Looking to the future of space exploration, NASA and TopCoder have launched the "High Performance Fast Computing Challenge" to improve the performance of their Pleiades supercomputer. Credit: NASA/MSFC
TORONTO, CANADA – Could NASA’s new rocket bring a probe to sample the geysers of Saturn’s moon Enceladus, or ferry human explorers to the surface of Mars? Representatives of contractor Boeing think so.
They’ve put together some ideas for sending their Space Launch System to these far-flung destinations, which they presented at the International Astronautical Congress today (Oct. 1).
Bear in mind that the SLS hasn’t yet flown — it’s slated for 2018 if funding lasts and the schedule holds — and the destinations below are just in the conceptual stage. The gallery below summarizes some of the destinations SLS could visit. For more information, check out this brochure by Boeing.
Enceladus
Artist’s conception of the Cassini spacecraft flying amid geysers on Enceladus, a moon of Saturn. Credit: Karl Kofoed / NASA
The icy moon of Saturn is known as a hotspot for geysers; earlier this year, scientists found 101 gushers using data from the prolific Cassini probe. Using the SLS could bring a satellite there in four years, as opposed to about seven with rockets on the market today, according to Boeing. It also could carry a heavier spacecraft.
Europa
Artist’s conception of Europa’s surface, backdropped by planet Jupiter. Credit: NASA/JPL-Caltech
Europa is known to have a subterranean ocean, and it also is capable of spewing water plumes — as researchers using the Hubble Space Telescope discovered earlier this year. The SLS could get to Europa a lot faster than a launch with an Atlas, according to Boeing — it would only take two years to fly there directly as opposed to more than six years with the Atlas, which would need to fly by Venus first to pick up some speed.
Trojan asteroids
Artist’s diagram of Jupiter and some Trojan asteroids nearby the gas giant. Credit: NASA/JPL-Caltech
Trailing before and after Jupiter are more than a million asteroids that are called Trojans. This means any probe in the area would have no lack of targets to study, providing it had enough fuel on board. A mission profile from Boeing suggests the SLS could bring a spacecraft out there that could swing by a target at least half a dozen times.
Mars
Artist’s impression of astronauts exploring Mars. Credit: NASA/Pat Rawlings, SAIC
One of the largest challenges of getting to Mars is figuring out how to send all the life-support equipment and food that humans require — on top of the humans themselves! Since SLS is a heavy-lift rocket, Boeing is trying to position its rocket as the ideal one to get humans to Mars. But it remains to be seen what concept works best to get people out there.
The Moon
Artist’s impression of astronauts on the moon. This image was used to illustrate a landing concept of NASA’s now defunct Constellation program. Credit: John Frassanito and Associates / NASA
Boeing has an idea to bring a lander down to the Moon that could then lift off multiple times in search of other destinations. Such a concept would require a hefty amount of fuel and equipment. If it works, Boeing says the SLS could assist with plans for lunar mining and other exploration ideas.
This dramatic view looks across the region of Enceladus' geyser basin and down on the ends of the Baghdad and Damascus fractures that face Saturn. The image, which looks approximately in the direction of Saturn, was taken from a more elevated viewpoint than other Cassini survey images of this area of the moon's south pole. Credit: NASA/JPL-Caltech/SSI
Scientists analyzing the reams of data from NASA’s Cassini orbiter at Saturn have discovered 101 geysers erupting from the intriguing icy moon Enceladus and that the spewing material of liquid water likely originates from an underground sea located beneath the tiny moons ice shell, according to newly published research.
The geysers are composed of tiny icy particles, water vapor and trace amounts of simple organic molecules. They were first sighted in Cassini imagery snapped during flyby’s of the 310-mile-wide (500 kilometers wide) moon back in 2005 and immediately thrust Enceladus forward as a potential abode for alien life beyond Earth and prime scientific inquisition.
Liquid water, organic molecules and an energy source are the key requirements for life as we know it.
The eruptions emanated from a previously unknown network of four prominent “tiger stripe” fractures, named Damascus, Baghdad, Cairo and Alexandria sulci, located at the south polar region of Saturn’s sixth largest moon.
Using imagery gathered over nearly seven years of surveys by Cassini’s cameras, researchers generated a survey map of the 101 geysers erupting from the four tiger strips.
This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface. Image Credit: NASA/JPL-Caltech/Space Science Institute
The new findings and theories on the physical nature of how the geysers erupt have been published in two articles in the current online edition of the Astronomical Journal.
Scientists had initially postulated that the origin of the geysers could be frictional heating generated from back and forth rubbing of the opposing walls of the tiger stripe fractures that converted water ice into liquids and vapors. Another theory held that the opening and closing of the fractures allowed water vapor from below to reach the surface.
The geysers locations was eventually determined to coincide with small local hot spots erupting from one of the tiger stripe fractures after researchers compared low resolution thermal emission maps with the geysers’ locations and found the greatest activity at the warmest spots.
After later high-resolution data was collected in 2010 by Cassini’s heat-sensing instruments the geysers were found to coincide with small-scale hot spots, measuring only a few dozen feet (or tens of meters) across.
“Once we had these results in hand we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team from the Space Science Institute in Boulder, Colorado, and lead author of the first paper. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”
This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. While some jets are strongly tilted, it is clear the jets on average lie in four distinct “planes” that are normal to the surface at their source location. Image credit: NASA/JPL-Caltech/Space Science Institute
“Thanks to recent analysis of Cassini gravity data, the researchers concluded the only plausible source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water,” according to a NASA press release.
These are very exciting results in the search for life beyond Earth and clearly warrant a follow up mission.
“In casting your sights on the geysering glory of Enceladus, you are looking at frozen mist that originates deep within the solar system’s most accessible habitable zone,” writes Porco in her Captain’s Log summary of the new findings.
Surveyor’s Map of Enceladus’ Geyser Basin – On this polar stereographic map of Enceladus’ south polar terrain, all 101 geysers have been plotted whose source locations have been determined in Cassini’s imaging survey of the moon’s geyser basin. Credit: NASA/JPL-Caltech/SSI
The Cassini-Huygens mission is a cooperative project between NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI). Cassini was launched by a Titan IV rocket in 1997 and arrived at Saturn in 2004.
In 2005 Cassini deployed the Huygens probe which landed on Titan, Saturn’s largest moon sporting oceans of organic molecules and another prime location in the search for life.
The Cassini mission will conclude in 2017 with an intentional suicide dive into Saturn to prevent contamination on Titan and Enceladus – but lots more breathtaking science will be accomplished in the meantime!
Stay tuned here for Ken’s Earth & Planetary science and human spaceflight news.
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
We’re spoiled, don’t you know? It was 10 years ago today that the Cassini spacecraft entered Saturn’s system, and it has been busily beaming back pictures of the ringed planet and its (many) moons ever since. We’ve learned more about seasons on Titan, investigated plumes on Enceladus, and examined phenomena such as auroras on Saturn.
Embedded in this story are 20 of our favourite pictures from Universe Today’s archive of Cassini discoveries, which you can check out below the jump.
It’s only a fraction of the more than 332,000 images received from the spacecraft, which is in excellent health and has seen its mission extended three times past its original 2008 expiry date. Additionally, more than 3,000 scientific papers have been generated. More cool stats in this NASA infographic.
The full mosaic from the Cassini imaging team of Saturn on July 19, 2013… the “Day the Earth Smiled”In this unique mosaic image combining high-resolution data from the imaging science subsystem and composite infrared spectrometer aboard NASA’s Cassini spacecraft, pockets of heat appear along one of the mysterious fractures in the south polar region of Saturn’s moon Enceladus. Image credit: NASA/JPL/GSFC/SWRI/SSISaturn, imaged by Cassini on approach. Credit: CICLOPSTitan and Dione as seen by Cassini. Credit: NASA/JPL/Space Science InstituteThis image taken by the Cassini orbiter on Oct. 15, 2007, shows Saturn’s A and F rings, the small moon Epimetheus and smog-enshrouded Titan, the planet’s largest moon. The image is colorized to approximate the scene as it might appear to human eyes. (Credit: NASA/JPL/Space Science Institute)Cassini imaging scientists used views like this one to help them identify the source locations for individual jets spurting ice particles, water vapor and trace organic compounds from the surface of Saturn’s moon Enceladus. Credit: NASARaw image from Cassini on May 18. Credit: NASA/JPL/SSIHemispheric color differences on Saturn’s moon Rhea are apparent in this false-color view from NASA’s Cassini spacecraft. This image shows the side of the moon that always faces the planet. Image Credit: NASA/JPL/SSIThree of Saturn’s moons bunch together in this image by Cassini. Credit: NASA/JPL/Space Science Institute. Click for larger image.This mosaic of Titan was created from the first flyby of the moon by Cassini in 2004. Credit: NASA/JPL/SSPhoebe imaged by the Cassini spacecraft. Image Credit: NASACassini VIMS image of specular reflections in one of Titan’s lakes from a flyby on July 24, 2012 (NASA/JPL-Caltech/SSI/Jason W. Barnes et al.)A crescent Dione was seen by Cassini on January 29, 2011 from approximately 767,922 kilometers away. Credit: NASA/JPL/SSIRhea, as seen by Cassini. Credit: NASACassini captured this startling image of Saturn’s moon Hyperion. Photo Credit: NASA/JPLets of water ice particles spew from Saturn’s moon Enceladus in this image obtained by NASA’s Cassini spacecraft on Aug. 13, 2010. Image credit: NASA/JPL/SSIThis false-color composite image shows Saturn’s rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini’s visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on Nov. 1, 2008. Credit: NASA/JPL/University of ArizonaThis mosaic of images from NASA’s Cassini spacecraft shows three fan-like structures in Saturn’s tenuous F ring. Such “fans” suggest the existence of additional objects in the F ring. Image credit: NASA/JPL/SSICassini came within 25 kilometers (15.6 miles) of the surface of Enceladus on Oct. 5, 2008. Image credit: NASA/JPL/Space Science Institute
Jets of icy particles bursting from Saturn's moon Enceladus are shown in this Cassini image taken on November 2005. Credit: NASA/ESA/ASI.
Ever since the Cassini spacecraft first spied water vapor and ice spewing from fractures in Enceladus’ frozen surface in 2005, scientists have hypothesized that a large reservoir of water lies beneath that icy surface, possibly fueling the plumes. Now, gravity measurements gathered by Cassini have confirmed that this enticing moon of Saturn does in fact harbor a large subsurface ocean near its south pole.
“For the first time, we have used a geophysical method to determine the internal structure of Enceladus, and the data suggest that indeed there is a large, possibly regional ocean about 50 kilometers below the surface of the south pole,” says David Stevenson from Caltech, a coauthor on a paper on the finding, published in the current issue of the journal Science. “This then provides one possible story to explain why water is gushing out of these fractures we see at the south pole.”
Artist’s impression of the possible interior of Enceladus based on Cassini’s gravity investigation. The data suggest an ice outer shell and a low-density, rocky core with a regional water ocean sandwiched between at high southern latitudes. Cassini images were used to depict the surface geology in this artwork. The mission discovered plumes of ice and water vapour jetting from fractures – nicknamed ‘tiger stripes’ – at the moon’s south pole in 2005. Credit: NASA/JPL-Caltech.
On three separate flybys in 2010 and 2012, the spacecraft passed within 100 km of Enceladus, twice over the southern hemisphere and once over the northern hemisphere.
During the flybys, the gravitational tug altered a spacecraft’s flight path ever so slightly, changing its velocity by just 0.2–0.3 millimeters per second.
As small as these deviations were, they were detectable in the spacecraft’s radio signals as they were beamed back to Earth, providing a measurement of how the gravity of Enceladus varied along the spacecraft’s orbit. These measurements could then be used to infer the distribution of mass inside the moon.
For example, a higher-than-average gravity ‘anomaly’ might suggest the presence of a mountain, while a lower-than-average reading implies a mass deficit.
On Enceladus, the scientists measured a negative mass anomaly at the surface of the south pole, accompanied by a positive one some 30-40 km below.
“By analyzing the spacecraft’s motion in this way, and taking into account the topography of the moon we see with Cassini’s cameras, we are given a window into the internal structure of Enceladus,” said lead author Luciano Iess.
“This is really the only way to learn about internal structure from remote sensing,” Stevenson added.
The only way to get more precise measurements would be to put seismometers on Enceladus’s surface. And that’s not going to happen anytime soon.
Stevenson said the key feature in the gravity data was the negative mass anomaly at Enceladus’s south pole. This happens when there is less mass in a particular location than would be expected in the case of a uniform spherical body. Since there is a known depression in the surface of Enceladus’s south pole, the scientists expected to find a negative mass anomaly. However, the anomaly was quite a bit smaller than would be predicted by the depression alone.
“The perturbations in the spacecraft’s motion can be most simply explained by the moon having an asymmetric internal structure, such that an ice shell overlies liquid water at a depth of around 30–40 km in the southern hemisphere,” Iess said.
While the gravity data cannot rule out a global ocean, a regional sea extending from the south pole to 50 degrees S latitude is most consistent with the moon’s topography and high local temperatures observed around the fractures – called ‘tiger stripes’ at Enceladus south pole.
Many have said Enceladus is one of the best places in the Solar System to look for life. Noted scientist Carolyn Porco and Chris McKay have a recent paper out titled, “Follow the Plume: The Habitability of Enceladus,” where they say that since analysis of the plume by the Cassini mission indicates that the “steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts” that samples from the plume jetting out into space are accessible with a low-cost flyby mission. “No other world has such well-studied indications of habitable conditions.”
These latest findings by Cassini make a mission to Enceladus even more enticing.
Saturn makes a beautifully striped ornament in this natural-color image, showing its north polar hexagon and central vortex (Credit: NASA/JPL-Caltech/Space Science Institute)
Cassini couldn’t make it to the mall this year to do any Christmas shopping but that’s ok: we’re all getting something even better in our stockings than anything store-bought! To celebrate the holiday season the Cassini team has shared some truly incredible images of Saturn and some of its many moons for the world to “ooh” and “ahh” over. So stoke the fire, pour yourself a glass of egg nog, sit back and marvel at some sights from a wintry wonderland 900 million miles away…
Thanks, Cassini… these are just what I’ve always wanted! (How’d you know?)
Saturn’s southern hemisphere is growing more and more blue as winter approaches there — a coloration similar to what was once seen in the north when Cassini first arrived in 2004:
Saturn’s southern hemisphere images from a million miles away (Credit: NASA/JPL-Caltech/Space Science Institute)
(The small dark spot near the center right of the image above is the shadow of the shepherd moon Prometheus.)
Titan and Rhea, Saturn’s two largest moons, pose for Cassini:
Rhea (front) and Titan, images by Cassini in June 2011 (Credit: NASA/JPL-Caltech/Space Science Institute)
The two moons may look like they’re almost touching but in reality they were nearly half a million miles apart!
Titan’s northern “land of lakes” is visible in this image, captured by Cassini with a special spectral filter able to pierce through the moon’s thick haze:
Titan images by Cassini on Oct. 7, 2013 (Credit: NASA/JPL-Caltech/Space Science Institute)
The frozen, snowball-like surface of the 313-mile-wide moon Enceladus:
Enceladus: a highly-reflective and icy “snowball in space” (Credit: NASA/JPL-Caltech/Space Science Institute)
(Even though Enceladus is most famous for its icy geysers, first observed by Cassini in 2005, in these images they are not visible due to the lighting situations.)
Seen in a different illumination angle and in filters sensitive to UV, visible, and infrared light the many fractures and folds of Enceladus’ frozen surface become apparent:
View of the trailing face of Enceladus (Credit: NASA/JPL-Caltech/Space Science Institute)
Because of Cassini’s long-duration, multi-season stay in orbit around Saturn, researchers have been able to learn more about the ringed planet and its fascinating family of moons than ever before possible. Cassini is now going into its tenth year at Saturn and with much more research planned, we can only imagine what discoveries (and images!) are yet to come in the new year(s) ahead.
“Until Cassini arrived at Saturn, we didn’t know about the hydrocarbon lakes of Titan, the active drama of Enceladus’ jets, and the intricate patterns at Saturn’s poles,” said Linda Spilker, the Cassini project scientist at NASA’s Jet Propulsion Laboratory. “Spectacular images like these highlight that Cassini has given us the gift of knowledge, which we have been so excited to share with everyone.”
This view of Saturn's moon Enceladus and its prominent plumes was taken by the Cassini spacecraft on April 2, 2013. Credit: NASA/JPL-Caltech/Space Science Institute.
We can never get enough of seeing those intriguing jets and plumes from Saturn’s moon Enceladus, especially this great view from the Cassini spacecraft where the plumes are back-it from the Sun while the moon’s surface is lit with reflected light from Saturn. And as you can see, those jets are still firing. There are close to 100 geyser jets of varying sizes near Enceladus’s south pole spraying water vapor, icy particles, and organic compounds out into space. If you look closely, you’ll see the entire plume is as large as the moon itself.
Can we please send another spacecraft just to study this fascinating moon?
The image was taken in blue light with the Cassini spacecraft narrow-angle camera on April 2, 2013, when Cassini was about 517,000 miles (832,000 kilometers) from Enceladus.
Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus. Credit: NASA/JPL/SSI.
The geyser jets of Enceladus don’t shoot out in a continuous stream, but are more like an adjustable garden hose nozzle, says Cassini scientist Matt Hedman, author of a new paper about the inner workings of this fascinating tiger-striped moon. Observations from Cassini has found that the bright plume emanating from Enceladus’ south pole varies predictably. The fluctuating factor appears to be how far or close Enceladus is to its home planet, Saturn.
Scientists have hypothesized that the intensity of the jets likely varied over time, but until now had not been able to show they changed in a recognizable pattern. Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini’s visual and infrared mapping spectrometer (VIMS), and looking at data gathered since 2004 when Cassini entered Saturn’s orbit. In 2005, the jets that form the plumes were discovered.
“The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water,” said Christophe Sotin, a co-author and Cassini team member. “Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present.”
This set of images from NASA’s Cassini mission shows how the gravitational pull of Saturn affects the amount of spray coming from jets at the active moon Enceladus. Enceladus has the most spray when it is farthest away from Saturn in its orbit (inset image on the left) and the least spray when it is closest to Saturn (inset image on the right). Credit: NASA/JPL-Caltech/University of Arizona/Cornell/SSI.
The scientists say this new finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon. This is the first clear observation the bright plume emanating from Enceladus’ south pole varies predictably. The findings were published in a scientific paper in this week’s edition of Nature.
The VIMS instrument, which enables the analysis of a wide range of data including the hydrocarbon composition of the surface of another Saturnian moon, Titan, and the seismological signs of Saturn’s vibrations in its rings, collected more than 200 images of the Enceladus plume from 2005 to 2012.
These data show the plume was dimmest when the moon was at the closest point in its orbit to Saturn. The plume gradually brightened until Enceladus was at the most distant point, where it was three to four times brighter than the dimmest detection. This is comparable to moving from a dim hallway into a brightly lit office.
Adding the brightness data to previous models of how Saturn squeezes Enceladus, the scientists deduced the stronger gravitational squeeze near the planet reduces the opening of the tiger stripes and the amount of material spraying out. They think the relaxing of Saturn’s gravity farther away from planet allows the tiger stripes to be more open and for the spray to escape in larger quantities.
“Cassini’s time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are,” said Linda Spilker, Cassini project scientist at JPL. “We’ve come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our Solar System formed.”
Enceladus has likely been subject to other gravitational forces over time as well. Previous studies have shown that over hundreds of millions of years, an existing gravitational interaction between Enceladus and another moon, Dione, has caused the orbit of Enceladus to grow increasingly more elongated, or eccentric.
In turn, this produced much more tidal stress in the past and scientists think that contributed to the wide-scale fracturing and friction within Enceladus’ icy crust. The friction leads to melting of internal ice and produces an ocean and eruptions of water and organics on the surface.
Plumes from Enceladus' geysers are illuminated by reflected light from Saturn. Credit: NASA/JPL-Caltech, Space Science Institute.
According to planetary scientist and Cassini imaging team leader Carolyn Porco, about 98 geyser jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds out into space. The spray from those geysers are evident in this new image from Cassini, showing a big, beautiful plume, illuminated by light reflected off of Saturn. Look closely to see that the plume is as large as the moon itself.
Cassini first discovered the jets of water ice particles in 2005, and since then scientists have been trying to learn more about how they behave, what they are made of and – most importantly – where they are coming from. The working theory is that Enceladus has a liquid subsurface ocean, and pressure from the rock and ice layers above combined with heat from within force the water up through surface cracks near the moon’s south pole. When this water reaches the surface it instantly freezes, sending plumes of ice particles hundreds of miles into space.
A patchwork network of frozen ridges and troughs cover the face of Enceladus. Credit: NASA/ESA, image processed by amateur astronomer Gordan Ugarkovic.
Cassini has flown through the spray several times now, and instruments have detected that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth’s oceans.
Enceladus is just 504 kilometers (313 miles) across, but it potentially could be one of the best spots in the solar system for finding life.
The top image was taken on January 18, 2013. This view looks toward the Saturn-facing side of Enceladus, and was taken when Cassini was approximately 483,000 miles (777,000 kilometers) from Enceladus. Image scale is 3 miles (5 kilometers) per pixel.
The second, face-on, color view of Enceladus was taken by the Cassini spacecraft on January 31 2011, from a distance of 81,000 km, and processed by amateur astronomer Gordan Ugarkovic.
A fine recent view of Saturn as captured by Daniel Robb. (Credit & Copyright: Daniel Robb/Universe Today flickr community. All rights reserved).
A star party favorite is about to return to evening skies.
The planet Saturn can now be spied low to the southeast for northern hemisphere observers (to the northeast for folks in the southern) rising about 1-2 hours after local sunset this early April. That gap will continue to close until Saturn is opposite to the Sun in the sky later this month and rises as the Sun sets.
Opposition occurs on April 28th at 8:00 UT/4:00AM EDT. Saturn will shine at magnitude +0.1 and appear 18.8” in diameter excluding the rings, which give it a total angular diameter of 43”.
Saturn has just passed into the faint constellation Libra for 2013, although its springtime retrograde loop will bring it back into Virgo briefly. Both the 2013 and 2014 opposition will occur in Libra. Saturn will also pass 26’ from +4.2 Kappa Virginis on July 3rd as it moves back into Virgo while in retrograde before resuming direct motion back into Libra.
Saturn currently lies about 15° to the lower left of the +1.04 magnitude star Spica, also known as Alpha Virginis. Remember the handy saying to “Spike to Spica” from the handle of the Big Dipper asterism to locate the region. Another handy finder tip; stars twinkle, planet generally don’t. That is, unless your skies are extremely turbulent!
With an orbital period 29.46 years, Saturn moves slowly eastward year to year, taking 2-3 years to cross through each constellation along the ecliptic.
Oppositions are roughly 378 days apart and thus move forward on our calendar by about two weeks a year. Successive oppositions also move about 13° eastward per year.
Saturn as imaged by the author on June 11th, 2012.
Oppositions of the ringed planet are also currently becoming successively favorable for southern observers over the coming years. Saturn crossed into the southern celestial hemisphere some years back, and will be at its southernmost in 2018.
Saturn won’t pass north of the celestial equator again until early 2026. Saturn is 15 million kilometres farther from us than opposition last year as its moving toward aphelion in 2018.
Saturn will reach eastern quadrature this summer on July 28th and stand its highest south at sunset northern hemisphere observers. South of the equator, it will pass directly overhead or transit to the north. Saturn will be with us for most of the remainder of 2013 in evening skies until reaching solar conjunction on November 6th.
Looking at Saturn with binoculars, you’ll immediately note that something is amiss.
You’re getting a view similar to that of Galileo, who sketched Saturn as a sort of “double handled cup.” In fact, it wasn’t until 1655 that Christian Huygens correctly hypothesized that the rings of Saturn are a flat disk that is not physically in contact with the planet.
Huygens also discovered the large moon Titan. Shining at magnitude +8.5 and taking 16 days to orbit Saturn, Titan is the second largest moon in our solar system after Ganymede. Titan would easily be a planet in its own right if it orbited the Sun. Titan is easily picked out observing Saturn at low power through a telescope.
Saturn’s system of moons visible through a small telescope. orientation is for May 9th, 2013. (Created by the author using Starry Night).
Observing Saturn at slightly higher magnification, five moons interior to Titan become apparent. From outside in, they are Rhea, Dione, Tethys, Enceladus, and Mimas. Exterior to Titan is the curious moon of Iapetus. Taking 79 days to complete one orbit of Saturn, Iapetus varies in brightness from magnitude +11.9 to +10.2, or a factor of over 5 times. Arthur C. Clarke placed the final monolith in the book adaptation of 2001: A Space Odyssey on Iapetus for this reason. Close-ups from the Cassini spacecraft reveal a two-faced world covered with a dark leading hemisphere and a bright trailing side, but alas, no alien artifacts.
But the centerpiece of observing Saturn through a telescope is its brilliant and complex system of rings. The A, B, and C rings are easily apparent through a backyard telescope, as is the large spacing known as the Cassini Gap.
The rings are also currently tilted in respect to our Earthly vantage point. The rings were edge-on in 2009 and vanish when this occurs every 15-16 years.
This year, we see the rings of Saturn at a respectable 19 ° opening and widening. The rings will appear at their widest at over 25° in 2017 and then become edge-on again in 2025.
The average tilt (in degrees) of Saturn’s ring system as seen from Earth spanning 2008-2026. (Graph created by author).
The ring system of Saturn adds 0.7 magnitudes of overall brightness to the planet at opposition this year.
Another interesting optical phenomenon to watch for in the days leading up to opposition is known as the “opposition surge” in brightness, or the Seeliger effect. This is a retro-reflector effect familiar to many as high-beam headlights strike a highway sign. Think of the millions of particles making up Saturn’s rings as tiny little “retro-reflectors” focusing sunlight back directly along our line of sight. The opposition surge has been noted for other planets, but it’s most striking for Saturn when its rings are at their widest.
The disk of Saturn will cast a shadow straight back onto the rings around opposition and thus vanish from our view. The shadow across the back of the rings will then become more prominent over subsequent months, reaching its maximum angle at quadrature this northern hemisphere summer and then beginning to slowly slide back behind the planet again. A true challenge is to glimpse the disk of the through the Cassini gap in the rings… you’ll need clear steady skies and high magnification for this one!
It’s also interesting to note a very shallow partial lunar eclipse occurs with Saturn nearby just three days prior to opposition on April 25th. Saturn will appear 4° north of the Moon and it may be just possible to image both in the same frame.
The location of Saturn and the Full Moon during the April 25th partial eclipse. (Created by the author using Starry Night).
Saturn takes about 30 years to make its way around the zodiac. I remember just beginning to observe Saturn will my new 60mm Jason refractor as a teenager in 1983 as it crossed the constellation Virgo.Hey, I’ve been into astronomy for over one “Saturnian year” now… where will the next 30 years find us?
Saturn's moon Enceladus sprays its salty sea out into space. Those plumes are rich in phosphates. (NASA/JPL/SSI/J. Major)
Thanks to the Cassini mission we’ve known about the jets of icy brine spraying from the south pole of Saturn’s moon Enceladus for about 8 years now, but this week it was revealed at the 44th Lunar and Planetary Science Conference outside Houston, Texas that Enceladus’ jets very likely reach all the way down to the sea — a salty subsurface sea of liquid water that’s thought to lie beneath nearly 10 kilometers of ice.
Enceladus’ jets were first observed by the Cassini spacecraft in 2005. The jets constantly spray fine particles of ice into space which enter orbit around Saturn, creating the hazy, diffuse E ring in which Enceladus resides.
Emanating from deep fissures nicknamed “tiger stripes” that gouge the 512-km (318-mile) -wide moon’s south pole the icy jets — and the stripes — have been repeatedly investigated by Cassini, which has discovered that not only do the ice particles contain salts and organic compounds but also that the stripes are surprisingly warm, measuring at 180 Kelvin (minus 135 degrees Fahrenheit) — over twice as warm as most other regions of the moon.
Where the jets are getting their supply of liquid water has been a question scientists have puzzled over for years. Is friction caused by tidal stresses heating the insides of the stripes, which melts the ice and shoots it upwards? Or do the fissures actually extend all the way down through Enceladus’ crust to a subsurface ocean of liquid water, and through tidal pressure pull vapor and ice up to the surface?
“Baghdad Sulcus,” one of many tiger stripe fissures on Enceladus (NASA/JPL/SSI)
Researchers are now confident that the latter is the case.
In a presentation at the Lunar and Planetary Science Conference titled “How the Jets, Heat and Tidal Stresses across the South Polar Terrain of Enceladus Are Related” (see the PDF here) Cassini scientists note that the amount of heating due to tidal stress seen along Enceladus’ tiger stripes isn’t nearly enough to cause the full spectrum of heating observed, and the “hot spots” that have been seen don’t correlate with the type of heating caused by shear friction.
Instead, the researchers believe that heat energy is being carried upwards along with the pressurized water vapor from the subsurface sea, warming the areas around individual vents as well as serving to keep their channels open.
With 98 individual jets observed so far on Enceladus’ south polar terrain and surface heating corresponding to each one, this scenario, for lack of a better term… seems legit.
What this means is that not only does a moon of Saturn have a considerable subsurface ocean of liquid water with a heat source and Earthlike salinity (and also a bit of fizz) but also that it’s spraying that ocean, that potentially habitable environment, out into local space where it can be studied relatively easily — making Enceladus a very intriguing target for future exploration.
“To touch the jets of Enceladus is to touch the most accessible salty, organic-rich, extraterrestrial body of water and, hence, habitable zone, in our solar system.”
– Cassini imaging team leader Carolyn Porco et al.
Enceladus is actively spraying its habitable zone out into space (NASA/JPL/SSI)
Research notes via C. Porco, D. DiNino, F. Nimmo, CICLOPS, Space Science Institute at Boulder, CO, and Earth and Planetary Sciences at UC Santa Cruz, CA.
Top image: color-composite of Enceladus made from raw Cassini images acquired in 2010. The moon is lit by reflected light from Saturn while the jets are backlit by the Sun.
