Posted on by Jason Major

Pacific Glory

An optical phenomenon known as a “glory” is seen over a cloud-covered Pacific Ocean in this image from NASA’s Aqua satellite, acquired on June 20, 2012. Although the colors may make it look like a rainbow, the process behind its formation is somewhat different.

As vortices spiral off the leeward side of Guadalupe Island, off the western coast of Baja California, a shimmering spectrum of colors highlights a glory just west of the island. Glories are created when light from the Sun reflects back toward an observer off water droplets within clouds or fog. They are often seen from airplanes as a bright ring of light encircling a silhouetted shadow of the aircraft below, but are also visible from the ground and, sometimes, even from space.

From the NASA Earth Observatory website:

Although glories may look similar to rainbows, the way light is scattered to produce them is different. Rainbows are formed by refraction and reflection; glories are formed by backward diffraction. The most vivid glories form when an observer looks down on thin clouds with droplets that are between 10 and 30 microns in diameter. The brightest and most colorful glories also form when droplets are roughly the same size.

From the ground or an airplane, glories appear as circular rings of color. The space shuttle Columbia observed a circular glory from space in 2003. In the image above, however, the glory does not appear circular. That’s because MODIS scans the Earth’s surface in swaths perpendicular to the path followed by the satellite. And since the swaths show horizontal cross sections through the rings of the glory, the glory here appears as two elongated bands of color that run parallel to the path of the satellite, rather than a full circle.

Glories always appear around the spot directly opposite the Sun, from the perspective of the viewer. This spot is called the anti-solar point. To visualize this, imagine a line connecting the Sun, a viewer, and the spot where the glory appears. In this case, the anti-solar point falls about halfway between the two colored lines of the glory.

Click here to download the full-size image.

NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response. Read more here.

Posted on by Jason Major

There’s a Hole in the Sky!

A vast hole in the cloud cover seen over the southern Pacific

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Well, not the sky exactly, but definitely in the clouds!

This image, acquired by NASA’s Aqua satellite on June 5, shows an enormous oval hole in the clouds above the southern Pacific Ocean, approximately 500 miles (800 km) off the southwestern coast of Tasmania. The hole itself is several hundred miles across, and is the result of high pressure air in the upper atmosphere.

According to Rob Gutro of NASA’s Goddard Space Flight Center, “This is a good visible example of how upper-level atmospheric features affect the lower atmosphere, because the cloud hole is right under the center of a strong area of high pressure. High pressure forces air down to the surface blocking cloud formation. In addition, the altocumulus clouds are rotating counter-clockwise around the hole, which in the southern hemisphere indicates high pressure.”

The northwestern tip of Tasmania and King Island can be seen in the upper right of the image.

The Aqua mission is a part of the NASA-centered international Earth Observing System (EOS). Launched on May 4, 2002, Aqua has six Earth-observing instruments on board, collecting a variety of global data sets about the Earth’s water cycle. Read more about Aqua here.

Posted on by Jason Major

On the Edge of Titan

Titan's haze-covered limb seen by Cassini on June 6

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Here’s a quick look at one of my favorite cosmic photo subjects – the varying layers of atmosphere that enshroud Saturn’s enormous moon Titan. The image above is a color-composite made from three raw images acquired by Cassini during its latest flyby.

On June 7 Cassini approached Titan within 596 miles (959 km) and imaged portions of the moon’s northwest quadrant with its radar instrument, as well as conducted further investigations of areas near the equator where surface changes were detected in 2010.

The image here was assembled from three raw images captured in red, green and blue visible light channels. It reveals some structure in the upper hydrocarbon haze layers that extend upwards above the moon’s opaque orange clouds — reaching 400-500 km in altitude, Titan’s atmosphere is ten times thicker than Earth’s!

The June 6 flyby was the second in a series of passes that will take Cassini into a more inclined orbit, where it will reside for the next three years as it investigates Saturn’s polar regions and obtains better views of its ring system.

Read more about the flyby here.

Image: NASA/JPL/Space Science Institute. Composite by J. Major.

Posted on by Jason Major

On The Hunt For High-Altitude Microorganisms

Design of an XCOR Lynx spacecraft (XCOR Aerospace)

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The United States Rocket Academy has announced an open call for entries in its High Altitude Astrobiology Challenge, a citizen science project that will attempt to collect samples of microbes that may be lurking in Earth’s atmosphere at the edge of space.

Earth’s biosphere has been discovered to extend much higher than once thought — up to 100,000 feet (30,480 meters) above the planet’s surface. Any microorganisms present at these high altitudes could be subject to the mutating effects of increased radiation and transported around the globe in a sort of pathogenic jet-stream.

What sort of microbes may exist at the upper reaches of the atmosphere?

Citizens in Space, a project run by the U.S. Rocket Academy, is offering a $10,000 prize for the development of an open-source and replicable  collection device that could successfully retrieve samples of high-altitude microorganisms, and could fly as a payload aboard an XCOR Lynx spacecraft.

XCOR Aerospace is a private California-based company that has developed the Lynx, a reusable launch vehicle that has suborbital flight capabilities. Low-speed test flights are expected to commence later this year, with incremental testing to take place over the following months.

Any proposed microbe collection devices would have to fit within the parameters of the Lynx’s 2kg Aft Cowling Port payload capabilities — preferably a 10 x 10 x 20 cm CubeSat volume — and provide solutions for either its retraction (in the case of extended components) or retrieval (in the case of ejected hardware.)

The contest is open to any US resident or non-government team or organization, and submissions are due by February 13, 2013. The chosen design will fly on 10 contracted Lynx flights in late 2013 or early 2014, and possibly even future missions.

Find out more about the challenge on the Citizens in Space site here, and check out an animation of the XCOR Lynx spacecraft below:

Posted on by Jason Major

Antarctica’s Ice Being Eaten Away From Below

The 820-foot-wide crack in Antarctica's Pine Island Glacier, seen from DC-8 during Operation IceBridge (Credit: NASA/DMS)


Data collected from a NASA ice-watching satellite reveal that the vast ice shelves extending from the shores of  western Antarctica are being eaten away from underneath by ocean currents, which have been growing warmer even faster than the air above.

The animation above shows the circulation of ocean currents around the western Antarctic ice shelves. The shelf thickness is indicated by the color; red is thicker (greater than 550 meters), while blue is thinner (less than 200 meters).

Launched in January 2003, NASA’s ICESat (Ice, Cloud and land Elevation Satellite) studied the changing mass and thickness of Antarctica’s ice from its location in polar orbit. An international research team used over 4.5 million surface height measurements collected by ICESat’s GLAS (Geoscience Laser Altimeter System) instrument from Oct. 2005 to 2008. They concluded that 20 of the 54 shelves studied — nearly half — were losing thickness from underneath.

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Most of the melting ice shelves are located in west Antarctica, where the flow of inland glaciers to the sea has also been accelerating — an effect that can be compounded by thinning ice shelves which, when grounded to the offshore seabed, serve as dams to hold glaciers back.

Melting of ice by ocean currents can occur even when air temperature remains cold, maintaining a steady process of ice loss — and eventually increased sea level rise.

“We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt,” said Hamish Pritchard of the British Antarctic Survey in Cambridge and the study’s lead author . “The oceans can do all the work from below.”

The study also found that Antarctica’s winds are shifting in response to climate change.

“This has affected the strength and direction of ocean currents,” Pritchard said. “As a result warm water is funnelled beneath the floating ice. These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”

ICESat completed operations in 2010 and was decommissioned in August of that year. Its successor ICESat-2 is anticipated to launch in 2016.

Read more on NASA’s news release here.

Animation credit: NASA/Goddard CGI Lab

Posted on by Jason Major

Saturn’s “Wispy” Moon Has An Oxygen Atmosphere

Cassini has detected molecular oxygen ions around Saturn's icy Dione

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There’s oxygen around Dione, a research team led by scientists at New Mexico’s Los Alamos National Laboratory announced on Friday. The presence of molecular oxygen around Dione creates an intriguing possibility for organic compounds — the building blocks of life — to exist on other outer planet moons.

Dione's signature "wispy lines" are actually the bright walls of long cliff faces. (NASA/JPL/SSI)

One of Saturn’s 62 known moons, Dione (pronounced DEE-oh-nee) is 698 miles (1,123 km) in diameter. It orbits Saturn at about the same distance that our Moon orbits Earth. Heavily cratered and crisscrossed by long, bright scarps, Dione is made mostly of water ice and  rock. It makes a complete orbit of Saturn every 2.7 days.

Data acquired during a flyby of the moon by the Cassini spacecraft in 2010 have been found by the Los Alamos researchers to confirm the presence of molecular oxygen high in Dione’s extremely thin atmosphere — so thin, in fact, that scientists prefer the term exosphere.

While you couldn’t take a deep breath on Dione, the presence of O2 indicates a dynamic process in action.

“The concentration of oxygen in Dione’s atmosphere is roughly similar to what you would find in Earth’s atmosphere at an altitude of about 300 miles,” said Robert Tokar, researcher at Los Alamos National Laboratory and lead author of the paper published in Geophysical Research Letters.  “It’s not enough to sustain life, but—together with similar observations of other moons around Saturn and Jupiter—these are definitive examples of a process by which a lot of oxygen can be produced in icy celestial bodies that are bombarded by charged particles or photons from the Sun or whatever light source happens to be nearby.”

On Dione the energy source is Saturn’s powerful magnetic field. As the moon orbits the giant planet, charged ions in Saturn’s magnetosphere slam into the surface of Dione, stripping oxygen from the ice on its surface and crust. This molecular oxygen (O2) flows into Dione’s exosphere, where it is then steadily blown into space by — once again — Saturn’s magnetic field.

Cassini’s instruments detected the oxygen in Dione’s wake during an April 2010 flyby.

Molecular oxygen, if present on other moons as well (say, Europa or Enceladus) could potentially bond with carbon in subsurface water to form the building blocks of life. Since there’s lots of water ice on moons in the outer solar system, as well as some very powerful magnetic fields emanating from planets like Jupiter and Saturn, there’s no reason to think there isn’t more oxygen to be found… in our solar system or elsewhere.

Read the news release from the Los Alamos National Laboratory here.

 

Image credits: NASA/JPL/Space Science Institute. Research citation: Tokar, R. L., R. E. Johnson, M. F. Thomsen, E. C. Sittler, A. J. Coates, R. J. Wilson, F. J. Crary, D. T. Young, and G. H. Jones (2012), Detection of exospheric O2+ at Saturn’s moon Dione, Geophys. Res. Lett., 39, L03105, doi:10.1029/2011GL050452.

 

Posted on by Jason Major

Beneath the Surface: Seeing Jupiter’s Hidden Storms

Juno will repeatedly dive between the planet and its intense belts of charged particle radiation, coming only 5,000 kilometers (about 3,000 miles) from the cloud tops at closest approach. (NASA/JPL-Caltech)


Launched on August 5, 2011, NASA’s Juno spacecraft will arrive at Jupiter in 2016 to study its magnetic field and atmosphere. Using its suite of science instruments Juno will peer inside the gas giant’s thick clouds, revealing hidden structures and powerful storms. To help people visualize what it means to see the invisible, JPL’s visual strategist Dan Goods created the exhibit above, titled Beneath the Surface. It’s an installation of lights, sound and fog effects that dramatically recreates what Juno will experience as it orbits Jupiter. By using their cell phone cameras, viewers can see lightning “storms” hidden beneath upper, opaque layers of “atmosphere”… in much the same way Juno will.

Goods explains: “Humans are only able to see a little, tiny sliver of what there is available in light. There’s gamma rays, microwaves, ultraviolet and infrared light also, and infrared is close enough to the visible part of the spectrum that cell phone cameras can pick it up. Cell phones normally produce more grainy photos at night because they don’t try to cut out the infrared light the way higher-end digital cameras do so in this case, the cell phone cameras are an advantage.” (Via the Pasadena Weekly.)

I had a chance to meet Dan Goods during a Tweetup event for the Juno launch at Kennedy Space Center. He’d brought a table that had magnetic elements set beneath a flat black surface, and by passing a handheld magnet over the table you could “detect” the different magnetic fields… in some cases rather strongly, even though they were all obviously invisible. It was an ingenious way that Juno’s abilities could be demonstrated in a “hands-on” manner.

Watch my video of the Juno launch from the KSC press site.

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Beneath the Surface takes that kind of demonstration to an entirely new level.

“I love to work with the world of things that are right in front of you but you just can’t see,” Goods said. “With Juno, there’s all this structure just under the surface of Jupiter, but humans can develop tools that help us understand things we’d never have seen before.”

The exhibit was installed at the Pasadena Museum of California Art until January 8. It will now travel to science museums around the country.

Video: watch how the exhibit was constructed.

Juno’s primary goal is to improve our understanding of Jupiter’s formation and evolution. The spacecraft will spend a year investigating the planet’s origins, interior structure, deep atmosphere and magnetosphere. Juno’s study of Jupiter will help us to understand the history of our own solar system and provide new insight into how planetary systems form and develop in our galaxy and beyond.

Explore the Juno mission more at http://missionjuno.swri.edu/.

Posted on by Paul Scott Anderson

Titan’s Layered Atmosphere is Surprisingly Earth-Like

Titan's thick, smog-like upper atmosphere obscures our view of the lower atmosphere and surface. The much smaller moon Enceladus is also seen in this image. Credit: NASA/JPL

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Titan, the largest moon of Saturn, is in some ways the most Earth-like world in the solar system, with a thick nitrogen atmosphere, rain, rivers, lakes and seas. Albeit it is much colder, and liquid methane/ethane takes the place of water, but the hydrological processes are quite similar to those here. There may, however, also be a liquid water-ammonia ocean below the surface. Now, new research suggests that Titan is Earth-like in another way as well, with a layered lower atmosphere similar to ours.

It’s been long known that Titan has a dense atmosphere; you can’t even see the surface due to a thick smog-like upper haze composed of hydrocarbons. As it turns out, the lower atmosphere has two distinct layers; the lowest layer, like on Earth, is known as the boundary layer, which has the most influence on climate and weather.

There has been a lot of uncertainty about the nature of Titan’s lower atmosphere, so scientists developed a 3-D climate model to try to answer those questions – previous data from Voyager 1, Cassini and Huygens had led to conflicting results. This was largely due to the fact that the lower atmosphere can’t be observed directly because of the opaque upper atmosphere. The new climate model shows that there are two lower layers which are distinct from each other as well as from the upper atmosphere. The lowest boundary layer is about 800 metres (2,600 feet) thick while the next layer is about 2 kilometers (1.2 miles) deep.

According to Paulo Penteado from the Institute of Astronomy, Geophysics and Atmospheric Science at the University of São Paulo in Brazil, “The most interesting point is that their model shows the presence of two different boundaries, the lower one caused by the daily heating and cooling of the surface – and varying in height during the day – and the higher one caused by the seasonal change in global air circulation.”

Benjamin Charnay from the French National Centre for Scientific Research (CNRS) in Paris and lead author of the study, adds: “This unprecedented organisation of the boundary layer has several consequences. It controls the atmospheric circulation and wind patterns in the lower atmosphere; it controls the size and spacing of dunes on Titan; it could imply the formation of boundary layer clouds (of methane on Titan). Such clouds seem to have been observed but not explained.”

These differences are surprising, since Titan receives far less solar energy from the Sun than Earth does. This solar insulation, which determines temperature variations in the atmosphere, is 1,000 times weaker on Titan than on Earth. Such a dynamic atmosphere on Titan was unexpected, but it may hold clues as to the formation of our own atmosphere. This could also be extrapolated to exoplanets; if a smaller world so far from the Sun can have unanticipated Earth-like conditions, how many exoplanets, now being discovered by the thousands, could as well?

The findings were published in the January 15, 2012 issue of Nature Geoscience.

From the abstract:

“We conclude that Titan’s troposphere is well structured, featuring two boundary layers that control wind patterns, dune spacing and cloud formation at low altitudes.”

The abstract and article are here. The full article is available for $18.00 US or by subscription to Nature Geoscience.

Posted on by Jason Major

Titan’s Colorful Crescent

Titan's thick atmosphere shines in backlight sunlight

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Made from one of the most recent Cassini images, this is a color-composite showing a backlit Titan with its dense, multi-layered atmosphere scattering sunlight in different colors. Titan’s atmosphere is made up of methane and complex hydrocarbons and is ten times as thick as Earth’s. It is the only moon in our solar system known to have a substantial atmosphere.

Titan’s high-level hydrocarbon haze is nicely visible as a pale blue band encircling the moon.

Color image of Titan and sister moon Dione, seen by Cassini on Dec. 10. (NASA/JPL/SSI and J. Major)

At 3,200 (5,150 km) miles wide, Titan is one of the largest moons in the solar system – even larger than Mercury. Its thick atmosphere keeps a frigid and gloomy surface permanently hidden beneath opaque clouds of methane and hydrocarbons.

This image was made from three raw images acquired by Cassini on December 13. The raw images were in the red, green and blue visible light channels, and so the composited image you see here approximates true color.

This particular flyby of Titan (designated T-79) gave Cassini’s instruments a chance to examine Titan in many different wavelengths, as well as map its surface and measure its atmospheric temperature. Cassini passed by the giant moon at a distance of about 2,228 miles (3,586 kilometers) traveling 13,000 mph (5.8 km/sec). Read more on the flyby page here.

Credit: NASA / JPL / Space Science Institute. Edited by Jason Major.

See more color-composite images of Titan and other moons of Saturn on my Flickr set here.

Posted on by Jason Major

What is Airglow?

Recent photo from the ISS showing the airglow layer

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In many of the photos that we have featured recently from astronauts aboard the International Space Station, a glowing greenish-yellow band can be seen just above Earth’s limb. I’ve been asked before what this is, so I thought I’d explain it here. This is a phenomenon known as “airglow”.

A photochemical reaction that occurs high in the atmosphere, airglow is the result of various atoms, molecules and ions that get excited (chemistry-excited, that is… not “whee!”-excited) by ultraviolet radiation from the Sun and then release that energy as visible – as well as infrared – light when they return to their “normal” state. It’s not entirely unlike glow-in-the-dark toys or paint!

This light is most visible to the crew of the ISS when it is orbiting over the night side of the planet, and thus is seen in images like the one above. It appears like a thin band because viewing the atmosphere at a shallow angle – rather than directly down through it – increases the airglow layer’s relative visibility.

Most of visible airglow comes from oxygen atoms and molecules, which glow green… as commonly seen in the aurora. Other contributing elements include sodium and nitrogen. While present in the atmosphere at all layers, the region that glows visibly is typically constrained to a narrow band 85 – 95km (53-60 miles) high. The band itself is usually about 6 – 10km (4-6 miles) wide. The reason for this is that below those heights the atoms and molecules are more concentrated and collide more readily, releasing their energy sooner, and above it the density of the atoms is too low to do much colliding at all (to put it very simply.)

There are a lot of other factors involved with airglow as well, such as temperature and altitude, as well as different kinds of airglow depending on when in the day they occur. Nightglow is not exactly the same as dayglow, and then there’s even twilightglow… one could say there’s a lot glowing on in the upper atmosphere!

I’m here all week, folks.

You can read more about airglow in this informative article by the Institute of Astronomy and Astrophysics (Instituto de Astronomía y Física del Espacio) in Buenos Aires. Image credit: NASA.