[meteorite-list] Meteorite Picture of the Day
Today's Meteorite Picture of the Day: Plainview Contributed by: Werner Schroer http://www.tucsonmeteorites.com/mpodmain.asp?DD=11/06/2015 __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] Study Questions Dates for Cataclysms on Early Moon, Earth
http://news.wisc.edu/24103 Study questions dates for cataclysms on early moon, Earth by David Tenenbaum University of Wisconsin October 16, 2015 Phenomenally durable crystals called zircons are used to date some of the earliest and most dramatic cataclysms of the solar system. One is the super-duty collision that ejected material from Earth to form the moon roughly 50 million years after Earth formed. Another is the late heavy bombardment, a wave of impacts that may have created hellish surface conditions on the young Earth, about 4 billion years ago. Both events are widely accepted but unproven, so geoscientists are eager for more details and better dates. Many of those dates come from zircons retrieved from the moon during NASA's Apollo voyages in the 1970s. A study of zircons from a gigantic meteorite impact in South Africa, now online in the journal Geology, casts doubt on the methods used to date lunar impacts. The critical problem, says lead author Aaron Cavosie, a visiting professor of geoscience and member of the NASA Astrobiology Institute at the University of Wisconsin-Madison, is the fact that lunar zircons are "ex situ," meaning removed from the rock in which they formed, which deprives geoscientists of corroborating evidence of impact. "While zircon is one of the best isotopic clocks for dating many geological processes," Cavosie says, "our results show that it is very challenging to use ex situ zircon to date a large impact of known age." Although many of their zircons show evidence of shock, "once separated from host rocks, ex situ shocked zircons lose critical contextual information," Cavosie says. The "clock" in a zircon occurs as lead isotopes accumulate during radioactive decay of uranium. With precise measurements of isotopes scientists can calculate, based on the half life of uranium, how long lead has been accumulating. If all lead was driven off during asteroid impact, the clock was reset, and the amount of accumulated lead should record exactly how long ago the impact occurred. Studies of lunar zircons have followed this procedure to produce dates from 4.3 billion to 3.9 billion years ago for the late heavy bombardment. To evaluate the assumption of clock-resetting by impact, Cavosie and colleagues gathered zircons near Earth's largest impact, located in South Africa and known to have occurred 2 billion years ago. The Vredefort impact structure is deeply eroded, and approximately 90 kilometers across, says Cavosie, who is also in the Department of Applied Geology at Curtin University in Perth, Australia. "The original size, estimated at 300 kilometers diameter, is modeled to result from an impactor 14 kilometers in diameter," he says. The researchers searched for features within the zircons that are considered evidence of impact, and concluded that most of the ages reflect when the zircons formed in magma. The zircons from South Africa are "out of place grains that contain definitive evidence of shock deformation from the Vredefort impact," Cavosie says. "However, most of the shocked grains do not record the age of the impact but rather the age of the rocks they formed in, which are about 1 billion years older." The story is different on Earth, says zircon expert John Valley, a professor of geoscience at UW-Madison. "Most zircons on Earth are found in granite, and they formed in the same process that formed the granite. This has led people to assume that all the zircons were reset by impact, so the ages they get from the Moon are impact ages. Aaron is saying to know that, you have to apply strict criteria, and that's not what people have been doing." The accuracy of zircon dating affects our view of Earth's early history. The poorly understood late heavy bombardment, for example, likely influenced when life arose, so dating the bombardment topped a priority list of the National Academy of Sciences for lunar studies. Did the giant craters on the moon form during a brief wave or a steady rain of impacts? "It would be nice to know which," Valley says. "The question of what resets the zircon clock has always been very complicated. For a long time people have been saying if zircon is really involved in a major impact shock, its age will be reset, so you can date the impact. Aaron has been saying, 'Yes, sometimes, but often what people see as a reset age may not really be reset.' Zircons are the gift that keep on giving, and this will not change that, but we need to be a lot more careful in analyzing what that gift is telling us." __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] Vitamin B3 Might Have Been Made in Space, Delivered to Earth by Meteorites
http://www.nasa.gov/content/goddard/vitamin-b3-might-have-been-made-in-space-delivered-to-earth-by-meteorites/ Vitamin B3 Might Have Been Made in Space, Delivered to Earth by Meteorites Bill Steigerwald NASA's Goddard Space Flight Center, Greenbelt, Md. william.a.steigerw...@nasa.gov April 17, 2014 Ancient Earth might have had an extraterrestrial supply of vitamin B3 delivered by carbon-rich meteorites, according to a new analysis by NASA-funded researchers. The result supports a theory that the origin of life may have been assisted by a supply of key molecules created in space and brought to Earth by comet and meteor impacts. "It is always difficult to put a value on the connection between meteorites and the origin of life; for example, earlier work has shown that vitamin B3 could have been produced non-biologically on ancient Earth, but it's possible that an added source of vitamin B3 could have been helpful," said Karen Smith of Pennsylvania State University in University Park, Pa. "Vitamin B3, also called nicotinic acid or niacin, is a precursor to NAD (nicotinamide adenine dinucleotide), which is essential to metabolism and likely very ancient in origin." Smith is lead author of a paper on this research, along with co-authors from NASA's Goddard Space Flight Center in Greenbelt, Md., now available online in the journal Geochimica et Cosmochimica Acta. This is not the first time vitamin B3 has been found in meteorites. In 2001 a team led by Sandra Pizzarello of Arizona State University, in Tempe discovered it along with related molecules called pyridine carboxylic acids in the Tagish Lake meteorite. In the new work at Goddard's Astrobiology Analytical Laboratory, Smith and her team analyzed samples from eight different carbon-rich meteorites, called "CM-2 type carbonaceous chondrites" and found vitamin B3 at levels ranging from about 30 to 600 parts-per-billion. They also found other pyridine carboxylic acids at similar concentrations and, for the first time, found pyridine dicarboxylic acids. "We discovered a pattern - less vitamin B3 (and other pyridine carboxylic acids) was found in meteorites that came from asteroids that were more altered by liquid water. One possibility may be that these molecules were destroyed during the prolonged contact with liquid water," said Smith. "We also performed preliminary laboratory experiments simulating conditions in interstellar space and showed that the synthesis of vitamin B3 and other pyridine carboxylic acids might be possible on ice grains." Scientists think the solar system formed when a dense cloud of gas, dust, and ice grains collapsed under its own gravity. Clumps of dust and ice aggregated into comets and asteroids, some of which collided together to form moon-sized objects or planetesimals, and some of those eventually merged to become planets. Space is filled with radiation from nearby stars as well as from violent events in deep space like exploding stars and black holes devouring matter. This radiation could have powered chemical reactions in the cloud (nebula) that formed the solar system, and some of those reactions may have produced biologically important molecules like vitamin B3. Asteroids and comets are considered more or less pristine remnants from our solar system's formation, and many meteorites are prized samples from asteroids that happen to be conveniently delivered to Earth. However, some asteroids are less pristine than others. Asteroids can be altered shortly after they form by chemical reactions in liquid water. As they grow, asteroids incorporate radioactive material present in the solar system nebula. If enough radioactive material accumulates in an asteroid, the heat produced as it decays will be sufficient to melt ice inside the asteroid. Researchers can determine how much an asteroid was altered by water by examining chemical and mineralogical signatures of water alteration in meteorites from those asteroids. When asteroids collide with meteoroids or other asteroids, pieces break off and some of them eventually make their way to Earth as meteorites. Although meteorites are valued samples from asteroids, they are rarely recovered immediately after they fall to Earth. This leaves them vulnerable to contamination from terrestrial chemistry and life. The team doubts the vitamin B3 and other molecules found in their meteorites came from terrestrial life for two reasons. First, the vitamin B3 was found along with its structural isomers - related molecules that have the same chemical formula but whose atoms are attached in a different order. These other molecules aren't used by life. Non-biological chemistry tends to produce a wide variety of molecules -- basically everything permitted by the materials and conditions present -- but life makes only the molecules it needs. If contamination from terrestrial life was the source of the vitamin B3 in the meteorites, th
[meteorite-list] MAVEN Reveals Speed of Solar Wind Stripping Martian Atmosphere
November 05, 2015 RELEASE 15-217 NASA Mission Reveals Speed of Solar Wind Stripping Martian Atmosphere NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission has identified the process that appears to have played a key role in the transition of the Martian climate from an early, warm and wet environment that might have supported surface life to the cold, arid planet Mars is today. MAVEN data have enabled researchers to determine the rate at which the Martian atmosphere currently is losing gas to space via stripping by the solar wind. The findings reveal that the erosion of Mars' atmosphere increases significantly during solar storms. The scientific results from the mission appear in the Nov. 5 issues of the journals Science and Geophysical Research Letters. "Mars appears to have had a thick atmosphere warm enough to support liquid water which is a key ingredient and medium for life as we currently know it," said John Grunsfeld, astronaut and associate administrator for the NASA Science Mission Directorate in Washington. "Understanding what happened to the Mars' atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere. Learning what can cause changes to a planet's environment from one that could host microbes at the surface to one that doesn't is important to know, and is a key question that is being addressed in NASA's journey to Mars." MAVEN measurements indicate that the solar wind strips away gas at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second. "Like the theft of a few coins from a cash register every day, the loss becomes significant over time," said Bruce Jakosky, MAVEN principal investigator at the University of Colorado, Boulder. "We've seen that the atmospheric erosion increases significantly during solar storms, so we think the loss rate was much higher billions of years ago when the sun was young and more active." In addition, a series of dramatic solar storms hit Mars' atmosphere in March 2015, and MAVEN found that the loss was accelerated. The combination of greater loss rates and increased solar storms in the past suggests that loss of atmosphere to space was likely a major process in changing the Martian climate. The solar wind is a stream of particles, mainly protons and electrons, flowing from the sun's atmosphere at a speed of about one million miles per hour. The magnetic field carried by the solar wind as it flows past Mars can generate an electric field, much as a turbine on Earth can be used to generate electricity. This electric field accelerates electrically charged gas atoms, called ions, in Mars' upper atmosphere and shoots them into space. MAVEN has been examining how solar wind and ultraviolet light strip gas from of the top of the planet's atmosphere. New results indicate that the loss is experienced in three different regions of the Red Planet: down the "tail," where the solar wind flows behind Mars, above the Martian poles in a "polar plume," and from an extended cloud of gas surrounding Mars. The science team determined that almost 75 percent of the escaping ions come from the tail region, and nearly 25 percent are from the plume region, with just a minor contribution from the extended cloud. Ancient regions on Mars bear signs of abundant water - such as features resembling valleys carved by rivers and mineral deposits that only form in the presence of liquid water. These features have led scientists to think that billions of years ago, the atmosphere of Mars was much denser and warm enough to form rivers, lakes and perhaps even oceans of liquid water. Recently, researchers using NASA's Mars Reconnaissance Orbiter observed the seasonal appearance of hydrated salts indicating briny liquid water on Mars. However, the current Martian atmosphere is far too cold and thin to support long-lived or extensive amounts of liquid water on the planet's surface. "Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate," said Joe Grebowsky, MAVEN project scientist from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "MAVEN also is studying other loss processes -- such as loss due to impact of ions or escape of hydrogen atoms -- and these will only increase the importance of atmospheric escape." The goal of NASA's MAVEN mission, launched to Mars in November 2013, is to determine how much of the planet's atmosphere and water have been lost to space. It is the first such mission devoted to understanding how the sun might have influenced atmospheric changes on the Red Planet. MAVEN has been operating at Mars for just over a year and will complete its primary science mission on Nov. 16. To view an animation simulating the loss of atmosphere and water on Mars: http://svs.gsfc.nasa.gov/goto?4370 For more information and images on Mars? lost atmosphe
[meteorite-list] Historic Rosetta Mission to End with Crash Into Comet
http://www.nature.com/news/historic-rosetta-mission-to-end-with-crash-into-comet-1.18713 Historic Rosetta mission to end with crash into comet There were other options, but super close-up shots on descent will provide science bonanza. Elizabeth Gibney nature.com 04 November 2015 A year since a probe called Philae made history by touching down on a comet, the team that pulled off the feat is plotting a different kind of landing. Next September, the European Space Agency will crash Philae's mothership Rosetta into the icy dust ball, but as gently as possible. The dramatic act will bring the mission to an abrupt end - and give Rosetta's wealth of sensors and instruments their closest view of the comet yet. "The crash landing gives us the best scientific end-of-mission that we can hope for," says Rosetta project scientist Matt Taylor. The collision will be emotional for the scientists, some of whom have worked on the mission since its inception in 1993. "There will be a lot of tears," says Taylor. Launched in 2004, the Rosetta orbiter caught up with the comet 67P/Churyumov-Gerasimenko ten years later as the rock was travelling from deep in space towards the Sun - and dropped Philae onto the surface a few months later, on 12 November. Scientists have not heard from Philae since July, and don't know if they will do so again, but Rosetta's operations to survey the comet from orbit are in full swing. However, the orbiter can't keep up this work indefinitely. Funding for the mission runs out in September 2016 - and by that time 67P/Churyumov-Gerasimenko will be well on its way back out into deep space, where the solar-powered orbiter will receive too little sunlight to function. Discussions about what to do with Rosetta when that happens have continued for more than a year. Rosetta flight director Andrea Accomazzo says that, ideally, Rosetta would hibernate while the comet remains in deep space, then be resurrected when 67P again approaches the Sun in 4 or 5 years' time. But the cold of deep space would probably damage the craft, Accomazzo says; others fear that fuel and other resources would run out. Moreover, many of the mission's principal investigators (PIs) began their work more than 20 years ago and "there's no point putting an old experiment with old PIs into hibernation", jokes Kathrin Altwegg, a planetary scientist at the University of Bern. Crash-landing Rosetta emerged as the preferred option last year, but only now are orbiter navigators and operators working out how to go about it. Rosetta's closest encounter with the comet so far was from 8 kilometres above the surface, when it dispatched Philae. The current thinking sees Rosetta spiral down to a similar distance next August before creeping ever closer in elliptical orbits and crashing in September, says mission manager Patrick Martin - but that could still change. Although Philae sent back some data during its descent, Rosetta has more powerful - and more varied - sensors and instruments. The orbiter will also descend much more slowly than Philae did, allowing it to gather more data and better pictures. Once it gets to 4 kilometres, for example, Rosetta should be able to distinguish between the gases emerging from each of the duck-shaped comet's two lobes to determine whether the regions vary in composition, says Altwegg, who leads the team behind ROSINA (the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis). That could shed light on the environments in which each was formed. Rosetta's cameras will get their best-resolution shots of the comet's surface yet - less than 1 centimetre per pixel once the craft is within 500 metres of the surface, adds Holger Sierks, PI for Rosetta's OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System). This will allow researchers to look at surface properties and link these to comet activity that Rosetta has observed from orbit. Over and out How far into the descent Rosetta will be able to send data back to mission control will depend on whether engineers can design the final trajectory such that the craft crashes on the side of the comet that faces Earth. Navigating while close to the comet will be difficult because the body's gravitational field is uneven, but spacecraft-operations manager Sylvain Lodiot hopes that the orbiter will transmit until the very end. The crash will definitely be a hard stop to the mission, he says, however gentle the landing. Designed to manoeuvre in orbit, once Rosetta is on the comet's surface it will no longer be able to point its antenna to communicate with Earth. Similarly, it will not be able to angle its solar array, so it will lose power, says Lodiot. "Once we touch, hit or crash, whatever you want to call it, it's game over." Before then, though, the mission still has much to accomplish. As the comet approached the Sun, it heated up, with vaporizing ice causing more and more gas and du
Re: [meteorite-list] Very Bright Fireball Over Europe on Halloween Night
Hi Doug- I don't think atmospheric extinction normally plays much of a role in color perception of bright meteors. You don't get a full magnitude difference between red and blue until you are about 15° above the horizon, or about four air masses. And even at a magnitude difference, I'd only expect a small impact on perceived color. Angle, however, translates to apparent speed, and I do think that might be an important factor in how people perceive color. I will say, however, that I haven't found any sort of systematic shift in color reports based on the distance from the fireball to the witness. Chris *** Chris L Peterson Cloudbait Observatory http://www.cloudbait.com On 11/4/2015 8:25 PM, Doug Ross wrote: Thanks for the very informative and interesting discussion. Could the altitude, angle and distance from which a meteor is viewed also affect perceived color? Seems to me that the air between the fireball and the witness might significantly filter the colors, in the same way that the sun can appear red at sunset, viewed at a low angle through more atmosphere. Doug Ross __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Witness information that is more helpful than color
I seek color in submitted witness reports, not necessarily to provide additional scientific information (although it's data, so I wouldn't completely rule out that possibility), but rather, to understand how people see things differently, and to make for a more complete public report, since public education about fireball events is part of our function. Meteor color is as much a part of the phenomenon as brightness, speed, fragmentation, and everything else. The fact that we can't directly convert color into composition doesn't mean we shouldn't include this information in a complete report. Chris *** Chris L Peterson Cloudbait Observatory http://www.cloudbait.com On 11/4/2015 4:48 PM, Matson, Rob D. via Meteorite-list wrote: Hi John, I think there are definitely things that can be learned by looking at the spectroscopy of fireball emissions, but of course such data are rare. And human eyeballs/brains are a poor substitute. We don't have the necessary spectral resolution, and of course the optical response is far from flat. It is perhaps not coincidental that green-blue (0.498 microns) is the peak of our scotopic response. Deep red (>0.63 microns) sensitivity is almost non-existent in scotopic vision, so even if a fireball had a significant red component, a much smaller green component would swamp it just due to our spectral response. Since nothing really diagnostic can be learned from a witness's perception of a fireball's color (as far as the meteoroid's composition is concerned), I see little point in asking them or encouraging them to report it. The next best thing that a novice witness can report (other than an accurate time and duration) is the slope of the meteor track relative to the horizon -- perhaps using a clockface analogy to avoid scary geometry. If I know the approximate fall zone reasonably accurately, a distant observer's slope approximation can greatly narrow down the true flight bearing, even without azimuth information (which can already be inferred from their location relative to the fall with greater accuracy than they can report). Mike Hankey has put together some very nice tools on the AMS site for amateurs to contribute useful information, concentrating on those things that non-technical people are reasonably good at. With enough witnesses, the average solution can sometimes be fairly accurate, even if the individual reports are all over the place. --Rob __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
[meteorite-list] AD- .99 Meteorite Auction, Participate Today!
Dear Meteorite List Members, I have several auctions ending today, started at only .99 with no reserve! Many more over the next several days. Click here to see them: http://stores.ebay.com/Outer-Space-Rocks/_i.html?rt=nc&LH_Auction=1&_sid=16403087&_trksid=p4634.c0.m309 eBay " Outer Space Rocks " store with exceptional quality meteorites and auctions: http://stores.ebay.com/Outer-Space-Rocks Website dedicated to the ultra rare, beautiful, and scientifically important meteorites from North West Africa: http://nwameteorite.com/home-.html Thank You and Have a Great Day! John Higgins IMCA # 9822 Meteoritical Society Member President, Outer Space Rocks LLC John Higgins Outer Space Rocks Meteorite Collection email: geohigg...@yahoo.com __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Very Bright Fireball Over Europe on Halloween Night
Op 5-11-2015 om 2:48 schreef "Beatty, Kelly" : this discussion is timely. what you've noted is exactly my understanding. just yesterday I came across a high-profile blog about these fireballs, Phil Plait's? and the writer stated that most of the light comes from the superheated vaporized particle as it ablates. suspecting this was wrong, I looked in several places for the correct information -- IMO, AMS, RASC Handbook, etc -- and yet I didn't really find the physics spelled out explicitly. (maybe I was looking in the wrong places?) the closest I came was this post by Peter Jenniskens (http://leonid.arc.nasa.gov/meteor.html), which was equivocal. Information on this indeed is not very consolidated but spread far and wide in primary literature, some dating to the '30-ies to '60-ies when Millman did a lot of groundbreaking spectroscopic work on meteors. More recent work on meteor spectra has been done by a.o. Borovicka. Chris Peterson rightly points to the influence of human physiology on colour perception: as he mentions, especially under low light level conditions the human eye is not as perceptive for each colour. Take also into account that on average 1 in 4 males have a form of colour blindness. Age plays a role as well: deep sky observers know that young people see planetary nebula as blue, while older people see them more greenish: this is due to the yellowing of the cornea with age. In other words: coupling meteor colours to meteor composition indeed is not as straight forward as some pretend. - Marco - Dr Marco (asteroid 183294) Langbroek Dutch Meteor Society (DMS) e-mail: d...@marcolangbroek.nl http://www.dmsweb.org http://www.marcolangbroek.nl - __ Visit our Facebook page https://www.facebook.com/meteoritecentral and the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com https://pairlist3.pair.net/mailman/listinfo/meteorite-list
