Novas medições do Observatório Espacial Herschel mostram que o cometa Hartley 2, que vem do distante Cinturão de Kuiper, contém água com a mesma "assinatura" química dos oceanos da Terra. esta região remota do Sistema Solar, com distância entre 30 e 50 vezes maior do que aquela que separa a Terra do Sol, abriga corpos rochosos e gelados, entre os quais Plutão, outros planetas anãos e inúmeros cometas.
"Nossos resultados com o Herschel indicam que cometas podem ter desempenhado um papel importante, trazendo grandes quantidades de água à Terra em seus primórdios," disse Dariusz Lis, pesquisador associado sênior de física do Instituto de Tecnologia da Califórnia, em Pasadena, e coautor de um artigo publicado na revista Nature, na versão, em 5 de outubro. "Esta descoberta aumenta substancialmente as reservas de água dos mares, semelhante à da Terra, no Sistema Solar, com a inclusão, agora, de corpos celestes gelados originários do Cinturão de Kuiper."
Cientistas acreditam que a Terra era, no princípio, quente e seca, de maneira que a água, fundamental para a vida, deve ter sido trazida milhões de anos mais tarde, com o impacto de asteroides e cometas. Até agora, nenhum dos cometas anteriormente estudados continha água como a existente na Terra. No entanto, as observações de Hartley 2 feitas pelo Hersche, a primeira observação profunda a observar água em um cometa vindo do Cinturão de Kuiper Belt, mudam a figura.
O Herschel espiou o interior da coma do cometa, que é a sua atmosfera fina e gasosa. A coma se desenvolve quando a matéria gelada em um cometa se vaporiza em sua aproximação do Sol. Esse envelope brilhante circunda a bola de gelo suja do núcleo do cometa, e se posiciona atrás do astro, como uma cauda.
O Herschel detectou os vestígios, ou "assinatura" de água vaporizada em sua coma e para surpresa dos cientistas, o Hartley 2 tinha 50% mais "água pesada" do que outros cometas analisados até então.Na água pesada, um dos dois átomos de hidrogênio comum é substituído pelo isótopo pesado de hidrogênio, chamado deutério. A proporção entre a água pesada e a leve, ou comumr, é a mesma no Hartley 2 e na superfície da Terra. A quantidade de água pesada de um cometa está relacionada ao meio ambiente onde o cometa se formou.
Rastreando a trajetória do Hartley 2 enquanto ele voava em direção às vizinhanças da Terra, no Sistema Solar interior, a cada seis anos e meio, astrônomos descobriram que ele vem dos Cinturão de Kuiper. Os cinco cometas além do Hartley 2 cujas proporções de água pesada e água comum foram obtidas, vieram todos de uma região ainda mais distante no Sistema Solar, chamada Nuvem de Oort. Esse enxame de corpos celestes, 10.000 vezes mais distante do que o Cinturão de Kuiper, é a fonte da maioria dos cometas documentados.
Dadas as altas proporções de água pesada observadas nos cometas da Nuvem de Oort Cloud em comparação à dos oceanos da Terra, astrônomos concluíram que a contribuição dos cometas para o volume total de água da Terra estaria em cerca de 10%. Asteroides, que são geralmente encontrados em uma faixa entre Marte e Júpiter e que ocasionalmente chegam às vizinhanças da Terra, pareciam ser os maiores depósitos de água. Os resultados recentes, no entanto, indicam que cometas vindos do Cinturão de Kuiper Belt teriam feito um trabalho antes subestimado, trazendo água para a Terra.
Como tais objetos chegaram a ter essa intrigante água oceânica é uma pergunta desconcertante. Astrônomo esperavam que cometas do Cinturão de Kuiper tivessem ainda mais água pesada do que os da Nuvem de Oort Cloud porque estes, acredita-se, teriam se formado mais próximos ao Sol do que os cinturão de Kuiper. Por conseguinte, corpos provenientes da Nuvem de Oort deveriam ter menos água congelada em seu interior em período anterior à sua projeção até a margem, quando o Sistema Solar evoluiu.
"Nosso estudo indica que nossa compreensão da distribuição dos elementos mais leves e seus isótopos, bem como da dinâmica do Sistema Solar primordial, está incompleta," disse o coautor Geoffrey Blake, professor de ciência planetária e química do Caltech. "No Sistema Solar primordial, cometas e asteroides se moveriam por toda a volta, e parece que alguns deles caíram na Terra, criando os oceanos."
Astronomers have found a new cosmic source for the same kind of water that appeared on Earth billions of years ago and created the oceans. The findings may help explain how Earth's surface ended up covered in water.
New measurements from the Herschel Space Observatory show that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. This remote region of the solar system, some 30 to 50 times as far away as the distance between Earth and the sun, is home to icy, rocky bodies including Pluto, other dwarf planets and innumerable comets.
"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth," said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature, published online today, Oct. 5. "This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt."
Scientists theorize Earth started out hot and dry, so that water critical for life must have been delivered millions of years later by asteroid and comet impacts. Until now, none of the comets previously studied contained water like Earth's. However, Herschel's observations of Hartley 2, the first in-depth look at water in a comet from the Kuiper Belt, paint a different picture.
Herschel peered into the comet's coma, or thin, gaseous atmosphere. The coma develops as frozen materials inside a comet vaporize while on approach to the sun. This glowing envelope surrounds the comet's "icy dirtball"-like core and streams behind the object in a characteristic tail.
Herschel detected the signature of vaporized water in this coma and, to the surprise of the scientists, Hartley 2 possessed half as much "heavy water" as other comets analyzed to date. In heavy water, one of the two normal hydrogen atoms has been replaced by the heavy hydrogen isotope known as deuterium. The ratio between heavy water and light, or regular, water in Hartley 2 is the same as the water on Earth's surface. The amount of heavy water in a comet is related to the environment where the comet formed.
By tracking the path of Hartley 2 as it swoops into Earth's neighborhood in the inner solar system every six-and-a-`half years, astronomers know that it comes from the Kuiper Belt. The five comets besides Hartley 2 whose heavy-water-to-regular-water ratios have been obtained all come from an even more distant region in the solar system called the Oort Cloud. This swarm of bodies, 10,000 times farther afield than the Kuiper Belt, is the wellspring for most documented comets.
Given the higher ratios of heavy water seen in Oort Cloud comets compared to Earth's oceans, astronomers had concluded that the contribution by comets to Earth's total water volume stood at approximately 10 percent. Asteroids, which are found mostly in a band between Mars and Jupiter but occasionally stray into Earth's vicinity, looked like the major depositors. The new results, however, point to Kuiper Belt comets having performed a previously underappreciated service in bearing water to Earth.
How these objects ever came to possess the telltale oceanic water is puzzling. Astronomers had expected Kuiper Belt comets to have even more heavy water than Oort Cloud comets because the latter are thought to have formed closer to the sun than those in the Kuiper Belt. Therefore, Oort Cloud bodies should have had less frozen heavy water locked in them prior to their ejection to the fringes as the solar system evolved.
"Our study indicates that our understanding of the distribution of the lightest elements and their isotopes, as well as the dynamics of the early solar system, is incomplete," said co-author Geoffrey Blake, professor of planetary science and chemistry at Caltech. "In the early solar system, comets and asteroids must have been moving all over the place, and it appears that some of them crash-landed on our planet and made our oceans."
New measurements from the Herschel Space Observatory show that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. This remote region of the solar system, some 30 to 50 times as far away as the distance between Earth and the sun, is home to icy, rocky bodies including Pluto, other dwarf planets and innumerable comets.
"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth," said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature, published online today, Oct. 5. "This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt."
Scientists theorize Earth started out hot and dry, so that water critical for life must have been delivered millions of years later by asteroid and comet impacts. Until now, none of the comets previously studied contained water like Earth's. However, Herschel's observations of Hartley 2, the first in-depth look at water in a comet from the Kuiper Belt, paint a different picture.
Herschel peered into the comet's coma, or thin, gaseous atmosphere. The coma develops as frozen materials inside a comet vaporize while on approach to the sun. This glowing envelope surrounds the comet's "icy dirtball"-like core and streams behind the object in a characteristic tail.
Herschel detected the signature of vaporized water in this coma and, to the surprise of the scientists, Hartley 2 possessed half as much "heavy water" as other comets analyzed to date. In heavy water, one of the two normal hydrogen atoms has been replaced by the heavy hydrogen isotope known as deuterium. The ratio between heavy water and light, or regular, water in Hartley 2 is the same as the water on Earth's surface. The amount of heavy water in a comet is related to the environment where the comet formed.
By tracking the path of Hartley 2 as it swoops into Earth's neighborhood in the inner solar system every six-and-a-`half years, astronomers know that it comes from the Kuiper Belt. The five comets besides Hartley 2 whose heavy-water-to-regular-water ratios have been obtained all come from an even more distant region in the solar system called the Oort Cloud. This swarm of bodies, 10,000 times farther afield than the Kuiper Belt, is the wellspring for most documented comets.
Given the higher ratios of heavy water seen in Oort Cloud comets compared to Earth's oceans, astronomers had concluded that the contribution by comets to Earth's total water volume stood at approximately 10 percent. Asteroids, which are found mostly in a band between Mars and Jupiter but occasionally stray into Earth's vicinity, looked like the major depositors. The new results, however, point to Kuiper Belt comets having performed a previously underappreciated service in bearing water to Earth.
How these objects ever came to possess the telltale oceanic water is puzzling. Astronomers had expected Kuiper Belt comets to have even more heavy water than Oort Cloud comets because the latter are thought to have formed closer to the sun than those in the Kuiper Belt. Therefore, Oort Cloud bodies should have had less frozen heavy water locked in them prior to their ejection to the fringes as the solar system evolved.
"Our study indicates that our understanding of the distribution of the lightest elements and their isotopes, as well as the dynamics of the early solar system, is incomplete," said co-author Geoffrey Blake, professor of planetary science and chemistry at Caltech. "In the early solar system, comets and asteroids must have been moving all over the place, and it appears that some of them crash-landed on our planet and made our oceans."
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