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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

Yesterday’s post—which featured a gory painting of medieval deer hunting—makes one feel sorry for the poor beleaguered deer, which are surely among the most beautiful and graceful of all animals.  And those painted deer were being pursued by crossbow hunters—imagine how much worse things would be with high-powered rifles.  Well actually you don’t have to imagine–here in North America, the dominant cervid, the magnificent white-tailed deer (Odocoileus virginianus) was severely overhunted in the 1800’s as hunters shot wild deer and sold the venison at the market.  Deer populations crashed down below 400,000.  Entire regions of the country lost the white-tailed deer completely.  The sacred animal of Artemis was in deep trouble across the United States.

Deer hunting in 1916

To rectify this situation, the Lacy Act, the first federal wildlife law, was passed in 1900.  The law banned the interstate trafficking of venison (along with other wild game).  Then the Great Depression and the Second World War came along and everything changed again.  During the Depression, rural landholders were forced to move into cities to make a living and land which had been under the plough began to grow back into forest.  When World War II broke out a generation of hunters went abroad to shoot at the Axis instead of whitetails.  After the war, in the 1950s, a clever biologist named Crockford invented a dart-gun system for capturing white-tailed deer and releasing them into habitats where they had died out. So deer made a comeback but their predators did not.  Wolves, grizzlies, cougars, jaguars, alligators, and lynxes were relegated to the deep forest and swamp of protected national parks.

So by the end of the twentieth century, white-tailed deer populations were spiking out of control (heading to well above 30 million) and this in turn had a terrible effect on the forests.  When a forest is partially or wholly timbered (or when it is denuded by some natural means such as a tornado) there is a succession of plant growth which after decades leads back to a mature hardwood forest.  The first plants to grow back are meadow plants–short-lived annual herbs and meter-tall woody plants. Over the course of years these weeds give way to hardwood seedlings like oak and maple which can tolerate the shade created by the provisional meadow growth.  However, in areas overpopulated by deer, the woody meadow plants are nipped up by starving deer and other tree seedlings which can out-compete the great forest trees for nutrient gathering (but which are not shade-tolerant to survive the meadow plants) then flourish.  Beeches, wild cherries, or exotic invaders grow up and the trees of the great forest take lifetimes to supplant them (if they do at all).  In the meantime the overpopulated deer begin to starve and suffer diseases even as they damage the forests.  A strange truth of ecosystems is that predators are nearly as necessary as their prey—even hardy generalists like the white-tailed deer which can live almost anywhere need population controls for their own good (as well as that of the forest).  Perhaps the ancient Greeks were wise to decide that their goddess of the wilderness was both a hunter and a protector of animals and trees.

The white-tailed deer (Odocoileus virginianus)

Biologists, foresters, rangers, and sportsmen are all trying to unscramble the secrets to ecosystem equilibrium, but there might not be any real long-term balance.  The tropical swamps and forests of the Eocene gave way to the temperate woodlands of the Oligocene (where the first tiny deer developed in Europe) which in turn led to the savannahs of the Miocene which allowed artiodactyl grazers to radiate out across the world.  But it is hard to think in such big terms and it is uncomfortable to think about what will come next.  Something within me longs for homeostasis—for the right number of lovely deer beneath the tall native oaks and tulip poplars forever and ever.

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