Monday, April 21, 2014

A Planet You Can Believe In

The tiny Saturnian moon of Enceladus was in the news a few weeks ago.  Data sent back from  the Cassini spacecraft indicated the possibility of a subsurface body of water the size of Lake Superior, lying about 20 to 25 miles beneath the moon’s icy face.  No one has actually observed this underground sea, though geysers of ice crystals have been detected at the moon’s south pole.  There is no direct evidence, only a series of inferences based on analysis of the satellite’s gravitational field.  Discrepancies in the strength of the gravitational field at the south pole have been measured; this has led some to speculate that only liquid water would have sufficient density to account for these differences. Thus, there must be an enormous underground body of liquid water near the south pole.

A variety of life forms have adapted to living in the eternal darkness of Earth’s underground rivers and lakes—and have thrived in even more extreme environments.  Why not deep within Enceladus, at the bottom of its silent subterranean sea, kept warm by the intense gravitational pulls of Saturn and its sister moons?  This possibility makes Enceladus a fourth candidate among worlds in our solar system that may harbor life. The others are Mars, Europa, a moon of Jupiter, and Titan, another moon of Saturn.

Pretty slim pickings.

However, the now decrepit Kepler telescope, which so far has confirmed the presence of 962 exoplanets, has provided data identifying “the first validated, Earth-size planet in the habitable zone of another star,” according to Dr. Quintana of the SETI Institute and Ames Research Center.  (It has conveniently accomplished this just as the Kepler planet-finding mission came to an end last year.)  

The planet is called Kepler 186f.  Some researchers suspect that, like Earth, the exoplanet is made up largely of iron, rock, ice and liquid water, probably has a rocky surface, and experiences a gravitational field similar to that of our world.  But in the absence of any data about the planet’s mass, the only thing known with any certainty is its relative size—small—and its distance from the sun it orbits.

Kepler 186f shares its star with four other inner planets.  Its sun is not like ours at all and is classified as a red dwarf—not nearly as young or as bright or as warm as ours.  One scientist remarked that Kepler 186f would receive less light than the planet Mars receives from our sun.  It would seem to be a dim, cold place, mostly frozen unless it possesses an insulating atmosphere.  The year on Kepler 186f is only 130 days long.  Keplerians, if they exist, must file income taxes about every 4 months.

Replication of these results, ordinarily expected of scientific research, will not be likely.  Kepler 186f is 500 light years away—so a visit there will not be possible in this millennium.  It is too far out in space for serious scientific study, yet just distant enough to inspire imaginative speculation and fervent exobiological faith.

Several scientists are calling a mission to Enceladus though, which relatively speaking, is right in our back yard.  If samples of ice crystals from its southern geysers can be brought back to earth, they might be found to contain extraterrestrial microbes—or worse.  Mars has been a bust—not even the exhalations of microbes can be found there.  But science has demonstrated again and again, conclusively, without a doubt, without need for replication, that wondrous energetic life exists on just one planet in the entire universe—ours, of course.  Life was created and placed here, long ago.  Its purpose is to spread far beyond its home planet, and bring color, noise and movement to all the dark silent worlds that surround us.   

(For related discussions, see also Enceladus! and How Many Extraterrestrials Are There?)

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