NASA's GRAIL Creates Most Accurate Moon Gravity Map

This image depicting the porosity of the lunar highland crust was derived using bulk density data from NASA's GRAIL mission and independent grain density measurements from NASA's Apollo moon mission samples as well as orbital remote-sensing data. Image credit: SA/JPL-Caltech/ IPGP.

Twin NASA probes orbiting Earth's moon have generated the highest resolution gravity field map of any celestial body. The new map, created by the Gravity Recovery and Interior Laboratory (GRAIL) mission, is allowing scientists to learn about the moon's internal structure and composition in unprecedented detail. Data from the two washing machine-sized spacecraft also will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved. The gravity field map reveals an abundance of features never before seen in detail, such as tectonic structures, volcanic landforms, basin rings, crater central peaks and numerous simple, bowl-shaped craters. Data also show the moon's gravity field is unlike that of any terrestrial planet in our solar system. These are the first scientific results from

GRAIL's Gravity Tour of the Moon: This movie shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012. Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. Video credit: NASA/JPL-Caltech/MIT/GSFC.

the prime phase of the mission, and they are published in three papers in the journal Science. "What this map tells us is that more than any other celestial body we know of, the moon wears its gravity field on its sleeve," said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. "When we see a notable change in the gravity field, we can sync up this change with surface topography features such as craters, rilles or mountains." According to Zuber, the moon's gravity field preserves the record of impact bombardment that characterized all terrestrial planetary bodies and reveals evidence for fracturing of the interior extending to the deep crust and possibly the mantle. This impact record is preserved, and now precisely measured, on the moon. The probes revealed the bulk density of the moon's highland crust is substantially lower than generally assumed. This low-bulk crustal density agrees well with data obtained during the final Apollo lunar missions in the early 1970s, indicating that

This map shows the gravity field of the moon as measured by NASA's GRAIL mission. Image credit: NASA/ARC/MIT.

local samples returned by astronauts are indicative of global processes. "With our new crustal bulk density determination, we find that the average thickness of the moon's crust is between 21 and 27 miles (34 and 43 kilometers), which is about 6 to 12 miles (10 to 20 kilometers) thinner than previously thought," said Mark Wieczorek, GRAIL co-investigator at the Institut de Physique du Globe de Paris. "With this crustal thickness, the bulk composition of the moon is similar to that of Earth. This supports models where the moon is derived from Earth materials that were ejected during a giant impact event early in solar system history." The map was created by the spacecraft transmitting radio signals to define precisely the distance between them as they orbit the moon in formation. As they fly over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly. "We used gradients of the gravity field in order to highlight smaller and narrower structures than could be seen in previous datasets," said Jeff Andrews-Hanna, a GRAIL guest scientist with the Colorado School of Mines in Golden. "This data revealed a population of long, linear gravity anomalies, with lengths of hundreds of kilometers, crisscrossing the surface. These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features

Gravity Recovery And Interior Laboratory (GRAIL) spacecrafts. Image credit: NASA/JPL-Caltech

on the moon, and understanding them will tell us about its early history."While results from the primary science mission are just beginning to be released, the collection of gravity science by the lunar twins continues. GRAIL's extended mission science phase began Aug. 30 and will conclude Dec. 17. As the end of mission nears, the spacecraft will operate at lower orbital altitudes above the moon. When launched in September 2011, the probes were named GRAIL A and B. They were renamed Ebb and Flow in January by elementary students in Bozeman, Mont., in a nationwide contest. Ebb and Flow were placed in a near-polar, near-circular orbit at an altitude of approximately 34 miles (55 kilometers) on Dec. 31, 2011, and Jan. 1, 2012, respectively. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for NASA's Science Mission Directorate in Washington. GRAIL is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems of Denver built the spacecraft. To view the lunar gravity map, visit http://bit.ly/grailtour . For more information about the mission, visit:http://www.nasa.gov/grail . JPL is a division of the California Institute of Technology in Pasadena. Images (mentioned), Video (mentioned), Text, Credits: NASA / Dwayne Brown / JPL / DC Agle / Massachusetts Institute of Technology / Sarah McDonnell. Greetings, Orbiter.ch Source: Orbiter.ch Space News

Read More........→January 01, 2013

The "water nymph" of the Yucatan Peninsula

The find has been named Naia, Greek for "water nymph".

"Pristine prehistoric skeleton of teenage girl found in underwater cave" : by Sheryl Ubelacker, May 16th, 2014, CTV News,  The pristine skeleton of a teenaged girl who lived about 13,000 years ago, discovered in a deep, water-filled underground cavern in the sprawling cave system in Mexico's Yucatan Peninsula, is providing archeologists with an unprecedented glimpse into the history of the early inhabitants of the Americas. Given the name Naia, Greek for "water nymph," the remains of the 15- or 16-year-old girl were found at the bottom of the boulder-strewn, underwater chamber dubbed Hoyo Negro -- "black hole" in Spanish -- along with the scattered bones of 26 large animal species, among them sabre-tooth tigers, giant ground sloths and cave bears. "Sealed off by water and darkness for over 8,000 years, it is a time capsule of the environment and human life in central America at the end of the Ice Age, when glaciers across the globe trapped massive amounts of water as ice and sea level was far lower than it is today," said American paleontologist Jim Chatters, head of an international research team investigating the site and its archeological treasures. Chatters, the first scientist to study the prehistoric skeleton known as Kennewick Man that was found in Washington state in 1996, described Hoyo Negro as being like a miniature of California's La Brea tar pits, "only without the tar and with considerably better preservation." At the time of Naia's death, the caves would have been dry and accessible, he told a media teleconference. "Perhaps seeking fresh water in the dark passages, animals and at least one human fell into this inescapable ... trap." Naia's remains were discovered in 2007 by three Mexican cave divers exploring an underwater cavern, deep in the Yucatan jungle about eight kilometres from the Caribbean coast. In a 50-metre-deep sinkhole within the cavern, the girl's skull was resting on a boulder, "laying upside-down with a perfect set of teeth and dark eye sockets looking back at us," said diver Alberto Nava. After the divers reported their find to the National Institute of Anthropology and History in Mexico, a consortium of 16 scientists and cave explorers from Mexico, the U.S. and Canada was formed in 2011 to photograph and document the site, and to collect fossilized flora and fauna samples for testing. "A big part of it has just been trying to map the locations of things and get the shape of the tunnels and cavern, and mapping locations of human bones and animal bones," said Ed Reinhardt, a professor of geography and earth sciences at McMaster University in Hamilton who is part of the research team. His role is studying microfossils, such as those of single-celled animals, and water salinity, within Hoyo Negro. But beyond the stunning discovery of Naia's skeletal remains in her watery grave, reported Thursday in the journal Science, is what DNA from her bones is telling researchers about the origins of the Western Hemisphere's first peoples and their link to modern-day native Americans. Based on carbon-dating and other chronology testing, the researchers estimate "the small, slight" girl lived between 12,000 and 13,000 years ago. DNA was extracted from one of Naia's teeth and scientists sequenced what's called mitochondrial DNA, which is passed from mother to child. The results show the girl is related, maternally at least, to today's native Americans, meaning both would trace their lineage to Beringia -- the land masses on either side of the ancient land bridge now covered by the Bering Sea that was used by prehistoric people to migrate from northeast Asia into what is now Alaska and southward into Central and South America. Those first migrants have been dubbed the Clovis people. Whether all early inhabitants of the Americas came across the Bering land bridge or somehow migrated from elsewhere in the world remains a controversial question because of the differences in skull shape and facial features among prehistoric fossilized remains discovered across the Americas and modern-day indigenous populations. Naia's skull shape and facial features are considered "Paleoamerican" and differ from native Americans living today in the Western Hemisphere. "Because she exhibits the distinctive Paleoamerican skull and facial features, the study shows for the first time that Paleoamericans with these distinctive features can have Beringian ancestry," said Deborah Bolnick, a genomic anthropologist at the University of Texas at Austin. Bolnick said the physical differences between them are likely due to evolutionary changes that occurred either in Beringia or in the Americas over the last 9,000 years, rather than the two groups having separate origins. "Mitochondrial DNA for this individual does not exclude the possibility of separate ancestry for some Paleoamericans, but our results provide no evidence for an early migration to the Americas from other regions of the world -- southeast Asia, Australia or Europe -- as some have proposed," she said. "Instead, our results suggest that Paleoamericans and contemporary native Americans both have Beringian ancestry." Reinhardt of McMaster said Hoyo Negro, which is now off-limits to the public because unauthorized divers have disturbed the artifacts, said the cathedral-like site is breathtakingly beautiful, with crystal-clear water surrounded by white limestone walls. But for Naia, who may have been seeking fresh water in the cavern and accidentally plunged into the sinkhole and could find no escape, it must have been a terrifying experience, he said. "When we're diving the site, it's spectacular, but the reality is this pit was a bit of a house of horrors in the sense that you would drop and perhaps survive the fall but not have any light. You wouldn't know the extent of the cavern. You'd be in a pool of water (at the bottom), kind of thrashing around trying to get out. "Yeah, it would have been a pretty awful way to die for sure." Source: Article

Read More........→May 18, 2014