Posted on by Jason Major

Photo Treat: Enceladus, Titan and Saturn’s Rings

Color-composite image from Cassini raw data acquired on March 12, 2012. (NASA/JPL/SSI/J. Major)

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Little Enceladus and enormous Titan are seen on either side of Saturn’s rings in this image, a color-composite made from raw images acquired by Cassini on March 12, 2012. The original images were taken in red, green and blue color channels, and with a little Photoshop editing I combined them into a roughly true-color view of what Cassini saw as it passed within 1,045,591 km of Enceladus.

Follow along with the Cassini mission here.

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

Posted on by Tammy Plotner

Weekly SkyWatcher’s Forecast – March 19-25, 2012

NGC 2539 - Credit: Palomar Observatory Courtesy of Caltech

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Greetings, fellow SkyWatchers! The week starts off with new Moon and the perfect opportunity to do a Messier Marathon. The planets continue to dazzle as we not only celebrate the Vernal Equinox, but the March Geminid meteor shower as well! If that doesn’t get your pulsar racing – nothing will. It’s time to get out your binoculars and telescopes and meet me in the backyard!

Monday, March 19 – Right now the Moon is between the Earth and the Sun, and you know what that means…New Moon! Tonight we’ll start in northern Puppis and collect three more Herschel studies as we begin at Alpha Monoceros and drop about four fingerwidths southeast to 19 Puppis.

NGC 2539 (Right Ascension: 8 : 10.7 – Declination: -12 : 50) averages around 6th magnitude and is a great catch for binoculars as an elongated hazy patch with 19 Puppis on the south side. Telescopes will begin resolution on its 65 compressed members, as well as split 19 Puppis – a wide triple. Shift about 5 degrees southwest and you find NGC 2479 (Right Ascension: 7 : 55.1 – Declination: -17 : 43) directly between two finderscope stars. At magnitude 9.6 it is telescopic only and will show as a smallish area of faint stars at low power. Head another degree or so southeast and you’ll encounter NGC 2509 (Right Ascension: 8 : 00.7 – Declination: -19 : 04) – a fairly large collection of around 40 stars that can be spotted in binoculars and small telescopes.

Tuesday, March 20 – Today is Vernal Equinox, one of the two times of the year that day and night become equal in length. From this point forward, the days will become longer – and our astronomy nights shorter! To the ancients, this was a time a renewal and planting – led by the goddess Eostre. As legend has it, she saved a bird whose wings were frozen from the winter’s cold, turning it into a hare which could also lay eggs. What a way to usher in the northern spring!

With the Moon still out of the picture, let’s finish our study of the Herschel objects in Puppis. Only three remain, and we’ll begin by dropping south-southeast of Rho and center the finder on a small collection of stars to locate NGC 2489 (Right Ascension: 7 : 56.2 – Declination: -30 : 04). At magnitude 7, this bright collection is worthy of binoculars, but only the small patch of stars in the center is the cluster. Under aperture and magnification you’ll find it to be a loose collection of around two dozen stars formed in interesting chains.

The next are a north-south oriented pair around 4 degrees due east of NGC 2489. You’ll find the northernmost – NGC 2571 (Right Ascension: 8 : 18.9 – Declination: -29 : 44) – at the northeast corner of a small finderscope or binocular triangle of faint stars. At magnitude 7, it will show as a fairly bright hazy spot with a few stars beginning to resolve with around 30 mixed magnitude members revealed to aperture. Less than a degree south is NGC 2567 (Right Ascension: 8 : 18.6 – Declination: -30 : 38). At around a half magnitude less in brightness, this rich open cluster has around 50 members to offer the larger telescope, which are arranged in loops and chains.

Congratulations on completing these challenging objects!

Are you up for another challenge? Then test your ability to judge magnitude as Mars has now dimmed to approximately -1.0. Does it look slightly different in size and brightness than it did a week or so ago? Keep watching!

Wednesday, March 21 – Take your telescopes or binoculars out tonight to look just north of Xi Puppis for a celebration of starlight known as M93 (Right Ascension: 7 : 44.6 – Declination: -23 : 52). Discovered in March of 1781 by Charles Messier, this bright open cluster is a rich concentration of various magnitudes that will simply explode in sprays of stellar fireworks in the eyepiece of a large telescope. Spanning 18 light-years of space and residing more than 3400 light-years away, it contains not only blue giants, but lovely golds as well. Jewels in the night…

Thursday, March 22 – Today in 1799 Friedrich Argelander was born. He was a compiler of star catalogues, studied variable stars and created the first international astronomical organization.

Tonight let’s celebrate no Moon and have a look at an object from an alternative catalog that was written by Lacaille, and which is about two fingerwidths south of Eta Canis Majoris.

Also known as Collinder 140, Lacaille’s 1751 catalog II.2 “nebulous star cluster” is a real beauty for binoculars and very low power in telescopes. More than 50% larger than the Full Moon, it contains around 30 stars and may be as far as 1000 light-years away. When re-cataloged by Collinder in 1931, its age was determined to be around 22 million years. While Lacaille noted it as nebulous, he was using a 15mm aperture reflector, and it is doubtful that he was able to fully resolve this splendid object. For telescope users, be sure to look for easy double Dunlop 47 in the same field.

Now, kick back and enjoy a spring evening with two meteor showers. In the northern hemisphere, look for the Camelopardalids. They have no definite peak, and a screaming fall rate of only one per hour. While that’s not much, at least they are the slowest meteors – entering our atmosphere at speeds of only 7 kilometers per second!

Far more interesting to both hemispheres will be the March Geminids which peak tonight. They were first discovered and recorded in 1973 and then confirmed in 1975. With a much faster fall rate of about 40 per hour, these slower than normal meteors will be fun to watch! When you see a bright streak, trace it back to its point of origin. Did you see a Camelopardalid, or a March Geminid?

Friday, March 23 – Today in 1840, the first photograph of the Moon was taken. The daguerreotype was exposed by American astronomer and medical doctor J. W. Draper. Draper’s fascination with chemical responses to light also led him to another first – a photo of the Orion Nebula.

Our target for tonight is an object that’s better suited for southern declinations – NGC 2451 (Right Ascension: 7 : 45.4 – Declination: -37 : 58). As both a Caldwell object (Collinder 161) and a southern skies binocular challenge, this colorful 2.8 magnitude cluster was probably discovered by Hodierna. Consisting of about 40 stars, its age is believed to be around 36 million years. It is very close to us at a distance of only 850 light-years. Take the time to closely study this object – for it is believed that due to the thinness of the galactic disk in this region, we are seeing two clusters superimposed on each other.

With the Moon out of the picture early, why not get caught up in a galaxy cluster study – Abell 426. Located just 2 degrees east of Algol in Perseus, this group of 233 galaxies spread over a region of several degrees of sky is easy enough to find – but difficult to observe. Spotting Abell galaxies in Perseus can be tough in smaller instruments, but those with large aperture scopes will find it worthy of time and attention.

At magnitude 11.6, NGC 1275 (Right Ascension: 3 : 19.8 – Declination: +41 : 31) is the brightest of the group and lies physically near the core of the cluster. Glimpsed in scopes as small as 150 mm aperture, NGC 1275 is a strong radio source and an active site of rapid star formation. Images of the galaxy show a strange blend of a perfect spiral being shattered by mottled turbulence. For this reason NGC 1275 is thought to be two galaxies in collision. Depending on seeing conditions and aperture, galaxy cluster Abell 426 may reveal anywhere from 10 to 24 small galaxies as faint as magnitude 15. The core of the cluster is more than 200 million light-years away, so it’s an achievement to spot even a few!

Saturday, March 24 – Today is the birthday of Walter Baade. Born in 1893, Baade was the first to resolve the Andromeda galaxy’s individual stars using the Hooker telescope during World War II blackout times, and he also developed the concept of stellar populations. He was the first to realize that there were two types of Cepheid variables, thereby refining the cosmic distance scale. He is also well known for discovering an area towards our galactic center which is relatively free of dust, now known as “Baade’s Window.”

Just after sunset, you really need to take a look out your western window for a really beautiful bit of scenery. As the sky darkens, look for the very tender crescent Moon lit with “Earthshine”. Above it you will see bright Jupiter. Above that you will see blazing Venus. And, if that’s not enough, just a little higher will bring you to the Pleiades! What a great way to start a weekend evening!

With the Moon so near the horizon, we have only a short time to view its features. Tonight let’s start with a central feature – Langrenus – and continue further south for crater Vendelinus. Spanning 92 by 100 miles and dropping 14,700 feet below the lunar surface, Vendelinus displays a partially dark floor with a west wall crest catching the brilliant light of an early sunrise. Notice also that its northeast wall is broken by a younger crater – Lame. Head’s up! It’s an Astronomical League challenge.

Once the Moon has set, revisit M46 in Puppis – along with its mysterious planetary nebula NGC 2438. Follow up with a visit to neighboring open cluster M47 – two degrees west-northwest. M47 may actually seem quite familiar to you already. Did you possibly encounter it when originally looking for M46? If so, then it’s also possible that you met up with 6.7 magnitude open cluster NGC 2423 (Right Ascension: 7 : 37.1 – Declination: -13 : 52), about a degree northeast of M47 and even dimmer 7.9 magnitude NGC 2414 (Right Ascension: 7 : 33.3 – Declination: -15 : 27 ) as well. That’s four open clusters and a planetary nebula all within four square arc-minutes of sky. That makes this a cluster of clusters!

Let’s return to study M47. Observers with binoculars or using a finderscope will notice how much brighter, and fewer, the stars of M47 are when compared to M46. This 12 light-year diameter compact cluster is only 1600 light-years away. Even as close as it is, not more than 50 member stars have been identified. M47 has about one tenth the stellar population of larger, denser, and three times more distant, M46.

Of historical interest, M47 was “discovered” three times: first by Giovanni Batista Hodierna in the mid-17th century, then by Charles Messier some 17 years later, and finally by William Herschel 14 years after that. How is it possible that such a bright and well-placed cluster needed “re-discovery?” Hodierna’s book of observations didn’t surface until 1984, and Messier gave the cluster’s declination the wrong sign, making its identification an enigma to later observers – because no such cluster could be found where Messier said it was!

Sunday, March 25 – Today in 1655, Titan – Saturn’s largest satellite – was discovered by Christian Huygens. He also discovered Saturn’s ring system during this same year. 350 years later, the probe named for Huygens stunned the world as it reached Titan and sent back information on this distant world. How about if we visit Saturn? You’ll find the creamy yellow planet located about a fistwidth northwest of bright, white Spica! Even a small telescope will reveal Titan, but remember… it orbits well outside the ring plane, so don’t mistake it for a background star! While you’re there, look closely around the ring edges for the smaller moons. A 4.5” telescope can easily show you three of them. How about the shadow the rings on the planet’s surface? Or how about the shadow of the planet on the rings? Is the Cassini division visible? If you have a larger telescope, look for other ring divisions as well. All are part and parcel of viewing incredible Saturn!

If you missed yesterday evening’s scenic line-up, don’t despair. Just after the Sun sets tonight – and above the western horizon – you’ll find the young Moon very closely paired with Jupiter. Keep traveling eastward (up) and you’ll encounter Venus. Continue east and the next stop is M45. Watch in the days ahead as the Moon sweeps by, continuing to provide us with a show! Need more? Then check out Leo and Mars! You’ll find a great triangulation of Regulus to the west, Mars to the east and Algieba to the north. If you didn’t know better, you’d almost swear the Lion swallowed the red planet.

Tonight let’s return to our previous studies of the Moon and revisit a challenging crater. Further south than Vendelinus, look for another large, mountain-walled plain named Furnerius, located not too far from the terminator. Although it has no central peak, its walls have been broken numerous times by many smaller impacts. Look at a rather large one just north of central on the crater floor. If skies are stable, power up and search for a rima extending from the northern edge. Keep in mind as you observe that our own Earth has been pummeled just as badly as its satellite.

On this day in 1951, 21 cm wavelength radiation from atomic hydrogen in the Milky Way was first detected. 1420 MHz H I studies continue to form the basis of a major part of modern radio astronomy. If you would like to have a look at a source of radio waves known as a pulsar, then aim your binoculars slightly more than a fistwidth east of bright Procyon. The first two bright stars you encounter will belong to the constellation of Hydrus and you will find pulsar CP0 834 just above the northernmost – Delta.

Unitl next week? May all your journeys be at light speed!

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

Moons Large and Small

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It may be one of the best images from Cassini yet this year! Cloud-covered Titan and tiny Prometheus (can you see it just above the rings on the right?) are literally dwarfed by their parent Saturn in an image captured on Jan. 5, 2012.

Prometheus’ pinpoint shadow can also be seen on Saturn’s cloud tops, just inside the thin, outermost F ring shadow at bottom left.

The two moons themselves couldn’t be more different; Titan, 3,200 miles (5,150 km) wide, is wrapped in a nitrogen and methane atmosphere ten times thicker than Earth’s and is covered with vast plains of dark hydrocarbon dunes and crisscrossed by rivers of liquid methane.

Prometheus imaged by Cassini in Dec. 2009.

Prometheus, on the other hand, is a potato-shaped shepherd moon 92 miles long and 53 miles wide (148 x 53 km) that orbits Saturn just inside the narrow, ropy F ring. While it doesn’t have an atmosphere, it does create some impressive effects on the icy material in the ring!

Another moon, Pandora, casts its shadow onto Saturn just outside the F ring shadow at bottom center. 50 miles (80 km) wide, Pandora shepherds the outer edge of the F ring but is itself not visible in this image. Watch an animation here.

This image was featured on the Cassini Imaging Central Laboratory for Operations (CICLOPS) website on Feb. 28, 2012. The view looks toward the southern, unilluminated side of the rings from about 1 degree below the ringplane.

Image credit: NASA / JPL / Space Science Institute.

Posted on by Jason Major

A Balanced Budget on Titan

Titan and Dione seen on December 10, 2011 by the Cassini spacecraft. (NASA/JPL/SSI/J. Major)

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It’s been said many times that the most Earthlike world in our solar system is not a planet at all, but rather Saturn’s moon Titan. At first it may not seem obvious why; being only a bit larger than the planet Mercury and coated in a thick opaque atmosphere containing methane and hydrocarbons, Titan sure doesn’t look like our home planet. But once it’s realized that this is the only moon known to even have a substantial atmosphere, and that atmosphere creates a hydrologic cycle on its surface that mimics Earth’s – complete with weather, rain, and gully-carving streams that feed liquid methane into enormous lakes – the similarities become more evident. Which, of course, is precisely why Titan continues to hold such fascination for scientists.

Now, researchers have identified yet another similarity between Saturn’s hazy moon and our own planet: Titan’s energy budget is in equilibrium, making it much more like Earth than the gas giant it orbits.

A team of researchers led by Liming Li of the Department of Earth and Atmospheric Sciences at the University of Houston in Texas has completed the first-ever investigation of the energy balance of Titan, using data acquired by telescopes and the Cassini spacecraft from 2004 to 2010.

Energy balance (or “budget”) refers to the radiation a planet or moon receives from the Sun versus what it puts out. Saturn, Jupiter and Neptune emit more energy than they receive, which indicates an internal energy source. Earth radiates about the same amount as it receives, so it is said to be in equilibrium… similar to what is now shown to be the case for Titan.

Blue hazes hover high above thicker orange clouds over Titan's south pole (NASA/JPL/SSI)

The energy absorption and reflection rates of a planet’s – or moon’s! – atmosphere are important clues to the state of its climate and weather. Different balances of energy or changes in those balances can indicate climate change – global cooling or global warming, for instance.

Of course, this doesn’t mean Titan is a balmy world. At nearly 300 degrees below zero (F) it has an environment that even the most extreme Earth-based life would find inhospitable. Although Titan’s atmosphere is ten times thicker than Earth’s its composition is very different, permitting easy passage of infrared radiation (a.k.a. “heat”) and thus exhibits an “anti-greenhouse” effect, unlike Earth or, on the opposite end of the scale, Venus.

Still, some stable process is in place on Saturn’s moon that allows for distribution of solar energy across its surface, within its atmosphere and back out into space. With results due in from Cassini from a flyby on Jan. 2, perhaps there will soon be even more clues as to what that may be.

Read more about Earth’s changing energy budget here.

The team’s report was published in the AGU’s Geophysical Research Letters on December 15, 2011. Li, L., et al. (2011), The global energy balance of Titan, Geophys. Res. Lett., 38, L23201, doi:10.1029/2011GL050053.

Posted on by Nancy Atkinson

Colorful Holiday Treats from Saturn

The moons Titan and Dione are photographed with rings and Saturn in the background. Credit: NASA/JPL-Caltech/Space Science Institute

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“Hey! Look what our Santa at Saturn has sent our way!” said Carolyn Porco, the Cassini imaging team lead, in a post on Twitter. This wonderful collection of just-released colorful images from the Saturn system are a holiday gift from the Cassini and CICLOPS (Cassini Imaging Central Laboratory for Operations)team.

Above, Saturn’s third-largest moon, Dione, can be seen through the haze of the planet’s largest moon, Titan, in this view of the two posing before the planet and its rings from NASA’s Cassini spacecraft.

More treats below!

Saturn's moon Tethys, with its stark white icy surface, peeps out from behind the larger, hazy, colorful Titan in this view of the two moons obtained by NASA's Cassini spacecraft. Saturn's rings lie between the two. Credit: NASA/JPL-Caltech/Space Science Institute
These views from NASA's Cassini spacecraft look toward the south polar region of Saturn's largest moon, Titan, and show a depression within the moon's orange and blue haze layers near the south pole. Credit: NASA/JPL-Caltech/Space Science Institute
The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
Saturn's largest moon, Titan, appears deceptively small paired here with Dione, Saturn's third-largest moon, in this view from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

To see more details and larger versions of these images, visit the CICLOPS website. (And thanks, Carolyn and team for the beautiful gifts!)

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

Enceladus Gives Cassini Some Radar Love

New radar images from Encealdus' south pole show high amounts of surface texturing. NASA/JPL-Caltech/SSI.

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Cassini’s done it again! Soaring over Saturn’s moon Enceladus back on November 6, the spacecraft obtained the highest-resolution images yet of the moon’s south polar terrain, revealing surface details with visible, infrared and radar imaging that have never been seen before.

Of particular interest are new image swaths acquired by the spacecraft’s synthetic-aperture radar (SAR) instrument, which has never before been used on Enceladus. The radar, which is highly sensitive to surface textures, reveals some extremely bright regions that have surprised scientists.

Detail of the radar-imaged area (enlarged). NASA/JPL-Caltech/SSI.

“It’s puzzling why this is some of the brightest stuff Cassini has seen,” said Steve Wall, deputy team lead of Cassini’s radar team based at NASA’s Jet Propulsion Laboratory in Pasadena. “One possibility is that the area is studded with rounded ice rocks. But we can’t yet explain how that would happen.”

The SAR images did not focus on the moon’s now-famous “tiger stripe” fractures (called sulci) which are the sources of its icy jets. Instead, Cassini scanned areas a few hundred miles around the stripes. These regions have not been extensively imaged before and this new data shows surface patterns and elevations that had been previously unknown.

Some of the steep grooves in the imaged areas were shown to be as deep as 2,100 feet (650 m), and 1.2 miles (2 km) wide.

Cassini passed by the 318-mile (511-km) -wide moon at 04:49 UTC on November 6, 2011. Cassini’s radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries. Previously used to image the surface of Titan, which is hidden from view by a thick atmosphere, this is the first time the instrument was used on Enceladus.

Here’s a video from the imaging team below:

See the news release on the NASA mission page here, or on the Cassini mission page maintained by JPL.

Posted on by Amy Shira Teitel

Could Electrical Sprites Hold the Key to Extraterrestrial Life?

Full color image of a red lightning sprite.

 

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In 1989, meteorologists discovered sprites. Not the spirits, elves, or pixies that pepper Shakespearean comedies but their equally elusive electrical namesakes. Lightning sprites are large scale electrical discharges inside the clouds above storms that make the upper atmosphere glow, sort of like a fluorescent lightbulb.

Meteorologists have already determined that sprites likely aren’t unique to Earth. In fact, this elusive form of lightning might be common throughout the solar system. Now, researchers at Tel Aviv University are asking whether the presence of sprites on other planets could indicate the presence of organic material in their atmospheres.  

The layers of our atmosphere. Image credit: National Weather Service, JetStream Online School for Weather.

Though not an uncommon phenomena, sprites are incredibly hard to find and observe. They can only be captured with highly sensitive high speed cameras. Sprites occur in the Earth’s Mesosphere, layer between the stratosphere and the thermosphere – about 50 km (31 miles) to 90 km (56 miles) high. At this altitude, the gases that make up our atmosphere are much thinner and unable to hold heat from the Sun making the average temperature a chilly 5°F (-15°C) to as low as -184°F (-120°C).

But gases at this altitude are still thick enough to slow meteors – this is where they burn up and create what we see as meteor showers. Gases in the mesosphere are also thick enough to light up with sprites, providing a window into the composition of our atmosphere. Sprites, which glow reddish-orange, indicate the kinds of molecules present in this layer of the atmosphere.

Lightning isn’t a rare occurrence in our solar system, which leads researchers to suspect sprites might be found on Jupiter, Saturn, and Venus – all planets with the right environment for strong electrical storms. Just like on Earth, sprites found on these planets could open a window in their atmospheric composition, conductivity, and possibly point to the presence of exotic compounds.

Jupiter and Saturn present the most exciting environments. Both gas giants experience lightening storms with flashes more than 1,000 as powerful as those found on Earth. It’s on these planets that Ph.D. student Daria Dubrovin, with her supervisors Prof. Colin Price of Tel Aviv University’s Department of Geophysics and Planetary Sciences and Prof. Yoav Yair at the Open University of Israel, is focussing on.

Dubrovin has re-created these planetary atmospheres in a lab to study the presence of sprites in space. Or, as she describes her work, “We make sprites in a bottle.” She hopes this will provide a new understanding of electrical and chemical processes on other planets.

A sprite as it might appear in Saturn's atmosphere, created in a TAU lab. Image credit: American Friends, Tel Aviv University

What’s more, understanding lightning on other worlds could help researchers understand the possibility of life on other worlds. As Dubrovin points out, lightning is commonly accepted as the generator of organic molecules that turned early Earth’s ocean into the life-filled primordial soup. Increased study of lightning on other planets could give another clue into the presence of extraterrestrial life. Their research could easily be applied to exoplanets, not just bodies in our solar system.

A lightning storm on Saturn has Dubrovin pretty excited. It’s currently producing over 100 electrical flashes per second, a rare occurrence even within the planet’s volatile cloud layers. If researchers could successfully gather images of higher altitude sprites from the Cassini spacecraft (currently in orbit around Saturn), it would not only yield information on the storm below but also add to the general knowledge base of sprites and lightning on other planets.

Video of Sprites from the University of Alaska

Source: Tel Aviv University

Posted on by Nancy Atkinson

It’s Been a Stormy Year on Saturn (and Cassini’s been there to watch!)

Saturn's northern storm marches through the planet's atmosphere in the top right of this false-color mosaic from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

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Nearly a year ago a small, bright white storm emerged on Saturn’s northern hemisphere. This storm has now wrapped around the planet, creating a colossal atmospheric disturbance that has become the largest storm seen on the planet since 1990. And the Cassini spacecraft has been there to see it all.

“It is the singular distinction of being in orbit, and able to turn a scrutinizing eye wherever it is needed, that has allowed us to be present to witness this extraordinary phenomenon,” said Carolyn Porco, the Cassini Imaging Team Leader. “The storm has spread to become a planet-encircling colossus, a wide kaleidoscopic band of commingled waves, vortices, and eddies, all in continuous swirling motion …. a mesmerizing display of snaking, sensuous, churning, turning, chaotic, roiling atmospheric turmoil.”

If Porco sounds like she’s waxing poetic, she has good reason. The images put out by the Cassini imaging team today are a “sublime visual extravaganza,” and both true and false color images are gorgeous to behold.

This is nearly true-color view by Cassini of the storm. Credit: Credit: NASA/JPL-Caltech/Space Science Institute

The huge storm extends around Saturn’s northern hemisphere and from north to south spread approximately 9,000 miles, or 15,000 kilometers. It has become the largest observed on Saturn in the past 21 years, and the largest by far ever observed on the planet from an interplanetary spacecraft. What timing for Cassini to be there!

“Seven years of chasing such opportunities across the solar system’s most magnificent planetary system have already made Cassini one of the most scientifically productive planetary missions ever flown,” said Porco on the CICLOPS website. “And with any luck, there’ll be a great deal more to come.”

These false-color mosaics from NASA's Cassini spacecraft chronicle the changing appearance of the huge storm that developed from a small spot in Saturn's northern hemisphere. Here Cassini captures the changes over the short time span of one Saturn day; the two images were taken 11 hours apart. Credit: NASA/JPL-Caltech/Space Science Institute

Cassini has taken hundreds of images of this storm as part of the imaging team’s “Saturn Storm Watch” campaign. Cassini has been able to take quick looks at the storm in between other scheduled observations, of either Saturn or its rings and moons.

Other instruments on Cassini have detected the storm’s electrical activity and revealed it to be a convective thunderstorm. Its active convecting phase ended in late June, but the turbulent clouds it created linger in the atmosphere today.

“The Saturn storm is more like a volcano than a terrestrial weather system,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena, Calif. “The pressure builds up for many years before the storm erupts. The mystery is that’s there’s no rock to resist the pressure – to delay the eruption for so many years.”

This storm’s 200-day active period makes it the longest-lasting planet-encircling storm ever seen on Saturn. The previous record holder was an outburst sighted in 1903 which lingered for 150 days. The large disturbance imaged 21 years ago by NASA’s Hubble Space Telescope was comparable in size to the current storm. That 1990 storm lasted for only 55 days.

This series of images from NASA's Cassini spacecraft shows the development of the largest storm seen on the planet since 1990. Credit: NASA/JPL-Caltech/Space Science Institut

See more images and animations of the storm at the CICLOPS imaging website.

Sources: CICLOPS, NASA