I find reading about NASA's various spacecraft always interesting. I just wish I had more time to keep up with the volume of information NASA makes available. This Cassini story is from February and is about the flyby in late Novemver 2009 of Saturn's icy moon Enceladus. I hope you enjoy this story as much as I did. - @dmgerbino

In this unique mosaic image combining high-resolution data from the imaging science subsystem and composite infrared spectrometer aboard NASA's Cassini spacecraft, pockets of heat appear along one of the mysterious fractures in the south polar region of Saturn's moon Enceladus. Image credit: NASA/JPL/GSFC/SWRI/SSI
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Newly released images from last November's swoop over Saturn's icy moon Enceladus by NASA's Cassini spacecraft reveal a forest of new jets spraying from prominent fractures crossing the south polar region and yield the most detailed temperature map to date of one fracture.

The new images from the imaging science subsystem and the composite infrared spectrometer teams also include the best 3-D image ever obtained of a "tiger stripe," a fissure that sprays icy particles, water vapor and organic compounds. There are also views of regions not well-mapped previously on Enceladus, including a southern area with crudely circular tectonic patterns.

The images and additional information are online at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

"Enceladus continues to astound," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "With each Cassini flyby, we learn more about its extreme activity and what makes this strange moon tick."

For Cassini's visible-light cameras, the Nov. 21, 2009 flyby provided the last look at Enceladus' south polar surface before that region of the moon goes into 15 years of darkness, and includes the most detailed look yet at the jets.

Scientists planned to use this flyby to look for new or smaller jets not visible in previous images. In one mosaic, scientists count more than 30 individual geysers, including more than 20 that had not been seen before. At least one jet spouting prominently in previous images now appears less powerful.

"This last flyby confirms what we suspected," said Carolyn Porco, imaging team lead based at the Space Science Institute in Boulder, Colo. "The vigor of individual jets can vary with time, and many jets, large and small, erupt all along the tiger stripes."

Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus. Image credit: NASA/JPL/SSI
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A new map that combines heat data with visible-light images shows a 40-kilometer (25-mile) segment of the longest tiger stripe, known as Baghdad Sulcus. The map illustrates the correlation, at the highest resolution yet seen, between the geologically youthful surface fractures and the anomalously warm temperatures that have been recorded in the south polar region. The broad swaths of heat previously detected by the infrared spectrometer appear to be confined to a narrow, intense region no more than a kilometer (half a mile) wide along the fracture.

In these measurements, peak temperatures along Baghdad Sulcus exceed 180 Kelvin (minus 135 degrees Fahrenheit), and may be higher than 200 Kelvin (minus 100 degrees Fahrenheit). These warm temperatures probably result from heating of the fracture flanks by the warm, upwelling water vapor that propels the ice-particle jets seen by Cassini's cameras. Cassini scientists will be testing this idea by investigating how well the hot spots correspond with the jet sources.

"The fractures are chilly by Earth standards, but they're a cozy oasis compared to the numbing 50 Kelvin (-370 Fahrenheit) of their surroundings," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground. Results like this make Enceladus one of the most exciting places we've found in the solar system."

Some of Cassini's scientists infer that the warmer the temperatures are at the surface, the greater the likelihood that jets erupt from liquid. "And if true, this makes Enceladus' organic-rich, liquid sub-surface environment the most accessible extraterrestrial watery zone known in the solar system," Porco said.

The Nov. 21 flyby was the eighth targeted encounter with Enceladus. It took the spacecraft to within about 1,600 kilometers (1,000 miles) of the moon's surface, at around 82 degrees south latitude.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md., where the instrument was built.

More details are also available at the imaging team's website http://ciclops.org and the composite infrared spectrometer team's website http://cirs.gsfc.nasa.gov.

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Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@jpl.nasa.gov

2010-061

The Mutating Mars Hoax

August 25, 2010:  It spreads, it mutates, it refuses to die.

For the seventh year in a row, the Mars Hoax is infecting email boxes around the world. Passed from one reader to another, the message states that on August 27th Mars will approach Earth and swell to the size of a full Moon. "NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN," the email declares--always in caps.

News flash: It's not true.

Here are the facts. On August 27, 2010, Mars will be 314 million km from Earth, about as far away as it can get. Mars will shine in the western sky after sunset like a tiny red star of ordinary brightness. If you didn't know it was there, you probably wouldn't notice.

The origins of the Hoax can be traced back to 2003 when Mars really did swell to unusual proportions. On August 27th of that year, Mars came within 56 million km of Earth—the nearest it has been in 60,000 years. People marveled at the orange brilliance of Mars in the night sky and crowded around telescopes for clear views of the planet's towering volcanoes, ruddy plains and glistening polar ice caps. At the height of the display, Mars was about 75 times smaller than the full Moon.

That's when "the virus" was born.

Someone, somewhere, reasoned as follows: If Mars is 75 times smaller than the Moon, then magnifying it 75 times should make it equal to the Moon. Early versions of the Hoax encouraged readers to get out their telescopes and insert a 75x eyepiece: "At a modest 75 times magnification," the message stated, "Mars will look as big as the full Moon to the naked eye."

Soon, the Hoax was vectoring around the internet, making copies of itself and mutating. Advanced versions of the virus, sleeker and less wordy than its ancestors, omitted the magnification and simply stated, "Mars will look as big as the full Moon to the naked eye!" Before long, the year was omitted, too. August 27, 2003, became August 27, and the Hoax became immortal. Indeed, years of stories contradicting the Hoax have failed to stamp it out. This is the fourth vaccination by Science@NASA alone.

Tolerant readers point out that the Mars Hoax is not really a hoax, because it is not an intentional trick. The original composer probably believed everything he or she wrote in the message. If so, even the name of the Mars Hoax is wrong!

Here's what you should do on August 27th. Go outside at sunset and face west. The bright light you see shining through the twilight is lovely Venus. Grab a pair of binoculars and scan the sky around Venus. A few degrees to the right, you'll come across a little orange star-like object. That is Mars.

Now go back inside and delete that email.

Author: Dr. Tony Phillips | Credit: Science@NASA

For additional information check out Joe Rao's article, Mars Watch: A Complete Viewing Guide on Space.com

A Puzzling Collapse of Earth's Upper Atmosphere

 

July 15, 2010:  NASA-funded researchers are monitoring a big event in our planet's atmosphere. High above Earth's surface where the atmosphere meets space, a rarefied layer of gas called "the thermosphere" recently collapsed and now is rebounding again.

"This is the biggest contraction of the thermosphere in at least 43 years," says John Emmert of the Naval Research Lab, lead author of a paper announcing the finding in the June 19th issue of the Geophysical Research Letters (GRL). "It's a Space Age record."

The collapse happened during the deep solar minimum of 2008-2009—a fact which comes as little surprise to researchers. The thermosphere always cools and contracts when solar activity is low. In this case, however, the magnitude of the collapse was two to three times greater than low solar activity could explain.

"Something is going on that we do not understand," says Emmert.

The thermosphere ranges in altitude from 90 km to 600+ km. It is a realm of meteors, auroras and satellites, which skim through the thermosphere as they circle Earth. It is also where solar radiation makes first contact with our planet. The thermosphere intercepts extreme ultraviolet (EUV) photons from the sun before they can reach the ground. When solar activity is high, solar EUV warms the thermosphere, causing it to puff up like a marshmallow held over a camp fire. (This heating can raise temperatures as high as 1400 K—hence the name thermosphere.) When solar activity is low, the opposite happens.

Lately, solar activity has been very low. In 2008 and 2009, the sun plunged into a century-class solar minimum. Sunspots were scarce, solar flares almost non-existent, and solar EUV radiation was at a low ebb. Researchers immediately turned their attention to the thermosphere to see what would happen.

How do you know what's happening all the way up in the thermosphere?

Emmert uses a clever technique: Because satellites feel aerodynamic drag when they move through the thermosphere, it is possible to monitor conditions there by watching satellites decay. He analyzed the decay rates of more than 5000 satellites ranging in altitude between 200 and 600 km and ranging in time between 1967 and 2010. This provided a unique space-time sampling of thermospheric density, temperature, and pressure covering almost the entire Space Age. In this way he discovered that the thermospheric collapse of 2008-2009 was not only bigger than any previous collapse, but also bigger than the sun alone could explain.

One possible explanation is carbon dioxide (CO₂).

When carbon dioxide gets into the thermosphere, it acts as a coolant, shedding heat via infrared radiation. It is widely-known that CO₂ levels have been increasing in Earth's atmosphere. Extra CO₂ in the thermosphere could have magnified the cooling action of solar minimum.

"But the numbers don't quite add up," says Emmert. "Even when we take CO₂ into account using our best understanding of how it operates as a coolant, we cannot fully explain the thermosphere's collapse."

According to Emmert and colleagues, low solar EUV accounts for about 30% of the collapse. Extra CO₂ accounts for at least another 10%. That leaves as much as 60% unaccounted for.

In their GRL paper, the authors acknowledge that the situation is complicated. There's more to it than just solar EUV and terrestrial CO₂. For instance, trends in global climate could alter the composition of the thermosphere, changing its thermal properties and the way it responds to external stimuli. The overall sensitivity of the thermosphere to solar radiation could actually be increasing.

"The density anomalies," they wrote, "may signify that an as-yet-unidentified climatological tipping point involving energy balance and chemistry feedbacks has been reached."

Or not.

Important clues may be found in the way the thermosphere rebounds. Solar minimum is now coming to an end, EUV radiation is on the rise, and the thermosphere is puffing up again. Exactly how the recovery proceeds could unravel the contributions of solar vs. terrestrial sources.

"We will continue to monitor the situation," says Emmert.

For more information see Emmert, J. T., J. L. Lean, and J. M. Picone (2010), Record-low thermospheric density during the 2008 solar minimum, Geophys. Res. Lett., 37, L12102.

Author: Dr. Tony Phillips | Credit: Science@NASA

 

Tom Keene ( @tomkeene_ ),

Bloomberg radio host of Bloomberg Surveillance and Bloomberg on the Economy, re-tweeted an amazing picture of the Aurora Australis (the Southern Lights) from the International Space Station. Below is the official release picture and story from NASA. Enjoy....it's awesome.

 

Starry-Eyed Hubble Celebrates 20 Years of Awe and Discovery

April 22, 2010: NASA's best-recognized, longest-lived, and most prolific space observatory zooms past a threshold of 20 years of operation this month. On April 24, 1990, the space shuttle and crew of STS-31 were launched to deploy the Hubble Space Telescope into a low Earth orbit. What followed was one of the most remarkable sagas of the space age. Hubble's unprecedented capabilities made it one of the most powerful science instruments ever conceived by humans, and certainly the one most embraced by the public. Hubble discoveries revolutionized nearly all areas of current astronomical research, from planetary science to cosmology. And, its pictures were unmistakably out of this world. This brand new Hubble photo is of a small portion of one of the largest seen star-birth regions in the galaxy, the Carina Nebula. Towers of cool hydrogen laced with dust rise from the wall of the nebula. The scene is reminiscent of Hubble's classic "Pillars of Creation" photo from 1995, but is even more striking in appearance. The image captures the top of a three-light-year-tall pillar of gas and dust that is being eaten away by the brilliant light from nearby bright stars. The pillar is also being pushed apart from within, as infant stars buried inside it fire off jets of gas that can be seen streaming from towering peaks like arrows sailing through the air.

Biggest, Deepest Crater Exposes Hidden, Ancient Moon

Shortly after the Moon formed, an asteroid smacked into its southern hemisphere and gouged out a truly enormous crater, the South Pole-Aitken basin, almost 1,500 miles across and more than five miles deep.

Image 1: This is elevation map covering the eastern portion of South Pole-Aitken basin, including the Apollo Basin, made using data from Japan’s Kaguya spacecraft. The false colors indicate height; red represents highlands, and blue represents the lowest areas. Dashed circles mark the location of the main and inner ring of Apollo. The dashed line marks the location of the topographic profile illustrated in the Image 2 below. Credit: Japan Aerospace Exploration Agency/NASA
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"This is the biggest, deepest crater on the Moon -- an abyss that could engulf the United States from the East Coast through Texas," said Noah Petro of NASA’s Goddard Space Flight Center in Greenbelt, Md. The impact punched into the layers of the lunar crust, scattering that material across the Moon and into space. The tremendous heat of the impact also melted part of the floor of the crater, turning it into a sea of molten rock.

That was just an opening shot. Asteroid bombardment over billions of years has left the lunar surface pockmarked with craters of all sizes, and covered with solidified lava, rubble, and dust. Glimpses of the original surface, or crust, are rare, and views into the deep crust are rarer still.

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