quinta-feira, 31 de maio de 2012

Meteorites brought methane to Mars

Methane in the Martian atmosphere was generated from organic matter in meteorites that landed on the surface of the planet, say European scientists. A multinational team was involved in the study, in which particles of the Murchison meteorite, which is similar to those that fall onto the Martian surface, were irradiated with UV light.

As reported in Nature, irradiation at UV levels believed to be the same as those on Mars released significant amounts of methane. The gas originated from carbonaceous material embedded in the meteorite.

Carbon dioxide (95%), nitrogen and argon form most of the atmosphere, with methane a trace component. Its lifetime on Mars is quite short at a few hundred years, so it needs to be constantly replenished to maintain a steady concentration. This new discovery offers an explanation for its continuous production and for the involvement of meteorites, which had been ruled out previously.

Hydrogen isotope ratio measurements confirmed that the released methane is definitely extraterrestrial and not a terrestrial anomaly. However, stable carbon isotope measurements are similar to those of terrestrial microbes, so they will be of limited value in future Mars missions.

The results might help to cast some light on the recently observed variations of methane levels across the Martian surface and will be invaluable in trying to establish whether any methane on Mars is produced by microbial life.

Fonte: Spectroscopynow

domingo, 27 de maio de 2012

Non-Biological Carbon in Martian Meteorites

This 4.5 billion-year-old rock, labeled meteorite ALH84001, is believed to have once been a part of Mars and to contain fossil evidence that primitive life may have existed on Mars more than 3.6 billion years ago. Image credit: NASA/JSC/Stanford University

NASA-funded research on Mars meteorites that landed on Earth shows strong evidence that very large molecules containing carbon, which is a key ingredient for the building blocks of life, can originate on the Red Planet. These macromolecules are not of biological origin, but they are indicators that complex carbon chemistry has taken place on Mars.

Researchers from the Carnegie Institution for Science in Washington who found reduced carbon molecules now have better insight into the chemical processes taking place on Mars. Reduced carbon is carbon that is bonded to hydrogen or itself. Their findings also may assist in future quests for evidence of life on the Red Planet. The findings are published in Thursday’s online edition of Science Express.

“These findings show that the storage of reduced carbon molecules on Mars occurred throughout the planet’s history and might have been similar to processes that occurred on the ancient Earth,” said Andrew Steele, lead author of the paper and researcher from Carnegie. “Understanding the genesis of these non-biological, carbon-containing macromolecules on Mars is crucial for developing future missions to detect evidence of life on our neighboring planet.”

Finding molecules containing large chains of carbon and hydrogen has been one objective of past and present Mars missions. Such molecules have been found previously in Mars meteorites, but scientists have disagreed about how the carbon in them was formed and whether it came from Mars. This new information proves Mars can produce organic carbon.

“Although this study has not yielded evidence that Mars has or once may have supported life, it does address some important questions about the sources of organic carbon on Mars,” said Mary Voytek, director of NASA’s Astrobiology Program at the agency’s Headquarters in Washington. “With the Curiosity rover scheduled to land in August, these new research results may help Mars Science Laboratory scientists fine-tune their investigations on the surface of the planet by understanding where organic carbon may be found and how it is preserved.”

Scientists have theorized that the large carbon macromolecules detected on Martian meteorites could have originated from terrestrial contamination from Earth or other meteorites, or chemical reactions or biological activity on Mars.

Steele’s team examined samples from 11 Martian meteorites from a period spanning about 4.2 billion years of Martian history. They detected large carbon compounds in 10 of them. The molecules were found inside grains of crystallized minerals.

Using an array of sophisticated research techniques, the team was able to show that at least some of the macromolecules of carbon were indigenous to the meteorites themselves and not contamination from Earth.

The team next looked at the carbon molecules in relation to other minerals in the meteorites to see what kinds of chemical processing these samples endured before arriving on Earth. The crystalline grains encasing the carbon compounds provided a window into how the carbon molecules were created. Their findings indicate that the carbon was created by volcanic activity on Mars and show that Mars has been doing organic chemistry for most of its history.

In a separate paper published by American Mineralogist, Steele and his team report their findings on the same meteorite announced in 1996 to contain possible -- but subsequently discounted -- relics of ancient biological life on Mars. Called ALH84001, the meteorite was found to also contain organic macromolecules of non-biological origin.

The Steele team’s research indicates that Mars does have a pool of reduced carbon. Their findings should help scientists involved in current and future Mars missions distinguish non-biologically formed carbon molecules from potential life.

Fonte: Astrobio.net

sábado, 26 de maio de 2012

Meteoritos de Marte têm moléculas orgânicas, mas não biológicas

Busca de vida em Marte

"Moléculas orgânicas descobertas em meteorito marciano".

Se isto lhe parece familiar, eventualmente até com um cheiro de naftalina, não precisa se preocupar.

Juntamente com as "descobertas de água em Marte" e as impressionantes "descobertas de água na Lua", em volumes que chegaram a ser comparados aos oceanos da Terra, o assunto é polêmico e, por isso mesmo, repetitivo.

Moléculas com grandes cadeias de carbono e hidrogênio - os chamados blocos básicos de construção de toda a vida na Terra -, têm sido alvos das missões a Marte desde as sondas Viking, nos anos 1970.

Pelo menos 10 anos antes disso, essas moléculas já haviam sido encontradas em meteoritos de Marte caídos aqui na Terra.

Mas, desde essas primeiras descobertas, os cientistas têm discordado sobre como essas moléculas orgânicas teriam se formado, e se elas teriam ou não vindo realmente de Marte.

Moléculas orgânicas em Marte

Um novo estudo, publicado hoje na revista Science, fornece fortes argumentos de que este carbono teria se originado realmente em Marte, não sendo fruto de contaminação terráquea.

Mas a ressalva deve ser feita com ênfase, dizem os cientistas: as moléculas de carbono marciano não têm origem biológica.

Ou seja, as moléculas de carbono não são "prova da existência de vida em Marte", elas se originaram de processos vulcânicos.

Se elas se juntaram para formar vida marciana no futuro do planeta - depois que as rochas agora estudadas foram arrancadas de lá - é assunto que permanece em aberto.

Os que os cientistas argumentam é, essas moléculas orgânicas - ou seja, moléculas à base de carbono - não são moléculas biológicas. Embora os compostos orgânicos de carbono sejam essenciais para a vida, eles podem ser criados também por processos não-biológicos.

De resto, não há consenso entre os cientistas sobre a origem dessas macromoléculas de carbono detectadas nos meteoritos marcianos - simplesmente não há dados suficientes para qualquer conclusão definitiva.

Fora aqueles que argumentam que sua origem é a contaminação em outros meteoritos ou aqui na Terra mesmo, os argumentos dividem-se entre reações químicas em Marte, ou restos de vida biológica nos primórdios do planeta.

Origem vulcânica

Andrew Steele e seus colegas examinaram amostras de 11 meteoritos marcianos, cujas idades abrangem cerca de 4,2 bilhões de anos de história marciana.

Para fugir dos argumentos da contaminação, eles procuraram pelas moléculas no interior dos cristais dos meteoritos, sem quebrar esses cristais, usando uma técnica chamada espectroscopia Raman, que usa o espalhamento da luz de um laser no material para determinar sua estrutura atômica e sua composição química.

A equipe detectou compostos de carbono grandes em 10 dos meteoritos estudados, no interior dos grânulos cristalizados dos minerais, demonstrando que pelo menos algumas dessas moléculas são de fato marcianas.

Seus resultados indicam que o carbono foi formado durante o vulcanismo em Marte, mostrando que a química orgânica está presente na maior parte da vida de Marte - de resto, uma boa notícia para a busca de sinais de vida em Marte.

"Entender a gênese dessas macromoléculas não-biológicas de carbono é crucial para o desenvolvimento de futuras missões para detectar sinais de vida em nosso planeta vizinho," disse Steele.

Fonte: Inovação Tecnológica /Brasil

quinta-feira, 24 de maio de 2012

What the Lotus Valley meteorite can tell us

A fallen meteorite in Coloma, Calif. could tell us about the origins of our solar system, according to a talk given by UC Davis associate professor of geology Qing-Zhu Yin last Sunday.

“If confirmed, what we have in hand is perhaps the most primitive materials, preserved in pristine condition in cold storage (never been heated and/or altered too much that the fragile organic matters are still preserved) for 4.567 billion years before it fell on Earth on April 22, 2012,” Yin said.

If initial examinations are correct, this particular meteorite could be a rare find for science. Due to the nature of this meteorite, its discovery and examination could provide new insight into the formation of planets and even life.

“It is one of those very rare carbonaceous chondrites [unmodified meteorites], which contains first or earliest solid objects in our solar system,” Yin said.

The meteorite shows even further potential for study in the creation of the solar system; while Yin focuses on the meteorite’s chemical makeup, UC Davis associate research geologist Gary Acton looks at how those elements affect magnetic fields.

Studying the magnetic fields of our sun as it was forming, called a protosun, can provide researchers and scientists with further knowledge into the formation of planets, due to a stream of gas rotating outward at high speed from the protosun. This stream is called “x-wind.” The composition of the meteorite in Lotus Valley can give Acton information on the protosun that formed it.

“X-wind took the particles that came close to the protosun [due to magnetic fields] and blew them back out,” Acton said. “Those dust particles accumulated into what became the planets, so this was one way that the planets may have formed.”

Because this meteorite is so important to researchers, it is vital that it is recovered in a timely manner. Unfortunately, due to the possibility of the meteorite disintegrating and to the presence of “meteorite hunters” – general public individuals seeking to sell any recovered pieces – the researchers and scientists searching Lotus Valley in Coloma have encountered some difficulty.

“I am very concerned that these specimens remain in the hands of private collectors and professional meteorite hunters with no accessibility to science,” Yin said. “The scientific community needs access to these special samples for research. The value is truly priceless.”

Yin urges that community support is necessary and hopes for these meteorite pieces to come into the hands of scientists, particularly due to the proximity of the meteorite’s fall location to UC Davis.

“We are privileged to be an academic institution closest to the ground zero,” said Yin. “To collect the samples as much as we can, we need your help. We need volunteers, we need your ideas, we need your donation, whichever way you could help to be part of this historic event, please let us know.”

To help in the discovery of pieces of this meteorite, contact Yin via e-mail at qyin@ucdavis.edu.

Fonte: theaggie.org

segunda-feira, 21 de maio de 2012

Será que geólogos italianos encontraram o meteorito Tunguska?

No jornal da União Americana de Geofísica Geochemistry, Geophysics, Geosystems (Geoquímica, Geofísica, Geosystemas) foi publicado um relatório dos geólogos italianos que afirmam finalmente ter encontrado algo que é muito semelhante ao famoso fragmento do meteorito de Tunguska.

A equipe italiana liderada por Luca Gasperini do Istituto da Ciência Marítima em Bolonha, trabalha mais de um ano no lugar de queda do meteorito.

Vários anos atrás, eles justificaram a hipótese que o Lago Cheko, situado a 8 km do epicentro da explosão constitui uma cratera. Agora, examinando o fundo do lago parecido com um cone com digitalização sísmica e magnética, eles descobriram uma grande pedra no centro do fragmento, o qual, de acordo com a hipótese, é um fragmento do meteorito Tunguska. "Anomalia" descoberta por eles fica em 10 km da profundidade no ponto mais profundo do lago.

O meteorito Tunguska, ou seja, "evento de Tunguska", literalmente abalou o mundo em 30 de junho de 1908, e ainda permanece um mistério. A explosão que em seguida trovejou sobre a Sibéria, avaliada em 40-50 megatons. Queimou mais de 2.000 quilômetros quadrados de floresta de coníferas e causou uma onda sísmica que dois vezes contornou a Terra e estabeleceu na Europa as noites brancas. Os cientistas não podem chegar a conclusão o que isto era - um cometa de gelo ou asteróide gigante.

Conseguiram apenas descobrir que a explosão ocorreu a uma altitude de 5-10 km, mas ainda agora nenhum dos fragmentos do objeto espacial caído não foi encontrado. Agora um deles pode ser encontrado. Resta apenas tirá-lo.

Fonte: portuguese.ruvr.ru

Who found Meteor Crater and when?

There is a high ridge that goes all around the crater and there is no way that it can be seen from the ground.

Well, about this ridge. I, my own personal self, have never seen this ridge, but I have to assume it is not exactly Himalayan in size.

Next, the meteor that created Meteor Crater did so about 50,000 years ago, so you pretty much have to assume that some folks that were around here before the Europeans showed up must have found the crater.

As long as we're discussing such matters, I've always wondered what the first people to see the Grand Canyon must have thought of it. They must have said, in whatever language they spoke, "Holy moley, look at that."

Or maybe not.

Anyway, I don't know who the first Europeans to see the crater might have been, but I do know that it was formed when a nickel-iron meteorite about 54 yards across hit the spot with an impact of about 10 megatons.

At first, a geologist named Grove Karl Gilbert pronounced in 1891 it had been caused by a volcano.

In 1903, a mining engineer named Daniel Moreau Barringer figured out the true cause of the crater, but geologists expressed some doubts about his idea.

Finally, in 1960, a researcher named Eugene Shoemaker proved beyond a doubt that the crater was formed by the impact of a large meteorite.

Fonte: azcentral.com

sexta-feira, 11 de maio de 2012

O meteorito de Chaves, o asteróide Vesta e a sonda Dawn

O geólogo José Fernando Monteiro interessou-se pelo meteorito de Chaves e, em 1988, classificou-o. Disse que o meteorito, que tinha caído em 1925 na aldeia de Vilarelho da Raia, a oito quilómetros de Chaves, era um pedacinho do asteróide Vesta, o segundo maior do sistema solar. Esta sexta-feira, a revistaScience publica um conjunto de artigos com os primeiros resultados da sonda espacial Dawn, a esquadrinhar Vesta desde Julho do ano passado, que vão ao encontro da classificação do geólogo português. 

Fernando Monteiro morreu em 2005, aos 43 anos. O estudioso de meteoritos e de crateras de impacto tinha classificado o meteorito de Chaves ainda na sua tese de mestrado, no final da década de 1980. É um howardito, um tipo raro de meteoritos, disse então Fernando Monteiro, que foi, aliás, o primeiro português a classificar um meteorito.

A hipótese de Vesta como a fonte destes meteoritos ganhou força quando, em 1996, o telescópio Hubble descobriu uma enorme cratera no pólo sul do asteróide. Alguma coisa colidiu com o asteróide e arrancou-lhe um valente bocado que deixou uma enorme cicatriz e atirou inúmeros fragmentos para o espaço.

Conhecida como Reia Sílvia, essa cratera do Vesta foi passada a pente fino pela sonda Dawn – lançada no espaço em 2007 da agência norte-americana NASA –, tal como todo o restante asteróide.

Vários artigos, entre os seis publicados na Science por equipas internacionais, identificam agora este asteróide como sendo realmente a fonte dos meteoritos do tipo howardito, e também do tipo eucrito e diogenito, que por vezes atingem a Terra. O olhar próximo do asteróide, como nunca antes sucedeu, revelou que os minerais na superfície do asteróide são os mesmos que estão presentes naqueles tipos de meteoritos.

Mais: com 19 quilómetros de profundidade e 500 quilómetros de diâmetro (um pouco menos do que o próprio asteróide, que tem 530), a Reia Sílvia é suficientemente grande para dela terem resultado os meteoritos do tipo howardito, eucrito e diogenito.

Assim sendo, fica reforçada a tese de que o meteorito de Chaves veio de Vesta até Portugal. Deste meteorito, recuperaram-se quase três quilos: o maior fragmento, com 2,4 quilos, está no Museu do Instituto Superior de Engenharia do Porto, enquanto outros dois (de 200 e 120 gramas) encontram-se no Museu e Laboratório Mineralógico e Geológico da Faculdade de Ciências do Porto. O Museu de História Natural de Paris tem ainda 61 gramas.

Asteróide é um planeta bebé

Mas Vesta, que foi descoberto em 1807, está cravejado de crateras resultantes do impacto de meteoritos. Reia Sílvia é a mais recente, formada há aproximadamente 1000 milhões de anos, quase por cima de outra, a Veneneia, de 400 quilómetros de diâmetro. Ora o estudo dos materiais ejectados nestas e noutras colisões, que os arrancaram de camadas menos superficiais, permitiu concluir que Vesta já não é um mero asteróide, mas um planeta bebé.

No início da sua formação e do sistema solar, há 4500 milhões de anos, Vesta estava a caminho de se tornar um planeta, à medida que ia atraindo e acumulando mais matéria. Estava a formar camadas internas distintas, como a Terra, com uma crosta, um manto e um núcleo de ferro (com 110 quilómetros de diâmetro). É aliás o único asteróide que se sabe ter sobrevivido desde os tempos conturbados do início do sistema solar, em que tudo chocava com tudo, facto que os cientistas atribuem à existência do núcleo de ferro.

A sua geologia revela assim características da Lua, dos planetas terrestres e dos asteróides. “Vesta é um corpo de transição entre os asteróides e os planetas. É semelhante a muitos pequenos planetóides que foram os blocos de construção dos planetas e, ao mesmo tempo, tem muitas características de um pequeno planeta, tendo derretido e formado uma crosta e núcleo”, disse David O’Brien, um dos cientistas da missão, citado num comunicado.

Ao ir ao encontro destes calhaus que sobraram da formação de planetas rochosos, como a Terra, Marte e Mercúrio, ideia da NASA é que a Dawn permita compreender melhor a formação do sistema solar. A sonda vai manter-se perto do Vesta até Agosto, altura em que seguirá viagem até Ceres, o maior asteróide do sistema solar, onde chegará em 2015.

“Vesta é uma janela para o passado inicial da história do sistema solar. A compreensão da história dos impactos no sistema solar é importante para compreender a evolução da Lua e dos planetas, incluindo como a vida evoluiu na Terra. Com o estudo dos impactos em Vesta através das suas crateras, podemos saber mais sobre os impactos na Terra primitiva”, referiu ainda David O’Brien. “Os dados da Dawn permitiram que Vesta deixasse de ser um objecto desfocado com alguns pixéis nas imagens do telescópio espacial Hubble, para se tornar um objecto geológico, que podemos estudar do ponto de vista geológico”, acrescentou, por sua vez, Aileen Yingst, também da missão.

Se cá estivesse, Fernando Monteiro, um dos poucos cientistas portugueses que estudava meteoritos e as suas crateras, só podia ficar contente com os primeiros resultados da visita da Dawn ao Vesta.


quinta-feira, 10 de maio de 2012

Palestra no IGEO desmitifica informações sobre meteoritos

Numa promoção do Curso de Pós-Graduação em Geologia da UFBA, o Prof. Gian Paolo Sighinolfi, da Università di Modena e Reggio Emilia, Itália, faz palestra sobre “Os meteoritos – do mito à ciência” na próxima quarta-feira (16 de maio), às 16h, no Auditório Yeda de Andrade Ferreira, do Instituto de Geociências da UFBA (IGEO). A queda de corpos sólidos do céu sempre preencheu de maravilha como também assustou o Homem desde o seu aparecimento sobre a Terra.As primeiras descrições de corpos sólidos caídos do céu foram feitas pelo homem do período Paleolítico-Neolítico, através de pinturas rupestres e gravações presentes em várias partes da Terra, em particular por populações residentes no norte da África, na área do atual deserto do Sahara. A primeira referência em linguagem escrita sobre a queda de meteoritos foi feita pelos egípcios, há cerca de 2.400 anos A.C.

O material extraterrestre mais antigo coletado, e que sobreviveu até nossos dias, é o meteorito de Ensisheim, caído na Alsácia, em 1492. Este evento foi descrito e gravado por vários autores. Em 1794 um cientista de Viena (Chladni) estudou um meteorito caído em Pallas, na Sibéria, e concluiu que a pedra tinha que ser de origem extraterrestre. A partir desta época o aspecto mítico do fenômeno dos meteoritos (pedra do Diabo ou de Deus), começou a desaparecer e deu lugar ao enfoque e abordagem científica do evento.

A partir do início do século XX os dados sobre os meteoritos constituíram o suporte básico para ciências muito diversificadas como a cosmologia física e química, geologia, geofísica, física do estado sólido, e não por último à própria biologia. Se os nossos conhecimentos sobre a queda de corpos sólidos (poeira cósmica, micro e macrometeoritos, material vítreo de impactos, corpos asteroidais) na Terra podem ser considerados satisfatórios, o impacto de material gasoso (cometas) continua ainda envolto em muito mistério e fonte de muitas hipóteses. No presente são possíveis candidatos a impacto de cometa os eventos de: 1 - Sílica Glass (Sahara, fronteira Egito – Líbia, 30 milhões de anos atrás); 2 - Tunguska (Sibéria, 30 de junho de 1908); e 3 - Curuçá (Amazonas, 13 de agosto de 1931). A ciência de amanhã deverá interpretar tais mistérios.

Fonte: Planetauniversitario.com

quinta-feira, 3 de maio de 2012

Want to get rich? Meteorites are worth three times as much as gold

Residents of the Western United States got a surprise wake-up call on Sunday, April 22 in the form of a fireball, which then exploded. Immediately after the event, 911 call centers in both states were flooded with calls reporting the event. According to some witnesses, the explosion was so powerful that it even caused buildings to shake. So, with a meteor explosion taking place comes the obvious question: did pieces of the space rock survive the fall all the way to Earth's surface?

Short answer, yes.

Peter Jenniskens is one of the world's most dedicated, and successful, meteorite hunters. Taking known data from last weekend's event, Jenniskens was able to deduce where fragments of the meteorite, if they survived at all, would have landed. Result: a tiny, 4 gram sample of the meteorite, which was enough to identify the space rock as a carbonaceous chrondite, a rare type of meteorite. In addition, several other fragments have also been found in the area, too.

As NASA continues to investigate this major event, it is asking the public for help in the form of photos, videos, and fragments of the space rock. The hope: photographic evidence will be able to help pin down a trajectory, which could solve the question of whether the exploding meteor was a Lyrid or not.

Another point of interest: meteorite fragments are worth a lot of money, too, roughly 3.5 times the value of gold.

So far, 46 grams of the meteorite, a rare carbonaceous chondrite, have been found. In today's market, that would bring in roughly $9000. The reason for the high value? Carbonaceous chrondrites are rare, extremely rare. Counting last month's event, only three such meteorites have landed in the united States, with the other coming in 1936 and 1950. Reason for the rarity? Chrondrites are fragile and often completely burn up on atmospheric entry.

So, if you live in California or Nevada, here's a good reason to keep one's eyes on the ground as, with meteorites, it's a case of finders keepers.

Source: Examiner.com

quarta-feira, 2 de maio de 2012

Meteorite Hunting: Five Tips For Finding Space Rocks

Earth is under constant bombardment by space rocks. When they crash and burn through the atmosphere, most of the debris gets lost to the oceans, while some is buried or gradually weathered away. Nonetheless, plenty of chunks of fallen meteors, or meteorites, are strewn across the accessible parts of the planet. So far, more than 40,000 meteorites have been found and catalogued, and countless more are still out there, waiting to be chanced upon.

If you need further incentive for finding something that was forged at the birth of our sun and contains secrets about the nature of our solar system, there's this: Space rocks are worth as much as $1,000 per gram. The following tips will get you started on your search, but be warned: This extraterrestrial treasure hunt requires hard work and dedication.

Step 1. Get permission
Before you plan a meteorite hunt, make sure that if you find one, you'll be allowed to keep it. Space rocks found in national parks belong to the federal government and cannot legally be kept, said David Kring, a meteorite scientist at the University of Arizona's Lunar and Planetary Institute.
The law is ambiguous regarding ownership of meteorites found on the 264 million acres of public lands, mostly in the American West (and including many of the country's meteorite hotspots), that are managed by the Bureau of Land Management (BLM). According to Bob Verish, a meteorite recovery expert who has found hundreds of meteorites, some BLM offices consider meteorites to be artifacts, and thus regard them as government property, but the vast majority of BLM offices do not. It's a pretty safe bet that any meteorites found on public lands will be yours to keep, Verish said — "so just go ahead and meteorite hunt."
But if you don't want to take the risk of finding something that could theoretically be confiscated in the future, you're better off searching on privately owned land. Get permission to do so. "Meteorites belong to the land owner," Kring said. "Anytime a person wants to look for meteorites, arrangements with the land owner should be made first."
Step 2. Pick a good spot
In a world full of rocks, narrowing your search is key. "Meteorites fall anywhere, but they are easiest to spot where there are few terrestrial rocks," said Alan Rubin, a geochemist at the University of California, Los Angeles, who specializes in characterizing newly discovered meteorites. [What If the Sky Actually Fell?]
The best hunting grounds are large, barren expanses where a dark rock — meteorites tend to be blackish — is easy to spot. Deserts, such as Southern California's Mojave Desert, and icy regions, such as Antarctica, are ideal. "Furthermore, the dry conditions in all of these regions (even Antarctica) help preserve the specimens — i.e., they are less altered by liquid water," Rubin told Life's Little Mysteries.
Within the Mojave or another desert, ancient, dry lake beds are ideal places to search, because their surfaces have likely been exposed for millennia. According to O. Richard Norton and Lawrence Chitwood in their book "Field Guides to Meteors and Meteorites" (Springer, 2008), many meteorites have been found in the Mojave Desert's Rosamond, Muroc and Lucerne dry lakes, among others.
You can also search in "strewn fields," or zones where meteorites from a single space rock were dispersed as it broke up during atmospheric entry. There are well-known strewn fields located near New Mexico's Glorieta Mountain, as well as Holbrook and Franconia in Arizona. Since 1995, thousands of stony meteorites have also been recovered in what appears to be two overlapping strewn fields in Gold Basin, Ariz.
Lastly, the Great Plains is an area with scant terrestrial rocks, so out-of-this-world ones come in higher proportions. "Any new rocks farmers dig up have a good chance of being meteoritic," Norton and Chitwood wrote. "Ask permission to scout the fence rows where rocks are often thrown. More than one meteorite has been found in a farmer's rock pile, or propping open a screen door."
Step 3. Search for new arrivals
Some space rock hunters aren't content to simply look for long-lost meteorites. For folks like Robert Ward, a professional meteorite hunter who last month found a piece of a meteor that was seen crashing through Earth's atmosphere above California the day before, the thrill is finding new arrivals.
Furthermore, when a newly fallen meteorite can be matched with the trajectory of the meteor that deposited it, this enables scientists to determine both its mineral content and what part of space it originated from. In the same vein as sending a space probe to an asteroid or comet and collecting a sample — but infinitely cheaper — finding a meteorite whose incoming trajectory is known can reveal fresh information about the structure and composition of a distant region of the solar system.
So, when a new fireball is spotted screeching toward Earth's surface, how do you go about finding the meteorites it deposited along its path? Bill Cooke, head of NASA's Meteoroid Environment Office, said you need to identify the ground below an incoming meteor's "dark flight" — the part of its trajectory after it slows below 3 or 4 kilometers per second, at which point it no longer burns and produces light.
"If an accurate trajectory is available, dark flight calculations are performed to figure out where pieces of various sizes may strike the ground. These calculations are posted on the Internet, usually on the meteorobs or meteorites list," Cooke wrote in an email.
Recently, Marc Fries of the Carnegie Institute of Washington developed a technique to locate falls without the need for a precise trajectory or dark flight. Fries uses Doppler weather radar to detect a "rain" of meteoritic particles falling to the ground, permitting rapid location of meteorite fall zones. It was this technique that defined the fall area for the California meteorite and led to Ward's find. Fries' blog, Radar Obs of Meteor Events, is "perhaps THE URL for a meteorite hunter to check," Cooke wrote.
Step 4. Harness the power of magnetism
When preparing for your desert hunting trip, Verish recommends packing plenty of water, snake guards and sunglasses; he also warns against going it alone, and advises meteorite hunters to ride out in two vehicles in case one breaks down.
Also, don't forget your metal detector. "Most meteorites contain at least some metallic iron-nickel and so will be at least somewhat magnetic and set off metal detectors," Rubin wrote in an email.
However, Verish said the best meteorite hunters "find them by eye." Not only can you cover more ground if you're not blindly waving a wand back and forth, but some of the more elusive and thus more remarkable types of meteorites do not contain metal, and can be discovered only by carefully scouring the ground for odd-looking rocks. "These are lunar meteorites, Martian meteorites and igneous meteorites (achondrites) derived from asteroids (essentially basalts)," Rubin wrote.
Step 5. Share with science
If you spot what you think might be a specimen from space, ask yourself these questions: Is the rock black or brown? Is it solid, without pores, and dense compared to most other rocks in the area? If a corner of the sample is ground slightly, is the interior metallic silver? (If there is no grinding, don't grind it). Is the sample magnetic? If you answered yes to all of these questions, you probably have a genuine, 4.5-billion-year-old piece of the cosmos.
Go ahead and put it on your mantle, but please take a moment to share news of your find with scientists. Though thousands of meteorites have been catalogued already, each new one is a fresh data point, and could contain a key to one of the many unanswered questions about the solar system's formation and evolution.
"Hunters can send samples in to meteorite researchers for them to be classified properly," Rubin wrote. "But there is a price for this service: researchers generally demand 20 grams or 20 percent of the total amount of a specimen (whichever is the lesser amount) for their university or museum collections in return for analysis."

Fonte: huffingtonpost.com