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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

Antarctica Seen from Space

Imagine standing high above planet Earth and looking down at the blue and white band of seas surrounding Antarctica.  You are looking at one of the most important features of the Earth’s surface.  The turning of the planet and strong westerly winds drive the cold deep waters of the Southern Ocean into the planet’s largest and most powerful current system, the Antarctic Circumpolar Current (ACC).  The clockwise current isolates the frozen continent into its own self-replicating climate. Since there are no great land masses lying in the ring of open water at these latitudes, the ACC also forces waters from the ocean depths up to the surface.  This upwelling brings rich nutrients from the depths and causes immense blooms of phytoplankton (which in turn nurture life throughout all the world-ocean).  Additionally the current stirs the circulation of the Atlantic, Pacific, and Indian Oceans.

The ACC has been known to sailors for centuries.  A sailing ship can travel west along the current with great speed (if the sailors have the bravery and stamina to confront the fierce winds of “the roaring forties”).   The “clipper route” was the fastest sailing route around the world, but it was dangerous.  The three great capes (Cape Horn, the Cape of Good Hope, and Cape Leeuwin) all claimed innumerable lives as did wind, ice, and storm.  Today the clipper route has been abandoned as self-powered ships bring their cargoes of plastic junk straight across the ocean from China (and then cut across the Panama Canal) but sailing enthusiasts still recognize the fastest way to ride the wind around the planet.  The major circumnavigation sailboat races all travel the clipper route.

“Roaring Forties” (Gordon Frickers, oil on canvas)

The true history and significance of the ACC vastly exceeds the paltry recent concerns of navigation and world trade.  Geologists estimate that the ACC current began spinning around 34 million years ago at the end of the Eocene epoch as Antarctica split from Australia and drifted further south.  Back when Antarctica and Australia were still connected, the great amalgamated continent was a place where cold southern water and chill weather mixed together with tropical warmth—thus causing the whole planet to warm up.  However when Antarctica broke away and drifted south, it started a series of climate feedback loops.  The oceans around the continent began to freeze and ice started to build up on the mountains.  An entire continental ecosystem began to change in the cold.  The tropical forests (which had been filled with strange marsupials) began to die and become tundra.  As the Oligocene progressed and Drake’s Passage widened, the rivers–once filled with catfish–turned to ice.  The landmasses of Antarctica became crushed down under immense glaciers.  Antarctica died in the cold.  By 15 million years ago it became as it is now–home to only tardigrades, lichen, and a handful of visiting birds and seals.

The Transantarctic Mountains (photo by John Goodge)

Even now the Antarctic Circumpolar Current still isolates the continent from the warmth of the rest of the world.  Yet through upwelling of iron and other nutrients, the current bolsters an immense fecundity of phytoplankton–the great primary producer of the ocean.  Masses of copepods and krill feed on the algae and the diatoms and they in turn are eaten by fish, mollusks, mammals, birds, filter feeders…everything.  The great southern oceans are among the most diverse and strange habitats for living things.  It is there that the largest mollusk on the planet is found—which is the subject of an upcoming post.

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