Nasa Technology News

Climatologists have long known that human-produced greenhouse gases have been the dominant drivers of Earth's observed warming since the start of the Industrial Revolution. But other factors also affect our planet's temperature. Of these, the ocean plays a dominant role. Its effects helped nudge global temperatures slightly higher in 2009, and, according to NASA scientists, could well contribute to making 2010 the warmest year on record.

Covering 71 percent of our planet's surface, the ocean acts as a global thermostat, storing energy from the sun, keeping Earth's temperature changes moderate and keeping climate change gradual. In fact, the ocean can store as much heat in its top three meters (10 feet) as the entire atmosphere does.

"The vast amount of heat stored in the ocean regulates Earth's temperature, much as a flywheel regulates the speed of an engine," said Bill Patzert, an oceanographer and climatologist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The ocean has a long history of capturing and giving up heat generated by both human activities and natural cycles; it is the thermal memory of the climate system."

Heat and moisture from the ocean are constantly exchanged with Earth's atmosphere in a process that drives our weather and climate. Scientists at NASA and elsewhere use a variety of direct and satellite-based measurements to study the interactions between the ocean and atmosphere.

"These interactions result in large-scale global climate effects, the largest of which is the El Niño-Southern Oscillation," explained Josh Willis, a JPL oceanographer and climate scientist. This climate pattern appears in the tropical Pacific Ocean roughly every four to 12 years and has a powerful impact on the ocean and the atmosphere. It can disrupt global weather and influence hurricanes, droughts and floods. It can also raise or lower global temperatures by up to 0.2 degrees Celsius (0.4 degrees Fahrenheit).

The oscillation pattern is made up of linked atmospheric and oceanic components. The atmospheric component is called the Southern Oscillation, a pattern of reversing surface air pressure that see-saws between the eastern and western tropical Pacific. The ocean's response to this atmospheric shift is known as either "El Niño" or "La Niña" (Spanish for "the little boy" and "the little girl," respectively).

Where the wind blows

During El Niño, the normally strong easterly trade winds in the tropical eastern Pacific weaken, allowing warm water to shift toward the Americas and occupy the entire tropical Pacific. Heavy rains tied to this warm water move into the central and eastern Pacific. El Niño can cause drought in Indonesia and Australia and disrupt the path of the atmospheric jet streams over North and South America, changing winter climate.

Large El Niños, such as the most powerful El Niño of the past century in 1997 to 1998, tend to force Earth's average temperatures temporarily higher for up to a year or more. Large areas of the Pacific can be one to two degrees Celsius (around two to four degrees Fahrenheit) above normal, and the average temperature of the ocean surface tends to increase. The current El Niño began last October and is expected to continue into mid-2010. Scientists at NASA's Goddard Institute of Space Studies in New York estimate that if this pattern persists, 2010 may well go down as the warmest year on record.

El Niño's cold counterpart is La Niña. During La Niña, trade winds are stronger than normal, and cold water that usually sits along the coast of South America gets pushed to the mid-equatorial region of the Pacific. La Niñas are typically associated with less moisture in the air and less rain along the coasts of the Americas, and they tend to cause average global surface temperatures to drop. The last La Niña from 2007 to 2009 helped make 2008 the coolest year of the last decade. The end of that La Niña last year and subsequent transition into an El Niño helped contribute to last year's return to near-record global temperatures.

All the ocean's a stage

Both El Niño and La Niña play out on a larger stage that operates on decade-long timescales. The Pacific Decadal Oscillation, or PDO for short, describes a long-term pattern of change in the Pacific Ocean that alternates between cool and warm periods about every five to 20 years. The PDO can intensify the impacts of La Niña or diminish the impacts of El Niño. In its "cool, negative phase," warm water, which causes higher-than-normal sea-surface heights (because warmer water expands and takes up more space), forms a horseshoe pattern that connects the north, west and south Pacific with cool water in the middle. In its "warm, positive phase," these warm and cool regions are reversed, and warm water forms in the middle of the horseshoe.

Such phase shifts of the PDO result in widespread changes in Pacific Ocean temperatures and have significant global climate implications. During the 1950s and 1960s, the PDO was strongly negative, or cool, and global temperatures seemed to level off. During most of the 1980s, 1990s and 2000s, the Pacific was locked in a strong positive, or warm, PDO phase and there were many El Niños. We are currently in the early stages of a cool PDO phase that began around 2006. Cool, negative phases tend to dampen the effects of El Niños.

Willis said the PDO, El Niño and La Niña can strongly affect global warming due to increased greenhouse gases. "These natural climate phenomena can sometimes hide global warming caused by human activities, or they can have the opposite effect of accentuating it," he explained.

With the spacecraft on the opposite side of the solar system and beyond the orbit of Mars, the trajectory correction maneuver began at 5:21 p.m. EST (2:21 p.m. PST) on Feb. 17. Stardust's rockets fired for 22 minutes and 53 seconds, changing the spacecraft's speed by 24 meters per second (54 miles per hour).

Stardust's maneuver placed the spacecraft on a course to fly by the comet just before 8:42 p.m. PST (11:42 p.m. EST) on Feb. 14, 2011 – Valentine's Day. Time of closest approach to Tempel 1 is important because the comet rotates, allowing different regions of the comet to be illuminated by the sun's rays at different times. Mission scientists want to maximize the probability that areas of interest previously imaged by NASA's Deep Impact mission in 2005 will also be bathed in the sun's rays and visible to Stardust's camera when it passes by.

"We could not have asked for a better result from a burn with even a brand-new spacecraft," said Tim Larson, project manager for the Stardust-NExT at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This bird has already logged one comet flyby, one Earth return of the first samples ever collected from deep space, over 4,000 days of flight and approximately 5.4 billion kilometers (3.4 billion miles) since launch."

Launched on Feb. 7, 1999, Stardust became the first spacecraft in history to collect samples from a comet and return them to Earth for study. While its sample return capsule parachuted to Earth in January 2006, mission controllers were placing the still viable spacecraft on a trajectory that would allow NASA the opportunity to re-use the already-proven flight system if a target of opportunity presented itself. In January 2007, NASA re-christened the mission "Stardust-NExT" (New Exploration of Tempel), and the Stardust team began a four-and-a-half year journey to comet Tempel 1. This will be humanity's second exploration of the comet – and the first time a comet has been "re-visited."

"Stardust-NExT will provide scientists the first opportunity to see the surface changes on a comet between successive visits into the inner solar system," said Joe Veverka, principal investigator of Stardust-NExT from Cornell University, Ithaca, N.Y. "We have theories galore on how each close pass to the sun causes changes to a comet. Stardust-NExT should give some teeth to some of these theories, and take a bite out of others."

Along with the high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution, and flux of dust emitted into the coma, and provide important new information on how Jupiter family comets evolve and how they formed 4.6 billion years ago.

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for the NASA Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University is the mission's principal investigator. Lockheed Martin Space Systems, Denver Colo., built the spacecraft and manages day-to-day mission operations.

For more information about Stardust-NExT, please visit:

http://stardustnext.jpl.nasa.gov

Since WISE began its scan of the entire sky in infrared light on Jan. 14, the space telescope has beamed back more than a quarter of a million raw, infrared images. Four new, processed pictures illustrate a sampling of the mission's targets -- a wispy comet, a bursting star-forming cloud, the grand Andromeda galaxy and a faraway cluster of hundreds of galaxies. The images are online at http://www.nasa.gov/mission_pages/WISE/multimedia/images20100216.html .

"WISE has worked superbly," said Ed Weiler, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington. "These first images are proving the spacecraft's secondary mission of helping to track asteroids, comets and other stellar objects will be just as critically important as its primary mission of surveying the entire sky in infrared."

One image shows the beauty of a comet called Siding Spring. As the comet parades toward the sun, it sheds dust that glows in infrared light visible to WISE. The comet's tail, which stretches about 10 million miles, looks like a streak of red paint. A bright star appears below it in blue.

"We've got a candy store of images coming down from space," said Edward (Ned) Wright of UCLA, the principal investigator for WISE. "Everyone has their favorite flavors, and we've got them all."

During its survey, the mission is expected to find perhaps dozens of comets, including some that ride along in orbits that take them somewhat close to Earth's path around the sun. WISE will help unravel clues locked inside comets about how our solar system came to be.

Another image shows a bright and choppy star-forming region called NGC 3603, lying 20,000 light-years away in the Carina spiral arm of our Milky Way galaxy. This star-forming factory is churning out batches of new stars, some of which are monstrously massive and hotter than the sun. The hot stars warm the surrounding dust clouds, causing them to glow at infrared wavelengths.

WISE will see hundreds of similar star-making regions in our galaxy, helping astronomers piece together a picture of how stars are born. The observations also provide an important link to understanding violent episodes of star formation in distant galaxies. Because NGC 3603 is much closer, astronomers use it as a lab to probe the same type of action that is taking place billions of light-years away.

Traveling farther out from our Milky Way, the third new image shows our nearest large neighbor, the Andromeda spiral galaxy. Andromeda is a bit bigger than our Milky Way and about 2.5 million light-years away. The new picture highlights WISE's wide field of view -- it covers an area larger than 100 full moons and even shows other smaller galaxies near Andromeda, all belonging to our "local group" of more than about 50 galaxies. WISE will capture the entire local group.

The fourth WISE picture is even farther out, in a region of hundreds of galaxies all bound together into one family. Called the Fornax cluster, these galaxies are 60 million light-years from Earth. The mission's infrared views reveal both stagnant and active galaxies, providing a census of data on an entire galactic community.

"All these pictures tell a story about our dusty origins and destiny," said Peter Eisenhardt, the WISE project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "WISE sees dusty comets and rocky asteroids tracing the formation and evolution of our solar system. We can map thousands of forming and dying solar systems across our entire galaxy. We can see patterns of star formation across other galaxies, and waves of star-bursting galaxies in clusters millions of light years away."