NASA's EPOXI Mission Sets Up for Comet Flyby

NASA's Deep Impact/EPOXI spacecraft flew past Earth on June 27, 2010, to get a boost from Earth’s gravity. It is now on its way to comet Hartley 2, depicted in this artist’s concept, with a planned flyby this fall. › Larger image

Earlier today, navigators and mission controllers for NASA's EPOXI mission watched their computer screens as 23.6 million kilometers (14.7 million miles) away, their spacecraft successfully performed its 20th trajectory correction maneuver. The maneuver refined the spacecraft's orbit, setting the stage for its flyby of comet Hartley 2 on Nov. 4. Time of closest approach to the comet was expected to be about 10: 02 a.m. EDT (7:02 a.m. PDT).

Today's trajectory correction maneuver began at 2 p.m. EDT (11 a.m. PDT) today, when the spacecraft fired its engines for 60 seconds, changing the spacecraft's velocity by 1.53 meters per second (3.4 mph).

"We are about 23 million miles and 36 days away from our comet," said EPOXI project manager Tim Larson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "I can't wait to see what Hartley 2 looks like."

On Nov. 4, the spacecraft will fly past the comet at a distance of about 700 kilometers (435 miles). It will be only the fifth time in history that a spacecraft has been close enough to image a comet's nucleus, and the first time in history that two comets have been imaged with the same instruments and same spatial resolution.

"We are imaging the comet every day, and Hartley 2 is proving to be a worthy target for exploration," said Mike A'Hearn, EPOXI principal investigator from the University of Maryland, College Park.

EPOXI is an extended mission that utilizes the already "in flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as "Deep Impact."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA's Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission's principal investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission's extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

For more information about EPOXI visit http://epoxi.umd.edu/.

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• Atmosphere Checked, One Mars Year Before a Landing...
• Sentinels of Climate Change
• New Views of Saturn's Aurora, Captured by Cassini

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Atmosphere Checked, One Mars Year Before a Landing

This artist's concept shows NASA's Mars Reconnaissance Orbiter, whose Mars Climate Sounder instrument has been profiling the Martian atmosphere for four years. The instrument has just begun a campaign to examine atmospheric conditions for the Martian season and hour when the next Mars rover will land in 2012. › Full image and caption

What will the Martian atmosphere be like when the next Mars rover descends through it for landing in August of 2012?

An instrument studying the Martian atmosphere from orbit has begun a four-week campaign to characterize daily atmosphere changes, one Mars year before the arrival of the Mars Science Laboratory rover, Curiosity. A Mars year equals 687 Earth days.

The planet's thin atmosphere of carbon dioxide is highly repeatable from year to year at the same time of day and seasonal date during northern spring and summer on Mars.

The Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter maps the distribution of temperature, dust, and water ice in the atmosphere. Temperature variations with height indicate how fast air density changes and thus the rates at which the incoming spacecraft slows down and heats up during its descent.

"It is currently one Mars year before the Mars Science Laboratory arrival season," said atmospheric scientist David Kass of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This campaign will provide a set of observations to support the Mars Science Laboratory engineering team and Mars atmospheric modelers. The information will constrain the expected climate at their landing season. It will also help define the range of possible weather conditions on landing day."

During the four years the Mars Climate Sounder has been studying the Martian atmosphere, its observations have seen conditions only at about three in the afternoon and three in the morning. For the new campaign, the instrument team is inaugurating a new observation mode, looking to both sides as well as forward. This provides views of the atmosphere earlier and later in the day by more than an hour, covering the range of possible times of day that the rover will pass through the atmosphere before landing.

JPL, a division of the California Institute of Technology, provided the Mars Climate Sounder instrument and manages the Mars Reconnaissance Orbiter and Mars Science Laboratory projects for NASA's Science Mission Directorate, Washington. For more about NASA's Mars exploration program, see http://marsprogram.jpl.nasa.gov .

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• Sentinels of Climate Change
• New Views of Saturn's Aurora, Captured by Cassini
• Spring on Titan brings sunshine and patchy clouds

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Sentinels of Climate Change

An Antarctic iceberg. Scientists estimate West Antarctica is losing between 60 and 150 billion tons of ice per year. Global Ice Viewer Interactive

Ice currently covers more than 10 percent of our watery planet, yet its volume is continuing to decline at a staggering pace in response to our warming world. A new NASA interactive tool lets you take a close-up tour of some of the places around our planet where climate change is taking a toll on Earth’s ice cover, including:

• Greenland, where the massive Ilulissat Glacier is depositing 35 to 50 cubic kilometers of icebergs into the ocean each year, raising sea level (a cubic kilometer is about 264.2 billion gallons, enough to fill 400,000 Olympic-size pools)
• The Arctic, where sea ice continues to decline in both area and volume
• Antarctica, where massive ice shelves the size of some small U.S. states have collapsed in recent years

Experience the Global Ice Viewer: http://climate.nasa.gov/GlobalIceViewer/index.cfm .

New Views of Saturn's Aurora, Captured by Cassini

This false-color composite image, constructed from data obtained by NASA's Cassini spacecraft, shows the glow of auroras streaking out about 1,000 kilometers (600 miles) from the cloud tops of Saturn's south polar region. Image credit: NASA/JPL/University of Arizona/University of Leicester
› Full image and caption | › Download wallpaper of this image

A new movie and images showing Saturn's shimmering aurora over a two-day period are helping scientists understand what drives some of the solar system's most impressive light shows.

The new, false-color images and video are available online at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The movie and images are part of a new study that, for the first time, extracts auroral information from the entire catalogue of Saturn images taken by the visual and infrared mapping spectrometer instrument (VIMS) aboard NASA's Cassini spacecraft. These images and preliminary results are being presented by Tom Stallard, lead scientist on a joint VIMS and Cassini magnetometer collaboration, at the European Planetary Science Congress in Rome on Friday, Sept. 24.

In the movie, the aurora phenomenon clearly varies significantly over the course of a Saturnian day, which lasts around 10 hours 47 minutes. On the noon and midnight sides (left and right sides of the images, respectively), the aurora can be seen to brighten significantly for periods of several hours, suggesting the brightening is connected with the angle of the sun. Other features can be seen to rotate with the planet, reappearing at the same time and the same place on the second day, suggesting that these are directly controlled by the orientation of Saturn's magnetic field.

"Saturn's auroras are very complex and we are only just beginning to understand all the factors involved," Stallard said. "This study will provide a broader view of the wide variety of different auroral features that can be seen, and will allow us to better understand what controls these changes in appearance."
Auroras on Saturn occur in a process similar to Earth's northern and southern lights. Particles from the solar wind are channeled by Saturn's magnetic field toward the planet's poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light. At Saturn, however, auroral features can also be caused by electromagnetic waves generated when the planet's moons move through the plasma that fills Saturn's magnetosphere.

Previous data from Cassini have contributed to a number of detailed snapshots of the aurora. But understanding the overall nature of the auroral region requires a huge number of observations, which can be difficult because Cassini observation time close to Saturn is in high demand, Stallard said.

However, VIMS observations of numerous other scientific targets also include auroral information. Sometimes the aurora can be clearly seen, but sometimes Stallard and colleagues add multiple images together to produce a signal. This wide set of observations allows Cassini scientists to understand the aurora in general, rather than the beautiful specific cases that dedicated auroral observations allow, Stallard said.

Stallard and his colleagues have investigated about 1,000 images from the 7,000 that VIMS has taken to date of Saturn's auroral region.

The new, false-color images show Saturn's aurora glowing in green around the planet's south pole. The auroral information in the two images was extracted from VIMS data taken on May 24, 2007, and Nov. 1, 2008. The video covers about 20 Earth hours of VIMS observations, from Sept. 22 and 23, 2007.

"Detailed studies like this of Saturn's aurora help us understand how they are generated on Earth and the nature of the interactions between the magnetosphere and the uppermost regions of Saturn's atmosphere," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson. Stallard's work on Saturn's auroras is funded by the Science and Technologies Facilities Council, Swindon, U.K.

Spring on Titan brings sunshine and patchy clouds

False-color image of cloud cover dissolving over Titan's north pole and clouds appearing in the southern mid latitudes. › Full image and caption

The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with polar skies clearing since the equinox in August last year. The visual and infrared mapping spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan regularly since the spacecraft entered orbit around Saturn in 2004. Now, a group led by Sébastien Rodriguez, a Cassini VIMS team collaborator based at Université Paris Diderot, France, has analyzed more than 2,000 VIMS images to create the first long-term study of Titan's weather using observational data that also includes the equinox. Equinox, when the sun shone directly over the equator, occurred in August 2009.

Rodriguez is presenting the results and new images at the European Planetary Science Congress in Rome on Sept. 22.

Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister world" to Earth because it has a surface covered with organic material and an atmosphere whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.

A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed significant atmospheric changes between July 2004 (early summer in Titan's southern hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud activity has recently decreased near both of Titan's poles. These regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox.

Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. "However, we are now seeing evidence of a seasonal circulation turnover on Titan – the clouds at the south pole completely disappeared just before the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with predictions from models and we are expecting to see cloud activity reverse from one hemisphere to another in the coming decade as southern winter approaches."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

For a full version of this release, go to: http://www.europlanet-eu.org/outreach/index.php?option=com_content&task=view&id=288&Itemid=41

For more information about Cassini, go to: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

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Laser Tool for Studying Mars Rocks Delivered to JPL

The ChemCam instrument for NASA's Mars Science Laboratory mission uses a pulsed laser beam to vaporize a pinhead-size target, producing a flash of light from the ionized material -- plasma -- that can be analyzed to identify chemical elements in the target. › Full image and caption

The NASA Mars Science Laboratory Project's rover, Curiosity, will carry a newly delivered laser instrument named ChemCam to reveal what elements are present in rocks and soils on Mars up to 7 meters (23 feet) away from the rover.

The laser zaps a pinhead-sized area on the target, vaporizing it. A spectral analyzer then examines the flash of light produced to identify what elements are present.

The completed and tested instrument has been shipped to JPL from Los Alamos for installation onto the Curiosity rover at JPL.

ChemCam was conceived, designed and built by a U.S.-French team led by Los Alamos National Laboratory, Los Alamos, N.M.; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the Centre National d'Études Spatiales (the French national space agency); and the Centre d'Étude Spatiale des Rayonnements at the Observatoire Midi-Pyrénées, Toulouse, France.

For more information, see the Los Alamos National Laboratory news release at http://www.lanl.gov/news/releases/mars_mission_laser_tool_heads_to_jpl_newsrelease.html .

Information about the Mars Science Laboratory mission is available at http://marsprogram.jpl.nasa.gov/msl/ and http://www.nasa.gov/msl .

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Mars Rover Opportunity Approaching Possible Meteorite

NASA's Mars Exploration Rover Opportunity used its panoramic camera to capture this view of a dark rock that may be an iron meteorite. Part of the rim of Endurance Crater is on the horizon. › Full image and caption

Images that NASA's Mars Exploration Rover Opportunity took at the end of an 81-meter (266-foot) drive on Sept. 16 reveal a dark rock about 31 meters (102 feet) away. The rover's science team has decided to go get a closer look at the toaster-sized rock and determine whether it is an iron meteorite.

"The dark color, rounded texture and the way it is perched on the surface all make it look like an iron meteorite," said science-team member Matt Golombek of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Opportunity has found four iron meteorites during the rover's exploration of the Meridiani Planum region of Mars since early 2004. Examination of these rocks has provided information about the Martian atmosphere, as well as the meteorites themselves.

The newfound rock has been given the informal name "Oileán Ruaidh" (pronounced ay-lan ruah), which is the Gaelic name for an island off the coast of northwestern Ireland. The rock is about 45 centimeters (18 inches) wide from the angle at which it was first seen.

Opportunity has driven 23.3 kilometers (14.5 miles) on Mars. The drive to this rock will take the total combined distance driven by Opportunity and its twin, Spirit, to more than 31 kilometers (19.26 miles).

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover mission for the NASA Science Mission Directorate, Washington. Opportunity landed on Mars in January 2004 for what was planned as a three-month mission. For more information about the mission, see http://marsrovers.jpl.nasa.gov.

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NASA Study Shows Desert Dust Cuts Colorado River Flow

Dust-covered snow in the San Juan Mountains. Image credit: NASA/JPL-Snow Optics Laboratory
Full image and caption

Snowmelt in the Colorado River basin is occurring earlier, reducing runoff and the amount of crucial water available downstream. A new study shows this is due to increased dust caused by human activities in the region during the past 150 years.

The study, led by a NASA scientist and funded by the agency and the National Science Foundation, showed peak spring runoff now comes three weeks earlier than before the region was settled and soils were disturbed. Annual runoff is lower by more than five percent on average compared to pre-settlement levels.

The findings have major implications for the 27 million people in the seven U.S. states and Mexico who rely on the Colorado River for drinking, agricultural and industrial water. The results were published in this week's Proceedings of the National Academy of Sciences.

The research team was led by Tom Painter, a snow hydrologist at both NASA's Jet Propulsion Laboratory in Pasadena, Calif., and UCLA. The team examined the impact of human-produced dust deposits on mountain snowpacks over the Upper Colorado River basin between 1915 and 2003. Studies of lake sediment cores showed the amount of dust falling in the Rocky Mountains increased by 500 to 600 percent since the mid-to-late 1800s, when grazing and agriculture began to disturb fragile but stable desert soils.

The team used an advanced hydrology model to simulate the balance of water flowing into and out of the river basin under current dusty conditions, and those that existed before soil was disturbed. Hydrologic data gathered from field studies funded by NASA and the National Science Foundation, and measurements of the absorption of sunlight by dust in snow, were combined with the modeling.

More than 80 percent of sunlight falling on fresh snow is typically reflected back into space. In the semi-arid regions of the Colorado Plateau and Great Basin, winds blow desert dust east, triggering dust-on-snow events. When dark dust particles fall on snow, they reduce its ability to reflect sunlight. The snow also absorbs more of the sun's energy. This darker snow cover melts earlier, with some water evaporating into the atmosphere.

Earlier melt seasons expose vegetation sooner, and plants lose water to the atmosphere through the exhalation of vapor. The study shows an annual average of approximately 35-billion cubic feet of water is lost from this exhalation and the overall evaporation that would otherwise feed the Colorado River. This is enough water to supply Los Angeles for 18 months.

"The compressed mountain runoff period makes water management more difficult than a slower runoff," Painter said. "With the more rapid runoff under dust-accelerated melt, costly errors are more likely to be made when water is released from and captured in Colorado River reservoirs."

Prior to the study, scientists and water managers had a poor understanding of dust-on-snow events. Scientists knew from theory and modeling studies that dust could be changing the way snowfields reflect and absorb sunlight, but no one had measured its full impact on snowmelt rates and runoff over the river basin. The team addressed these uncertainties by making systematic measurements of the sources, frequency and snowmelt impact of dust-on-snow events.

"These researchers brought together their collective expertise to provide a historical context for how the Colorado River and its runoff respond to dust deposition on snow," said Anjuli Bamzai, program director in the National Science Foundation's Division of Atmospheric and Geospace Sciences in Arlington, Va. "The work lays the foundation for future sound water resource management."

Painter believes steps can be taken to reduce the severity of dust-on-snow events in the Colorado River basin. He points to the impact of the Taylor Grazing Act of 1934 for potential guidance on how dust loads can be reduced. The act regulated grazing on public lands to improve rangeland conditions. Lake sediment studies show it decreased the amount of dust falling in the Rocky Mountains by about one quarter.

"Restoration of desert soils could increase the duration of snow cover, simplifying water management, increasing water supplies and reducing the need for additional reservoir storage of water. Peak runoff under cleaner conditions would then come later in summer, when agricultural and other water demands are greater," Painter said.

"It could also at least partially mitigate the expected regional impacts of climate change, which include reduced Colorado River flows, increased year-to-year variability in its flow rate, and more severe and longer droughts," he added. "Climate models project a seven to 20 percent reduction in Colorado River basin runoff in this century due to climate change."

Other institutions participating in the study include the National Snow and Ice Center in Boulder, Colo.; U.S. Geological Survey Southwest Biological Center in Moab, Utah; University of Washington in Seattle; Center for Snow and Avalanche Studies in Silverton, Colo.; and the University of Colorado-NOAA Western Water Assessment in Boulder.

For more information about NASA and agency programs, visit: http://www.nasa.gov . JPL is managed for NASA by the California Institute of Technology in Pasadena. 

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Five Things About NASA's Mars Curiosity Rover

 

An artist's concept illustrates what the Mars rover Curiosity will look like on Mars.  › Full image and caption › Mars Science Laboratory Fact Sheet

Mars Science Laboratory, aka Curiosity, is part of NASA's Mars Exploration Program, a long-term program of robotic exploration of the Red Planet. The mission is scheduled to launch from Cape Canaveral, Fla., in late 2011, and arrive at an intriguing region of Mars in August 2012. The goal of Curiosity, a rolling laboratory, is to assess whether Mars ever had an environment capable of supporting microbial life and conditions favorable for preserving clues about life, if it existed. This will help us better understand whether life could have existed on the Red Planet and, if so, where we might look for it in the future.

1. How Big Is It?: The Mini Cooper-sized rover is much bigger than its rover predecessors, Spirit, Opportunity and Pathfinder. Curiosity is twice as long (about 2.8 meters, or 9 feet) and four times as heavy as Spirit and Opportunity, which landed in 2004. Pathfinder, about the size of a microwave oven, landed in 1997.

2. Landing--Where and How: In November 2008, possible landing sites were narrowed to four finalists, all linked to ancient wet conditions. NASA will select a site believed to be among the most likely places to hold a geological record of a favorable environment for life. The site must also meet safe-landing criteria. The landing system is similar to a sky crane heavy-lift helicopter. After a parachute slows the rover's descent toward Mars, a rocket-powered backpack will lower the rover on a tether during the final moments before landing. This method allows landing a very large, heavy rover on Mars (instead of the airbag landing systems of previous Mars rovers). Other innovations enable a landing within a smaller target area than previous Mars missions.

3. Toolkit: Curiosity will use 10 science instruments to examine rocks, soil and the atmosphere. A laser will vaporize patches of rock from a distance, and another instrument will search for organic compounds. Other instruments include mast-mounted cameras to study targets from a distance, arm-mounted instruments to study targets they touch, and deck-mounted analytical instruments to determine the composition of rock and soil samples acquired with a powdering drill and a scoop.

4. Big Wheels: Each of Curiosity's six wheels has an independent drive motor. The two front and two rear wheels also have individual steering motors. This steering allows the rover to make 360-degree turns in-place on the Mars surface. The wheels' diameter is double the wheel diameter on Spirit and Opportunity, which will help Curiosity roll over obstacles up to 75 centimeters (30 inches) high.

5. Rover Power: A nuclear battery will enable Curiosity to operate year-round and farther from the equator than would be possible with only solar power.

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NASA's LRO Exposes Moon's Complex, Turbulent Youth

Map showing global compositional variations measured by the Diviner lunar radiometer aboard NASA's Lunar Reconnaissance Orbiter. Image credit: NASA/GSFC/UCLA/JPL › Full image and caption

The moon's surface is more complex than previously thought and was bombarded by two distinct populations of asteroids or comets in its youth, according to three new papers in the Sept. 17 issue of Science that describe data from NASA's Lunar Reconnaissance Orbiter.

Two of the papers describe data from LRO's Diviner Lunar Radiometer Experiment instrument that reveal the complex geologic processes that forged the lunar surface. The data showed previously unseen compositional differences in the crustal highlands, and confirmed the presence of anomalously silica-rich material in five distinct regions.

All minerals and rocks absorb and emit energy with unique signatures that reveal their identity and formation mechanisms. For the first time, the Diviner instrument is providing scientists with global, high-resolution infrared maps of the moon, enabling them to make a definitive identification of silicate minerals commonly found within its crust. "Diviner is literally viewing the moon in a whole new light," said Benjamin Greenhagen of NASA's Jet Propulsion Laboratory in Pasadena, Calif., lead author of one of the Diviner papers.

Lunar geology can be roughly broken down into two categories – the anorthositic highlands, rich in calcium and aluminium, and the basaltic "maria," giant impact basins filled with solidified lava flows that are abundant in iron and magnesium. Both of these crustal rocks are considered the direct result of crystallization from lunar mantle material, the partially molten layer beneath the crust.

Diviner's observations have confirmed that most lunar terrains have signatures consistent with compositions in these two broad categories. But they have also revealed lunar soil compositions with more sodium than that of typical anorthosite crust. The widespread nature of these soils reveals that there may have been variations in the chemistry and cooling rate of the magma ocean that formed the early lunar crust, or they could be the result of secondary processing of the early lunar crust.

Most impressively, in several locations around the moon, Diviner has detected highly silicic minerals such as quartz, potassium-rich and sodium-rich feldspar -- minerals that are only associated with highly evolved lithologies, or rocks that have undergone extensive magmatic processing. Detection of silicic minerals at these locations is significant, as they occur in areas previously shown to exhibit anomalously high abundances of the element thorium, another proxy for highly evolved lithologies.

"The silicic features we've found on the moon are fundamentally different from the more typical basaltic mare and anorthositic highlands," said Timothy Glotch of Stony Brook University, N.Y., lead author of the second Diviner paper. "The fact that we see this composition in multiple geologic settings suggests that there may have been multiple processes producing these rocks."

One thing not apparent in the data is evidence for pristine lunar mantle material, which previous studies have suggested may be exposed at some places on the lunar surface. Even in the South Pole Aitken basin, also known as SPA, the largest, oldest, and deepest impact crater on the moon -- deep enough to have penetrated through the crust and into the mantle -- there is no evidence of mantle material.

The implications of this are as yet unknown. Perhaps there are no such exposures of mantle material, or maybe they occur in areas too small for Diviner to detect. But it's likely that if the impact that formed this crater did excavate any mantle material, it has since been mixed with crustal material from later impacts inside and outside the basin.

"The new Diviner data will help in selecting the appropriate landing sites for potential future robotic missions to return samples from SPA," Greenhagen said. "We want to use these samples to date the SPA-forming impact and potentially study the lunar mantle, so it's important to use Diviner data to identify areas with minimal mixing."

In the other paper, lead author James Head of Brown University in Providence, R.I., describes an analysis of a detailed global topographic map of the moon created using LRO's Lunar Orbiter Laser Altimeter. This new dataset shows that the older highland impactor population can be clearly distinguished from the younger population in the lunar maria. The highlands have a greater density of large craters, implying that the earlier population of impactors had a proportionally greater number of large fragments than the population characterizing later lunar history, Head said.

Head said details about impactor populations on the moon have implications for the earliest history of all the planets in the inner solar system, including Earth. "Like the Rosetta stone, the lunar record can be used to translate the 'hieroglyphics' of the poorly preserved impact record on Earth," he said.

NASA's Goddard Space Flight Center in Greenbelt, Md., built and manages the Lunar Reconnaissance Orbiter, a NASA mission with international participation from the Institute for Space Research in Moscow. JPL designed, built and operates the Diviner instrument. The University of California, Los Angeles is the home institution of Diviner's principal investigator, David Paige. LOLA was built by Goddard.

A more detailed release on the LRO results is available at http://www.nasa.gov/lro . More information is also available on the Diviner website at http://diviner.ucla.edu.

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A Growing La Nina Chills Out the Pacific

La Niña continues to strengthen in the Pacific Ocean, as shown in the latest satellite data of sea surface heights from the NASA/European Ocean Surface Topography Mission/Jason-2 satellite. The image is based on the average of 10 days of data centered on Sept. 3, 2010. Higher (warmer) than normal sea surface heights are indicated by yellows and reds, while lower (cooler) than normal sea surface heights are depicted in blues and purples. Green indicates near-normal conditions. › Full image and caption 

The tropical Pacific Ocean has transitioned from last winter's El Niño conditions to a cool La Niña, as shown by new data about sea surface heights, collected by the U.S-French Ocean Surface Topography Mission (OSTM)/Jason-2 oceanography satellite.

This OSTM/Jason-2 image of the Pacific Ocean is based on the average of 10 days of data centered on Sept. 3, 2010. A new image depicts places where the Pacific sea surface height is higher (warmer) than normal as yellow and red, with places where the sea surface is lower (cooler) than normal as blue and purple. Green indicates near-normal conditions. Sea surface height is an indicator of how much of the sun's heat is stored in the upper ocean.

La Niña ocean conditions often follow an El Niño episode and are essentially the opposite of El Niño conditions. During a La Niña episode, trade winds are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. La Niña episodes change global weather patterns and are associated with less moisture in the air over cooler ocean waters, resulting in less rain along the coasts of North and South America and the equator, and more rain in the far Western Pacific.

"This La Niña has strengthened for the past four months, is strong now and is still building," said Climatologist Bill Patzert of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It will surely impact this coming winter's weather and climate.

"After more than a decade of mostly dry years on the Colorado River watershed and in the American Southwest, and only one normal rain year in the past five years in Southern California, water supplies are dangerously low," Patzert added. "This La Niña could deepen the drought in the already parched Southwest and could also worsen conditions that have fueled Southern California's recent deadly wildfires."

NASA will continue to track this change in Pacific climate.

The comings and goings of El Niño and La Niña are part of a long-term, evolving state of global climate, for which measurements of sea surface height are a key indicator. JPL manages the U.S. portion of the OSTM/Jason-2 mission for NASA's Science Mission Directorate, Washington, D.C.

For more information on NASA's ocean surface topography missions, see: http://sealevel.jpl.nasa.gov/ .

To view the latest Jason-1 and OSTM/Jason-2 data, see http://sealevel.jpl.nasa.gov/science/jason1-quick-look/. 

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• NASA's Next Mars Rover Rolls Over Ramps
• Deadly Tides Mean Early Exit for Hot Jupiters
• NASA Opens Space Station for Biological Research f...

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NASA's Next Mars Rover Rolls Over Ramps

 

NASA's next Mars rover, Curiosity, drives up a ramp during a test at NASA's Jet Propulsion Laboratory, Pasadena, Calif., on Sept. 10, 2010. › Full image and caption

The rover Curiosity, which NASA's Mars Science Laboratory mission will place on Mars in August 2012, has been rolling over ramps in a clean room at NASA's Jet Propulsion Laboratory to test its mobility system.

Curiosity uses the same type of six-wheel, rocker-bogie suspension system as previous Mars rovers, for handling uneven terrain during drives.  Its wheels are half a meter (20 inches) in diameter, twice the height of the wheels on the Spirit and Opportunity rovers currently on Mars.

Launch of the Mars Science Laboratory is scheduled for 2011 during the period from Nov. 25 to Dec. 18. The mission is designed to operate Curiosity on Mars for a full Martian year, which equals about two Earth years.

A public lecture by Mars Science Laboratory Chief Scientist John Grotzinger, of the California Institute of Technology in Pasadena, will take place at JPL on Thursday, Sept. 16, beginning at 7 p.m. PDT Time (10 p.m. EDT). Live video streaming, supplemented by a real-time web chat to take public questions, will air on Ustream at http://www.ustream.tv/channel/nasajpl .

JPL, a division of Caltech, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington.  More information about the mission is online at: http://mars.jpl.nasa.gov/msl/ .

View my last 3 blog postings... 

• Deadly Tides Mean Early Exit for Hot Jupiters
• NASA Opens Space Station for Biological Research f...
• Caught in the Act: Fireballs Light up Jupiter

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Deadly Tides Mean Early Exit for Hot Jupiters

Bad news for planet hunters: most of the "hot Jupiters" that astronomers have been searching for in star clusters were likely destroyed long ago by their stars. In a paper accepted for publication by the Astrophysical Journal, John Debes and Brian Jackson of NASA's Goddard Space Flight Center in Greenbelt, Md., offer this new explanation for why no transiting planets (planets that pass in front of their stars and temporarily block some of the light) have been found yet in star clusters. The researchers also predict that the planet hunting being done by the Kepler mission is more likely to succeed in younger star clusters than older ones.

"Planets are elusive creatures," says Jackson, a NASA Postdoctoral Program fellow at Goddard, "and we found another reason that they're elusive."

When astronomers began to search for planets in star-packed globular clusters about 10 years ago, they hoped to find many new worlds. One survey of the cluster called 47 Tucanae (47 Tuc), for example, was expected to find at least a dozen planets among the roughly 34,000 candidate stars. "They looked at so many stars, people thought for sure they would find some planets," says Debes, a NASA Postdoctoral Program fellow at Goddard. "But they didn't."

More than 450 exoplanets (short for "extrasolar planets," or planets outside our solar system) have been found, but "most of them have been detected around single stars," Debes notes.

"Globular clusters turn out to be rough neighborhoods for planets," explains Jackson, "because there are lots of stars around to beat up on them and not much for them to eat." The high density of stars in these clusters means that planets can be kicked out of their solar systems by nearby stars. In addition, the globular clusters surveyed so far have been rather poor in metals (elements heavier than hydrogen and helium), which are the raw materials for making planets; this is known as low metallicity.

Debes and Jackson propose that hot Jupiters—large planets that are at least 3 to 4 times closer to their host stars than Mercury is to our sun—are quickly destroyed. In these cramped orbits, the gravitational pull of the planet on the star can create a tide—that is, a bulge—on the star. As the planet orbits, the bulge on the star points a little bit behind the planet and essentially pulls against it; this drag reduces the energy of the planet's orbit, and the planet moves a little closer to the star. Then the bulge on the star gets bigger and saps even more energy from the planet's orbit. This continues for billions of years until the planet crashes into the star or is torn apart by the star's gravity, according to Jackson's model of tidal orbital decay.

"The last moments for these planets can be pretty dramatic, as their atmospheres are ripped away by their stars' gravity," says Jackson. "It has even been suggested recently the hot Jupiter called WASP-12B is close enough to its star that it is currently being destroyed."

Debes and Jackson modeled what would have happened in 47 Tuc if the tidal effect were unleashed on hot Jupiters. They recreated the range of masses and sizes of the stars in that cluster and simulated a likely arrangement of planets. Then they let the stars' tides go to work on the close-in planets. The model predicted that so many of these planets would be destroyed, the survey would come up empty-handed. "Our model shows that you don't need to consider metallicity to explain the survey results," says Debes, "though this and other effects will also reduce the number of planets."

Ron Gilliland, who is at the Space Telescope Science Institute in Baltimore and participated in the 47 Tuc survey, says, "This analysis of tidal interactions of planets and their host stars provides another potentially good explanation—in addition to the strong correlation between metallicity and the presence of planets—of why we failed to detect exoplanets in 47 Tuc."

In general, Debes and Jackson's model predicts that one-third of the hot Jupiters will be destroyed by the time a cluster is a billion years old, which is still juvenile compared to our solar system (about 4-1/2 billion years old). 47 Tuc has recently been estimated to be more than 11 billion years old. At that age, the researchers expect more than 96% of the hot Jupiters to be gone.

The Kepler mission, which is searching for hot Jupiters and smaller, Earth-like planets, gives Debes and Jackson a good chance to test their model. Kepler will survey four open clusters—groups of stars that are not as dense as globular clusters—ranging from less than half a billion to nearly 8 billion years old, and all of the clusters have enough raw materials to form significant numbers of planets, Debes notes. If tidal orbital decay is occurring, Debes and Jackson predict, Kepler could find up to three times more Jupiter-sized planets in the youngest cluster than in the oldest one. (An exact number depends on the brightness of the stars, the planets' distance from the stars, and other conditions.)

"If we do find planets in those clusters with Kepler," says Gilliland, a Kepler co-investigator, "looking at the correlations with age and metallicity will be interesting for shaping our understanding of the formation of planets, as well as their continued existence after they are formed."

If the tidal orbital decay model proves right, Debes adds, planet hunting in clusters may become even harder. "The big, obvious planets may be gone, so we'll have to look for smaller, more distant planets," he explains. "That means we will have to look for a much longer time at large numbers of stars and use instruments that are sensitive enough to detect these fainter planets."

The Kepler mission is managed by NASA's Ames Research Center, Moffett Field, Calif., for the Science Mission Directorate at NASA Headquarters in Washington.

View my last 3 blog postings...

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NASA Opens Space Station for Biological Research from NIH Grants

NASA is enabling biomedical research with National Institutes of Health (NIH) grants that take advantage of the unique microgravity environment aboard the International Space Station to explore fundamental questions about important health issues.

The NIH Biomedical Research on the International Space Station (BioMed-ISS) awards are the next step in a new partnership to apply the national laboratory to research that complements NASA's own space studies. The NIH studies include research on how bones and the immune system weaken in space.

"This marks the beginning of a new era in microgravity-based research with the International Space Station turning the corner from construction to use as a new national laboratory," said Mark Uhran, assistant associate administrator for space station, NASA Headquarters in Washington.

In 2005 Congress recognized the immense promise the station holds for U.S.-led science and technology efforts. It opened the U.S. portion of the facility to federal agencies, university and private sector researchers by designating the station as a national laboratory. In addition to NIH, NASA has similar research agreements with the Departments of Defense, Agriculture and Energy and the National Science Foundation.

Scientists will conduct their experiments under a two-stage mechanism. The first is a ground-based preparatory phase to allow investigators to meet select milestones and technical requirements. The second is an experimental phase on the space station that will include preparing the experiments for launch, working with astronauts to conduct them on orbit and performing subsequent data analyses on Earth.

"BioMed-ISS offers a novel opportunity for gaining scientific insights that would not otherwise be possible through ground-based means," said Stephen I. Katz, M.D., Ph.D., director of the NIH's National Institute of Arthritis and Musculoskeletal and Skin Diseases and NIH liaison to NASA. "The beauty of this initiative is that it offers an unprecedented opportunity for benefitting human health on earth, while leveraging the American public's investment in the ISS."

NIH is hosting three rounds of competition for the initiative. The first round of grants for the ground-based phase, totaling an estimated $1,323,000, has been awarded as follows:

Paola Divieti, M.D., Ph.D., Massachusetts General Hospital/Harvard Medical School, Boston: Weight-bearing activities contribute to the development and maintenance of bone mass, while weightlessness and immobility, as experienced by the astronauts and bedridden and immobilized patients, can result in bone loss and a weakened skeleton. Osteocytes, the most common type of bone cell, are believed to have gravity-sensing abilities. These cells play a key role in bone remodeling, a process that is vital to skeletal health. In studying osteocytes in a gravity-free environment, Divieti aims to uncover new therapeutic targets for osteoporosis and related bone diseases.

Millie Hughes-Fulford, Ph.D., Northern California Institute for Research and Education, San Francisco: The immune system, which protects the body against foreign substances, is suppressed in space. A reduction in the immune response also occurs in the elderly, who, like the astronauts, are at increased risk for infection. As a former astronaut, Hughes-Fulford, a former payload specialist on the STS-40 Spacelab Life Sciences shuttle mission in 1991, aims to apply lessons learned from studies of immune cells in microgravity to a new model for investigating the loss of immune response in older women and men.

Declan McCole, Ph.D., University of California, San Diego: The movement of toxins from intestines to other organs in the body is a major source of illness in the United States. A major factor in disease stems from the ability of toxins to compromise the natural barrier function of cells in the gastrointestinal tract. Using microgravity based three-dimensional cell culture models, McCole plans to generate insights regarding the barrier properties of the intestines, and explore how the absence of gravity affects a toxin's ability to diminish this barrier.

For more information about NIH and NASA activities, visit:

http://www.niams.nih.gov/News_and_Events/NIH_NASA_Activities/

For information about the International Space Station, visit:

http://www.nasa.gov/station

For more information about NIH and its programs, visit:

http://www.nih.gov
 

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• Caught in the Act: Fireballs Light up Jupiter
• NASA Data Shed New Light About Water and Volcanoes...
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Caught in the Act: Fireballs Light up Jupiter

A fleeting bright dot on each of these images of Jupiter marks a small comet or asteroid burning up in the atmosphere. The image on the left was taken on June 3, 2010, by amateur astronomer Anthony Wesley, who was visiting a friend in Broken Hill, Australia, when he obtained the image with a 37-centimeter (14.5-inch) telescope. › Full image and caption

Amateur astronomers working with professional astronomers have spotted two fireballs lighting up Jupiter's atmosphere this summer, marking the first time Earth-based telescopes have captured relatively small objects burning up in the atmosphere of the giant planet. The two fireballs – which produced bright freckles on Jupiter that were visible through backyard telescopes – occurred on June 3, 2010, and August 20, 2010, respectively.

A new paper that includes both pros and amateurs, led by Ricardo Hueso of the Universidad del País Vasco, Bilbao, Spain, appears today in the Astrophysical Journal Letters. In the paper, astronomers estimate the object that caused the June 3 fireball was 8 to 13 meters (30 to 40 feet) in diameter. The object is comparable in size to the asteroid 2010 RF12 that flew by Earth on Wednesday, Sept. 8, and slightly larger than the asteroid 2008 TC3, which burned up above Sudan two years ago.

An impact of this kind on Earth would not be expected to cause damage on the ground. The energy released by the June 3 fireball as it collided with Jupiter's atmosphere was five to 10 times less than the 1908 Tunguska event on Earth, which knocked over tens of millions of trees in a remote part of Russia. Analysis is continuing on the Aug. 20 fireball, but scientists said it was comparable to the June 3 object.

"Jupiter is a big gravitational vacuum cleaner," said Glenn Orton, a co-author on the paper and an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It is clear now that relatively small objects, remnants of the formation of the solar system 4.5 billion years ago, still hit Jupiter frequently. Scientists are trying to figure out just how frequently."

Orton and colleagues said this kind of discovery couldn't have been made without amateur astronomers around the world, whose observations of Jupiter provide a near round-the-clock surveillance that would be impossible to do with the long lines of scientists waiting to use the large telescopes. Amateur astronomers, for example, were the first to see the dark spot that appeared on Jupiter in July 2009 as the result of an impact. Professional astronomers are still analyzing that impact.

Anthony Wesley, an amateur astronomer from Murrumbateman, Australia, who was also the first to take a picture of that dark spot on Jupiter in July 2009, was the first to see the tiny flash on June 3. Amateur astronomers had their telescopes trained on Jupiter that day because they were in the middle of "Jupiter season," when the planet is high in the sky and at its largest size, as seen by backyard telescopes.

Wesley was visiting an amateur astronomer friend about 1,000 kilometers (600 miles) away in Broken Hill, and he set a digital video camera to record images from his telescope at about 60 frames per second. He was watching the live video on a computer screen at his friend's house when he saw a two-and-a-half-second-long flash of light near the limb of the planet.

"It was clear to me straight away it had to be an event on Jupiter," he said. "I'm used to seeing other momentary flashes in the camera from cosmic ray impacts, but this was different. Cosmic ray strikes last only for one frame of video, whereas this flash gradually brightened and then faded over 133 frames."

Wesley sent a message out on his e-mail list of amateur and professional astronomers, which included Orton. After receiving Wesley's e-mail, Christopher Go of Cebu, Philippines -- who like Wesley, is an amateur astronomer -- checked his own recordings and confirmed that he had seen a flash, too.

Before Wesley's work, scientists didn't know these small-size impacts could be observed, Hueso explained. "The discovery of optical flashes produced by objects of this size helps scientists understand how many of these objects are out there and the role they played in the formation of our solar system," Hueso said.

For three days afterward, Hueso and colleagues looked for signs of the impact in high-resolution images from larger telescopes: NASA's Hubble Space Telescope, Gemini Observatory telescopes in Hawaii and Chile, the Keck telescope in Hawaii, the NASA Infrared Telescope Facility in Hawaii and the European Southern Observatory's Very Large Telescope in Chile. Scientists analyzed the images for thermal disruptions and chemical signatures seen in previous images of Jupiter impacts. In this case, they saw no signs of debris, which allowed them to limit the size of the impactor.

Based on all these images, and particularly those obtained by Wesley and Go, the astronomers were able to confirm the flash came from some kind of object – probably a small comet or asteroid – that burned up in Jupiter's atmosphere. The impactor likely had a mass of about 500 to 2,000 metric tons (1 million to 4 million pounds), probably about 100,000 times less massive than the object in July 2009.

Calculations also estimated this June 3 impact released about 1 to 4 quadrillion joules (300 million to 1 billion watt-hours) of energy. The second fireball, on Aug. 20, was detected by the amateur Japanese astronomer Masayuki Tachikawa and later confirmed by Aoki Kazuo and Masayuki Ishimaru. It flashed for about 1.5 seconds. The Keck telescope, observing less than a day later, also found no subsequent debris remnants. Scientists are still analyzing this second flash.

Although collisions of this size had never before been detected on Jupiter, some previous models predicted around one collision of this kind a year. Another predicted up to 100 such collisions. Scientists now believe the frequency must be closer to the high end of the scale.

"It is interesting to note that whereas Earth gets smacked by a 10-meter-sized object about every 10 years on average, it looks as though Jupiter gets hit with the same-sized object a few times each month," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL, who was not involved in the paper. "The Jupiter impact rate is still being refined and studies like this one help to do just that."

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