Mission designed to unlock asteroids' secrets

NASA's Dawn spacecraft aims for the curious Vesta and Ceres

A half-dozen spacecraft launched by the United States and Europe have flown past or landed on asteroids. A Japanese mission that attempted to collect samples of an asteroid is due back on Earth in three years.

But NASA's Dawn spacecraft, scheduled for launch near dawn Thursday, is designed to bring a new day to asteroid science.

Dawn will aim for the solar system's vast asteroid belt, a collection of rocky materials left over from the formation of the planets, for closeup studies of Vesta and Ceres, two of the largest celestial bodies in the belt region.

Scientists expect Dawn's eight-year, $449 million mission to provide new insight into the early phase of the planet-building process that began more than 4.5 billion years ago.

Dawn was designed to steer into orbit around Vesta to map the terrain and study the mineral makeup, then depart for Ceres to conduct a second orbital reconnaissance.

Just hints so far

The spacecraft is scheduled for launch from Cape Canaveral Air Force Station, Fla., aboard a Delta II rocket.
If successful, Dawn will become the first spacecraft to orbit a solar system body and then travel through space to circle another.

"To go to one body, leave and go to another is sort of what science fiction has always been about," said Christopher Russell, the University of California, Los Angeles space physicist who serves as the Dawn mission's chief scientist.

The Hubble Space Telescope and other powerful observatories offer only scant clues of what Vesta and Ceres must be like, revealing hints of past volcano activity on the first and water on the second.

Most of the asteroid belt orbits the sun between Mars and Jupiter.

"So, we are going out to two bodies, which are quite different as far as we can tell. One seems dry like our moon. The other seems to have a lot of water in it," Russell said. "On our planet, water is very important. We will try to understand why some bodies are very wet out there and some very dry."

Plans to launch the mission earlier this year encountered a series of problems with the assembly of Dawn's rocket launcher, bad weather and difficulties establishing a ground tracking network.

The first stop on Dawn's journey is Vesta, an asteroid the size of Arizona that offers a glimpse at the processes that produced the solar system's rocky inner planets - Mercury, Venus, Earth and Mars.

Ceres, the final stop, is about the size of Texas and was recently reclassified from asteroid to dwarf planet by astronomers. Ceres, which may have a thin atmosphere, could offer clues about the processes that folded water-born minerals into the final assembly of the icy moons of the outer planets - Jupiter, Saturn, Neptune and Uranus.

Far-off sling shot

Scientists believe the thousands of rocky objects in the asteroid belt were once destined to collide and clump together until they became a full-fledged planet. However, the assembly process was interrupted by the strong gravitational forces of Jupiter, the solar system's biggest planet.
Dawn's liftoff will initiate a 3.2 billion mile journey that will swing the spacecraft into orbit around Vesta in August 2011.

After circling Vesta for seven months, Dawn will depart for Ceres. The final leg of Dawn's long journey will take nearly three years. Reaching Ceres in February 2015, the probe will orbit for at least six months of observations.

In April 2009, Dawn will speed close enough to Mars for the gravitational field of the Red Planet to sling the spacecraft outward with additional velocity.

Uncharted terrain

Ceres was discovered in 1801 by the Italian astronomer Giuseppe Piazzi. Largest of the planetary fragments in the asteroid belt, Ceres is curiously planetlike. Ceres is spherical and possesses enough of a gravity field to pull the heaviest of its minerals to the core. It may have a weak atmosphere, a thick layer of water frozen below a dusty surface and perhaps frost-covered polar caps.
Last year, those qualities convinced the International Astronomical Union to upgrade Ceres' status from asteroid to dwarf planet - the same reclassification that resulted in the more controversial demotion of Pluto from planet to dwarf planet.

Vesta was discovered a half-dozen years after Ceres by the German astronomer Heinrich Wilhelm Olbers. Distant observations reveal a somewhat spherical shape with a surface of frozen lava that oozed from a hot interior shortly after Vesta formed.

At Vesta's south pole is a large crater that was gouged out by a collision with another asteroid. Some of the material blasted away from Vesta by the powerful impact may have reached the Earth as meteorites.

Technorati : Mission, asteroids', designed unlock, secrets

New Negatively-Charged Molecule Discovered

Astronomers using data from the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) have found the largest negatively-charged molecule yet seen in space. The discovery of the third negatively-charged molecule, called an anion, in less than a year and the size of the latest anion will force a drastic revision of theoretical models of interstellar chemistry, the astronomers say.

"This discovery continues to add to the diversity and complexity that is already seen in the chemistry of interstellar space," said Anthony J. Remijan of the National Radio Astronomy Observatory (NRAO). "It also adds to the number of paths available for making the complex organic molecules and other large molecular species that may be precursors to life in the giant clouds from which stars and planets are formed," he added.

A team of scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) found negatively-charged octatetraynyl in a cold, dark cloud of molecular gas. A second team headed by Remijan found octatetraynyl in the envelope of gas around an old, evolved star. In both cases the molecule, a chain of eight carbon atoms and one hydrogen atom, had an extra electron, giving it a negative charge.

About 130 neutral and about a dozen positively-charged molecules have been discovered in space, but the first negatively-charged molecule was not discovered until late last year. The largest previously-discovered negative ion found in space has six carbon atoms and one hydrogen atom.

Ultraviolet light from stars can knock an electron off a molecule, creating a positively-charged ion. Astronomers had thought that molecules would not be able to retain an extra electron, and thus a negative charge, in interstellar space for a significant time. "That obviously is not the case," said Mike McCarthy of the CfA. "Anions are surprisingly abundant in these regions."

"Until recently, many theoretical models of how chemical reactions evolve in interstellar space have largely neglected the presence of anions. This can no longer be the case, and this means that there are many more ways to build large organic molecules in cosmic environments than have been explored," said Jan M. Hollis of NASA's Goddard Space Flight Center (GSFC).

Remijan and his colleagues found the octatetraynyl anions in the envelope of the evolved giant star IRC +10 216, about 550 light-years from Earth in the constellation Leo. They found radio waves emitted at specific frequencies characteristic of the charged molecule by searching archival data from the GBT, the largest fully-steerable radio telescope in the world.

Another team from the Harvard-Smithsonian Center for Astrophysics found the same characteristic emission when they observed a cold cloud of molecular gas called TMC-1 in the constellation Taurus. These observations also were done with the GBT. In both cases, preceding laboratory experiments by the CfA team showed which radio frequencies actually are emitted by the molecule, and thus told the astronomers what to look for.

"It is essential that likely interstellar molecule candidates are first studied in laboratory experiments so that the radio frequencies they can emit are known in advance of an astronomical observation," said Frank Lovas of the National Institute of Standards and Technology (NIST).

Both teams announced their results in the July 20 edition of the Astrophysical Journal Letters.

"With three negatively-charged molecules now found in a short period of time, and in very different environments, it appears that many more probably exist. We believe that we can discover more new species using very sensitive and advanced radio telescopes such as the GBT, once they have been characterized in the laboratory," said Sandra Bruenken of the CfA.

"Further detailed studies of anions, including astronomical observations, laboratory studies, and theoretical calculations, will allow us to use them to reveal new information about the physical and chemical processes going on in interstellar space," said Martin Cordiner, of Queen's University in Belfast, Northern Ireland.

"The GBT continues to take a leading role in discovering, identifying and mapping the distribution of the largest molecules ever found in astronomical environments and will continue to do so for the next several decades," said Phil Jewell of NRAO.

In addition to Hollis, Lovas, Cordiner and Jewell, Remijan worked with Tom Millar of Queen's University in Belfast, Northern Ireland, and Andrew Markwick-Kemper of the University of Manchester in the UK.

Bruenken worked with McCarthy, Harshal Gupta, Carl Gottlieb, and Patrick Thaddeus, all of the Harvard-Smithsonian Center for Astrophysics.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

MORE NEWS.....

Astronomers have detected negatively charged molecules in space for the first time, suggesting the molecules may be more common than previously thought.

Previously, about 130 different neutral molecules and 14 positively charged molecules had been identified in space - but no negatively charged molecules were found.

Conventional wisdom held that these were rare because ultraviolet radiation from starlight would tend to strip away extra electrons, leaving behind only positive ions.

Now, astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, US, have found a negatively charged molecule in two nearby regions within the Milky Way. Composed of six carbon atoms, a hydrogen atom, and an extra electron, it is called a hexatriyne anion, or C6H-.

Curiously, the anion was found in two very different environments - a gas shell around the dying, red giant star IRC+10216 and the cold molecular cloud TMC-1, both of which lie about 500 light years from Earth.

Unknown cause

It is not yet clear what physical process actually led to the molecule's formation in those locations. "That's the point we're desperately eager to find out," says team member Patrick Thaddeus of the CfA.

The molecule may have formed in these gaseous regions after an extra proton was bumped off the neutral molecule hexatriyne, C6H2, or by an electron attaching to the neutral molecule C6H. The anion is present in both sources at a level of between 1% and 5% that of the neutral molecule C6H.

One clue to its formation may come from its size; C6H- is composed of more atoms than many of the neutral molecules that have been found in space.

"It was considered crazy that the first negatively charged molecule we found in space would be such a big molecule," Thaddeus says.

This large size may increase the molecule's stability. Previous research suggests electrons can attach themselves quite efficiently to carbon molecules when the molecules are composed of at least six carbon atoms.

Lurking undetected

To make the find, the CfA astronomers pored over data collected 11 years ago by Kentarou Kawaguchi at Okayama University in Japan. Kawaguchi's team found a series of spectral lines that could not be assigned to any known molecule in IRC+10216.

Back in the lab, the CfA team found the spectral lines matched C6H-. They then used the Green Bank Telescope to verify that the molecule was present in the red giant and in TMC-1.

The find suggests other negatively charged molecules are lurking in space and have not been detected because previous searches have focused on more diffuse gas clouds where the anions are not concentrated enough to produce a signal.

"This is a whole area of astrochemistry that we've just kind of been missing," says Robert McMahon, a chemist at the University of Wisconsin, Madison, US, who was not involved in the study.

Team member Michael McCarthy of the CfA says the researchers will search them out by first studying the spectral signatures of large anions, like C6H-, in the laboratory.

They have already found C4H- and C8H- in the lab and are now trying to find the molecules' signatures in space. The team says they may find these anions in IRC+10216 and TMC-1, since neutral or positively charged variations of these molecules have already been observed in the regions.

Technorati : Discovered, Molecule, Negatively-, New

Europe Moves Ahead With Weather Satellite Blacklist

European government officials may resent the fact that the U.S. government is forcing them to create a blacklist of organizations that will not be granted access to weather-satellite data from Europe's future polar-orbiting satellites, which will include U.S. government-supplied instruments. But they have nonetheless agreed to create such a list this year.

The list to be provided by the 18-nation Eumetsat organization will have the effect of determining what organizations may be denied data from Eumetsat's Metop satellites following a U.S. request during an emergency.

U.S. and European government authorities already have concluded the basic outlines of what is known as the Data Denial Implementation Plan. But government officials said the details remain sticky.

"What we have to agree to is a list of organizations, agencies and institutions that will be refused data following a U.S. request," one government official said. "The U.S. has some very specific ideas about who these people are. We don't like the idea. It's not something we're comfortable with. But if the question is: Will we resist it? The answer is: No. We will get this resolved this year."

Europe's Metop-1 satellite is scheduled for launch in June. It will be the first European polar-orbiting meteorological satellite, and will be part of a U.S.-European Joint Polar System. European instruments fly on U.S.-provided satellites, and the United States is providing instruments on the Metop spacecraft.

The joint collaboration is in keeping with the tradition of the nations contributing to the global World Weather Watch system, which distributes weather data the world over with little or no questions asked of those receiving the data. Europe's 18-nation Eumetsat organization of Darmstadt, Germany, and the U.S. National Oceanic and Atmospheric Administration (NOAA) are major hardware contributors to the World Weather Watch system. Japan, China and Russia also are major satellite-data contributors to the system.

The Eumetsat-NOAA data-denial agreement involves the U.S. Defense Department because the U.S. military and NOAA are merging their weather-satellite systems. This merger has given U.S. defense authorities a seat at the negotiating table, as longtime partners NOAA and Eumetsat set the boundaries of who can be refused data in a U.S.-declared emergency.

In an address to Eumetsat's governing council Nov. 29, NOAA Assistant Administrator Gregory W. Withee expressed frustration that the Data Denial Implementation Plan has not been settled despite the approach of the Metop launch.

Withee said in his address that the plan permits Eumetsat governments and approved third-party users continued access to U.S.-provided Metop instruments no matter what happens.

Mikail Rattenborg, director of operations at Eumetsat, agreed with Withee's assessment and said the U.S. side already has agreed to a compromise in the way the data denial will work. After initially proposing that the U.S. decide unilaterally when to curb access to its instruments - a technical challenge since Eumetsat will operate the Metop spacecraft - U.S. negotiators have accepted an approach that is more palatable to European authorities.

"The way the data denial process will work is that the U.S. will make a request to Eumetsat, and then Eumetsat will implement the request," Rattenborg said. "This is a very important step: The U.S. is delegating control of its instruments to Eumetsat. The second step is establishing a list of agencies that will not be subject to data denial, and that is taking a little more time. But I am optimistic we can get this done before the Metop launch."

Data-access policy to meteorological satellite data has long been a source of disagreement between the United States and Europe, with Europe opting to commercialize some weather images and the U.S. taking more of a free-access view. In this case, the roles are reversed, but because of security concerns, not business-model issues.

For the Metop satellites, Eumetsat will be technically able to switch off access to data for individual users, in keeping with its existing policy of differentiating between fee-paying and free-access user groups.

In a similar case, U.S. and European authorities spent months haggling over access to satellite navigation and timing data from Europe's Galileo satellite system, now in development. Galileo will resemble the U.S. GPS system, but will be civilian-financed and run as a business.

U.S. and European officials have agreed on a policy that would permit Galileo program managers to deny access to a localized area during a conflict, similar to the U.S. GPS navigation-warfare strategy.

Technorati : Ahead, Blacklist, Europe Moves, Satellite, Weather
Del.icio.us : Ahead, Blacklist, Europe Moves, Satellite, Weather
Ice Rocket : Ahead, Blacklist, Europe Moves, Satellite, Weather
Flickr : Ahead, Blacklist, Europe Moves, Satellite, Weather
Zooomr : Ahead, Blacklist, Europe Moves, Satellite, Weather
Buzznet : Ahead, Blacklist, Europe Moves, Satellite, Weather
Riya : Ahead, Blacklist, Europe Moves, Satellite, Weather
43 Things : Ahead, Blacklist, Europe Moves, Satellite, Weather