New findings from NEOWISE, the asteroid- and comet-hunting portion of NASA's Wide-field Infrared Survey Explorer mission, show that comet Hartley 2 leaves a pebbly trail as it laps the sun, dotted with grains as big as golf balls.

Previously, NASA's EPOXI mission, which flew by the comet on Nov. 4, 2010, found golf ball- to basketball-sized fluffy ice particles streaming off comet Hartley 2. NEOWISE data show that the golf ball-sized chunks survive farther away from the comet than previously known, winding up in Hartley 2's trail of debris. The NEOWISE team determined the size of these particles by looking at how far they deviated from the trail. Larger particles are less likely to be pushed away from the trail by radiation pressure from the sun.

The observations also show that the comet is still actively ejecting carbon dioxide gas at a distance of 2.3 astronomical units from the sun, which is farther away from the sun than where EPOXI detected carbon dioxide jets streaming from the comet. An astronomical unit is the average distance between Earth and the sun.

"We were surprised that carbon dioxide plays a significant role in comet Hartley 2's activity when it's farther away from the sun," said James Bauer, the lead author of a new paper on the result in the Astrophysical Journal. An abstract of the scientific paper is online at http://arxiv.org/abs/1107.2637, with the option of downloading a full PDF.

JPL manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more information visit http://www.nasa.gov/mission_pages/WISE/news/wise20110714.html

It's what Bill Patzert, a climatologist and oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., likes to call a "La Nada" – that puzzling period between cycles of the El Niño-Southern Oscillation climate pattern in the Pacific Ocean when sea surface heights in the equatorial Pacific are near average.

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. For the past three months, since last year's strong La Niña event dissipated, data collected by the U.S.-French Ocean Surface Topography Mission (OSTM)/Jason-2 oceanography satellite have shown that the equatorial Pacific sea surface heights have been stable and near average. Elsewhere, however, the northeastern Pacific Ocean remains quite cool, with sea levels much lower than normal. The presence of cool ocean waters off the U.S. West Coast has also been a factor in this year's cool and foggy spring there.

The current state of the Pacific is shown in this OSTM/Jason-2 image, based on the average of 10 days of data centered on June 18, 2011. The image depicts places where Pacific sea surface height is higher (warmer) than normal as yellow and red, while places where the sea surface is lower (cooler) than normal are shown in 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.

For oceanographers and climate scientists like Patzert, "La Nada" conditions can bring with them a high degree of uncertainty. While some forecasters (targeting the next couple of seasons) have suggested La Nada will bring about "normal" weather conditions, Patzert cautions previous protracted La Nadas have often delivered unruly jet stream patterns and wild weather swings.

In addition, some climatologists are pondering whether a warm El Niño pattern (which often follows La Niña) may be lurking over the horizon. Patzert says that would be perfectly fine for the United States.

"For the United States, there would be some positives to the appearance of El Niño this summer," Patzert said. "The parched and fire-ravaged southern tier of the country would certainly benefit from a good El Niño soaking. Looking ahead to late August and September, El Niño would also tend to dampen the 2011 hurricane season in the United States. We've had enough wild and punishing weather this year. Relief from the drought across the southern United States and a mild hurricane season would be very welcome."

Jason-2 scientists will continue to monitor Pacific Ocean sea surface heights for signs of El Niño, La Niña or prolonged neutral conditions.

For more information visit http://www.nasa.gov/topics/earth/features/lanada20110629.html

On June 7, 2011, Earth-orbiting satellites detected a flash of X-rays coming from the western edge of the solar disk. Registering only "M" (for medium) on the Richter scale of solar flares, the blast at first appeared to be a run-of-the-mill eruption--that is, until researchers looked at the movies.

"We'd never seen anything like it," says Alex Young, a solar physicist at the Goddard Space Flight Center. "Half of the sun appeared to be blowing itself to bits."

"In terms of raw power, this really was just a medium-sized eruption," says Young, "but it had a uniquely dramatic appearance caused by all the inky-dark material. We don't usually see that."

Solar physicist Angelos Vourlidas of the Naval Research Lab in Washington DC calls it a case of "dark fireworks."

"The blast was triggered by an unstable magnetic filament near the sun's surface," he explains. "That filament was loaded down with cool plasma, which exploded in a spray of dark blobs and streamers. "Cool" has a special meaning on the sun: The plasma blobs registered a temperature of 20,000 Kelvin or less. That is relatively cool. Most of the surrounding gas had temperatures between 40,000 K and 1,000,000 K.

The plasma blobs were as big as planets, many larger than Earth. They rose and fell ballistically, moving under the influence of the sun's gravity like balls tossed in the air, exploding "like bombs" when they hit the stellar surface.

Some blobs, however, were more like guided missiles. "In the movies we can see material 'grabbed' by magnetic fields and funneled toward sunspot groups hundreds of thousands of kilometers away," notes Young.

SDO also detected a shadowy shock wave issuing from the blast site. The 'solar tsunami' propagated more than halfway across the sun, visibly shaking filaments and loops of magnetism en route. [91 MB Quicktime] Long-range action has become a key theme of solar physics since SDO was launched in 2010. The observatory frequently sees explosions in one part of the sun affecting other parts. Sometimes one explosion will trigger another ... and another ... with a domino sequence of flares going off all around the star.

"The June 7th blast didn't seem to trigger any big secondary explosions, but it was certainly felt far and wide," says Young.

It's tempting to look at the movies and conclude that most of the exploded material fell back--but that wouldn't be true, according to Vourlidas. "The blast also propelled a significant coronal mass ejection (CME) out of the sun's atmosphere."

He estimates that the cloud massed about 4.5 x1015 grams, placing it in the top 5% of all CMEs recorded in the Space Age. For comparison, the most massive CME ever recorded was 1016 grams, only a factor of ~2 greater than the June 7th cloud. The amount of material that fell back to the sun on June 7 was approximately equal to the amount that flew away, Vourlidas says.

As remarkable as the June 7th eruption seems to be, Young says it might not be so rare. "In fact," he says, "it might be downright common."

Before SDO, space-based observatories observed the sun with relatively slow cadences and/or limited fields of view. They could have easily missed the majesty of such an explosion, catching only a single off-center snapshot at the beginning or end of the blast to hint at what actually happened.

If Young is right, more dark fireworks could be in the offing. Stay tuned.

For more information visit http://www.nasa.gov/mission_pages/sunearth/news/dark-fireworks.html

Scientists, photographers and amateur cloud watchers have been looking up with wonderment and puzzlement at "hole punch" clouds for decades. Giant, open spaces appear in otherwise continuous cloud cover, presenting beautiful shapes but also an opportunity for scientific investigation. A new paper published last week in Science inquires into how the holes get punched – airplanes are the culprit – and into the potential for the phenomenon's link to increased precipitation around major airports.

"It appears to be a rather widespread effect for aircraft to inadvertently cause some measureable amount of rain or snow as they fly through certain clouds," said lead author Andrew Heymsfield of the National Center for Atmospheric Research, Boulder, Co. "This is not necessarily enough precipitation to affect global climate, but it is likely to be noticeable around major airports in the midlatitudes."

NASA Langley Research Center cloud specialist Patrick Minnis was one of the co-authors on the paper. NASA satellites Aqua, Terra, CALIPSO and CloudSat were used in the analysis. The research was also partly funded by NASA grants.

Picture a layer of supercooled liquid water clouds stretching across the sky, like a sheet, in subfreezing temperatures. An airliner gaining altitude punches through the cloud layer, and leaves behind a void as if by a circular cookie-cutter. In some cases, the shape left behind is more ragged, or even more rectangular or canal-like. But the nearly perfect circle often makes for the most compelling sight in the sky. The ice particles grow at the expense of the supercooled water droplets and fall out of the cloud as snow. If the cloud layer is thin or if the water is not replenished the snow leaves a hole in the cloud.

"In other conditions, it may produce a somewhat continuous snow line," Minnis said, as has been observed around the Denver airport.

Web sites on the Internet are now devoted to collecting pictures of hole punch clouds from around the world. Scientists first reported observing hole punch clouds in the 1940s, according to the Science paper. They often lead to false reports of UFOs or rocket launches. But aside from being a notch in the belt for cloud-watchers, the "mechanisms of formation and the physics of the development, duration, and thus the extent of their effect have largely been ignored." Heymsfield and the other authors studied satellite images of hole punch clouds and then used computer models to simulate how the holes evolved after formation. Whether a plane is climbing or flying level through the cloud layer determines whether a "hole" is "punched" or a "canal" is "dug" through the clouds.

In addition to describing the physics of how planes form the holes in specific cloud types, the Science paper also looks at this "inadvertent" cloud seeding. The authors suggest that the effect is not large enough to have an impact on global climate, but that "regionally near major airports in midlatitudes during cool weather months it may lead to enhanced precipitation at the ground."

For more information visit http://www.nasa.gov/topics/earth/features/hole-punch.html