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Meanwhile…three quarters of a billion kilometers away, the Juno space probe continues its exploration of the gas giant Jupiter.   The probes orbit brings it to within 4,200 kilometers (2500 miles) of the cloudtops once every 53 days.  So far, Juno has made 10 such passes (out of a planned 12 before the mission’s end in July).  As the astrophysicists and planetary scientists work to make sense of mission data, NASA has made the raw image data available to the world.  Private citizens have used it to create these stunning images of the largest world in the Solar System.  Since I can’t even begin to explain the vast atmospheric complexities behind these swirling psychedelic wonders, I will leave them here without comment.  Marvel at our huge planetary neighbor with its marbelized super storms and spare a moment to thank Gerald Eichstädt & Seán Doran for putting these amazing pictures together.

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There are more pictures coming in from NASA’s Juno mission to Jupiter and they are amazing. The plucky space probe has entered an orbital pattern which causes it to swoop from one pole of the gas giant to the other in 2 short hours (that may not sound like a short period…but Jupiter is enormous). As it passes close to the gas giant, Juno has been able to photograph and record hitherto unknown features of the fifth planet from the sun—such as a magnetic field twice as powerful as predicted and intricate and heterogeneous ammonia weather systems.
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Perhaps the most stunning aspect of this new trove of data comes from Jupiter’s previously unexplored poles which are filled with intricate webs of cyclones—each up to 1400 kilometers in diameter. You can see them here on astonishing photos. Scientists are eager to learn more about the storms—and what lies beneath them. The coming months will feature even more beautiful images from the solar system’s grandest planet—and maybe we will get some answers too concerning what is under the clouds and what powers these colossal storms on our breathtaking neighbor.
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Based on what we are learning from the exoplanet surveys of the past decade, our galaxy is the home of an immense number of Jovian-size gas giant planets.  There are countless “hot Jupiters”–gas giants located close to their stars which whip around and around their orbits in ridiculously short “years”.  There are frigid slow gas giants and super massive ones—practically brown dwarves– which are larger than Jupiter.  There is an endless proliferation of Uranus and Neptune type giants. Imagine them all glittering in strange colors with weird shapes.  They are cloaked in alien clouds and covered in mysterious storms.  Who knows what lies beneath?

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All of these billions of giant planets seem pretty hypothetical to me as I sit here at my cramped & cluttered desk on solid little Earth.  Yet they exist.  They are out there in numbers too vast to comprehend. However, right now, NASA is conducting the most comprehensive exploration yet of the gas giant we can access.  Juno’s mission is just getting underway in earnest, and the largest gas giant in our own backyard should reveal lots about all of the billions which are out of reach.

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I am sad that I can neither understand nor convey the loftiness of this crazy ongoing mission. It is an astonishing undertaking—but we are so inundated by with murky political battles and vulgar popular drivel, that it is hard to see the utterly astonishing nature of this undertaking.

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Maybe I can put it in perspective somewhat. Imagine back to the year 1609 AD when Henry Hudson was first seeing the river which was later named after him. Before him was an exquisite expanse of islands, bays, and sparkling river. The vast waterway flowed down from unknown mountains into a bay surrounded by lovely islands.  The whole expanse was filled with flocks of unknown birds and schools of fish. Beyond the thriving marshes, mysterious forests were filled with moving shadows.

Now multiply that a billion times: replace Henry Hudson with a tiny fragile robot and replace the Hudson River with luminous gas oceans large enough to entirely submerge scores of Earths.  That is what is happening right now.  As you sit reading this on a little glowing screen, we are making fundamental discoveries about a whole planet.

On August 27, 2016, Juno executed the first of 36 orbital flybys over Jupiter. The doughty spacecraft was only 4,200 kilometers (2,500 miles) above Jupiter’s atmosphere. It sent back the first detailed images of the north pole of Jupiter—and it is unlike the rest of the planet.

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The North Pole of Jupiter as seen by Juno [NASA]

To quote Scott Bolton, one of the lead scientists of the Juno mission, “[The] first glimpse of Jupiter’s north pole…it looks like nothing we have seen or imagined before….It’s bluer in color up there than other parts of the planet, and there are a lot of storms. There is no sign of the latitudinal bands or zone and belts that we are used to — this image is hardly recognizable as Jupiter. We’re seeing signs that the clouds have shadows, possibly indicating that the clouds are at a higher altitude than other features.”

Jupiter’s clouds contain whole continent-like regions of air which are different than the rest of the planet’s storms and whirls.  We don’t yet know why or how, but we are finding out.  As we do so, we are peeling back a layer of mystery which surrounds all such worlds.

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Solar Radiation Streaming over the North Pole of Jupiter

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Happy (belated) Fourth of July! While everyone was out barbecuing and amusing themselves with colorful novelty explosions, there was big news in space exploration: NASA’s Juno probe, which launched from Earth five years ago, has finally reached the gas giant planet and entered orbit. The robot spacecraft, which is about the size of a basketball court, is now dancing nimbly amongst the system of moons and rings and radiation belts around the giant world.

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The probe is a remarkable spacecraft.  It traveled 2.7 billion kilometers (1.7 billion miles) to reach the exact orbit which NASA planned for it.  The secret behind its astonishing precision (even when traveling at 165,000 mph) is the autonomy of its sophisticated navigational computer.  Mission controllers do not have to radio the probe from half-way across the solar system (which would take minutes—or longer. Instead the probe navigates itself. The ship computer is shielded beneath a titanium vault to keep radiation from frying its clever electronic brain.

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Among the planets, Jupiter is a sort of greedy eldest child.  Scientists who study planetary formation believe that the gas giant formed first of all the planets and it took the lion’s share of available matter left over from the formation of the sun. Jupiter is more than twice as massive as all the other planets in our solar system put together: indeed, it is three hundred and eighteen times more massive than Earth.  Yet we know shockingly little about this bruiser. Very basic questions about Jupiter remain unanswered. For example we still do not know whether the planet has a rocky core beneath its vast colorful atmosphere.

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As we learn more about exoplanets which orbit other stars, questions about the formation of solar systems have become more numerous.  Astronomers have been particularly perplexed by the number of “hot Jupiters,” giant gas planets which are extremely close to their stars.  Was Jupiter such a world at some point before moving to its current location, or is it a huge freak?  We simply do not know.  Scientists would also like to know more about the unimaginably vast cloudscapes of Jupiter.  What dynamics move these huge bands of pressurized gas?

As Jupiter formed, it was bombarded by strange radiation.  The depths of Jupiter’s storms must still feature giant lightning strikes. This sort of treatment can cause hydrocarbons and ammonia to form amino acids.  Maybe life has a Jovian origin.  Maybe Jupiter still has life floating around like aerial zooplankton.  Again, we just don’t know much about the giant world…

Did anybody see that amazing episode of "Cosmos"?

Did anybody see that amazing episode of “Cosmos”?

However, now that Juno has arrived we can start to answer some of these questions.  The probe will go through various start-up and test sequences until Oct. 19 when it moves to a 14-day orbit of the planet and really starts scrutinizing our giant neighbor.

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Oh, one more thing—NASA has been getting better at PR to make space more accessible and “fun” for us laypeople following at home (as witnessed by the July 4th arrival).  Juno also has a crew of three Lego astronauts: Galileo, Jupiter, and Juno herself.  This leads me to write about Juno herself, for she is a terrifying figure among the gods.  More about her tomorrow!

Voyager I

Voyager I

Today (September 12, 2013) NASA announced that Voyager I has officially left the solar system.  The probe is the first human-made object to enter interstellar space: it is farther away from Earth than anything else people have ever made.  Launched on September 5, 1977, Voyager’s primary mission was to fly by Jupiter and Saturn and take pictures (and electromagnetic radiation readings) of the two worlds and their systems.  The probe reached Jupiter in 1979 and Saturn in 1980.  After a close fly-by of Titan, the moon with an atmosphere, the spacecraft was flung out of the plane of the solar system.  Only this summer has it reached the heliopause, where the sun’s electromagnetic energy is matched by the ambient energy of the cosmos (although since only minimal instruments are running on Voyager, astrophysicists may be a long time arguing about when exactly the craft slipped out of the solar system).

The Great Red Spot of Jupiter as imaged by Voyager I

The Great Red Spot of Jupiter as imaged by Voyager I

A Volcanic Eruption on Io (imaged by Voyager I)

A Volcanic Eruption on Io (imaged by Voyager I)

 

The Atmosphere of Titan (imaged by Voyager I)

The Atmosphere of Titan (imaged by Voyager I)

Voyager is not moving as quickly as the solar probes mentioned in yesterday’s post, but neither is it moving slowly (its current velocity is 38,000 miles per hour).  However such speed is minimal in the face of interstellar vastness (although Voyager is due to pass within 1.6 light years of the red dwarf star Gliese 445 in 40,000 years).

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In the Roman pantheon, Janus is the two-faced god of beginnings, limits, doors, gateways, and departure.  Unlike the other Greco-Roman deities, Janus was not imported from Greece to Rome.  How he arrived in the Roman pantheon is unclear: some scholars believe that he was originally a gatekeeping deity of the near East while others argue he was an original Latin deity who was worshipped in Italy before Rome rose to power.  Similarly there are different myths concerning his origin.  The most dramatic tale of his creation asserts that he was made by Uranus, god of the primal heavens as a love present for dark Hecate.  Janus despised being in the underworld so he escaped from Hecate by diving into the river Styx and swimming to the world above.

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After fleeing the underworld, Janus acted as one of the earliest kings of Rome in the golden era when the titans ruled the world, however at the end of the titanomachy—the epic war between titans and Olympians—he made the poor decision to give shelter to Saturn, hated father of Jupiter.  Jove was furious at Janus because of this betrayal and he cursed him with immobility and with a second face.  Thereafter Janus stood at the threshold of heaven to open and close the gate as Jupiter came and went.

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Janus was a popular god for the Romans and they worshipped him whenever they started a new venture or embarked on a trip.  January is named after the god and the first day of every month is dedicated to him. The ancient temple of Janus stood in the center of Rome was open during war and closed during times of peace.  Since the Romans were a warlike people the temple was rarely closed and sometimes stood open for hundreds of years at a time.

Gibbous Europa (Credit: Galileo Project, JPL, NASA)

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)

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)

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

Yuri Gagarin–the first human to go to space

Ferrebeekeeper has already posted about the aegis, the invulnerable shield of Jupiter/Zeus, which was fashioned by the king of the gods from the skin of his foster mother (and loaned to his favorite daughter.  However the concept of Jupiter’s shield has a larger significance.

Yesterday morning, an unknown object appears to have slammed into the planet Jupiter.  Oregon based astronomer Dan Petersen was watching the gas giant at 4:35 AM PST (September 10th, 2012) when a bright flash erupted from near the Jovian equator.  Another amateur astronomer, George Hall of Dallas, TX was filming the planet through his 12 inch telescope and recorded the flash (you can see the video here).

The September 10th, 2012 Flash on Jupiter (recorded by George Hall)

Thanks to the florid nature of science fiction entertainment, it is easy to imagine scaly green Guarillions testing out energy weapons against the huge planet, but the flash was almost certainly from a comet or asteroid striking the surface (we will know more as astronomers look at Jupiter this week).  Such impacts have proven to be much more common than imagined.

Jupiter has a mass of approximately 1.9 x 1027 kg (which is equivalent to 318 Earths).  The gas giant is 2.5 times more massive than all of the rest of the non-sun objects in the solar system added together. The sun itself comprises between 99.8% and 99.9% of the mass of the system (which should put some perspective on the precision required for our ongoing programs to scan the nearby galaxy for exoplanets).

Jupiter Relative to the Sun and the Earth (NASA Goddard Space Flight Center)

The huge mass of Jupiter (relative to other planets and moons) means that a great many asteroids, comets, meteors, and whatnot fall into its gravity well.  Were it not for Jupiter, these hazardous leftovers would otherwise fly all around the solar system willy-nilly knocking holes in things and creating unsafe conditions (just ask the poor dinosaurs about this).  The ancient myths of the Aegis provide a powerful metaphor for this protection. Jupiter does indeed provide a shield for the smaller planets:  If it did not suck up so many cosmic punches, who knows if life could even have survived?

(Lithograph by F. Heppenheimer)

An Artist’s conception of Jupiter seen from Amalthea

If you wanted to build a vacation home with a truly spectacular view, one of the possibilities you might consider is Jupiter’s moon Amalthea.  Discovered in 1892 by the American astronomer Edward Emerson Barnard (who also discovered Barnard’s star) Amalthea was the first Jovian moon discovered by someone other than Galileo Galilei.  Amalthea is the largest inner satellite of Jupiter and from its surface Jupiter would appear to take up 46.5 degrees of the sky (from the horizon to directly overhead is 90 degrees).  Amalthea is in synchronous rotation around Jupiter and so the planet would always appear in the same part of the sky (provided you were on the right part of the moon).  From Amalthea the sun would disappear behind the planet’s bulk for an hour and a half each revolution.

A digital rendering of Amalthea

The 66 known Jovian moons are largely named after the lovers and children of Jupiter/Zeus, however Amalthea is an exception: it is named for Jupiter’s step-mother the goat/nymph Amalthea who fed and cared for the young god as he quickly grew to adulthood and whose impervious skin was fashioned into the aegis of the king of the god.  The name Amalthea was used for the moon almost since it was discovered but was only formally adopted by the International Astronomical Union in 1975.

Amalthea Visited by the NASA spacecraft Galileo

Amalthea is a strange and mysterious moon which perplexes astronomers.  Its irregularly shape is somewhat like a potato and it is covered with deep craters and tall mountains.  The surface of the moon is deep red in color (in fact Amalthea is the reddest object in the solar system) however weird bright patches of green appearing on the mountain slopes–the nature of which is unknown.  The moon appears to be formed of ice and rubble, but if had formed where it now is during the early days of Jupiter, it would have melted.  The moon must have formed elsewhere and been captured by Jupiter—a recent paper speculated that it was originally a Trojan asteroid.  Since Amalthea is made of ice and heterogeneous rubble scientists are perplexed at why gravity has not rearranged its into a more spherical shape.  Since Amalthea is so close to Jupiter it’s orbit is decaying and it will one day fall into the gas giant (so you may want to get really good insurance on the vacation house I mentioned in the first paragraph).

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