive images. A fault in the right front wheel drive actuator terminated the drive. Sol 780: Spirit spent the day recharging batteries and re-transmitting information about the previous day's drive to Earth. Spirit collected additional imagery of the right front wheel. Sol 781: Spirit completed diagnostic tests and drove 3.9 meters (13 feet) using only five wheels. Diagnostic tests showed that the right-front-wheel problem involved the drive actuator, not the steering. Sol 782: Rover drivers planned a drive of approximately 12 meters (40 feet) using only five wheels. Sol 783 (March 17, 2006): The operations team planned to have Spirit spend the day sleeping to charge up the batteries. As of sol 781 (March 15, 2006), Spirit's total odometry was 6,797 meters (4.22 miles). __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Ice Layers Record Comet Creation (Deep Impact)
http://news.bbc.co.uk/2/hi/science/nature/4816712.stm Ice layers record comet creation By Paul Rincon BBC News March 17, 2006 The Deep Impact mission is casting new light on how comets formed and how they shed their ice in space. The US space agency probe sent a 370kg projectile crashing into Comet Tempel 1 and then studied the plume of debris with its suite of instruments. Nasa's mission scientists say images from last July's encounter reveal as many as seven different layers on the comet's surface. Their results were presented at a major science conference in Houston, US. Team member Mike Belton told the meeting he thought the layering was a sign of how comets like Tempel 1 were built up from lesser objects. Growing 'snowball' In the outer part of the early Solar System, smaller bodies called cometesimals collided and merged, gradually piling up to form the larger objects we know as comets. Similar collisions in the inner Solar System led to a loose accumulation of fragments that largely retained their internal structure. But primordial material in the outer regions was travelling at relatively lower speeds and contained less solid material. As the cometesimals hit the surface of a growing comet nucleus, they flowed on to the surface, researchers believe. Deep Impact's scientists think the interior structure of Tempel 1 resembles layers of material piled up on one another - a signature of the process that formed the icy body. Model conflict Data from the mission is also helping scientists understand how comets shed water-ice through sublimation, the phenomenon which sees a solid become a gas without first melting. When comets are heated by the Sun, ice sublimes and is lost to space in a process known as outgassing. Some scientists have proposed that this material is coming from deep below the surface crust of the comet. But temperature data from Tempel 1's nucleus suggests the material must be lost from only a few centimetres below the surface. The normal outgassing of the comet has been modelled by different people as coming from bare ice on the surface to subsurface ice that migrates through pores to escape, or from 40-50m below the surface, Deep Impact's chief scientist Mike A'Hearn told the BBC News website. I think it is clear from what we have here that the ice that is subliming is within the upper metre. Whether it's 5cm or 20cm below, I wouldn't want to say; but it's not below the top metre. That rules out a lot of the models. The new results from the mission were presented here at the Lunar and Planetary Science Conference in Houston, Texas. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Evidence Found for Large Impact Crater Off the Coast of Antarctica
http://news.bbc.co.uk/1/hi/sci/tech/4816794.stm Space impact clue in Antarctica By Paul Rincon BBC News March 17, 2006 Evidence for what may be a large and relatively recent impact crater has been found off the coast of Antarctica. Scientists say the evidence, if correct, points to a space rock some 5km across having crashed into the Ross Sea about three million years ago. This could have generated a huge tsunami, according to a member of the team investigating the collision. Details were reported at the Lunar and Planetary Science Conference in Houston, Texas. Glass hints Researchers from the Lamont-Doherty Earth Observatory in New York have been studying a 100km-wide depression, known as Bowers Crater, under the Ross Sea. Team members examined cores drilled from around the area to look for evidence of an impact. In the cores, they found microscopic glassy grains shaped like teardrops, spheres and dumbbells which are collectively known as tektites. Some scientists believe these are created when rock fragments are hurled high up into the atmosphere by the impact of a large meteoroid or asteroid, and then partially re-melt as they fall back to the ground. Other glasses were also found. These are thought to have been formed by cooling of the melted rock and sediment. Similar glasses can be formed through volcanism, but the Ross Sea specimens seem to have a distinct structure under the microscope. Wave trace The findings alone do not prove there was an impact in the area a few million years ago, but team member Dallas Abbott says she hopes to search the core material further for a mineral called shocked quartz. This type of quartz can be distinguished from normal quartz by characteristic lines visible under the microscope which are thought to be formed by the intense pressure of an impact. The presence of this mineral is considered most diagnostic of a space collision. Dr Abbott told the BBC News website that an impact in the Ross Sea would have generated a pretty big tsunami. The waves could have crashed against the shores of South America; but, she added, the geological history of that continent made it unlikely that evidence of this event would be found. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Fwd: Rocks From Space Picture of the Day - March 14, 2006
---BeginMessage--- http://www.spacerocksinc.com/March14.html ---End Message--- __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] Impact Structures - Simple vs Complex?
Hi Jeff, yes it does depend mainly on the size of the impactor and its velocity and the gravitational force of the body being impacted, Complex craters on the moon have a different set of minimum diameters than on Earth, yes there is an actual formula for it, I have lost it at the moment, this question does re-appear every now and then, if you locate the formulae for working it out, please let me know. Cheers, Kevin, VK3UKF. From: Jeff Kuyken [EMAIL PROTECTED] To: Meteorite List meteorite-list@meteoritecentral.com Subject: [meteorite-list] Impact Structures - Simple vs Complex? Date: Wed, 15 Mar 2006 23:01:29 +1100 MIME-Version: 1.0 Received: from six.pairlist.net ([209.68.2.254]) by bay0-mc4-f5.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.1830); Wed, 15 Mar 2006 15:12:10 -0800 Received: from six.pairlist.net (localhost [127.0.0.1])by six.pairlist.net (Postfix) with ESMTPid F01FC2C8C7; Wed, 15 Mar 2006 18:10:01 -0500 (EST) Received: from mu.pair.com (mu.pair.com [209.68.1.23])by six.pairlist.net (Postfix) with SMTP id 439ED2BCDCfor [EMAIL PROTECTED];Wed, 15 Mar 2006 07:03:04 -0500 (EST) Received: (qmail 5228 invoked by uid 7111); 15 Mar 2006 12:03:04 - Received: (qmail 5225 invoked from network); 15 Mar 2006 12:03:04 - Received: from mailwash5.pair.com (66.39.2.5)by mu.pair.com with SMTP; 15 Mar 2006 12:03:04 - Received: from localhost (localhost [127.0.0.1])by mailwash5.pair.com (Postfix) with SMTP id DA6988D6B1for meteorite-list@meteoritecentral.com;Wed, 15 Mar 2006 07:03:03 -0500 (EST) Received: from smtpout09-04.prod.mesa1.secureserver.net(smtpout09-04.prod.mesa1.secureserver.net [64.202.165.17])by mailwash5.pair.com (Postfix) with SMTP id 2C4FB8D6D8for meteorite-list@meteoritecentral.com;Wed, 15 Mar 2006 07:03:03 -0500 (EST) Received: (qmail 23541 invoked from network); 15 Mar 2006 12:03:02 - Received: from unknown (125.209.168.165)by smtpout09-04.prod.mesa1.secureserver.net (64.202.165.17) with ESMTP;15 Mar 2006 12:03:01 - X-Message-Info: yilqo4+6kc4QRUMVClUt1zMiCKX90vPxKNGP2ruFqAA= X-Original-To: [EMAIL PROTECTED] Delivered-To: [EMAIL PROTECTED] Delivered-To: arthur-meteoritecentral:[EMAIL PROTECTED] X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600. X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600. X-Mailman-Approved-At: Wed, 15 Mar 2006 18:09:50 -0500 X-BeenThere: meteorite-list@meteoritecentral.com X-Mailman-Version: 2.1.5 Precedence: list List-Id: Meteorite Discussion Forum meteorite-list.meteoritecentral.com List-Unsubscribe: http://six.pairlist.net/mailman/listinfo/meteorite-list,mailto:[EMAIL PROTECTED] List-Archive: http://six.pairlist.net/pipermail/meteorite-list List-Post: mailto:meteorite-list@meteoritecentral.com List-Help: mailto:[EMAIL PROTECTED] List-Subscribe: http://six.pairlist.net/mailman/listinfo/meteorite-list,mailto:[EMAIL PROTECTED] Errors-To: [EMAIL PROTECTED] Return-Path: [EMAIL PROTECTED] X-OriginalArrivalTime: 15 Mar 2006 23:12:11.0206 (UTC) FILETIME=[E38B8660:01C64885] Here's a question for those of you more familiar with impact structures on Earth. I believe I saw somewhere that craters fall into 2 main categories? simple and Complex with the later having a central uplift, concentric rings, etc among other things. My question is: How small can a complex crater be? Is there a definitive size restraint or does it completely depend on a multitude of variables such as the make-up of the impacting body, velocity, impact angle, target rock, etc? Any help is appreciated, Jeff Kuyken Meteorites Australia www.meteorites.com.au __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Did Earth Seed Life Elsewhere in the Solar System?
http://www.nature.com/news/2006/060313/full/060313-18.html Did Earth seed life elsewhere in the Solar System? Impacts on our planet could have sprayed life into space. Mark Peplow nature.com March 17, 2006 Earthly bacteria could have reached distant planets and moons after being flung into space by massive meteorite impacts, scientists suggest. The proposal neatly reverses the panspermia theory, which suggests that life on Earth was seeded by microbes on comets or meteorites from elsewhere. Both theories envision life spreading through the Solar System in much the same way that germs race around a crowded classroom, says Jeff Moore, a planetary scientist at NASA's Ames Research Center in Moffett Field, California. Once one planet comes down with life, they all get it. Spreading germs Impacts on Mars and the Moon are known to throw rocks into space that end up on Earth as small meteorites. But spraying Earth rocks towards the edges of the Solar System is more difficult, because the material has to move away from the Sun's strong gravity. To find out just how many rocks could reach the outer Solar System, a team of scientists used a computer model to track millions of fragments ejected by a simulated massive impact, such as the one that created the Chicxulub crater some 65 million years ago. Similar sized events are thought to have happened a few times in Earth's history. The researchers looked in part at how many Earthly fragments would reach environments thought to be relatively well suited to life, such as Saturn's moon Titan and Jupiter's moon Europa. I assumed the answer would be very, very few, says Brett Gladman, a planetary scientist at the University of British Columbia, Vancouver, Canada, who led the team. But Gladman was surprised to find that within 5 million years, about 100 objects would hit Europa, while Titan gets roughly 30 hits. He presented the results at the Lunar and Planetary Science Conference in League City, Texas, on 16 March. Tough journey But could bacteria survive the sudden heat and acceleration of being thrown into space? Other researchers at the conference suggest that they can. Wayne Nicholson, a microbiologist from the University of Florida in Gainesville, has tested the idea with a gun the size of a house at NASA's Ames Research Center. He and his colleagues fired a marble-sized pellet at about 5 kilometres per second into a plate that contained bacterial spores in water, in order to simulate a meteorite impact. The debris that scattered upwards was caught in sheets of foam, and the team found that about one in 10,000 bacteria survived. It's an experimental validation of a fairly well established calculation, says Moore. Crash landing Many astrobiologists believe that bacteria, once in space, could survive cosmic-radiation exposure during their trip. Unfortunately, a crash landing on Europa would almost certainly sterilize the few rocks that made it that far. But Titan is a different story, says Gladman. The moon's thick atmosphere would first shatter the meteorite before slowing the fragments down; the same process happens with meteorite impacts on Earth. It's a nice safety net, Gladman says. The heat of landing could even melt the ice and open up a short-lived pool of liquid for the visitors, he adds. At the conference, Gladman was asked whether, assuming a few bugs did make it safely on to Titan's surface, they could ever really thrive in the moon's chilly climes of about -170°C. That's for you guys to work out, he told the audience. I'm just the delivery boy. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Semi-Ad: Opinion asked
what do you think about that kind of auction, my friend Dr.Brinker set up? Item number: 6612147920 Well, education always play an important role? KNOW about your piece! In a more general sense, I think that curating a collection should mean much more than just amassing a pile of specimen (for reasons whatever...), e.g. it should include reading the specific literature, knowing how to preserve the collection (for yourself and those who will carry on later - our livespan is NOTHING compared to the history of these oldtimers! :-)), communicating with friends etc etc. This may consume a lot of time and extra money, besides just aquiring new pieces, but it will usually pay in the end... Btw I have heard that Martin from Munich, who asked the question, will turn a sound and brave .. yrs old on March 21, right at the edge of the season. Sorry, still no Buckleboo meteorite for you, Sir Mettmann, but anyway at least 26 recorded meteorite finds in history on that date of month and day. Alex Berlin/Germany __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Subject: [meteorite-list] Semi-Ad: Opinion asked
Martin; I have viewed the ebay auction earlier and thought to myself,HOW INGENIOUS,an info-auction that will teach the novice about the meteorite they are viewing and maybe bidding on.I hope your friend keeps up the good work,all sellers will benefit from this technique not to mention the general ebay public. I love it!!! Herman. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
