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One of the smaller moons in the Saturn system is Daphnis, a little 8 km (5 mile) irregular satellite which orbits the gas giant within the outer rings of the planet (although I guess really the famous rings themselves are composed of innumerable “moonlets”). Daphnis, which has the irregular shape of a potato, orbits Saturn in a 42-kilometer (26 mile) wide belt in the rings—the Keeler Gap. The moon is responsible for clearing this narrow track, and it is felt that by studying this interaction we may learn about accretion and the enigmatic happenings of the early solar system (when more things looked like Saturn). Here is a picture from NASA’s Cassini probe which was released yesterday which shows little Daphnis producing waves in the Keeler belt. What a remarkable image! I need to post more Cassini pictures here. They fill the heart with wonder and give us a chance to get off-planet for a little breather.
Since the moon does not orbit the Earth in a perfect circle, the perigee (the closest point that the moon comes in relation to the planet) changes from year to year. Tonight (November 14, 2016) marks the largest “supermoon” seen in six decades. The moon will not appear so large in the sky again until November 25, 2034.
According to ancient Algonquin lore, the full moons of autumn had various sacred names (well, at least according to the Farmer’s Almanac). The full August moon was the “Sturgeon Moon” because the great fish came together to mate at that time. Likewise, the September full moon occurred when the maize ripened and was thus called “the Corn Moon”. After the harvest, when the weather was perfect for hunting, the October full moon was “the Hunter’s Moon”. The full moon of November was known as the Beaver Moon, since it was an ideal time to trap beaver, which were out and about putting their affairs in order before winter (indeed the industrious rodents were nearly exterminated by trappers—but that is another story).
Tonight’s full moon is thus the Beaver Super Moon. You should go out and appreciate it! For who knows what the future will hold? There may be clouds on the night of November 25, 2034 or maybe you will be on a floating Venus colony with me. Maybe cruel Empress Ivanna will have you chained up and working underground, mining the last seams of coal to feed the Earth’s final sputtering machines. Maybe you will just be busy sending pointless administrative files to people.
Enjoy the Beaver Super Moon! Then later this week, in honor of the season, we will get back to talking about turkeys!
The North Pole of Enceladus during the October 30th, 2015 Cassini Flyby (NASA/ESA/ASI)
Since 2004, the Cassini spacecraft has been in orbit around Saturn. The robot probe (a joint effort of NASA, ESA, and the Italian space agency) received the most press when it launched a flying saucer lander onto Saturn’s planet-like moon Titan, but it is still out there doing amazing work. Last week, while I was busy writing about Halloween themes, the probe made its closest pass yet to Saturn’s ice moon, Enceladus. Enceladus is only 500 kilometers in diameter and it is coated in ice, but it is of great interest to scientists because ice plumes venting from the moon’s south pole seem to indicate a large polar subsurface ocean of liquid water. Warmed above freezing by tidal flux, this ocean beneath the ice probably has a thickness of around 10 km.
View of Enceladus’ south pole geyser, backlit by Saturn
On October 30th, Cassini flew by the icy moon at the dangerously close distance of 30 kilometers (18.6 miles). The probe was directly above the south pole of Enceladus and it collected a little flake of ice to analyze (which strikes me as incredibly amazing and beautiful). It will take some time for the ship’s devices to assay the drop of water from an alien ocean, but Cassini also snapped some photos which we already have. These are taken from point blank range above the south pole. The ocean is down there beneath the scratches and scars. What is the nature of this icy ocean? How long has it been there? Could it possibly harbor life?
2015 year of the goat: Blood red goats desport in front of the full moon as a symbol of this year’s Mid-Autumn festival
Today is a special day! Not only is it the Autumn Festival (Mooncake Day), a lunar harvest (and moon-viewing) festival celebrated by the Chinese and Vietnamese. It is also the last “supermoon” full lunar eclipse for the next 18 years. A “supermoon” happens when the moon is at the closest point in its orbit around Earth. From Earth’s surface (where most of my readers live) the moon thus appears 14% larger and 33% brighter than other full moons. When such a supermoon is eclipsed by the shadow of Earth, the event is known as a “blood moon” by imaginative neopagans and by fundamentalist Christians who hope the world will end soon (and by bloggers desperate for hits). The blood moon designation comes not just because of cultists’ violent fantasy, but because the moon takes on a red tinge during the event.
Blood Moon of 1493 (artist’s interpretation)
Bloodmoon eclipses are rare and there have been none for 33 years—then suddenly four in short succession: tonight’s eclipse will be the final of the batch. I missed the last bloodmoons thanks to clouds and scheduling mishaps…and who knows what I will be doing 18 years from now (hopefully showing beautiful paintings in a fancy gallery or directing cyborgs on a floating city above Venus…but probably decomposing or still working as a lackey in title insurance). Tonight’s event begins at 9:07 PM EST and maximum umbra (“shadow”) occurs at 10:48 PM.
I baked a turkey and made an almond pie for the celestial event (although dark clouds are already swirling on the horizon). Hopefully some of you will join me on rooftops, observatory turrets, and in special moon-viewing pavilions to watch the celestial show!
Update: Here is my drawing from the roof…it’s really hard to draw in the dark!
Artist’s conception of the New Horizons spacecraft flying past Pluto and Charon
More dramatic news from the far reaches of the solar system: NASA’s probe New Horizons has awakened from its nine year hibernation and is powering up to approach Pluto! Although it sounds like “New Horizons” is a boy band, NASA gave up on trying to launch every saccharine teenybopper act into the Kuiper belt (although that is a laudable goal): instead the probe is named after the fact that New Horizons is the first human spacecraft to explore the dwarf planet Pluto and its little moons Charon and Hydra. Launched in January of 2006, New Horizons set the record for the highest launch speed of a human-made object from Earth. The grand piano-sized spacecraft has spent the intervening years hurtling through the darkness of space–although it has periodically come to partial wakefulness to check in with mission control and to snap some dramatic flyby photos of famous locations along its trip (like this photo montage of Jupiter and Io). The craft also used Jupiter’s gravity well to increase its velocity.
Composite image of Jupiter and Io as photographed from New Horizons (NASA)
Since the time the probe was launched, astronomers have discovered two new miniature moons of Pluto: Kerberus and Styx. This means that New Horizons mission planners were forced to assess the possibility of a catastrophic collision with unseen debris or dust left over from these satellites. Computer models suggest that the likelihood of such an accident is remote, but, just in case, NASA has added two dramatic contingency plans for the mission. In one emergency plan, the probe’s satellite dish acts as a dust shield, in the other, the craft drops dangerously close to Pluto, where atmospheric drag has presumably cleared the surrounding space of particles. These worst case plans will almost certainly not be needed, although we will learn more as New Horizons gets closer to the dwarf planet.
After flying past Pluto next July, New Horizons will hurtle into the Kuiper belt where NASA hopes the probe will rendezvous with an icy Kuiper belt object so that we can learn more about these enigmatic leftovers from the creation of the solar system. The coming 7 months should be filled with excitement as we learn more about the Pluto system!
According to astronomers, on Tuesday April 15th 2014 the heavens over North America will feature a rare and magnificent spectacle—a blood moon! The term “blood moon” refers to a full lunar eclipse in which the earth’s umbral shadow completely covers the surface of the full moon. The lunar surface will actually look red because of refracted light from around the earth’s edges. I’m not sure how the term “blood moon” has come to eclipse the more scientific sounding “full lunar eclipse” (probably through internet click-baiting, like everything else) but you have to admit it sounds cool and scary. The phenomena will be visible from the western hemisphere from 1:58 AM EST into the wee hours (peaking between 3:00 AM and 4:00 AM) .
This is a pretty time of year and I am looking forward to sitting in the garden with some plum wine and honey cakes during the eclipse (assuming spring clouds do not intervene). Unfortunately some people have really gotten riled up by the “blood moon’s” dramatic Steven King rebranding. Pastor John Hagee of the Cornerstone Church in San Antonio, Texas has written a book about how tonight’s lunar eclipse (the first of a series of consecutive total lunar eclipses known as a “tetrad) will usher in the biblical end times. Dragons and apocalyptic horsemen will roam the world’s strip malls and Jesus will run around biting people and gouging out eyes…or something like that (I might have sort have glossed over the Book of Revelations after slogging through all those tedious Paul chapters of the New Testament).
John Hagee…well, he certainly looks trustworthy…
Some things get old and wear away, but charlatans trying to scare people with bargain basement eschatology never go out of style. However if you still want some mythology to go along your astronomy (but you aren’t quite ready for the last judgment) there is a Mayan heroine whose name was Xquic, which means “Blood Moon”. She was the daughter of one of the lords of Xibalba, the Mayan underworld, which was filled with tenebrous monsters and cannibal gods. Xquic fell in love with the severed head of a human hero and gave birth to the hero twins whose exploits changed the nature of the Mayan cosmos. Perhaps you could spare lovely Xquic a thought as you watch the moon darken and turn incarnadine—but maybe you’ll be to busy eating honey cakes… or fighting with the mounted incarnation of pestilence!
Oh man, Tuesday is going to be a long day…
Neptune’s Moon Triton photographed by Voyager 2 (NASA)
It is absolutely freezing here in Brooklyn—a great vortex of bitter Arctic air has swirled south across huge swathes of the nation. The temperature here is 9° Fahrenheit (or -13° Celsius). Imagine how much worse things are in Minnesota, where it is -14° Fahrenheit (or -25° Celsius). Brrr! It hurts my fingers to write about it–even in my overheated study (well—bedroom, really). Now truly stretch your mind from the frozen heartland of America to the edge of the planetary solar system. The largest moon of the ice giant Neptune is the moon Triton, discovered in 1846 by English astronomer/brewer William Lassell, and named for the son of Poseidon. On the surface of Triton temperatures plunge to 36…which is to say 36 K (Kelvin). To translate that is -237° Celsius or a bone chilling -395° Fahrenheit.
Artist’s rendering of an ice volcano on Triton with Neptune in the background (NASA)
Triton is a strange moon. It is the seventh largest moon in the solar system and it is the only large moon to orbit its planet in a direction opposite from the planet’s rotation (which is called a retrograde orbit). Since there is no model for retrograde moons forming from accretion disks, Triton must be a captured object from the Oort cloud—and, indeed, the moon is extremely similar in composition to Pluto and other dwarf planets of the Solar system’s distant periphery. Despite the extreme cold of Triton’s surface, the moon is geologically active. Like Earth, the moon is probably differentiated into layers: a core, a mantle, and a crust. The crust is formed of ice: frozen water, methane, and nitrogen. A large polar cap covers the southern pole, but much of the rest of the moon is a“cantaloupe” surface of melted and refrozen ice. The surface is (geologically) young. Cryovolcanic activity and tidal forces have kept the ice active. Cryovolcanoes were first spotted on Triton during the Voyager 2 flyby in 1989 (the first time such phenomenon were ever observed). Because of tidal warming (caused by gravitational interaction with Neptune), Triton may have once had a liquid ocean beneath the crust, but this has likely solidified assuming that there is no radioactive decay from the rocky core.
A size comparison of Earth, Earth’s moon, and Triton
Triton is closer to Neptune than the Earth’s moon is to Earth…and Neptune is seventeen times more massive than Earth. This doesn’t bode well for the long term future of Triton. Within the next three and a half billion years, the moon will either be pulled into Neptune’s surface and swallowed or it will be ripped to pieces and form a spectacular ring structure like Saturn’s.
China’s “Moon Rabbit” lunar rover separates from Chang’e moon lander (image from Beijing Aerospace Control Center)
It is time to congratulate the Chinese space agency for landing a probe and rover on the moon. The landing was the first “soft landing” (where no equipment is damaged) on the lunar surface in 37 years—so I am also happy that humankind is back on its nearest neighbor. The Chang’e lunar lander touched down on the Bay of Rainbows on Saturday Morning, December 14th (at least in EST). The Jade Rabbit rover successfully drove out onto the arid dust of the flat “bay” a few hours later. Hopefully the Chinese mission will continue to go successfully and the Chinese Space Agency will continue to launch ambitious space missions. With a command economy and authoritarian government, the People’s Republic could pour money into aerospace science and quickly push space exploration forward–much in the way that the Soviet Union did back in the glory days of the space race. Such a challenge would be good for international science, and it would be good to remind our worthless legislators here in the United States to work together to properly fund science, research, and development.
Chang’e
Chang’e is named after the goddess of the moon in classical Chinese myth, but her story is sad and ambiguous. It is a tale open to several different interpretations (which I will write about, but not now). The moon rabbit, also known as the jade rabbit was originally a pet of the lonely moon goddess, however because his story is far less tragic than hers (and because he is a lovable trickster-rabbit), he has become a figure of immense popularity. According to myth he is an apothecary who grinds medicines, spells, and immortality elixirs on behalf of the gods (and for himself–because what trickster doesn’t skim a little?).
The jade rabbit shows up everywhere in Chinese myth and culture. He even pops in for cameos in some of the great works of Chinese literature (for example, he is the final antagonist in “Journey to the West” wherein the heroes discover him masquerading as the princess of India!). More importantly, in East Asia, it is believed that the stains of the moon are the image of the jade rabbit. Although I have never been able to see the “man on the moon”, the jade rabbit is always there on a bright full moon. I am glad the Chinese space agency named their space probe after this master apothecary and superb trickster!
An optimistic artist’s conception of lunar farming
Earth is the only known home of life. For all of humankind’s aspirations and ambitions, we have only succeeded in walking on one other celestial body and putting a few people, rats, and ant colonies in some leaky tin cans in low Earth orbit (I’m sorry to be so brutally honest about Skylab, Mir, and ISS). This is deeply troubling since I believe humankind can only survive and redeem itself by moving into the heavens (although some of my cynical friends worry that we will only be exporting humankind’s problems and appetites wherever we go). Whatever the case, we are not moving very quickly towards the skies. Political gridlock, greed, and a lack of engineering and imagination have kept us from making any real progress at space-steading. So far we have proven to be maladroit stewards who are incapable of bearing life’s luminous seed into space (although we are amassing a nifty robot fleet around the solar system, and, despite our many flaws, we keep learning).
This is why I was so excited to see the most recent space exploration news: NASA recently announced that they are teaming up with the mad moguls of Google in a project to grow crops on the moon! The space agency is constructing a tiny (approximately 1 kilogram) capsule to grow a handful of plants on the lunar surface. The little growth capsule with its cargo of air water and seeds will be dropped off on the moon by the Moon Express (a lunar vehicle built by Google in hopes of obtaining the lunar X Prize).
The initial project will not exactly provide much produce for a lunar greengrocer. An online article by James Plafke describes the contents of the lunar garden canister, “Currently, the chamber can support 10 basil seeds, 10 turnip seeds, and around 100 Arabidopsis seeds. It also holds the bit of water that initiates the germination process, and uses the natural sunlight that reaches the moon to support the plant life.”
The Moon Farmer from Futurama
Arabidopsis is not exactly a favorite at the supermarket, but it was the first plant to be genetically sequenced and it is used in biology labs everywhere as a model organism. In a pinch though, the basil and turnips might be good for some sort of impromptu Italian farm-style dish. NASA will monitor the seed growth and development from Earth with an eye on how lunar gravity and radiation levels impact the germinating seeds and the growing plants. Admittedly the microfarm is a small step towards colonies beyond Earth, but at least it is a step (and frankly the beginnings of agriculture here on Earth were similarly small and incremental). Or, who knows? Maybe the turnips will climb out of the canister and start dragging their knuckles along the lunar plains and throwing rocks at the Chinese landers.
You never know where science will take you
Gibbous Europa
(Credit: Galileo Project, JPL, NASA)
Tonight is Yuri’s Night, when space enthusiasts around the world celebrate the first human trip to outer space made by Yuri Gagarin fifty two years ago. You can read about Yuri here. It is an excellent occasion to assess what is most exciting in space exploration. Unfortunately nobody has jumped forward to build a floating colony on Venus. Indeed NASA seems rather flat footed lately—building a series of colorless rockets and sending successive similar rovers to Mars. Fortunately there is one exciting mission which still has not definitively been cancelled because of budget stalemate.
Proposed Europa Clipper (NASA)
The Europa Clipper mission is a $2bn dollar project to launch a probe to Jupiter’s moon Europa, a large icy satellite covered in cracked ice. Europa is slightly smaller than Earth’s moon and has a thin oxygen atmosphere. It is one of the smoothest items in the solar system. Astronomers believe that an ocean of liquid water lies beneath Europa which is warmed by tidal flexing (a process which causes orbital and rotational energy to be converted into heat). The surface of Europa is bathed in exotic radiation which rips apart water molecules and leaves oxidants like hydrogen peroxide. All of this means that Europa is the most likely planet in the solar system to harbor unknown life. It has even been theorized that beneath the ice the ocean could have black smoker type environments–and just possibly thermal vent or “cold seep” ecosystems.
Artist’s concept of the cryobot and hydrobot probes (NASA)
Because of this, scientists have been anxious to get a closer look at the intriguing moon. Various proposals have been put forward for missions directly to the moon. The Pioneer and Voyager spacecraft took pictures of it as they flew through the solar system and subsequent missions also took readings and photos—but there has been no Europa-centric mission to really find out about the oceans below the cracked ice. One (amazing!) proposal was to send a nuclear powered melt probe to melt through the ice and sink to the bottom of the ocean, whereupon a mini-sub probe would emerge and explore the extraterrestrial ocean! That plan was shelved because it was too expensive (and nobody could figure out how to sterilize the probe). The proposed Europa Clipper mission is more modest but still quite amazing. Here’s how the Jet Propulsion Laboratory describes it:
The Europa Clipper mission would send a highly capable, radiation-tolerant spacecraft into a long, looping orbit around Jupiter to perform repeated close flybys of Europa.
The possible payload of science instruments under consideration includes radar to penetrate the frozen crust and determine the thickness of the ice shell, an infrared spectrometer to investigate the composition of Europa’s surface materials, a topographic camera for high-resolution imaging of surface features, and an ion and neutral mass spectrometer to analyze the moon’s trace atmosphere during flybys…The nominal Europa Clipper mission would perform 32 flybys of Europa at altitudes varying from 2700 km to 25 km.
That sounds amazing! Join me in lifting a glass to Yuri Gagarin and also join me in hoping that our moribund government funds this far-sighted mission to what might be life’s other home in the solar system!
Yuri Gagarin–the first human to go to space
