Dec 5 2011
From The Space Library
NASA Finds 'Merging Tsunami' Doubled Japan Destruction
WASHINGTON -- NASA and Ohio State University researchers have discovered the major tsunami generated by the March 2011 Tohoku-Oki quake centered off northeastern Japan was a long-hypothesized "merging tsunami." The tsunami doubled in intensity over rugged ocean ridges, amplifying its destructive power at landfall.
Data from NASA and European radar satellites captured at least two wave fronts that day. The fronts merged to form a single, double-high wave far out at sea. This wave was capable of traveling long distances without losing power. Ocean ridges and undersea mountain chains pushed the waves together along certain directions from the tsunami's origin.
The discovery helps explain how tsunamis can cross ocean basins to cause massive destruction at some locations while leaving others unscathed. The data raise hope that scientists may be able to improve tsunami forecasts.
Research scientist Y. Tony Song of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and professor C.K. Shum of The Ohio State University discussed the data and simulations that enabled them to piece the story together at a media briefing Monday, Dec. 5, at the American Geophysical Union meeting in San Francisco.
"It was a one in 10 million chance that we were able to observe this double wave with satellites," Song said. He is the principal investigator in the NASA-funded study.
"Researchers have suspected for decades that such 'merging tsunamis' might have been responsible for the 1960 Chilean tsunami that killed about 200 people in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now,” Song said. It was like looking for a ghost. A NASA-French Space Agency satellite altimeter happened to be in the right place at the right time to capture the double wave and verify its existence."
The NASA-Centre National d'Etudes Spaciales Jason-1] satellite passed over the tsunami on March 11, as did two other satellites -- the NASA-European Jason-2 and the European Space Agency's EnviSAT. All three carry radar altimeters, which measure sea level changes to an accuracy of a few centimeters. Each satellite crossed the tsunami at a different location, measuring the wave fronts as they occurred. Jason-1 launched 10 years ago this week on Dec. 7, 2001.
"We can use what we learned to make better forecasts of tsunami danger in specific coastal regions anywhere in the world, depending on the location and the mechanism of an undersea quake," Shum said.
The researchers think ridges and undersea mountain chains on the ocean floor deflected parts of the initial tsunami wave away from each other to form independent jets shooting off in different directions, each with its own wave front.
The sea floor topography nudges tsunami waves in varying directions and can make its destruction appear random. For that reason, hazard maps that try to predict where tsunamis will strike rely on sub-sea topography. Previously, these maps considered only topography near a particular shoreline. This study suggests scientists may be able to create maps that take into account all undersea topography, even sub-sea ridges and mountains far from shore.
Song and his team were able to verify the satellite data through model simulations based on independent data, including GPS data from Japan and buoy data from the National Oceanic and Atmospheric Administration's Deep-ocean Assessment and Reporting of Tsunamis program.
"Tools based on this research could help officials forecast the potential for tsunami jets to merge," Song said. "This, in turn, could lead to more accurate coastal tsunami hazard maps to protect communities and critical infrastructure."
NASA's Voyager Hits New Region at Solar System Edge
WASHINGTON -- NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space. Data obtained from Voyager over the last year reveal this new region to be a kind of cosmic purgatory. In it, the wind of charged particles streaming out from our sun has calmed, our solar system's magnetic field piles up and higher energy particles from inside our solar system appear to be leaking out into interstellar space.
"Voyager tells us now that we're in a stagnation region in the outermost layer of the bubble around our solar system," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "Voyager is showing that what is outside is pushing back. We shouldn't have long to wait to find out what the space between stars is really like."
Although Voyager 1 is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years.
The latest findings, described today at the American Geophysical Union's fall meeting in San Francisco, come from Voyager's Low Energy Charged Particle instrument, Cosmic Ray Subsystem and Magnetometer.
Scientists previously reported the outward speed of the solar wind had diminished to zero in April 2010, marking the start of the new region. Mission managers rolled the spacecraft several times this spring and summer to help scientists discern whether the solar wind was blowing strongly in another direction. It was not. Voyager 1 is plying the celestial seas in a region similar to Earth's doldrums, where there is very little wind.
During this past year, Voyager's magnetometer also detected a doubling in the intensity of the magnetic field in the stagnation region. Like cars piling up at a clogged freeway off-ramp, the increased intensity of the magnetic field shows that inward pressure from interstellar space is compacting it.
Voyager has been measuring energetic particles that originate from inside and outside our solar system. Until mid-2010, the intensity of particles originating from inside our solar system had been holding steady. But during the past year, the intensity of these energetic particles has been declining, as though they are leaking out into interstellar space. The particles are now half as abundant as they were during the previous five years.
At the same time, Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary.
"We've been using the flow of energetic charged particles at Voyager 1 as a kind of wind sock to estimate the solar wind velocity," said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "We've found that the wind speeds are low in this region and gust erratically. For the first time, the wind even blows back at us. We are evidently traveling in completely new territory. Scientists had suggested previously that there might be a stagnation layer, but we weren't sure it existed until now."
Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is 9 billion miles (15 billion kilometers) away from the sun.
NASA's Kepler Confirms Its First Planet in Habitable Zone of Sun-Like Star
MOFFET FIELD, Calif. -- NASA's Kepler mission has confirmed its first planet in the "habitable zone," the region where liquid water could exist on a planet’s surface. Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.
The newly confirmed planet, Kepler-22b, is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun. The planet is about 2.4 times the radius of Earth. Scientists don't yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets.
Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our sun recently were confirmed on the very edges of the habitable zone, with orbits more closely resembling those of Venus and Mars.
"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. "Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the biggest questions about our place in the universe."
Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or "transit," the stars. Kepler requires at least three transits to verify a signal as a planet.
"Fortune smiled upon us with the detection of this planet," said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. "The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season."
The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.
Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290 days around a sun-like star resembles that of our world. The planet's host star belongs to the same class as our sun, called G-type, although it is slightly smaller and cooler.
Of the 54 habitable zone planet candidates reported in February 2011, Kepler-22b is the first to be confirmed. This milestone will be published in The Astrophysical Journal.
The Kepler team is hosting its inaugural science conference at Ames Dec. 5-9, announcing 1,094 new planet candidate discoveries. Since the last catalog was released in February, the number of planet candidates identified by Kepler has increased by 89 percent and now totals 2,326. Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter.
The findings, based on observations conducted May 2009 to September 2010, show a dramatic increase in the numbers of smaller-size planet candidates.
Kepler observed many large planets in small orbits early in its mission, which were reflected in the February data release. Having had more time to observe three transits of planets with longer orbital periods, the new data suggest that planets one to four times the size of Earth may be abundant in the galaxy.
The number of Earth-size and super Earth-size candidates has increased by more than 200 and 140 percent since February, respectively.
There are 48 planet candidates in their star's habitable zone. While this is a decrease from the 54 reported in February, the Kepler team has applied a stricter definition of what constitutes a habitable zone in the new catalog, to account for the warming effect of atmospheres, which would move the zone away from the star, out to longer orbital periods.
"The tremendous growth in the number of Earth-size candidates tells us that we're honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable," said Natalie Batalha, Kepler deputy science team lead at San Jose State University in California. "The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods."
Veteran Space Shuttle Commander Chris Ferguson to Leave Agency
HOUSTON - Astronaut Chris Ferguson, the last commander of a space shuttle mission, has announced his plans to retire from NASA on Dec. 9. He will leave for a new job in the private sector.
"Chris has been a true leader at NASA," NASA Administrator Charles Bolden said, "not just as a commander of the space shuttle, but also as an exemplary civil servant, a distinguished Navy officer and a good friend. I am confident he will succeed in his next career as he brings his skill and talents to new endeavors."
Ferguson, a retired U.S. Navy captain, served as the commander for STS-135, the final flight of space shuttle Atlantis and the 135th and final mission of America's 30-year Space Shuttle Program.
Atlantis' flight was Ferguson's third trip to space. During the 13-day mission, he and his crew delivered approximately 10,000 pounds of supplies and spare parts to the International Space Station. Before his assignment to STS-135, Ferguson served as deputy chief of the Astronaut Office at NASA's Johnson Space Center in Houston.
"Chris has been a great friend, a tremendous professional and an invaluable asset to the NASA team and the astronaut office," said Peggy Whitson, chief of the Astronaut Office. "His exceptional leadership helped ensure a perfect final flight of the space shuttle, a fitting tribute to the thousands who made the program possible."
Media Invited to Orion Spacecraft Water Landing Test at Langley
HAMPTON, Va. - Reporters are invited to watch a test version of the Orion crew capsule take its final splash of the year Tuesday, Dec. 13, at the Hydro Impact Basin of NASA's Langley Research Center in Hampton, Va.
Testing began this summer to certify the Orion spacecraft for water landings. Orion will carry astronauts deeper into space than ever before, provide emergency abort capability, sustain the crew during space travel and ensure a safe re-entry and landing.
Since July, engineers have conducted six tests from different angles, heights and pitches to simulate varying sea conditions and impacts Orion could face upon landing in the Pacific Ocean.
The Hydro Impact Basin is 115 feet long, 90 feet wide and 20 feet deep. It is located at the west end of Langley's historic Landing and Impact Research Facility, where Apollo astronauts trained for moon walks.
