Otherworldly Pas De Deux

With components of the International Space Station in the view, NASA astronauts Andrew Feustel (right) and Michael Fincke are pictured during the STS-134 mission's third spacewalk. They coordinated their shared activity with NASA astronaut Greg Chamitoff, who stayed in communication with the pair and with Mission Control Center in Houston from inside the station.

Image Credit: NASA

Station Spacewalking Milestone Reached

Astronauts and cosmonauts have now spent 1,000 hours spacewalking for assembly and maintenance of the International Space Station. Spacewalkers Mike Fincke and Greg Chamitoff surpassed the 1,000th hour 4 hours and 47 minutes into today's spacewalk, at 5:02 a.m. EDT. It is the final spacewalk of this mission and the last ever by space shuttle astronauts.

Power and Data Grapple Fixture Connected to Boom

Greg Chamitoff, with assistance from Mike Fincke, released the six bolts holding the electrical flight grapple fixture to the space station boom and cut the grapple's cable. Using six bolts, Chamitoff then installed an adapter assembly on the boom. The pair then slid the power and data grapple fixture into place on it and secured it with four bolts. Now that the power and data grapple fixture has been added, the boom will be known as the Enhanced International Space Station Boom Assembly. The 50-foot boom now can be connected to the Canadarm, the space station's robotic arm, to double its reach.

The crews are cleaning up from the activity. The spacewalk timeline called for Fincke to stow the electrical flight grapple fixture they removed in Endeavour's cargo bay. However, in the interest of time, the spacewalkers will instead return the fixture to the airlock with them at the conclusion of today's spacewalk.

The next task will be to work on a spare arm for Dextre, the Canadian Special Purpose Dexterous Manipulator. The arm was delivered on the ExPRESS Logistics Carrier 3, where three expandable diameter fixture bolts held it in place for launch. Fincke and Chamitoff will release each of the bolts, making use of a specially designed pry rod, if required.

Mission Control also notified the spacewalkers that they would like to extend the spacewalk to approximately 7 hours and 30 minutes to allow them to accomplish the primary planned activities. Chamitoff will need to recharge his oxygen. He will skip a 15-minute task to inspect and perhaps tighten a tether on Dextre that has loosened some over time. If time allows, that task could be added back at the end of the spacewalk.

NASA-Funded Scientists Make Lunar Watershed Discovery

Dwayne Brown

Headquarters, Washington

 

Cathy Weselby

Ames Research Center, Moffett Field, Calif.

 

Maria Martinez

Southwest Research Institute, San Antonio

 

Richard Lewis

Brown University, Providence, R.I.

MOFFETT FIELD, Calif. -- A team of NASA-funded researchers has measured for the first time water from the moon in the form of tiny globules of molten rock, which have turned to glass-like material trapped within crystals. Data from these newly-discovered lunar melt inclusions indicate the water content of lunar magma is 100 times higher than previous studies suggested.

The inclusions were found in lunar sample 74220, the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The scientific team used a state-of-the-art ion microprobe instrument to measure the water content of the inclusions, which were formed during explosive eruptions on the moon approximately 3.7 billion years ago.

The results published in the May 26 issue of Science Express raise questions about aspects of the "giant impact theory" of how the moon was created. That theory predicted very low water content of lunar rock due to catastrophic degassing during the collision of Earth with a Mars-sized body very early in its history.

The study also provides additional scientific justification for returning similar samples from other planetary bodies in the solar system.

"Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors and the location and eruptive style of planetary volcanoes," said Erik Hauri, a geochemist with the Carnegie Institution of Washington and lead author of the study. "I can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the moon but throughout the inner solar system."

In contrast to most volcanic deposits, the lunar melt inclusions are encased in crystals that prevent the escape of water and other volatiles during eruption.

"These samples provide the best window we have on the amount of water in the interior of the moon where the orange glass came from," said science team member James Van Orman of Case Western Reserve University in Cleveland.

In a 2008 study led by Alberto Saal of Brown University in Providence, R.I., the same team reported the first evidence of water in lunar volcanic glasses. They used magma degassing models to estimate how much water was originally in the magmas before eruption.

Building on that study, a Brown undergraduate student, Thomas Weinreich, searched for and found the melt inclusions. With that data, the team measured the pre-eruption concentration in the magma and estimated the amount of water in the moon's interior.

"The bottom line is that in 2008, we said the primitive water content in the lunar magmas should be similar to lavas coming from the Earth's depleted upper mantle," Saal said. "Now, we have proven that is indeed the case."

The study also puts a new twist on the origin of water-ice detected in craters at the lunar poles by several recent NASA missions. The ice has been attributed to comet and meteor impacts, but the researchers believe it is possible that some of the ice came from water released by the eruption of lunar magmas eons ago.

The paper entitled, "High Pre-Eruptive Water Contents Preserved in Lunar Melt Inclusions," was written by Hauri, Weinreich, Saal, Van Oman and Malcolm Rutherford of Brown. The research is funded by NASA's Lunar Advanced Science and Exploration Research and Cosmochemistry Programs in Washington, the NASA Lunar Science Institute (NLSI) at the agency's Ames Research Center at Moffett Field, Calif., and the Astrobiology Institute at Ames.

The NLSI is a virtual organization enabling collaborative, interdisciplinary research in support of agency lunar science programs. The researchers are members of NLSI teams from the Southwest Research Institute in San Antonio and Brown. The institute uses technology to bring scientists together around the world, and it is comprised of seven competitively selected U.S. teams and several international partners. NASA's Science Mission and Exploration Systems Mission Directorates in Washington fund the institute.

For more information about the NLSI, visit http://lunarscience.nasa.gov.

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Fourth and Final Shuttle Astronaut Spacewalk Set

The mission’s fourth and final spacewalk with Mike Fincke and Greg Chamitoff is set to begin at 12:46 a.m. EDT and last approximately six and a half hours. The primary task of the spacewalk is to transfer the Orbiter Boom Sensor System from the shuttle to space station. If all goes as planned, the total number of hours spent spacewalking for International Space Station assembly and maintenance is expected to surpass 1,000.

It will be the last spacewalk by space shuttle crew members. (A spacewalk during the program’s final mission, STS-135, is to be conducted by space station residents.)

At about 8 p.m. Friday, Fincke will become the record-holder for the number of days a U.S. astronaut has spent in space, surpassing Peggy Whitson's total of 377 days.

Expedition 28 Crew Departs Star City

Expedition 28 crew members--Flight Engineer Satoshi Furukawa, left, Soyuz commander Sergei Volkov, center, and Flight Engineer Mike Fossum--answer reporters' questions during a press conference held on the grounds of the Gagarin Cosmonaut Training Center, Wednesday, May 25, 2011 in Star City, Russia. The crew later departed for Baikonur, Kazakhstan, in preparation for their June launch to the International Space Station.

Image Credit: NASA/Bill Ingalls

NASA'S Hubble Finds Rare 'Blue Straggler' Stars In Milky Way's Hub

Trent J. Perrotto

Headquarters, Washington                                    

 

Ray Villard/Kailash Sahu

Space Telescope Science Institute, Baltimore

 

WASHINGTON -- NASA's Hubble Space Telescope has found a rare class of oddball stars called blue stragglers in the hub of our Milky Way, the first detected within our galaxy's bulge.

Blue stragglers are so named because they seemingly lag behind in the aging process, appearing younger than the population from which they formed. While they have been detected in many distant star clusters, and among nearby stars, they never have been seen inside the core of our galaxy.

It is not clear how blue stragglers form. A common theory is that they emerge from binary pairs. As the more massive star evolves and expands, the smaller star gains material from its companion. This stirs up hydrogen fuel and causes the growing star to undergo nuclear fusion at a faster rate. It burns hotter and bluer, like a massive young star.

The findings support the idea that the Milky Way's central bulge stopped making stars billions of years ago. It now is home to aging sun-like stars and cooler red dwarfs. Giant blue stars that once lived there have long since exploded as supernovae. The results have been accepted for publication in an upcoming issue of The Astrophysical Journal. Lead author Will Clarkson of Indiana University in Bloomington, will discuss them today at the American Astronomical Society meeting in Boston.

"Although the Milky Way bulge is by far the closest galaxy bulge, several key aspects of its formation and subsequent evolution remain poorly understood," Clarkson said. "Many details of its star-formation history remain controversial. The extent of the blue straggler population detected provides two new constraints for models of the star-formation history of the bulge."

The discovery followed a seven-day survey in 2006 called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble peered at 180,000 stars in the crowded central bulge of our galaxy, 26,000 light-years away. The survey was intended to find hot Jupiter-class planets that orbit very close to their stars. In doing so, the SWEEPS team also uncovered 42 oddball blue stars with brightness and temperatures typical for stars much younger than ordinary bulge stars.

The observations clearly indicate that if there is a young star population in the bulge, it is very small. It was not detected in the SWEEPS program. Blue stragglers long have been suspected to be living in the bulge, but had not been observed because younger stars in the disk of our galaxy lie along the line-of-sight to the core, confusing and contaminating the view.

Astronomers used Hubble to distinguish the motion of the core population from foreground stars in the Milky Way. Bulge stars orbit the galactic center at a different speed than foreground stars. Plotting their motion required returning to the SWEEPS target region with Hubble two years after the first observations were made. The blue stragglers were identified as moving along with the other stars in the bulge.

"The size of the field of view on the sky is roughly that of the thickness of a human fingernail held at arm's length, and within this region, Hubble sees about a quarter million stars toward the bulge," Clarkson said. "Only the superb image quality and stability of Hubble allowed us to make this measurement in such a crowded field."

From the 42 candidate blue stragglers, the investigators estimate 18 to 37 are likely genuine. The remainder could be a mix of foreground objects and, at most, a small population of genuinely young bulge stars.

"The SWEEPS program was designed to detect transiting planets through small light variations" said Kailash Sahu, the principal investigator of the SWEEPS program. "Therefore the program could easily detect the variability of binary pairs, which was crucial in confirming these are indeed blue stragglers."

Hubble is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington. For images and more information about the findings, visit http://www.nasa.gov/hubble and http://hubblesite.org/news/2011/16.

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