Ceres bright spots may be ice; Dawn slips into orbit Friday

Rotation of Ceres captured in a sequence of images by NASA's Dawn spacecraft. The images were taken on Feb. 19, 2015, from a distance of nearly 29,000 miles (46,000 kilometers). Dawn observed Ceres for a full rotation of the dwarf planet, which lasts about nine hours. The images have a resolution of 2.5 miles (4 kilometers) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn captured a full ~9-hour-long rotation of Ceres in this series taken on Feb. 19, 2015 from a distance of nearly 29,000 miles (46,000 km). The images have a resolution of 2.5 miles (4 km) per pixel. Credit: NASA/JPL Caltech/UCLA/MPS/DLR/IDA

Ceres mysterious bright spots = icy volcanoes? Probably not, but the alternatives are just as intriguing. In a press conference Tuesday with scientists behind the Dawn mission, deputy principal investigator Carol Raymond explained that the brightest spot isn’t associated with a mound or peak as it would be if it were produced by oozing or eruption of ice in a cryovolcano.

Instead, they’re more likely ice or salts exposed on Ceres’ dark surface through impact.

showing bright wispy streaks thought to be ice revealed by subsidence of crater walls, are leading to the view that Phoebe is an icy-rich body overlain with a thin layer of dark material.

Have bright, icy spots been seen in craters anywhere else? Yes! Check out that 28-mile-wide crater at upper left on Saturn’s moon Phoebe. The bright, wispy streaks are thought to be ice revealed by subsidence (collapse) of crater walls, leading to astronomers to consider it an icy-rich body overlain with a thin layer of dark material. Credit: NASA/JPL

“The brightest may contain ice or salt,” said Raymond, adding that in 2014 the European Space Agency’s Herschel Space Telescope detected water vapor from two sectors on Ceres, one of them where the crater ringing the bright spots is located. Ice is a good fit based on how highly reflective the spots are, but if the original ice vaporized, it could have left bright salts behind that would also do the trick.

NASA will use Ceres' gravity and Dawn's ion propulsion engines to slowly spiral into close orbit around Ceres beginning this Friday. As the probe moves closer, we'll temporarily be facing the shadowed side of the dwarf planet. Credit:

NASA will use Ceres’ gravity and Dawn’s ion propulsion engines to slowly spiral into close orbit around Ceres beginning this Friday. As the probe moves closer, we’ll temporarily be facing the shadowed side of the dwarf planet. Credit:  NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“This mystery will be resolved, but it’s really got us on the edge of our seats,” said Raymond. We’ll have to sit tight for a little while before we know more. Dawn will be captured by Ceres’ gravity on Friday (March 6). As it spirals in closer to the dwarf planet we’ll see only its shadowed side for the time being. Not until April will we get see the sunlit face along with clearer, closer views of those spots.

New mosaic flat map of Ceres showing craters of all sizes, the bright spots, hilly terrain and more. Credit:

New mosaic flat map of Ceres showing craters of all sizes, the bright spots, hilly terrain and more. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ice is strongly suspected because Ceres is thought to harbor a thick layer of ice beneath its crust. We know this because it’s density is so much less than typical rocky asteroids and moons. Compared to the asteroid Vesta, Dawn’s first study target, Ceres is only 61% as dense, leading scientists to estimate that a quarter of its mass is in the form of water.

Based on Ceres’ size and location relatively near the Sun and the heat given off by the decay of the short-lived radioactive elements it possessed in its youth, the dwarf planet likely harbored a sub-surface ocean capped by an icy crust. That ocean would since have cooled down in the intervening 4 billion years into ice. This would explain why some of Ceres’ craters look relatively smooth with low rims. Ice allows for a certain amount of “relaxation” in crater shapes. Rugged floors smooth out and rims elevations decline.

Ceres’ current ice layer most likely contains salts that dissolved in the water at the time. Similar to what a salt lake leaves behind when it dries up, vaporizing ice can leave a crust or deposits of bright salt crystals.

New view of Ceres from Dawn show a very cratered dwarf planet. Credit:

New view of Ceres from Dawn show a very cratered dwarf planet. Click photo for an archive of Ceres images. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Raymond also mentioned the possibility of dust levitation by gases emanating from ice vaporizing just under the surface. Might we someday see small, bright “clouds” caught in the last rays of sunlight at Ceres’ day-night terminator?

Dawn project manager Robert Mase explained that Dawn’s first “science” orbit will happen in April. Throughout the year, mission control will be gradually lowering the spacecraft’s orbit all the way down to 235 miles (378 km) – nearly identical to that of the International Space Station. The main science mission will continue through June 2016.

“It’s clear that discoveries lie ahead as Ceres is revealed in stunning detail just like Vesta,” said Raymond.

Glowing comets and deep fried ice cream

Comet 67P/C-G taken on February 6 from a distance of 77 miles (124 km) to the comet center. We see the comet’s small lobe on the left and larger lobe to the right. The image has been processed to bring out the details of the comet’s jetting activity. Exposure time was 6 seconds. Credits: ESA/Rosetta/NAVCAM

Everything’s glowing! This new photo from the Rosetta spacecraft was taken on Feb. 6 and processed to show jets active all over comet 67P. They’re brightest and most effervescent in the Hapi region, the name given to the neck of the comet, but take a look around the nucleus. You can see that the entire comet is swathed in a soft, nebulous halo of vaporizing ices and dust motes.

Some of the grainy white spots around the comet’s nucleus are background noise brought to the fore as a consequence of processing the images to see the jets more clearly, but some is actual comet stuff jetted into 67P’s coma like dried leaves from a leafblower.

Rosetta’s moved out from the comet temporarily as part of an orbit change that will see it fly just 3.7 miles (6 km) of its surface this Saturday. Photos from the flyby will be downlinked to Earth Sunday and Monday.

In other comet news, a team of astronomers have simulated what happens to a comet’s ices when it nears the Sun. It’s not what you’d expect.

Familiar ice like that on ponds, lakes and clinking as ice cubes in a glass are made of neatly ordered arrangements of water molecules. Amorphous ice is also made of water but its structure is disordered. Credit: Wikipedia

“A comet is like deep fried ice cream,” said Murthy Gudipati of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., corresponding author of a recent study appearing in The Journal of Physical Chemistry. “The crust is made of crystalline ice, while the interior is colder and more porous. The organics are like a final layer of chocolate on top.”

Comets, which formed in the bitter cold of the outer solar system, are probably composed of amorphous ice, a form of water ice where the H20 molecules are randomly arranged instead of packed into neat lattices like those that make up the more familiar crystalline ice we use to chill our sodas.

Researchers at NASA’s Jet Propulsion Laboratory use a cryostat instrument, nicknamed “Himalaya,” to study the icy conditions under which comets form. Image credit: NASA/JPL-Caltech

First, the team flash-froze water vapor infused with carbon compounds called polycyclic aromatic hydrocarbons (PAHs) at -405° F to preserve the disorderly states of the water molecules and create amorphous ice. Then, using a cryostat instrument nicknamed “Himalaya”, they gradually raised the temperature of the mixture from -405° F to -190° F (-243° C to -123° C).

The PAHS stuck together and were expelled by the ice as it crystallized. With the carbon compounds now gone, the water molecules moved into the empty spaces linking up to form more compact crystalline ice.

That rings true when it comes to the Rosetta mission’s Philae lander which hit 67P/C-G with a big bounce proving it had a hard surface. Some of the dust seen around 67P might well have been “squeezed” out when amorphous ice transformed into the crystalline variety.

Similar to the fried ice cream pictured here, comets have cold, icy interiors surrounded by a crust of organics expelled when amorphous ice warms to become crystalline ice. Credit: Wikipedia

“What we saw in the lab — a crystalline comet crust with organics on top — matches what has been suggested from observations in space,” said Gudipati. Deep fried ice cream is really the perfect analogy, because the interior of the comets should still be very cold and contain the more porous, amorphous ice.”

Come fly with me to Mercury


MESSENGER flies over Mercury. The spacecraft blasted off from Cape Canaveral on August 3, 2004.

To commemorate this week’s 10th anniversary of the launch of NASA’s MESSENGER spacecraft to Mercury, NASA released this amazing video of a flight over the planet’s north polar region. The movie was assembled from 214 images taken once per second by the probe’s narrow-angle camera on June 8, 2014. Enjoy the cratery desolation.

As the photos were snapped, MESSENGER orbited at altitudes ranging from 71 to 102 miles (115 to 165 km), traveling at a speed of 2.3 miles per second relative to the surface.

One of the highest resolution pictures ever taken of Mercury’s surface shows a field of craters only 1.8 miles (3 km) wide photographed on June 11, 2014. MESSENGER will drop down much closer to the planet – only 31 miles – starting August 19. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

“This view is what a traveler on the MESSENGER spacecraft might see during low-altitude operations in the coming year,” said MESSENGER co-investigator Scott Murchie. “During the final phase of its mission, MESSENGER’s science instruments will use low-altitude operations like this to explore the surface and subsurface of Mercury at unprecedented resolution.”

Mercury is presently too close to the sun to see safely, but on August 2 it lined up in conjunction with Jupiter as seen through the coronagraph (sun-blocking device) on the Solar and Heliospheric Observatory. Credit: NASA/ESA

Mercury orbits closest to the sun of the eight planets, completing one revolution every 88 days. It has virtually no atmosphere and measures only about a thousand miles larger than Earth’s moon.

Daytime surface temperatures there can reach 801°F (427°C). Despite the extreme heat, MESSENGER’s instruments detected water ice in permanently shadowed craters in the planet’s polar regions.

Launched in August 2004, MESSENGER traveled 4.9 billion miles (7.9 billion km) to finally settle into orbit around the speedy planet on March 18, 2011. Its convoluted journey included 15 trips around the Sun and flybys of Earth once, Venus twice, and Mercury three times. All of this was done to slow the craft down so it could enter orbit about the planet. It’s returned more than 240,000 pictures so far, many of which you can browse HERE.

New Rosetta pix show comet craters – only 6 days to go!

The nucleus of comet 67P/Churyumov-Gerasimernko as seen from a distance of 1,200 miles (1,950 km) on July 29th, 2014. One pixel corresponds to approximately 121 feet (37 m). The bright neck region between the comet’s head and body is becoming more and more distinct. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Closer, closer, closer. Rosetta sent back more detailed images taken on July 30 that confirm the comet’s bright neck collar and show much more surface texture than earlier photos – including two craters! The collar’s light tone hints of fresh ice vaporizing in sunlight but could also be caused by different materials on that part of the comet’s surface. Maybe the next round of photos will offer a clue.

Two distinct craters stand out in this lower resolution navigation camera photo. What started out looking like a rubber ducky now reminds me of a primitive bird. The bright collar is also seen from this point of view. In 6 days, Rosetta will enter orbit around the comet. Credit: ESA/Rosetta/Navcam

The wider-view navigational camera sent back an even more fascinating image showing dual craters, one on each lobe, with hints of other crater or depressions in the ice. Comets, including 67P C-G, are made of mostly water ice and dry ice or frozen carbon dioxide. The ices act as glue to hold the dust, sand-sized grains and pebbly pieces of the comet together.

The inner coma of comet 67P/Churyumov-Gerasimenko is about 93 miles (150 km) across.  This image was taken on July 25th, 2014. The hazy circular structure on the right and the center of the coma are artifacts due to overexposure of the nucleus. Credit: ESA

When a comet’s orbit takes it into the inner solar system, some of the ice vaporizes, releasing dust and grit, along with a variety of gases like carbon monoxide, methanol, ethane and ammonia. The melange forms the comet’s coma or temporary atmosphere.

Next, the pressure of sunlight pushes back coma gases and dust to form tails – one of dust and the other of gas.

As Rosetta’s camera tried to record the coma, which is much fainter than the nucleus, the brighter nucleus was overexposed, creating an artifact. Taking pictures of comets is challenging enough, but evidently even more so when you’re standing right next to one!

* UPDATE 8/1: The ‘craters’ are more likely artifacts in processing of the image according to other sources.

With a tip of its rings, Saturn greets Earth on opposition day

The north face of the rings are tipped nearly wide open toward Earth this year, making for wonderful views of the planet through a small telescope. Notice that Saturn’s south polar region barely pokes out below the ring plane. This is a fun detail to try and see in a telescope. Credit: Anthony Wesley

Saturday is truly Saturn’s day this year. We mark the ringed planet’s opposition today, the time when it’s closest to Earth and brightest for 2014.

Opposition occurs when Earth passes between Saturn and the sun. When both planets lie on the same side of the sun, they’re almost 175 million miles closer than when they’re on opposite sides. That translates to a bigger, brighter Saturn. Because Saturn travels a little ways around its 29.5 year orbit every year, Earth requires about 13 days to catch up to it at each succeeding opposition. We’ll line up again next year on May 23.

Earth and Saturn are lined up with the sun today and 173 million miles closer than they’ll be in about six months when Saturn is in conjunction with the sun. Illustration: Bob King

The word opposition refers to Saturn being opposite the sun in the sky, rising when the sun sets and setting at sunrise. In a word, it’s visible all night long. Just about anytime you feel like pointing your telescope Saturn’s way, it awaits your gaze.

But before we talk telescope views, let’s take a minute to pinpoint the planet’s location in the evening sky. While it rises at sunset, it doesn’t clear the low trees until about an hour and a half later. Skywatchers at mid-northern latitudes will find it low in the southeastern sky around 10 o’clock well to the lower left of Mars, due south at that hour.

This map shows the sky around 10 p.m. local time tonight May 10 facing south-southeast. Saturn is smack in the middle of the dim constellation Libra below and to the left of Mars and Spica. Stellarium

Tonight the gibbous moon won’t be far from Mars, making it exceptionally easy to find the Red Planet. Swing down to the lower lower left of Mars to spot Saturn. You shouldn’t have trouble spotting it – at magnitude +0.1 it’s nearly as bright as Vega and a pale yellow-white. The ring bearer’s out all spring and summer, so there will be many opportunities to see it.

The ring bearer calls the dim zodiac constellation Libra the Scales home in 2014. Because the moon’s waxing toward full, it’s tricky at the moment to see Libra’s dim stars. Wait till after May 16 for a better view. Maybe then you’ll notice the whimsical “Saturn Cross” like I’ve been seeing the past couple weeks.

A whimsical “Saturn Cross” formed from Libra’s brightest stars with Saturn at its center. Libra precedes the gangly Scorpius the Scorpion with its bright star Antares. Viewing time shown is 1 a.m. in mid-May. Stellarium

The “Cross”, which just happens to be oriented north-south like the constellation Crux a.k.a. ‘Southern Cross’, is simply a different way to see Libra’s four most prominent stars. Saturn marks the center of the crossbeam.

If you’ve never seen the real Southern Cross, this might serve as a cheap, no-airplane-travel-required substitute. Mostly I bring it up as an easy way for you to add a new and rather faint constellation to your life list.

As Saturn travels around the sun in its 29.5 year orbit, we see one side of the rings for about 15 years, followed by an edgewise presentation. The rings – made of dirty water ice – are huge at some 155,000 miles wide (250,000 km), but they’re only about 30 feet thick and virtually disappear when seen edge-on.

That last happened in 2009. Since then they’re re-opened with the north face visible for some 15 years.

Saturn on April 6, 2014. Its clouds belt are less contrasty than Jupiter’s and except for the prominent north equatorial belt not easy to see. A small telescope and magnification as low as 30x will show the rings. Higher power will show the wide B-ring and thinner, outer A-ring. Also visible is the dim C-ring, the dusky band in the foreground crossing in front of the planet. Credit: Efrain Morales Rivera

This year the ring plane’s tipped open 21-22 degrees, nearly the maximum of 27 degrees which occurs in 2017. A large tip exposes lots of ring ice particles to sunlight, boosting the planet’s brightness.

Views of Saturn at different ring plane inclinations taken by the Hubble Space telescope. Rings are labeled in the top image. Credit: NASA/ESA

That’s all good news for both visual and telescopic observation. Even a 2.4-inch telescope will show the rings, with a larger instrument providing a brighter, larger picture and sharper resolution of the three brightest rings. I love the planet’s subtle colors through the eyepiece – the globe looks pale brown or butterscotch to my eye and the rings distinctly brighter and whiter.

Saturn and its brightest moons around 10 p.m. CDT tonight. Titan is brightest at magnitude 9 and very easy to see. North is up. Credit: Meridian software

Small scopes will also show the brightest moons including Titan, Rhea, Dione, Tethys and Iapetus. To find where the moons are on a given night and time, check out Sky and Telescope’s handy Saturn javascript utility, free Meridian software (used to make the diagram above) or download the $2.99 app SaturnMoons.

Saturn’s the best. No other sight in the sky elicits the wonder and amazement of guests at the telescope. Look at the ringed planet every night you can, and the more friends and family your share it with, the better.

Saturn makes a new moon named ‘Peggy’

The disturbance visible at the outer edge of Saturn’s A ring in this image from NASA’s Cassini spacecraft could be caused by an object replaying the birth process of icy moons. Credit: NASA/JPL

That bright swelling in Saturn’s A ring may very well be ice balls stirred up by a newborn moon nicknamed ‘Peggy’. Estimated at just a half-mile (1 km) across, the newcomer could be the first moon ever seen to form right before our eyes.

Images taken by the Cassini probe April 15, 2013, revealed several disturbances at the very edge of Saturn’s A ring, the outermost of the planet’s large, bright rings. One of them is the arc shown above that’s about 20 percent brighter than its surroundings and spans some 750 miles (1,200 km) long by 6 miles (10 km) wide. It even sports a little bump that interrupts the smooth profile of the ring’s edge.

“We have not seen anything like this before,” said Carl Murray of Queen Mary University of London, the report’s lead author. “We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right.”

The object probably won’t grow any larger and in fact, may even be falling apart according to astronomers. Like the rings, many of Saturn’s moons are composed of ice. It’s believed that long ago, the rings were larger and more massive and gave rise to larger moons like Enceladus and Titan in a similar birthing process. Today these moons are relatively far from the planet but may have migrated there after self-assembling via gravity within the ring plane.

Similar to how planets formed and migrated in the early solar system, scientists think that ice in Saturn’s rings stuck glommed together to form some of its many moons. Credit: NASA/JPL/Caltech

As exciting as the birth of a new moon is, I find it equally fascinating that Saturn’s ring system may serve as a model of the early solar system when it was little more than rings of rocky and icy debris surrounding the infant sun. From these dribs and drabs, all the planets, comets and asteroids took form.

We’re almost certain that most if not all the planets migrated through this debris-strewn traffic jam similar to what appears to have happened  at Saturn. Earth and the inner planets were likely farther from the sun billions of years ago and migrated inward, while Jupiter and Saturn took off in the opposite direction.

“Witnessing the possible birth of a tiny moon is an exciting, unexpected event,” said Cassini Project Scientist Linda Spilker, of NASA’s Jet Propulsion Laboratory. According to Spilker, Cassini’s orbit will move closer to the outer edge of the A ring in late 2016 and provide an opportunity to study Peggy in more detail. Maybe even take a picture.

If theory is proven true then Saturn’s rings are much depleted after a life of making moons, leaving only enough material left to fashion a mini-moon or two.

I’m rooting for Peggy to step out of the shadows and lead a life of her own. How wonderful it would be to witness the birth of a new Saturnian moon in our lifetime.

Tiptoe into the twilight zone to see Mercury at its best

Mercury stands alone low in the sky over grain elevators and freeways in this picture taken last night Jan. 27, 2014 in Duluth, Minn. Credit: Bob King

This week and next Mercury will be brightest and highest in the evening sky. Not until May will skywatchers in mid-northern latitudes have as good an opportunity to spy the planet that spins closest to the sun. That’s what makes it so tricky to see in the first place. Mercury never gets far enough from the sun to appear in a dark sky, forever lurking in the twilight zone.

Mercury will be visible for the next week low in the west-southwest sky at dusk. Start looking about 40-45 minutes after sundown. On Friday, a thin day-old moon will join the scene. Stellarium

Still, I was surprised how easy it was to see last night. Higher up than expected too. I bundled up and went out to look 45 minutes after sunset. Nothing. Where was Mercury? It turned out I was looking too low. Once I raised my gaze a bit, a solitary “star” popped into view about a fist above the southwestern horizon.

While the planet shines tonight at magnitude -0.5 (brighter than Vega and Arcturus) the hazier, thicker air near the horizon robs it of 1.2 magnitudes, dimming Mercury to magnitude +0.7 or about as bright as Altair in the Summer Triangle.  Still plenty easy to see with the naked eye.

I kept the planet in view until around 6:20 p.m. or more than an hour past sunset before subzero temps and 20 mph winds forced a retreat back into the car. If you’re in a mercurial mood, start looking about 45 minutes after sunset to the upper left of the brightest part of the lingering solar glow in the southwest. The planet hovers about 10-12 degrees (a little more than one fist held at arm’s length) high. Since Mercury has no bright company, if you see a single star in that direction, you’ve nailed it.

Only a spruce tree separates Venus from the crescent moon this morning Jan. 28, 2014. A similar but thinner crescent will be near Mercury in the evening sky on Friday Jan. 31. Credit: Bob King

To be on the safe side, you might consider toting along a pair of binoculars. I guarantee that once you find it with optical aid, you’ll quickly see Mercury with the naked eye.

Once you’ve fixed in your mind where Mercury is located along your local horizon, get ready for a really fine event. This Friday the 31st, an incredibly thin one-day-old moon will sidle up some 5 degrees to the lower right of the planet. Are you thinking pictures? So I am.

Place your camera on a tripod – or at least wedge it firmly against something – compose a scene including moon and planet and take a series of photos with your lens set anywhere from f/2.8 to 4.5. ISO 400 speed should be fine with exposures ranging from 2 seconds to 1/15 second. While you’ll get a decent photo with a standard lens, a 100-200mm telephoto lens will make for a tighter, more dramatic image.

As you stand in the cold clicking away or simply admiring Mercury, here are some interesting facts about the planet to warm your brain cells:

Color image of Mercury made by the MESSENGER probe. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

* At 3,032 miles (4,880 km) across, Mercury is smaller than Jupiter’s moon Ganymede and Saturn’s moon Titan.

* Mercury’s orbit is the most eccentric or least circular of all the planets. Its distance from the sun ranges from 29 to 44 million miles (46-70 million km).

* While Venus is slightly hotter, Mercury has one of the most extreme temperature ranges of any body in the solar system. With virtually no atmosphere to capture and distribute the sun’s heat, the sun-facing dayside of the planet tops out around 800 degrees Fahrenheit while the nightside dips to -297 F.

All the dayside heat leaks right back into space during the long night. And it is a L-O-N-G night. The sun’s enormous gravity has locked the little planet in a 3:2 rhythm or “resonance”. For every two orbits around the sun, Mercury rotates three times on its axis.

Since the planet completes an orbit in 88 days (one Mercury year), its day is twice as long as its year or 176 Earth days. Mercury’s sunny side bakes for nearly six months and then chills for another six. No wonder it experiences such extremes of hot and cold.

* Mercury’s slight axial tilt of just 0.03 degree means that craters at its poles are steeped in perpetual shadow and never heated by the sun, making them perfect places to trap volatile materials like ice and keep them frozen for a long, long time. New data from the MESSENGER spacecraft now gives strong evidence for ice holed up in some of these craters.

* Mercury has a large (by volume) partially molten iron core and a planet-wide magnetic field, a feature lacking on Venus and Mars.

Sesame Street’s Cookie Monster and a crater on Mercury appear to be related. Credit: NASA

* Mercury is the most cratered planet in the solar system. Unlike Earth, Mars and Venus, which have been extensively resurfaced through volcanic and tectonic processes, Mercury’s retains much of its ancient battered surface.

Cross the “snow line” to Saturn and relish its ancient ice

NASA’s Cassini spacecraft on July 29, 2011, shows Saturn’s A and F rings and five of its moons. From left, the moons are Janus, Pandora, Enceladus, Mimas and Rhea. Saturn is hidden at right behind Rhea. Credit: NASA/JPL-Caltech/Space Science Institute

Wipe the dust from an antique and you can begin to appreciate its vintage and workmanship. See beneath the space-worn colors of Saturn’s rings and moons and you might just get a glimpse of the primeval solar system. A new analysis of data from NASA’s Cassini spacecraft suggests that the Saturn system is tinted by “pollutants”.

Geysers of water ice crystals erupt from fissures in Enceladus’ south polar region in this photo taken by Cassini. Credit: NASA/JPL-Space Science Institute

The inner moons get whitewashed as they pass through water sprayed by geysers from the moon Enceladus. More distant moons wear a pale coating of red from particles of dust shed by Phoebe; the farther out they are from Saturn, the redder they appear.

Phoebe is an outer moon that may have once resided in the far-off Kuiper Belt beyond the planet Neptune before it was captured by the ringed planet.

Parts of the Saturn’s B-ring also appear faintly red perhaps from meteoroids that pepper the icy ring particles. Iron is a very common constituent of meteorites. Scientists think the reddish color could be either oxidized iron – better known as rust – formed when oxygen and iron combine in the presence of water –  or polycyclic aromatic hydrocarbons (PAHs), organic molecules common in tars and oil.

PAHs form in the atmospheres of aging, expanding stars when carbon and oxygen atoms are spat out into space. As they cool, the atoms bind together to form simple organic molecules and PAHs.

The precursors to the planets, called planetesimals, were mostly rocky stuff in the inner solar system within the snow or frost line. The outer planets formed from planetesimals composed of a mixture of rock and ice. Credit: Univ. of Colorado

Despite their diverse colors, data from Cassini’s visual and infrared mapping spectrometer (VIMS), which penetrates below the chemical veneer, found deep similarities. VIMS detected lots of water ice in both moons and rings, too much to have been deposited by recent comet collisions. The authors concluded that the ice must have formed around the birth of the solar system. How do you keep ice around that long? You either live in Duluth, Minn. or form it beyond the “snow line”, where temperatures are cold enough to keep things frozen almost forever.

Our solar system’s snow line starts at around 5 times the Earth’s distance from the sun or roughly at Jupiter’s distance. Indeed it’s the snow line which separates the inner terrestrial planets from the giant gas planets of the outer. Drop this side of the line and water either melts or vaporizes.

Saturn’s small 84-mile-long moon Prometheus creates a knot in the F-ring through its gravitational interaction with the icy ring particles. Prometheus may have formed from ring material. Credit: NASA/JPL-Space Science Institute

Cassini turned up another interesting fact. Saturn’s moon Prometheus has a similar reddish tint as the rings, hinting that it may have formed from ring material:

“The similar reddish tint suggests that Prometheus is constructed from material in Saturn’s rings,” said co-author Bonnie Buratti, a VIMS team member based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Scientists had been wondering whether ring particles could have stuck together to form moons — since the dominant theory was that the rings basically came from satellites being broken up.”

Saturn’s icy ring particles range in size from less than a millimeter to around 10 feet across. Credit: NASA/JPL-Space Science Institute

With Prometheus, the process may have worked the other way around, testing our assumptions once again.

Happy New Baktun and a joyous solstice to all

Circumscribed halo around last night’s half moon. Photo: Bob King

Today the Mayan calendar rolls over to a new Baktun or 144,000 day cycle as it has for centuries. Coincidentally, it’s also the first day of winter in the northern hemisphere and summer for folks down under. Winter tiptoed in at 5:12 a.m. (CST) this morning while many of us were snug in our beds. Looking out my window, the world looks much the same as it did yesterday – with a difference. It’s sunny!

Come join Duluth’s celebration of the solstice at the University of Minnesota-Duluth’s planetarium.

That means a clear sky tonight and a chance to celebrate the new season. If you live in the Duluth, Minn. region, the Marshall Alworth Planetarium will feature a special “End of the World – Winter Solstice” party with shows on the half-hour in the dome, telescope viewing, pizza, cider, a raffle and a free 2013 calendar. Cost is $8 per person or $15 per family. The event starts at 6 p.m. and runs until 9. More information HERE.

Only 8 hours and 32 minutes separate sunrise and sunset in Duluth, Minn. today. The rest belongs to the night. Solstice is combination of two Latin words – sol for sun and sistere to stand still. That’s what it feels like for a week or two at the time of the summer and winter solstices, when the sun reaches its highest and lowest points in the sky.

The seasons are caused by the 23.5 degree tilt of our axis. In summer, Earth’s north polar axis is tipped toward the sun, causing it to appear higher in the sky and making for longer days. Half an orbit later in winter, the north polar axis is tilted away from the sun, making for a low sun and short days. In spring and fall, the axis is tilted neither toward nor away and day and night are equal. Credit: Tau’olunga with additions by Bob King

On Dec. 21 the sun reaches its lowest altitude above the southern horizon at noon for the year. Here in Duluth, that’s about 20 degrees or two fists held at arm’s length. For Chicagoans, it’s 25 degrees, a bit higher. But if you live in Anchorage, the yellow orb of day climbs to just under 6 degrees before slinking back toward the west. My dear brother Mike who lives there must wait until 10:14 a.m. for the sun to rise today. With sunset at 3:42 p.m., he’ll need to be vigilant to catch sight of it. Buildings and trees could easily block the sun from view. .


Excellent, short video on how the seasons happen

These extremes of daylight and night are brought on by Earth’s tipped axis. If it ran straight up and down, much as Jupiter’s axis does, sunrise and sunset times would barely vary for your location. The sun would rise in the east and set in the west 12 hours later every day of the year. No variation and no seasons. Who wants that?

Thanks to the Earth’s tipped axis we experience the joys winter and the ice it brings. These are air bubbles trapped in pond ice near my home yesterday. Photo: Bob King

The tip ensures that the northern hemisphere of the planet tilts toward the sun in the summer and away in the winter. As a consequence, the sun appears very high in the sky in summer. Its longer, steeper path naturally means longer days and more intense heat. In the winter, we’re tipped away from the sun. Slanted, less intense solar rays and short days follow.

Vesta shown at 9:30 p.m. (CST) every 5 days now through Jan. 10, 2013 as it glides near the Hyades cluster. 97 Tauri is mag. 5.  Stars shown to 7.5 magnitude. Created with Chris Marriott’s SkyMap software

If you’re looking for an interesting astronomical treat in the night sky this solstice, face east anytime during the evening hours and find the brightest “star” you can see. That’s the planet Jupiter. Just below Jupiter is the bright star Aldebaran and a V-shaped pattern of stars called the Hyades star cluster. Not far from the cluster is the famous asteroid Vesta. You’ll recall it was was orbited and studied by NASA’s Dawn spacecraft this past year.

Vesta shines at magnitude 6.5 (just under the naked eye limit), as bright as it gets this year. The star-like asteroid is super easy to see right now in binoculars, especially with Jupiter to help point you there. Take a look the next clear night.

Curiosity’s history-making discovery a big misunderstanding

Bite mark left in the sand dune after Curiosity retrieved soil sample. It’s similar to lava rock found in Hawaii and contains feldspar, pyroxene and olivine. Other materials found in the sample will be revealed next week. Credit: NASA/JPL-Caltech

Do you want the good news or bad news first? OK, the bad news. Remember when we learned last week that Curiosity had made a “history changing” discovery in a Martian soil sample? Many of us speculated that the rover had detected the first organic, carbon-containing compounds on Mars.

Well, it turns out it was just a big misunderstanding between the MPR reporter and Mars Science Laboratory (MSL) project scientist John Grotzinger. During the original interview, Grotzinger explained to reporter Joe Palca that Curiosity had analyzed the first soil sample in its Sample Analysis at Mars instrument. While SAM can detect organics, Grotzinger’s reference to the discovery being “one for the history books” was actually a reference to the entire Mars mission, not a specific finding.

Panoramic view of Curiosity’s digs at the Rocknest site in Gale Crater on Mars. One barren-looking landscape! The photo is a composite of images taken in October and November. Click to enlarge. Credit: NASA-JPL/Caltech

Somehow the NPR reporter misinterpreted the excitement surrounding the first soil analysis with Grotzinger’s description of the mission as history-making. Each thought the other was talking about a different thing. Indeed at the time of the interview, the first sample had only begun to be analyzed, so NASA scientists wouldn’t have even known the details of its chemical contents. Results, described as “interesting” rather than earth-shaking, will be presented next week at a meeting of the American Geophysical Union in San Francisco. More on the topic HERE.

Since it’s still very early in the mission, we shouldn’t be too bothered if some sort of Holy Grail moment has yet to happen. Look at what Curiosity’s found so far – an ancient stream bed filled with water-rounded cobbles, layered buttes of sedimentary rock like a postcard from the Grand Canyon and a most amazing assortment of wind-sculpted rocks. And don’t forget – we got there in the first place and Curiosity couldn’t be healthier.

Does anyone doubt that handfuls of history-making discoveries lie ahead? My only frustration is that NASA didn’t attempt to correct the misunderstanding sooner through one of its many press releases.

View of Mercury’s north pole seen from above. Red denotes areas of permanent shadow as seen by the MESSENGER probe to date. The polar ice deposits imaged by Earth-based radar are in yellow. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory

Now for the good news. Mercury, a planet with a surface temperature hot enough to melt lead has been confirmed by MESSENGER probe to have ice deposits in its polar regions. What the heck? Given that it’s the closest planet to the sun, you’d think it an unlikely place for ice, but the little planet’s axis is tipped less than one degree, so areas around its poles are never exposed to sunlight. Since Mercury has no substantial atmosphere to capture and distribute heat, its surface temperature ranges from 800 degrees F in sunlight to 200 below in the polar regions.

While radio-bright areas likely due to ice have been detected from Earth by the giant Arecibo radio telescope in Puerto Rico as long ago as 1991, new data from NASA’s orbiting MESSENGER spacecraft confirm that water ice is indeed present both exposed on the surface as well as buried beneath dark, tar-like deposits.

The probe uses neutron spectroscopy to measure hydrogen concentrations within Mercury’s radar-bright regions. Based on the amount of hydrogen seen, scientists can estimate the volume of water ice present, because water, or H2O, is two parts hydrogen.

“The new data indicate the water ice in Mercury’s polar regions, if spread over an area the size of Washington, D.C., would be more than 2 miles thick,” said David Lawrence, a MESSENGER participating scientist.

The dark material could be a mix of organic compounds delivered by carbon-rich comets and asteroids several billion years ago during the solar system’s youth. Astronomers believe that Earth was similarly enriched by water and organics. I like the connection, and I like that polar opposites – excuse the pun – find a home together on a most unlikely planet. To read more about the discovery, click HERE.