Astrônomos apontam indícios de nono planeta no Sistema Solar

da France Presse, em Tóquio

Cientistas de uma universidade japonesa declararam nesta quinta-feira (28) que estão convencidos de que existe um nono planeta, até agora desconhecido, que gravita nos confins do nosso Sistema Solar e que algum dia será descoberto, caso os astrônomos tenham os meios necessários.
Os pesquisadores da Universidade de Kobe, no oeste do Japão, baseiam suas afirmações em simulações de computador.

Fernando D'Andrea/Southlogic Studios

Concepção artística do que seria o "Planeta X", apontado por pesquisadores japoneses como o nono do Sistema Solar

"Existe uma elevada probabilidade de que um planeta, do qual ignoramos a existência, com uma massa [equivalente] de 30% a 70% da Terra, na fronteira de nosso Sistema Solar", explicaram os cientistas em um comunicado.
"Se forem realizadas investigações em grande escala, este misterioso planeta será o 'Planeta X', sem dúvida, descoberto daqui uns dez anos, no máximo", dizem eles.
"Devido à temperatura muito baixa, sua superfície pode estar coberta de gelo, amônia congelada e metano", explicou o professor Tadashi Mukai.
Os estudos da equipe da Universidade de Kobe, coordenados pelo cientista brasileiro Patryk Sofia Lykawka e o professor Mukai, serão publicados em abril no "Astronomical Journal".
Substituição
Esta hipótese sobre a existência de um denominado "Planeta X" acontece depois que a comunidade científica decidiu, em 2006, excluir Plutão da lista de planetas de nosso Sistema Solar.
Plutão, corpo celeste descoberto em 1930 pelo astrônomo americano Clyde Tombaugh, foi rebaixado à categoria de "planeta anão", pois já não corresponde à nova definição, mais restritiva, que em 2006 foi adotada pela União Astronômica Internacional.
Desde aquela decisão, os oito planetas reconhecidos pela comunidade científica são: Mercúrio, Vênus, Terra, Marte, Júpiter, Saturno, Urano e Netuno.
A equipe de Kobe destacou que mais de 1.100 corpos celestes foram encontrados no cinturao de Kuiper desde meados dos anos 90.
"Mas seria a primeira vez que se descobre um corpo celeste desse tamanho, que é maior que Plutão", concluiu Mukai.

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Dúvida sobre água na Lua persiste após mapa da Nasa

Agência Estado

A Nasa, agência espacial americana, apresentou nessa quarta-feira o mais detalhado mapa já feito da região da cratera Shackleton, no pólo sul da Lua. Mas as imagens, obtidas pelo radar Goldstone, baseado no deserto de Mojave, nos EUA, não conseguiram dirimir a dúvida quanto à presença de água nessa área, tida como uma forte candidata para um futuro pouso de astronautas ou instalação de base lunar, ambos projetos que estão nos planos da agência espacial.Água poderá ser importante para futuras missões tripuladas, reduzindo não só a massa de víveres como a de combustível que precisaria ser levada da Terra para abastecer um posto avançado - da água pode-se extrair hidrogênio, que é usado como combustível de foguete, além de oxigênio.A “Visão para Exploração Espacial” anunciada pelo presidente dos EUA, George W. Bush, em 2004, pede um retorno de astronautas à Lua por períodos de permanência cada vez mais prolongados, começando a partir de 2015. Nos anos 90, duas sondas orbitais, Clementine e Lunar Prospector, detectaram sinais que poderiam ser de água congelada na região de Shackleton. Em 2003 e, depois em 2006, no entanto, o radiotelescópio de Arecibo, em Porto Rico, não foi capaz de confirmar a presença de massas de gelo na área. Já o sinal do radar Goldstone não conseguiu penetrar fundo o suficiente na superfície lunar para eliminar a dúvida.Ao apresentar os resultados do Goldstone, no entanto, representantes da Nasa mantiveram-se otimistas quanto às perspectivas de usar Shackleton para uma futura base, adiando a palavra final sobre a ausência ou presença de água para a sonda Lunar Reconnaissance Orbiter (LRO), que fará mapas 3D da superfície lunar e deverá ser lançada no final do ano.

Spitzer's eyes perfect for spotting diamonds in the sky

NASA/JPL NEWS RELEASE
Posted: February 26, 2008

 

Diamonds may be rare on Earth, but surprisingly common in space -- and the super-sensitive infrared eyes of NASA's Spitzer Space Telescope are perfect for scouting them, say scientists at the NASA Ames Research Center in Moffett Field, Calif.

This artist's concept shows a multitude of tiny diamonds next to a hot star. Diamonds are abundant in space. Credit: NASA/JPL-Caltech

Using computer simulations, researchers have developed a strategy for finding diamonds in space that are only a nanometer (a billionth of a meter) in size. These gems are about 25,000 times smaller than a grain of sand, much too small for an engagement ring. But astronomers believe that these tiny particles could provide valuable insights into how carbon-rich molecules, the basis of life on Earth, develop in the cosmos.

Scientists began to seriously ponder the presence of diamonds in space in the l980s, when studies of meteorites that crashed into Earth revealed lots of tiny nanometer-sized diamonds. Astronomers determined that 3 percent of all carbon found in meteorites came in the form of nanodiamonds. If meteorites are a reflection of the dust content in outer space, calculations show that just a gram of dust and gas in a cosmic cloud could contain as many as 10,000 trillion nanodiamonds.

"The question that we always get asked is, if nanodiamonds are abundant in space, why haven't we seen them more often?" says Charles Bauschlicher of Ames Research Center. They have only been spotted twice. "The truth is, we just didn't know enough about their infrared and electronic properties to detect their fingerprint."

To solve this dilemma, Bauschlicher and his research team used computer software to simulate conditions of the interstellar medium--the space between stars--filled with nanodiamonds. They found that these space diamonds shine brightly at infrared light ranges of 3.4 to 3.5 microns and 6 to 10 microns, where Spitzer is especially sensitive.

Astronomers should be able to see celestial diamonds by looking for their unique "infrared fingerprints." When light from a nearby star zaps a molecule, its bonds stretch, twist and flex, giving off a distinctive color of infrared light. Like a prism breaking white light into a rainbow, Spitzer's infrared spectrometer instrument breaks up infrared light into its component parts, allowing scientists to see the light signature of each individual molecule.

Team members suspect that more diamonds haven't been spotted in space yet because astronomers have not been looking in the right places with the right instruments. Diamonds are made of tightly bound carbon atoms, so it takes a lot of high-energy ultraviolet light to cause the diamond bonds to bend and move, producing an infrared fingerprint. Thus, the scientists concluded that the best place to see a space diamond's signature shine is right next to a hot star.

Once astronomers figure out where to look for nanodiamonds, another mystery is figuring out how they form in the environment of interstellar space.

"Space diamonds are formed under very different conditions than diamonds are formed on Earth," says Louis Allamandola, also of Ames.

He notes that diamonds on Earth form under immense pressure, deep inside the planet, where temperatures are also very high. However, space diamonds are found in cold molecular clouds where pressures are billions of times lower and temperatures are below minus 240 degrees Celsius (minus 400 degrees Fahrenheit).

"Now that we know where to look for glowing nanodiamonds, infrared telescopes like Spitzer can help us learn more about their life in space," says Allamandola.

Bauschlicher's paper on this topic has been accepted for publication in Astrophysical Journal. Allamandola was a co-author on the paper, along with Yufei Liu, Alessandra Ricca, and Andrew L. Mattioda, also of Ames.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

Of Planets and Palace Elephants

It was bad enough when, in August 2006, members of the International Astronomical Union decided to remove Pluto from the pantheon of major planets. Worse, Ceres and Eris got tossed into the fray.

Now how are we supposed to remember the planets in order? The tried-and-true mnemonic "My Very Educated Mother Just Served Us Nine Pizzas" doesn't, in the IAU's eyes, cut it anymore. Oh, I suppose you could substitute "Nachos" for the "Nine Pizzas," but still . . .

An illustration from 11 Planets: A New View of the Solar System.

David Aguilar / National Geographic

Thankfully, National Geographic has come to the rescue. Last year its books-for-kids division sponsored a contest for a nifty way to recall Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, and Eris in order. I would have entered, but I'm older than 14.

The winner, announced this week, is 10-year-old Maryn Smith of Great Falls, Montana. Her fourth-grade class at Riverview Elementary School cooked up a bunch of clever phrases, but in the end the class voted to submit Maryn's entry — which was "My Very Exciting Magic Carpet Just Sailed Under Nine Palace Elephants." Hers was selected from about 800 other submissions.

As you can imagine, the mnew mnemonic was big mnews in central Montana. It also gets a prominent mention in David Aguilar's book 11 Planets: A New View of the Solar System (just published by National Geographic) and in a song on Lisa Loeb's soon-to-be-released album for children.

Care to match wits with a 10-year-old? Try your hand at crafting a planet mnemonic of your own and put it in the comments below. You get extra credit if it makes sense with — and without — the inclusion of Ceres, Pluto, and Eris.

Liquid water found flowing on Mars? Scientists say no

UNIVERSITY OF ARIZONA NEWS RELEASE
Posted: March 2, 2008

 

Liquid water has not been found on the Martian surface within the last decade after all, according to new research.

The finding casts doubt on the 2006 report that the bright spots in some Martian gullies indicate that liquid water flowed down those gullies sometime since 1999.

"It rules out pure liquid water," said lead author Jon D. Pelletier of The University of Arizona in Tucson.

Pelletier and his colleagues used topographic data derived from images of Mars from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Since 2006, HiRISE has been providing the most detailed images of Mars ever taken from orbit.

The researchers applied the basic physics of how fluid flows under Martian conditions to determine how a flow of pure liquid water would look on the HiRISE images versus how an avalanche of dry granular debris such as sand and gravel would look.

"The dry granular case was the winner," said Pelletier, a UA associate professor of geosciences. "I was surprised. I started off thinking we were going to prove it's liquid water."

Finding liquid water on the surface of Mars would indicate the best places to look for current life on Mars, said co-author Alfred S. McEwen, a UA professor of planetary sciences.

"What we'd hoped to do was rule out the dry flow model -- but that didn't happen," said McEwen, the HiRISE principal investigator and director of UA's Planetary Image Research Laboratory.

An avalanche of dry debris is a much better match for their calculations and also what their computer model predicts, said Pelletier and McEwen.

Pelletier said, "Right now the balance of evidence suggests that the dry granular case is the most probable."

They added that their research does not rule out the possibility that the images show flows of very thick mud containing about 50 percent to 60 percent sediment. Such mud would have a consistency similar to molasses or hot lava. From orbit, the resulting deposit would look similar to that from a dry avalanche.

The team's research article, "Recent bright gully deposits on Mars: wet or dry flow?" is being published in the March issue of Geology. Pelletier and McEwen's co-authors are Kelly J. Kolb, a UA doctoral candidate, and Randy L. Kirk of the U.S. Geological Survey in Flagstaff, Arizona.

NASA funded the research.

In December 2006, Michael Malin and his colleagues published an article in the journal Science suggesting the bright streaks that formed in two Martian gullies since 1999 "suggest that liquid water flowed on the surface of Mars during the past decade."

Malin's team used images taken by the Mars Global Surveyor Mars Orbital Camera (MOC) of gullies that had formed before 1999. Repeat images taken of the gullies in 2006 showed bright streaks that had not been there in the earlier images.

The images are available here.

Subsequently, Pelletier and McEwen were at a scientific meeting and began chatting about the astonishing new finding. They discussed how the much more detailed images from HiRISE might be used to flesh out the Malin team's findings.

Pelletier had experience in using the stereoscopic computer-generated topographic maps known as digital elevation models (DEMs) to figure out how particular landscape features form.

DEMs are made using images of the landscape taken from two different angles. The Mars Reconnaissance Orbiter spacecraft is designed to regularly point at targets, enabling high-resolution stereo images, McEwen said.

Kirk made a DEM of the crater in the Centauri Montes region where the Malin team found a new bright streak in a gully.

Once the DEM was constructed, Pelletier used the topographic information along with a commercially available numerical computer model to predict how deposits in that particular gully would appear if left by a pure water flood versus how the deposits would appear if left by a dry avalanche.

The model also predicted specific conditions needed to create each type of debris flow.

"This is the first time that anyone has applied numerical computer models to the bright deposits in gullies on Mars or to DEMs produced from HiRISE images," Pelletier said.

When he compared the actual conditions of the bright deposit and its HiRISE image to the predictions made by the model, the dry avalanche model was a better fit.

"The dry granular case is both simpler and more closely matches the observations," Pelletier said.

"It's just a test," he said. It's either more like A or more like B. We were surprised that it was more like B."

Pelletier said these new findings indicate, "There are other ways of getting deposits that look just like this one that do not require water."

One of the team's next steps is using HiRISE images to examine similar bright deposits on less-steep slopes to sort out what processes might have formed those deposits.