Enhanced-color image of Hyperion from Sept. 26, 2005. (NASA/JPL/SSI)
On Sunday, May 31, the Cassini spacecraft will perform its last close pass of Hyperion, Saturn’s curiously spongelike moon. At approximately 9:36 a.m. EDT (13:36 UTC) it will zip past Hyperion at a distance of about 21,000 miles (34,000 km) – not its closest approach ever but considerably closer (by 17,500 miles/28,160 km) than it was when the image above was acquired.*
This will be Cassini’s last visit of Hyperion. It will make several flybys of other moons within Saturn’s equatorial plane over the course of 2015 before shifting to a more inclined orbit in preparation of the end phase of its mission and its operating life in 2017.
At 255 x 163 x 137 miles (410 x 262 x 220 km) in diameter, Hyperion is the largest of Saturn’s irregularly-shaped moons. Researchers suspect it’s the remnant of a larger body that was blown apart by an impact. Hyperion’s craters appear to have a “punched-in” look rather than having been excavated, and have no visible ejecta or secondary craters nearby.
Impacts on Hyperion tend to “punch in” the surface material, rather than blasting it out. (NASA/JPL/SSI. Edit by J. Major.)
Hyperion orbits Saturn in an eccentric orbit at a distance of over 920,000 miles (1.48 million km)…that’s almost four times the distance our Moon is from us! This distance – as well as constant gravitational nudges from Titan – prevents Hyperion from becoming tidally locked with Saturn like nearly all of its other moons are. In fact its rotation is more of haphazard tumble than a stately spin, making targeted observations of any particular regions on its surface virtually impossible.
Images from the May 31 flyby are expected to arrive on Earth 24 to 48 hours later.
As small as it is Hyperion is Saturn’s eighth-largest moon, although it appears to be very porous and has a density half that of water. Read more about Hyperion here and see more images of it from Cassini here and here.
*Cassini did come within 310 miles (500 km) of Hyperion on Sept. 26, 2005, but the images to make up the view above were acquired during approach.
UPDATE June 1, 2015: the raw images from Cassini’s flyby have arrived on Earth, check out a few below. (Looks like Cassini ended up with the same side of Hyperion again!)
Hyperion on May 31, 2015. Credit: NASA/JPL-Caltech/SSI. (Minor editing by J. Major.)Hyperion on May 31, 2015. Credit: NASA/JPL-Caltech/SSI.Hyperion on May 31, 2015. Credit: NASA/JPL-Caltech/SSI. (Minor editing by J. Major.)
Animation of images acquired by New Horizons on Jan. 27–Feb. 8, 2015. Hydra is in the yellow square, Nix is in the orange. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute.)
Now on the final leg of its journey to distant Pluto the New Horizons spacecraft has been able to spot not only the dwarf planet and its largest moon Charon, but also two of its much smaller moons, Hydra and Nix – the latter for the very first time!
The animation above comprises seven frames made of images acquired by New Horizons from Jan. 27 to Feb. 8, 2015 while the spacecraft was closing in on 115 million miles (186 million km) from Pluto. Hydra is noted by a yellow box and Nix is in the orange. (See a version of the animation with some of the background stars and noise cleared out here.)
“Professor Tombaugh’s discovery of Pluto was far ahead its time, heralding the discovery of the Kuiper Belt and a new class of planet. The New Horizons team salutes his historic accomplishment.”
– Alan Stern, New Horizons PI, Southwest Research Institute
Launched Jan. 19, 2006, New Horizons will make its closest pass of Pluto and Charon on July 14 of this year. It is currently 32.39 AU from Earth – over 4.84 billion kilometers away.
“It’s thrilling to watch the details of the Pluto system emerge as we close the distance to the spacecraft’s July 14 encounter,” said New Horizons science team member John Spencer from the Southwest Research Institute (SwRI). “This first good view of Nix and Hydra marks another major milestone, and a perfect way to celebrate the anniversary of Pluto’s discovery.”
Along with the distance between Earth and Pluto, New Horizons is also bridging the gap of history: a portion of Mr. Tombaugh’s ashes are being carried aboard the spacecraft, as well as several historic mementos.
Annotated and unannotated versions of the LORRI images from Feb. 8 (top and bottom); the right side has had Pluto’s glare and additional background stars removed. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Each frame in the animation is a combination of five 10-second images taken with New Horizons’ Long-Range Reconnaissance Imager (LORRI) using a special mode that increases sensitivity at the expense of resolution. Celestial north is inclined 28 degrees clockwise from the “up” direction in these images.
The dark streaks are a result of overexposure on the digital camera’s sensitive detector.
Pluto and its moons, most of which were discovered while New Horizons was in development and en route. Charon was found in 1978, Nix and Hydra in 2005, Kerberos in 2011, and Styz in 2012. Credit: NASA/HST
Pluto has a total of five known moons: Charon, Hydra, Nix, Styx, and Kerberos. Pluto and Charon are within the glare of the image exposures and can’t be resolved separately, and Styx and Kerberos are too dim to be detected yet. But Hydra and Nix, each around 25–95 miles (40–150 km) in diameter, could be captured on camera.
More precise measurements of these moons’ sizes – and whether or not there may be even more satellites in the Pluto system – will be determined as New Horizons approaches its July flyby date.
Everywhere we look on Earth, we find life. Even in the strangest corners of planet. What other places in the Universe might be habitable?
There’s life here on Earth, but what other places could there be life? This could be life that we might recognize, and maybe even life as we don’t understand it.
People always accuse me of being closed minded towards the search for life. Why do I always want there to be an energy source and liquid water? Why am I so hydrocentric? Scientists understand how life works here on Earth. Wherever we find liquid water, we find life: under glaciers, in your armpits, hydrothermal vents, in acidic water, up your nose, etc.
Water acts as a solvent, a place where atoms can be moved around and built into new structures by life forms. It makes sense to search for liquid water as it always seems to have life here. So where could we go searching for liquid water in the rest of the Universe?
Under the surface of Europa, there are deep oceans. They’re warmed by the gravitational interactions of Jupiter tidally flexing the surface of the moon. There could be life huddled around volcanic vents within its ocean. There’s a similar situation in Saturn’s Moon Enceladus, which is spewing out water ice into space; there might be vast reserves of liquid water underneath its surface. You could imagine a habitable moon orbiting a gas giant in another star system, or maybe you can just let George Lucas imagine it for you and fill it with Ewoks.
The white dwarf G29-38 (Image Credit: NASA)
Let’s look further afield. What about dying white dwarf stars? Even though their main sequence days are over, they’re still giving off a lot of energy, and will slowly cool down over the coming billions of years. Brown dwarfs could get in on this action as well. Even though they never had enough mass to ignite solar fusion, they’re still generating heat. This could provide a safe warm place for planets to harbor life.
It gets a little trickier in either of these systems. White and brown dwarfs would have very narrow habitable zones, maybe 1/100th the size of the one in our Solar System. And it might shift too quickly for life to get started or survive for very long. This is our view, what we know life to be with water as a solvent. But astrobiologists have found other liquids that might work well as solvents too.
Artist concept of Methane-Ethane lakes on Titan (Credit: Copyright 2008 Karl Kofoed). Click for larger version.
What about life forms that live in oceans of liquid methane on Titan, or creatures that use silicon or boron instead of carbon. It might just not be science fiction after all. It’s a vast Universe out there, stranger than we can imagine. Astronomers are looking for life wherever makes sense – wherever there’s liquid water. And if they don’t find any there, they’ll start looking places that don’t make sense.
What do you think? When we first find life, what will be its core building block? Silicon? Boron? or something even more exotic?
And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!
Where did Mars’ moons Phobos and Deimos come from? How did they end up in orbit around Mars? This cool video from the folks at Kurzgesagt answers the most-oft asked questions about these mini moons.
You should also check out their other wonderful videos, like the one about our own Moon, below, which explains how big our Moon really is. The answer might surprise you.
This graphic imagines asteroid 243 Ida as it would fantastically hover over the city of St. Louis, Missouri. Credit and copyright: Ciro Villa.
So, how big is that space rock?
Sometimes when I see data on sizes and distances in relation to stuff out in space, it’s hard to get a frame of reference, since those two categories tend to lean towards the super-big. But now, I’ve got a little help. Space enthusiast and software engineer Ciro Villa has brought some of these references closer to home with these fun graphics that provide accurate size ratios and proportions of objects in space compared to places on Earth.
Villa calls these graphics “hovering celestial objects” and while all of these scenarios are impossible in real life, he’s placed large asteroids and moons next to Earthly locations to provide a good frame of reference for dimensions. Please note that most of these objects have absolutely no chance of colliding with Earth as they are not anywhere near our neighborhood and are not expected to visit it either.
“My representations are is purely for illustrative purposes,” Villa said. “I have maintained the size ratios and proportions as accurately as possible just to demonstrate the dimensions. This is mostly a ‘fun’ exercise.”
For example, I regularly drive through the St. Louis, Missouri metro area, so I have a sense of how big it is. Above, Villa places Asteroid 243 Ida — which has an average diameter of 31.4 km (19.5 miles) — to hover right above St. Louis. 31 km is about the distance from East St. Louis, Illinois to Creve Coeur, Missouri, which are the generally accepted eastern and western borders of the St. Louis metro area. I could probably drive across Ida in about 30 minutes — if it’s not rush hour, that is!
To create these graphics, Villa uses Google Maps, NASA data and Gimp image editing software. Again, these graphics are for fun, but I really find them useful!
And Villa provided a caveat: “Please note that I am not a professional graphic artist, so I’m sure people are going to find plenty of imperfections in these depictions,” he said. “The important point I am trying to convey is mainly the size dimensions comparing with a known area of Earth.”
Here are more:
Asteroids Orcus and Vanth hovering over Eastern Texas and Western Arkansas. Credit and copyright: Ciro Villa.
Here are a bigger pair of objects in comparison to an area of Eastern Texas and Western Arkansas. 90482 Orcus is a trans-Neptunian Kuiper belt object that is about 800 kilometers in diameter. Orcus has a fairly large moon orbiting it named Vanth, which is about 300 km in diameter.
Asteroid 433 Eros over Kennedy Space Center, Florida. Credit and copyright: Ciro Villa.
This asteroid might pay Earth a close visit, but not for a couple of million years. Eros is the second largest NEO (Near Earth Object), with a diameter of approximately 34 kilometers, and here Villa imagines Eros centered over the VAB (Vehicle Assembly Building) at Cape Canaveral, covering the Cape area from approximately the southern end of the Canaveral National Seashore to the Pine Island Conservation area, with the VAB in about the middle, as the crow (or sandhill crane) flies.
While Eros is technically an NEO, it made one of its closest passes of Earth in 2012 of 16.6 million miles (26.7 million km) and won’t pass that close again until 2056. A look ahead with orbital mechanics suggests that Eros may move to an Earth-crossing orbit in about two million years, given the right perturbations by gravitational interactions.
216 Kleopatra is an asteroid belt object shaped like a dog bone (or a deformed dumbell). Its length is approximately 217 kilometers; just about the size of New Jersey. Credit and copyright: Ciro Villa.
And to show the scale of several moons in our Solar System, Villa made these comparisons:
An imaginary graphic depicting how Deimos would look if it hovered over Paris, France. Credit and copyright: Ciro Villa.
“Deimos is about 15 kilometers across, so I have measured a portion of the city of Paris, France of about 5 Kilometers and properly scaled Deimos,” Villa said. “For added dramatics, I have purposely shown enough of Deimos hovering to show about 5 kilometers of Paris, to show some of the landmarks (notice the Eiffel tower). Had I decided to show all of Deimos, the scale would have been too large to recognize any of the landmarks of Paris.”
How Saturn’s moon Enceladus would look if it hovered over southern England. Credit and copyright: Ciro Villa.
Continuing these imaginary montages, here is one of our favorite moons, Enceladus, with an approximate diameter of about 500 kilometers, seen drifting over Southern England. That’s about the same distance from Plymouth to Leigh-on-the-Sea in the UK.
A graphic imagining asteroid Phoebe (Saturn IX) hovering Central Florida. Credit and copyright: Ciro Villa.
This last one is a bit personal for Villa, since he lives in Florida. Here, Saturn’s moon Phoebe hangs over Central Florida. “Phoebe shares an approximate diameter of 200 kilometers with the central portion of the state,” Villa said, “and I wanted to ‘play’ with my imagination a bit!”
Raw image of Saturn with two moons acquired by Cassini on March 11, 2014 (NASA/JPL-Caltech/SSI)
On March 11, NASA’s Cassini spacecraft was acquiring some images of Saturn’s back-lit limb when two of its moons decided to make an entrance. Like stage hands in a darkened theatre the moons quickly passed across the scene, moving between Saturn and the spacecraft and, because of exposure time and spacecraft motion, getting a bit blurred in the process.
In the image above the silhouette of one moon can be seen at bottom right — Mimas, perhaps — while another’s crescent can be made out at upper left… possibly Enceladus. Very cool!
Watch an animation of the moons below:
Two of Saturn’s moons drift into the scene on March 11, 2014 (NASA/JPL-Caltech/SSI. Animation by Jason Major.)
While I admit I’m not 100% sure which moons these are, based on their apparent shapes, positions, and relative sizes I’d make my guess that these are 318-mile (511-km) -wide Enceladus and the 246-mile (395-km) -wide Mimas.
Possible location of icy spray, if Enceladus is in fact this moon’s real name
Cassini was 843,762 miles (1,357,903 km) from Saturn when the images were acquired. And, if the larger moon at left is Enceladus, I’m thinking south in these images is up based on the barely-perceptible presence of a lighter area along its top edge that could be icy spray from its southern geysers. (See enlarged detail at right.)
Saturn, of course, is on the right. A small segment of the bright arc of its backlit limb is what’s running diagonally down across the image.
These images have not yet been calibrated or cataloged by NASA or the Cassini team.
See the latest raw images from Cassini on JPL’s mission page here.
*I say “dark moons” but actually Enceladus and Mimas are pretty bright, both being composed of a lot of ice. Enceladus is actually the most reflective world in the Solar System!
Cassini narrow-angle camera image of Janus from Sept. 10, 2013 (NASA/JPL-Caltech/SSI)
One of 62 moons discovered thus far orbiting giant Saturn, Janus is a 111-mile (179-km) -wide pockmarked potato composed of rock and ice rubble. The image above shows Janus as seen with Cassini’s narrow-angle camera on September 10, 2013, from a distance of 621,000 miles (1 million km), floating against the blackness of space.
Despite its apparent isolation in the image above, though, Janus isn’t alone. It shares its orbit around Saturn with its slightly smaller sister moon Epimetheus, and they regularly catch up to each other — and even switch places.
Janus and Epimetheus: Saturn’s “dancing moons” (NASA/JPL/SSI)
Janus and Epimetheus travel in nearly the same track, about 94,100 miles (151,500 km) out from Saturn. They occasionally pass each other, their gravity causing them to switch speeds and positions as they do; Janus goes faster and higher one time, slower and lower the next – but the two never come within more than about 6,200 miles of each other.
The two moons switch positions roughly every four years.
This scenario is referred to in astrophysics as a 1:1 resonance. Astronomers were initially confused when the moons were discovered in 1966 as it wasn’t known at the time that there were actually two separate moons in a single orbit. (This wasn’t confirmed until Voyager 1’s visit to Saturn in 1980.) It’s been suggested that Janus and Epimetheus will eventually come to orbit a single Lagrangian point around Saturn instead of trading places… in about another 20 million years.
The view above looks toward the Saturn-facing side of Janus. Covered in both dark and light colored material, Janus’ surface is thought to be coated with a layer of fine dust that slides down its steeper slopes, revealing the brighter ice beneath.
Cassini image of Janus from April 2010 (NASA/JPL-Caltech/SSI)
Animation of Iapetus briefly blocking a distant bright object. (NASA/JPL-Caltech/SSI. Assembled by Jason Major.)
It’s a cosmic cover-up! No, don’t put your tinfoil* hats on, this isn’t a conspiracy — it’s just Saturn’s moon Iapetus drifting in front of the bright star Gamma Orionis (aka Bellatrix) captured on Cassini’s narrow-angle camera on August 10, 2013.
Such an event is called an occultation, a term used in astronomy whenever light from one object is blocked by another — specifically when something visually larger moves in front of something apparently smaller. (The word occult means to hide or conceal… nothing mystical implied!)
The animation above was assembled from 19 raw images publicly available on the JPL Cassini mission site, stacked in Photoshop and exported as a gif. They’ve been rotated 90º from the originals but otherwise they’re right from Cassini’s camera.
Iapetus, seen above as just a thin crescent, is best known for its two-toned appearance. One half of the 914-mile-wide moon is bright and icy, the other coated with a layer of dark reddish material, giving it a real “yin-yang” appearance. (Ok, I guess that’s a little mystical. But purely coincidental.)
The Tao of Iapetus (NASA/JPL-Caltech/SSI)
It’s thought that the dark material originates from a more distant moon, Phoebe, which is being pelted by micrometeorites and shedding its surface out into orbit around Saturn, which eventually gets scooped up by the backwards-orbiting Iapetus.
The difference in albedo affects how Iapetus absorbs solar radiation too, causing the water ice beneath the darker material to evaporate over the course of its 79-Earth-day rotation and migrate around its surface, creating a sort of positive feedback loop.
While neat to look at, occultations are important to science because they provide a way to briefly peer into a world’s atmosphere (or in a small moon’s case, exosphere). Watching how light behaves as it passes behind the limb of a planet or moon lets researchers learn details of the air around it — however tenuous — pretty much for free… no probes or flybys needed!
The occulted star above is Bellatrix, the 1.6-magnitude star that marks Orion’s left shoulder.
Iapetus orbits Saturn at the considerable distance of 2,212,889 miles (3,561,300 km). Learn more about Iapetus here, and as always you can find more fantastic Cassini images from Carolyn Porco’s team at the Space Science Institute in Boulder, Colorado at the CICLOPS site here.
Just one of the many images from Cassini used to make up "Around Saturn"
In honor of this today’s Wave at Saturn and The Day the Earth Smiled events, celebrating images to be taken of Earth from Saturn, here’s a wonderful movie showing highlights from Cassini’s exploration of the giant planet, its magnificent rings, and fascinating family of moons.
Assembled by Fabio Di Donato in memory of astrophysicist, author and activist Margherita Hack, who passed away June 29 at the age of 91, this video is an impressive tour of the Saturnian system — and a truly stunning tribute as well.
“She made me love the stars,” Fabio wrote.
This video shows a selection from more than 200,000 pictures taken by the Cassini spacecraft around Saturn’s rings in a period between 2005 and 2013. RAW images were processed to PNG thanks to the Vicar-to-PNG procedure provided by Jessica McKellar.
The music is Jazz Suite No.2: VI Waltz 2 by Shostakovich, performed by the Armonie Symphony Orchestra.
As always, you can see the latest images and news from the Cassini mission here, and find out how your photo is going to be taken from 900 million miles away (and also 60 million miles away from Mercury!) here.
Video: Fabio Di Donato. Original images: NASA/JPL-Caltech/SSI.
P.S.: Want to get a personalized certificate saying you “Waved at Saturn?” Click here.
