NASA has released three new stunning color pictures taken by the Cassini spacecraft exploring the planet Saturn. The images show the giant planet, its golden rings and several moons.

Credit: NASA/JPL/University of Arizona Download larger image version here

This image was taken on August 8, 2004, with the Cassini spacecraft narrow angle camera in red, green, and blue filters. This image was taken 8.5 million kilometers (5.3 million miles) from Saturn. Contrast has been enhanced to aid visibility.

Credit: NASA/JPL/University of Arizona Download larger image version here

This color image was taken on August 15, 2004, with the Cassini spacecraft narrow angle camera, using the red, green, and blue filters. The image was taken 8.8 million kilometers (5.5 million miles) from Saturn. Contrast has been enhanced to aid visibility.

Credit: NASA/JPL/University of Arizona Download larger image version here

Prometheus and Pandora are often called the "F ring shepherds" as they control and interact with Saturn's interesting F ring, seen between them.

This image was taken on June 18, 2004, with the Cassini spacecraft narrow angle camera 8.2 million kilometers (5.1 million miles) from Saturn. It was created using the red, green, and blue filters. Contrast has been enhanced to aid visibility.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

Notícias Segunda-Feira, 23 de agosto de 2004   JC e-mail 2591, de 23 de Agosto de 2004.   A Via Láctea teria 13,6 bilhões de anos   Descobrir a idade da Via Láctea, um desafio para muitos astrônomos Alguns astrônbomos, a partir de dados do Observatório Paranal, no Chile, anunciaram nova estimativa para a galáxia que contém a Terra e todo Sistema Solar. O estudo foi feito por os integrantes da Agência Espacial Européia (ESA) e será publicado em breve pela revista Astronomy & Astrophysics. O trabalho do italiano Luca Pasquini e colaboradores deu o resultado de 13,6 bilhões de anos, com um desvio de 800 milhões para mais ou menos. Para chegar ao número, os cientistas usaram uma medição indireta. Primeiro, detectaram a quantidade de berílio presente em duas estrelas do aglomerado globular NGC 6397, cuja idade é estimada em 13,4 bilhões de anos – também com uma margem de erro de 800 milhões de anos. Como se acredita que o berílio esteja presente na Via Láctea desde a formação do sistema, cálculos matemáticos permitiram induzir o intervalo de tempo que existiu entre o surgimento das primeiras estrelas dessa região do cosmos e a formação do aglomerado onde o berílio foi flagrado. Como esse número ficou em cerca de 200 milhões de anos, ele foi somado à idade do NGC 6397, para dar o resultado final de 13,6 bilhões de anos. Se os cálculos dos astrônomos europeus estiverem corretos – debates importantes deverão ocorrer a partir da publicação dos dados –, os defensores da tese de que a Via Láctea surgiu logo após a era da escuridão causada pela grande explosão que provocou a origem do Universo terão mais um argumento a favor. As medidas mais precisas feitas até hoje apontam que o chamado Big Bang teria ocorrido há cerca de 13,7 bilhões de anos. (Agência Fapesp, 23/8)   Anterior Cinco novas luas revelam história de Netuno Próxima Epílogo alagoano: como o Mutum-de-Alagoas, ave que habitava a mata Atlântica e foi declarada extinta na natureza, passou de fantasma a símbolo de conservação Índice de Noticías - imprimir - enviar - comentário

Fonte:

	Backyard Telescope Helps Find New Planet By Robert Roy Britt Senior Science Writer posted: 24 August, 2004 11:00 a.m. ET

With the help of a modified backyard telescope, astronomers have discovered a giant planet orbiting another star. It is the first extrasolar world found with such modest equipment.

Large observatories pinned down the finding after 16 candidate planets were identified by a 4-inch (10-centimeter) telescope, in a professionally run search effort that uses off-the-shelf parts and complex computer analysis.

The technique, now proven to work, promises similar findings ahead.

Importantly, the process finds planets whose atmospheres can be probed with the Hubble Space Telescope, paving the way for a greater understanding of giant worlds around other stars. Hubble might even be able to detect a moon if one orbits the newfound planet.

Hot and fast

The planet is slightly bigger than Jupiter, circling a star 500 light-years from Earth, astronomers announced today. It is much closer to its star than Mercury is to the Sun, making a high-speed annual trip around the star in just 3.03 Earth-days. The planet is probably about 1,500 degrees Fahrenheit (816 Celsius), scientists said.

Dozens of other extrasolar planets have similar tight configurations.

The newly spotted object is called a transiting planet: It passes in front if its host star as seen from Earth, causing a slight dip in observed starlight that made the discovery possible. Only four other transiting planets have been discovered, all with large telescopes.

"We're really excited about this result, both because it proves the validity of our approach, and because the planet itself has some interesting properties," said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics and a co-leader of the Trans-Atlantic Exoplanet Survey (TrES).

Setting a standard

Most of the more than 120 known extrasolar planets have been found by an indirect means -- a slight wobble in the host star induced by the planet's tug -- that allows only a determination of mass and orbital characteristics.

With a transiting planet, however, astronomers can learn the diameter and even what's in its atmosphere, by studying the shadow it creates against the star and the light that is altered as it passes through the atmosphere. Three of the known transiting planets are too far away to have their air probed, however. Another, named HD 209458b, was the first planet outside our solar system for which an atmosphere has been detected.

The newest known transiting planet, named TrES-1, has not had its atmosphere examined yet, but its diameter has been roughly determined, and the result proved interesting.

Like the three faraway transiting planets, TrES-1 seems to be "only a smidge larger" than Jupiter, Charbonneau told SPACE.com. "HD 209458b, on the other hand, has been studied by Hubble, and has a very precisely measured size -- which is about 40 percent larger than Jupiter, which is a very significant increase."

Artist renderings of extrasolar planets

Theorists have a hard time explaining the large size of HD 209458b, given its known mass. TrES-1, though smaller, is about the same mass, in line with what astronomers would expect of an object made mostly of hydrogen and helium, as is Jupiter.

"Finding TrES-1 and seeing how normal it is makes us suspect that HD 209458b is an ‘oddball’ planet," Charbonneau said.

Closer look

The 16 planet candidates identified by the small telescope were then observed by others, including the 33-foot (10-meter) Keck Observatory in Hawaii. Most are stellar pairs -- a dim star passing in front of a brighter one, Charbonneau said. A few require additional observation to learn what they are.

Meanwhile, Charbonneau and his colleagues hope to use Hubble to examine TrES-1 more closely.

Hubble might find water in TrES-1, and it would "give us a much more precise measurement of the planet's size, and even allow us to search for moons," he said. A satellite is unlikely, however, given the likely history and current orbital configuration for the planet, the research team concluded.

No moons have ever been detected beyond our solar system, but some researchers have considered that such satellites would be logical places for life to exist around giant gaseous worlds that otherwise could not be expected to support biology.

A Jupiter-sized planet causes the light from its host star to dip by about 1/100th as it transits in front of it. This is what the result looks like on an astronomer's graph.

Timothy Brown of the National Center for Atmospheric Research and Edward Dunham of Lowell Observatory co-led the development of the TrES program. The discovery will be detailed in Astrophysical Journal Letters.

• About the TrES Telescope
• Youngest Planet
• Oldest Planet
• Hottest Planet
• Farthest Planet

---

Making a Mighty 4-inch Telescope

The TrES program has a handful of specially designed 4-inch telescopes operating at different locations around the world, generating 10 Gigabytes of data every night. Graduate student Roi Alonso of the Astrophysical Institute of the Canaries, off the coast of Africa, first identified 16 possible planet candidates in a survey of 12,000 stars.

SPACE.com asked David Charbonneau, who helped develop the setup, to explain the technical details of the telescopes:

"The mount is taken from a Meade LX200GPS telescope; we bought the complete system, and then removed the optical tube assembly," Charbonneau explained. "We then built our own instrument to go between the forks, consisting of an off-the-shelf 280mm camera lens (made by Leica), a filter wheel and shutter, and a CCD camera that was constructed at NASA's Jet Propulsion Laboratory. Although this camera was not commercially available at the time of construction, you can now purchase a camera with similar capabilities (notably, with the same number of pixels) from manufacturers such as Apogee Instruments; such camera are used by amateur astronomers. We also use an amateur guide camera, made by Santa Barbara Instruments Group.

"The system that first identified the TrES-1 planet is named STARE, and is the node located in the Canary Islands. Although it is largely constructed from similar components, it is important to note that this is a "Schmidt camera" design, which is not a simple lens, but rather an assembly of mirrors and corrector plates, which yields a similarly wide field-of-view."

Telstar 18 enters full commercial service over Asia LORAL NEWS RELEASE Posted: August 23, 2004 Loral Space & Communications today announced that Telstar 18, a powerful and flexible satellite designed to provide communication services across Asia, has completed its in-orbit testing and is now fully operational. "With Telstar 18 joining Telstar 10 over Asia, Loral now operates two of the most powerful and strategically placed satellites in that region," said Patrick Brant, president, Loral Skynet. "Telstar 18 covers a large area that stretches from Central Asia, through the Indian sub-continent, China, Korea, Japan, South East Asia, Australia and Hawaii. It offers our customers a strong footprint for intra-regional applications, as well as the ability to directly connect with the US." An artist's concept of Telstar 18. Credit: Loral   Built by Space Systems/Loral (SS/L) and operated by Loral Skynet, Telstar 18 was launched June 28, 2004 aboard a Sea Launch Zenit-3SL rocket. During the launch, the rocket's upper stage shut down early and placed the satellite in a lower than expected orbit. Engineers from SS/L, however, were able to raise the satellite to its proper orbital position at 138 degrees East longitude. The satellite still has sufficient on-board fuel to exceed its specified 13-year life. Telstar 18's users include well-known regional video and data providers, such as Smart Digital Communications Bhd, of Kuala Lumpur, Malaysia, and PSVN, Inc., which is based at the Hawaii Pacific Teleport. Loral's other satellite over Asia, Telstar 10/APSTAR-IIR, hosts one of the largest video communities in Asia at 76.5 degrees East longitude. In addition to transmitting innovative new applications, cable programming and direct-to-home broadcasting services, Telstar 18 is scheduled to begin hosting Skynet's SkyReach(SM) two-way IP-based networking solution in 2005. SkyReach is already available and in use by customers throughout the Americas, allowing organizations to create an instant infrastructure using a VSAT network, connecting offices between cities or around the globe. Telstar 18 carries a total of 54 active transponders, of which sixteen are high-power Ku-band transponders and thirty-eight are C-band transponders. In consideration for funding a portion of the satellite project's cost, APT Satellite Company Limited, Hong Kong, will initially use 68.5 percent of Telstar 18's transponder capacity for APSTAR-V services. The number of transponders used by APT will be reduced over time, ultimately to 54 percent of the satellite's capacity. Telstar 18 is a version of SS/L's space-proven 1300 satellite platform, which has an excellent record of reliable operation. The geostationary 1300 has a specified service life of 13 years and maintains station-keeping and orbital stability by using bipropellant propulsion and momentum-bias systems. In all, SS/L satellites have amassed more than 1,100 years of on-orbit service. A pioneer in the satellite industry, Loral Skynet continues to deliver the superior service quality and range of satellite solutions that have made it an industry leader for more than 40 years. Through the broad coverage of the Telstar satellite fleet in combination with its hybrid VSAT/fiber global network infrastructure, Skynet is a source for all broadcast, data network, Internet access, IP and systems integration needs. Headquartered in Bedminster, New Jersey, Loral Skynet is dedicated to providing secure, high-quality connectivity and communications. Space Systems/Loral is a premier designer, manufacturer, and integrator of powerful satellites and satellite systems. SS/L also provides a range of related services that include mission control operations and procurement of launch services. Based in Palo Alto, Calif., the company has an international base of commercial and government customers whose applications include broadband digital communications, direct-to-home broadcast, defense communications, environmental monitoring, and air traffic control. SS/L is ISO 9001:2000 certified.				Moon panorama This spectacular panoramic poster shows Apollo 15 commander Dave Scott on the Hadley Plain with the lunar module Falcon in the background.  U.S. STORE Space Flight Patches Poster This updated Space Flight Patch Poster is a complete photo collection of all United States human space flight mission patches through Columbia's ill-fated STS-107 flight.  U.S. STORE Apollo 10 DVD Pre-order The mission of Apollo 10 sent astronauts Stafford, Cernan and Young, veterans all, on a dress rehearsal for the lunar landing. This 2-DVD set presents an unparalleled chronicle of the Apollo 10 mission.  U.S. STORE  U.K. & WORLDWIDE STORE Fallen Heroes patch This special 12-inch embroidered patch commemorates the U.S. astronauts who made the ultimate sacrifice, honoring the crews of Apollo 1, Challenger and Columbia.  U.S. STORE Moon Rush This book examines how the exploration of space, specifically a commercial base on the Moon and Mars would transform our economies on the Earth as surely as the discovery of the New World transformed the old world of Europe.  U.S. STORE

http://spaceflightnow.com/news/n0408/23telstar18/

Abraços

José Geraldo Mattos

Beagle 2: Internal Investigation Suggests Mars Lander
"Most Likely" Crashed

By A.J.S. Rayl

Click to enlarge Artist's depiction of Beagle 2 as it was supposed to have opened on Mars. Image: Beagle 2 All Rights Reserved

24 August 2004

On December 19 last year, Beagle 2, a small British-built lander, ejected from its mothership, the European Space Agency's Mars Express, and started on its final trajectory to Isidis Planitia on the Red Planet. The U.K.'s first mission to another planet was to land on Christmas morning, pop open like a pocket watch, and begin a search for signs of life, past or present. Mars Express snapped several images of the tiny lander as it departed. Those images are the last anyone has seen or heard of it. Beagle 2 disappeared without a trace, to date, to be found.

Today, in the just-released Beagle2Mars Mission Report, the mission operations team analyzes a thorough list of possible failure mechanisms that could have sealed the fate of the British lander -- including electronic glitches, damage to the heat shield, a broken communications antenna, and collision with an unforeseen object, but suggests that Mars Express targeted Beagle 2 at the correct velocity and spin rate, and that it is "most likely" that it failed during entry, descent, and landing, as a result of atmospheric conditions or the airbags breaking on impact or the first bounce.

Since there is no radio telemetry or visual data of Beagle 2 post ejection from Mars Express, there is no way to unequivocally identify the cause of failure, and the report ultimately concludes: "No definitive cause could be identified due to the paucity of data."

Beagle2Mars is based on an internal investigation of the mission and is published in two parts: 1) the Mission Report chronicles and reviews the effort, noting its achievements, detailing potential causes of failure, and describing the search strategy to try and find the lander; 2) Lessons Learned and Management and Programmatics, reviews how the project was managed, the constraints it confronted, as well as documents lessons learned in every phase of the mission.

This report comes three months after ESA and the British government completed their investigation. Although those two entities jointly issued a set of recommendations, the report of that investigation was sealed to all except those with a need to know.

With what there is to compare, both reports are unified in citing the need for "improved characterizations of the Martian atmosphere," as "critical" to the success or failure of future missions. Both reports also agree that next time the lander must be viewed and treated as an integral part of the mission and not as an instrument as Beagle 2 was, that decisions to be made on projects promptly to give the mission time to retire the risks, and that changes in the way such a project is managed need to be made.

The team "strongly" recommends in the report "that any future combined orbiter and lander mission is managed and defined as a cohesive programme, with no part given less than equal priority."

The Beagle 2 project was "internally managed to high professional standards under severe interface, schedule and financing constraints," the team writes. "Some critical decisions were forced upon the program due to lack of time to undertake technically preferred tests, following lack of sufficient early funding, however all systems were tested." From the time the project began in early 1999 to June 2001, "only 19% of the work was completed" because of these reasons, "leaving just 20 months to delivery to Mars Express. The operations and ground system were developed successfully under similar schedule and funding pressure." That noted, they go on to point out that Beagle 2 "was delivered on time to the launch site" and was carried aloft by Mars Express and operated successfully throughout the cruise phase to Mars."

Colin Pillinger -- the father and driving force behind Beagle 2 -- has been saying since last spring that he thought the 'puppy,' as he had affectionately called his charge, probably crashed into the planet, because the atmosphere was impacted by a regional dust storm and was, consequently, less dense than anticipated. The data that is the basis of that belief comes from an instrument onboard Mars Express that indicated evidence of unusually low atmospheric density, according to the report, and from NASA's Mars Exploration Rovers, Spirit and Opportunity, both of which encountered atmospheric density surprisingly lower than models described. If Beagle 2 did encounter less resistance, its parachutes and airbags that were to cushion its fall would have been deployed too late or not at all.

Click to enlarge One of the last images of Beagle 2 taken by Mars Express. Image: ESA

In its investigation, the team found that a few glitches notwithstanding Beagle 2's systems operated nominally up to and through the process of ejection from Mars Express on December 19. They did discover and analyze a piece of debris of unknown size -- estimating it to be anywhere from ~2-3 millimeters to between 20 mm X 20 mm and 60 mm X 60 mm -- that appears in the images acquired by Mars Express to have followed Beagle 2 as it left the mothership. While the potential for that debris to have damaged and interfered with the Beagle's safe arrival cannot be ruled out, the team views the likelihood for that as "very low."

The internal investigation found no significant reason to doubt the operation of the main parachute, counter to one early hypothesis. Although the mission had failure issues with its first parachute design, the system that replaced it "met all of its specified requirements," according to the report.

After considering whether Beagle 2 might have landed in one of two large craters discovered within the predicted landing area, which would have hindered or damaged the lander's ability to signal, the team concludes in the report that the probability of the probe dropping into one of those was, like the debris and main parachute failure theories, "very low."

In chronicling the efforts to find Beagle 2, the team assessed a tiny speck on an image from Michael Malin's Mars Orbital Camera (MOC) onboard Mars Global Surveyor (MGS) as a possible candidate for the little lander. Malin has been imaging the landing sites of rovers Spirit and Opportunity, and agreed last January to join the search for the little British lander.That possibility turned out to be a small crater, and so the mystery of what happened to Beagle is likely to remain for awhile, if not forever. [If Beagle 2 did make it to the surface intact, it is possible that Mars Reconaissance Orbiter (MRO), which is scheduled to launch in 2009 and offers a better chance of getting higher resolution images of the landing area, may pinpoint its location.]

It is a universal truth in the realm of space exploration that landing on Mars is hard. One need only remember that the United States and former Soviet Union suffered a number of failures before actually touching down on Mars, and that, historically, an average of two out of every three missions to Mars have ended in failure.

Although Beagle 2 did not arrive safely, the team opines in the report that it should be acknowledged for advancing planetary lander technology in Europe, and the unprecedented accomplishments it did achieve, not the least of which is getting Europe turned on to exploring other planets. Indeed, Beagle 2 did capture the hearts of the United Kingdom and space enthusiasts around the world. The impact, the team contends, resounds today. "A Rubicon has been crossed," it writes in the report.

Meanwhile, Pillinger revealed at a press conference in London this morning that he is "looking at the future," and has written to NASA asking whether room can be found for a successor to Beagle on the much larger rover mission, Mars Science Laboratory (MSL), according to the Mail and Guardian. Slated to launch in 2009, MSL is an all-extraterrestrial terrain, long-range, long-duration robot rover that will explore the Red Planet for years to assess whether it could be a habitat for life -- past or present -- and to help verify if human explorers could exist there in the future. He has not yet received a reply.

Beagle 2 was a partnership between the Open University, where Pillinger is head of Planetary and Space Sciences, the University of Leicester, and EADS Astrium (U.K.), with other funding coming from ESA, the U.K.'s Office of Science and Technology of the Department of Trade and Industry, the Particle Physics and Astronomy Research Council (PPARC), the Wellcome Trust, the British National Space Center and the Millennium Commission. The report can be read in full at the University of Leicester.

This Week's Sky at a Glance
By Alan M. MacRobert

Some daily events in the changing sky for August 26 – September 4.

Early risers will find brilliant Venus, the "Morning Star," pairing up with much dimmer, distant Saturn around the end of August and the beginning of September. The planet pair falls in a rough diagonal line with Castor, Pollux, and Procyon in the remote background. Sky & Telescope diagram.

Thursday, August 26

Venus lights the eastern sky during dawn this week, with dimmer Saturn passing close by. Watch their relative positions change from morning to morning. The scene here is drawn for next Tuesday.

The bright star very high above the Moon this evening is Altair, 17 light-years away. The brightest star nearly straight overhead (for observers at midnorthern latitudes) is Vega, 25 light-years away.

Friday, August 27

Uranus is at opposition tonight (opposite the Sun in our sky). The 5.7-magnitude planet is easily seen in binoculars during summer and fall (even through moonlight), if you can pick out the constellation Aquarius and use a good finder chart.

The naked-eye eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 11:49 p.m. Eastern Daylight Time. Algol takes several additional hours to fade and to brighten. (For all times of Algol's minima, good worldwide, see our Algol predictor and comparison-star chart or print our complete list through the end of 2004.)

Saturday, August 28

Late this evening, look far to the lower left of the Moon for Fomalhaut, the Autumn Star, already on the rise.

Sunday, August 29

Full Moon (exact at 10:22 p.m. Eastern Daylight Time).

Monday, August 30

Algol should be at minimum light for a couple hours centered on 8:38 p.m. EDT.

Tuesday, August 31

Saturn is passing 2° upper left of Venus this morning and Wednesday morning.

The Big Dipper, seen as it's oriented in the northwest at dusk at this time of year. Can you resolve Mizar and little Alcor with your unaided eye? If not, binoculars will do the trick. Sky & Telescope illustration; photo courtesy Akira Fujii.

Wednesday, September 1

Look northwest at dusk this week to spot the Big Dipper, oriented as shown above.

Thursday, September 2

Look midway up the northeastern sky this week for W-shaped Cassiopeia. The right side of the W (the brighter side) is tilted up.

Friday, September 3

The two brightest stars in the early-evening sky are blue-white Vega almost straight overhead (for observers at midnorthern latitudes), and pale orange-yellow Arcturus shining in the west.

Saturday, September 4

Once the waning gibbous Moon rises into good view late tonight (around 11 or midnight), use binoculars to greet the seasonal return of the Pleiades, glittering not far to the Moon's left.

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper that you might want to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly foldout map in each issue of Sky & Telescope. Or download our free Getting Started in Astronomy flyer (which only has bimonthly maps).


This Week's Planet Roundup

Mercury begins to emerge into view very low in the east during dawn. Late in the week, look for it glimmering far to the lower left of bright Venus about 45 minutes before sunrise. Binoculars will help. (You can find your sunrise time by entering your location and current time zone into our almanac.)

Venus (magnitude –4.2, in Gemini) shines brightly high in the east before and during dawn — the bright Morning Star. Look for dimmer Saturn passing close by it this week.

Mars and Jupiter are hidden behind the glare of the Sun.

Saturn (magnitude +0.2, in Gemini) is near much brighter Venus before and during dawn; it's to Venus's left early in the week, and above Venus later in the week. They appear closest, 2° apart, on the mornings of August 31st and September 1st. Venus currently outshines Saturn by 60 times, for two reasons. First, Venus is 12 times closer to us. Second, it's about 13 times closer to the Sun, so it's illuminated by sunlight about 170 times more brilliant.

Uranus and Neptune (magnitudes 6 and 8, respectively, in Aquarius and Capricornus) are in the southeast to south during evening.

Pluto (magnitude 14, at the border of Ophiuchus and Serpens Cauda) is in the southwest right after dark. Finder charts for Uranus, Neptune, and Pluto are in the April Sky & Telescope, page 107, and at lower resolution online.

All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude are for North America. Eastern Daylight Time, EDT, equals Universal Time (UT or GMT) minus 4 hours.

Fonte:http://SkyandTelescope.com/observing/ataglance/

Abraços

José Geraldo Mattos

 

Gosta de fotografia? : http://www.terra.com.br/fotos/album.cgi/633910
___________________________________________
Universidade Federal de Santa Catarina
HU - Serviço de Controle Financeiro S/N
Trindade, Florianópolis, SC,Brasil
CEP 88.049-000 Fone (48) 9914.5078 ( 48) 331.9868
http://www.gea.org.br/scf
___________________________________________

Saturn's crescent moon Dione hangs before the Cassini spacecraft in this magnified image. The icy moon shows a hint of the bright, wispy features that mark its surface.

Credit: NASA/JPL/University of Arizona

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Scientists have pinpointed the source of a meteorite from the moon for the first time. Their unique meteorite records four separate lunar impacts.

They are the first to precisely date Mare Imbrium, the youngest of the large meteorite craters on the moon. That date, 3.9 billion years ago, is a new key date for lunar and even terrestrial stratigraphy, the scientists say, because life on Earth would have evolved only after heavy meteorite bombardment ended.

Geologists who found the meteorite and scientists from Swiss, Swedish, German, British, and Arizona laboratories who analyzed the unique stone report their work in the July 30 issue of Science. Swiss geologist Edwin Gnos is first author of the article titled "Pinpointing the Source of Lunar Meteorite: Implications for the Evolution of the Moon."

Gnos, Ali Al-Kathiri and Beda Hofmann found the 206-gram (7-ounce) meteorite in Oman on Jan. 16, 2002. The geologists were on a joint meteorite search expedition sponsored by the Government of Oman, the Natural History Museum of Berne and the University of Berne.

"The desert in Oman is the new place to find meteorites," said A.J. Tim Jull of the University of Arizona in Tucson. Jull directs the National Science Foundation - Arizona Accelerator Mass Spectrometry (AMS) Laboratory. He analyzed beryllium and carbon isotopes that told how long the meteorite was in space after it was launched from the moon and how long ago it fell to Earth at Oman.

Scientists who've acquired the special permits needed to search for meteorites in Oman and North Africa during the past half-dozen years have been amply rewarded, Jull said. Seven of the 30 known lunar meteorites have been found in Oman, and five have been found in North Africa. One was found in Australia and the rest have been found in Antarctica. Hot or cold, arid climates preserve meteorites from quickly weathering, Jull noted.

Gnos, Al-Kathiri and Hofmann recognized in the field that the meteorite was of lunar or martian origin because it wasn't magnetic. Meteorites from planetary bodies don't contain metal. And, typical of lunar rocks, it was greenish colored and contained white angular feldspar inclusions.

But when they tested it with a Geiger counter, they found it was no typical lunar rock. They found it contained high levels of radioactive uranium, thorium and potassium. Gamma ray-spectroscopy lab tests told them that the ratios between these elements fit only one enigmatic group of lunar rocks called "KREEP," the acronym of K for potassium, REE for rare earth elements, and P for phosphate.

"At that moment, it was clear that the rock had something to do with the large Imbrium impact basin, the right eye of the man in the moon," Gnos et al. report on the Web at http://www.geo.unibe.ch/sau169. The Imbrium impact basin on the lunar nearside is the only area where KREEP rocks are found. KREEP rocks are known both from samples returned by the Apollo missions and by NASA's Lunar Prospector Orbiter radioactivity survey in 1998-99.

The scientists conducted a battery of laboratory tests to piece together a detailed history of the meteorite, named Sayh al Uhaymir (SaU) 169. They summarize SaU 169's history:

• At 3.909 billion years ago, plus or minus 13 million years - An asteroid collides with the moon, forming the 1160 km (720-mile) diameter Imbrium impact basin. Crushed and molten rocks mix and solidify to form the main rock type in meteorite SaU 169.
  
  
• At 2.8 billion years ago - A meteorite hits the moon, forming the 25 km (15-mile) diameter Lalande crater south of the Imbrium basin. The impact blasts material, including the main rock type in SaU 169, from depth and deposits it as an ejecta blanket around the crater. The ejecta there mixes with other lunar soil.
  
  
• At 200 million years ago - Another impact brings the rock that will become a meteorite to within a half-meter (20 inches) of the lunar surface.
  
  
• At less than 340,000 years ago - Another impact hits the moon, producing a crater a few kilometers in diameter and ejects SaU 169 from the moon. The scientists studied NASA images and identified a young, 3 km (1.8-mile) diameter crater 70 km (43 miles) north-northeast of Lalande as the meteorite's likely launch site. Jull measured beryllium 10 in SaU 169 and determined the meteorite's moon-to-Earth transit time at around 300,000 years. He also measured carbon 14 in SaU 169, which shows the meteorite fell in present-day Oman around 9,700 years ago, plus or minus 1,300 years.

"Without the Apollo and Luna sampling programs, and especially the huge advance in knowledge of the Moon acquired during investigations in the last 20 - 30 years, we would only be able to tell that SaU 169 is an exceptional lunar rock," the scientists said on their Website. "Without background information from such missions as Clementine and Lunar Prospector, we could never have linked ages and chemical data with lunar surface information."

"SaU is a rock which demonstrates impressively how rocks can travel, like a ping-pong-ball, from one body to another," they said.

Cassini conducts major orbit adjustment maneuver
CASSINI MISSION CONTROL REPORT
Posted: August 23, 2004

The Cassini spacecraft successfully completed a 51-minute engine burn that will raise its next closest approach distance to Saturn by nearly 300,000 kilometers (186,000 miles). The maneuver was necessary to keep the spacecraft from passing through the rings and to put it on target for its first close encounter with Saturn's moon Titan on Oct. 26.

Mission controllers received confirmation of a successful burn at 11:15 a.m. Pacific Time today. The spacecraft is approaching the highest point in its first and largest orbit about Saturn. Its distance from the center of Saturn is about 9 million kilometers (5.6 million miles), and its speed just prior to today's burn was 325 meters per second (727 miles per hour) relative to Saturn. That means it is nearly at a standstill compared to its speed of about 30,000 meters per second (67,000 miles per hour) at the completion of its orbit insertion burn on June 30.

"Saturn orbit insertion got us into orbit and this maneuver sets us up for the tour," said Joel Signorelli, spacecraft system engineer for the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The maneuver was the third longest engine burn for the Cassini spacecraft and the last planned pressurized burn in the four-year tour. The Saturn obit insertion burn was 97 minutes long, and the deep space maneuver in Dec. 1998 was 88 minutes long.

"The October 26 Titan encounter will be much closer than our last one. We'll fly by Titan at an altitude of 1,200 kilometers (746 miles), 'dipping our toe' into its atmosphere," said Signorelli. Cassini's first Titan flyby on July 2 was from 340,000 kilometers (211,000 miles) away.

Over the next four years, the Cassini orbiter will execute 45 Titan flybys as close as approximately 950 kilometers (590 miles) from the moon. In January 2005, the European-built Huygens probe that is attached to Cassini will descend through Titan's atmosphere to the surface.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

Fonte:http://spaceflightnow.com/cassini/040823status.html

Abraços

Telescópio Chandra revela complexo colapso de supernovas

 da Agência Lusa

Uma fotografia espetacular transmitida do espaço pelo telescópio de raios-X Chandra, da Nasa (agência espacial norte-americana), mostra que o colapso das estrelas de nêutrons é muito mais complexo do que se julgava.

A imagem da supernova Cassiopéia, 200 vezes mais clara do que a transmitida há cinco anos pelo mesmo telescópio, oferece pistas sobre o que ocorreu nas primeiras etapas da explosão.

"Embora os restos dessa jovem supernova tenham sido intensamente estudados durante anos, essa observação é a mais detalhada de uma estrela em explosão", afirma Martin Laming, do Laboratório de Pesquisa Naval, em Washington, e membro da equipe científica do Centro de Vôos Espaciais Goddard, no Estado de Maryland.

Uma supernova é uma estrela em explosão que liberta uma grande quantidade de energia e por isso se torna nitidamente visível no espaço. Trata-se de "uma mina de ouro de dados, que os astrônomos estudarão durante muitos anos", disse Laming.

Nuvens puras

A imagem revela pela primeira vez duas estruturas que se estendem por dez anos-luz --nuvens de partículas mantidas virtualmente puras desde que a explosão foi detectada, há 340 anos.

Segundo os cientistas do Centro de Vôos Espaciais, a existência desses "jorros bipolares" poderá ser mais comum nas supernovas do que se julgava.

A análise espectrográfica revela que as nuvens são ricas em átomos de silício e bastante pobres em átomos de ferro, o que afasta a possibilidade de serem a causa da explosão estelar, pois se o fossem seriam ricos no ferro proveniente do núcleo da estrela.

A primeira imagem de Cassiopéia foi transmitida pelo Chandra no dia 19 de agosto de 1999, pouco menos de um mês depois que o telescópio partiu para o espaço no ônibus espacial Columbia.

O Chandra cumpriu a sua missão, com a duração inicialmente prevista de cinco anos, mas a Nasa decidiu prolongá-la por outros cinco anos devido ao êxito do equipamento.

Especial

Ar marciano vitimou sonda, diz Reino Unido

da Folha de S.Paulo

O grupo responsável pela Beagle-2, a sonda britânica que chegou a Marte no fim do ano passado, atribuiu a culpa da perda da nave à atmosfera do planeta vermelho.

Um relatório da ESA (Agência Espacial Européia), em maio, atribuiu o fracasso a mau gerenciamento, mas o grupo envolvido no projeto agora diz que o problema na verdade foi a atmosfera de Marte, que se mostrou mais rarefeita do que o esperado. A equipe tem a expectativa de construir outra nave da série.

Especial

A galaxy's fatal plunge

CHANDRA PHOTO RELEASE
Posted: August 22, 2004

These images offer a dramatic look at C153, a galaxy being ripped apart as it races at 4.5 million miles per hour through a distant cluster of galaxies. The infalling galaxy's gas is being stripped by the pressure of 20-million-degree Celsius gas that permeates the cluster.

Credit: X-ray: NASA/CXC/SAO/UMass/D. Wang et al. Optical: NASA/STScI/U. Alabama/W. Keel Radio: NRAO/ F. Owen Optical (OII): Gemini Obs./M. Ledlow

The Chandra X-ray image shows a tail of hot gas extending from C153. The temperature of the gas tail is about 10 million degrees Celsius, cooler than the surrounding cluster gas. This temperature difference is further evidence that gas is being stripped from the galaxy. The image taken in visible light from glowing oxygen ions shows a similar tail forming as gas with a temperature of about 10,000 degrees Celsius is pulled from the galaxy.

Hubble's broad band visible-light image reveals intricate detail in the distribution of stars and dust within C153. The galaxy exhibits evidence of a large-scale disturbance that has left its star-forming regions concentrated to one side of its disk and beyond. Dust features are twisted into chaotic patterns, obscuring any spiral pattern the galaxy once had.

Radio observations depict high-energy particles as they spiral through the galaxy's magnetic field, with some escaping in a perpendicular direction to the galaxy's disk. The high-energy particles probably came from a supermassive black hole.

Beagle 2: Internal Investigation Suggests Mars Lander
"Most Likely" Crashed

By A.J.S. Rayl

Click to enlarge Artist's depiction of Beagle 2 as it was supposed to have opened on Mars. Image: Beagle 2 All Rights Reserved

24 August 2004

On December 19 last year, Beagle 2, a small British-built lander, ejected from its mothership, the European Space Agency's Mars Express, and started on its final trajectory to Isidis Planitia on the Red Planet. The U.K.'s first mission to another planet was to land on Christmas morning, pop open like a pocket watch, and begin a search for signs of life, past or present. Mars Express snapped several images of the tiny lander as it departed. Those images are the last anyone has seen or heard of it. Beagle 2 disappeared without a trace, to date, to be found.

Today, in the just-released Beagle2Mars Mission Report, the mission operations team analyzes a thorough list of possible failure mechanisms that could have sealed the fate of the British lander -- including electronic glitches, damage to the heat shield, a broken communications antenna, and collision with an unforeseen object, but suggests that Mars Express targeted Beagle 2 at the correct velocity and spin rate, and that it is "most likely" that it failed during entry, descent, and landing, as a result of atmospheric conditions or the airbags breaking on impact or the first bounce.

Since there is no radio telemetry or visual data of Beagle 2 post ejection from Mars Express, there is no way to unequivocally identify the cause of failure, and the report ultimately concludes: "No definitive cause could be identified due to the paucity of data."

Beagle2Mars is based on an internal investigation of the mission and is published in two parts: 1) the Mission Report chronicles and reviews the effort, noting its achievements, detailing potential causes of failure, and describing the search strategy to try and find the lander; 2) Lessons Learned and Management and Programmatics, reviews how the project was managed, the constraints it confronted, as well as documents lessons learned in every phase of the mission.

This report comes three months after ESA and the British government completed their investigation. Although those two entities jointly issued a set of recommendations, the report of that investigation was sealed to all except those with a need to know.

With what there is to compare, both reports are unified in citing the need for "improved characterizations of the Martian atmosphere," as "critical" to the success or failure of future missions. Both reports also agree that next time the lander must be viewed and treated as an integral part of the mission and not as an instrument as Beagle 2 was, that decisions to be made on projects promptly to give the mission time to retire the risks, and that changes in the way such a project is managed need to be made.

The team "strongly" recommends in the report "that any future combined orbiter and lander mission is managed and defined as a cohesive programme, with no part given less than equal priority."

The Beagle 2 project was "internally managed to high professional standards under severe interface, schedule and financing constraints," the team writes. "Some critical decisions were forced upon the program due to lack of time to undertake technically preferred tests, following lack of sufficient early funding, however all systems were tested." From the time the project began in early 1999 to June 2001, "only 19% of the work was completed" because of these reasons, "leaving just 20 months to delivery to Mars Express. The operations and ground system were developed successfully under similar schedule and funding pressure." That noted, they go on to point out that Beagle 2 "was delivered on time to the launch site" and was carried aloft by Mars Express and operated successfully throughout the cruise phase to Mars."

Colin Pillinger -- the father and driving force behind Beagle 2 -- has been saying since last spring that he thought the 'puppy,' as he had affectionately called his charge, probably crashed into the planet, because the atmosphere was impacted by a regional dust storm and was, consequently, less dense than anticipated. The data that is the basis of that belief comes from an instrument onboard Mars Express that indicated evidence of unusually low atmospheric density, according to the report, and from NASA's Mars Exploration Rovers, Spirit and Opportunity, both of which encountered atmospheric density surprisingly lower than models described. If Beagle 2 did encounter less resistance, its parachutes and airbags that were to cushion its fall would have been deployed too late or not at all.

Click to enlarge One of the last images of Beagle 2 taken by Mars Express. Image: ESA

In its investigation, the team found that a few glitches notwithstanding Beagle 2's systems operated nominally up to and through the process of ejection from Mars Express on December 19. They did discover and analyze a piece of debris of unknown size -- estimating it to be anywhere from ~2-3 millimeters to between 20 mm X 20 mm and 60 mm X 60 mm -- that appears in the images acquired by Mars Express to have followed Beagle 2 as it left the mothership. While the potential for that debris to have damaged and interfered with the Beagle's safe arrival cannot be ruled out, the team views the likelihood for that as "very low."

The internal investigation found no significant reason to doubt the operation of the main parachute, counter to one early hypothesis. Although the mission had failure issues with its first parachute design, the system that replaced it "met all of its specified requirements," according to the report.

After considering whether Beagle 2 might have landed in one of two large craters discovered within the predicted landing area, which would have hindered or damaged the lander's ability to signal, the team concludes in the report that the probability of the probe dropping into one of those was, like the debris and main parachute failure theories, "very low."

In chronicling the efforts to find Beagle 2, the team assessed a tiny speck on an image from Michael Malin's Mars Orbital Camera (MOC) onboard Mars Global Surveyor (MGS) as a possible candidate for the little lander. Malin has been imaging the landing sites of rovers Spirit and Opportunity, and agreed last January to join the search for the little British lander.That possibility turned out to be a small crater, and so the mystery of what happened to Beagle is likely to remain for awhile, if not forever. [If Beagle 2 did make it to the surface intact, it is possible that Mars Reconaissance Orbiter (MRO), which is scheduled to launch in 2009 and offers a better chance of getting higher resolution images of the landing area, may pinpoint its location.]

It is a universal truth in the realm of space exploration that landing on Mars is hard. One need only remember that the United States and former Soviet Union suffered a number of failures before actually touching down on Mars, and that, historically, an average of two out of every three missions to Mars have ended in failure.

Although Beagle 2 did not arrive safely, the team opines in the report that it should be acknowledged for advancing planetary lander technology in Europe, and the unprecedented accomplishments it did achieve, not the least of which is getting Europe turned on to exploring other planets. Indeed, Beagle 2 did capture the hearts of the United Kingdom and space enthusiasts around the world. The impact, the team contends, resounds today. "A Rubicon has been crossed," it writes in the report.

Meanwhile, Pillinger revealed at a press conference in London this morning that he is "looking at the future," and has written to NASA asking whether room can be found for a successor to Beagle on the much larger rover mission, Mars Science Laboratory (MSL), according to the Mail and Guardian. Slated to launch in 2009, MSL is an all-extraterrestrial terrain, long-range, long-duration robot rover that will explore the Red Planet for years to assess whether it could be a habitat for life -- past or present -- and to help verify if human explorers could exist there in the future. He has not yet received a reply.

Beagle 2 was a partnership between the Open University, where Pillinger is head of Planetary and Space Sciences, the University of Leicester, and EADS Astrium (U.K.), with other funding coming from ESA, the U.K.'s Office of Science and Technology of the Department of Trade and Industry, the Particle Physics and Astronomy Research Council (PPARC), the Wellcome Trust, the British National Space Center and the Millennium Commission. The report can be read in full at the University of Leicester.