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TIME: Almanac 1990
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1990 Time Magazine Compact Almanac, The (1991)(Time).iso
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091189
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09118900.017
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1990-09-17
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SPACE, Page 65Postcards from a Distant WorldMysteries deepen as data pour in from Neptune and its icy moon
The Voyager 2 spacecraft last week swiveled its scanning
platform, looked over a metallic shoulder and opened the shutter
of its narrow-angle camera for one lingering goodbye picture of
Neptune and its icy moon, Triton. The resulting photo showed a pair
of lovely, pale white crescents reflecting off the most distant
planet and a moon that is the coldest known object in the solar
system.
After that farewell, Voyager turned its back on Neptune and
began an estimated 23-year trip toward the heliopause, the point
where the solar wind dies down and interstellar space begins. But
already, as Edward Stone, the Voyager mission's chief scientist,
put it, "this has been the journey of a lifetime."
There was little leisure for sentiment last week, as scientists
rushed to sort through the mountain of data still pouring in from
Voyager's close encounter with Neptune. Only a fraction of the
photographs snapped during the flyby have been processed, and the
bulk of the radio signals -- some 992 lbs. of magnetic tape -- is
only now being shipped from tracking stations to NASA's Jet
Propulsion Laboratory in Pasadena, Calif.
As in Voyager's close encounters with other planets, surprises
and puzzles abound. Neptune's Great Dark Spot, roughly the size of
earth, is perhaps its biggest mystery. One series of images showed
the spot revolving around the planet every 18.3 hours like a
twirling glob of pizza dough. Some astronomers think it is an
ocean; others, a giant gaseous storm soaring high above the planet.
The number of rings circling Neptune seemed to change from day
to day. At last count there was one broad sheet of dust and three
thin rings, one of them dotted at one spot with clumps of material
arrayed like sausage links. Closer to the planet's surface, Voyager
spotted thin wisps of cirrus clouds clinging to the Great Dark
Spot. These resembled misty clouds hugging a Swiss Alp in a high
wind.
Outside the rings, Voyager's radio antennas picked up the
crackle of a magnetic field tilted a rakish 50 degrees from the
planet's axis of rotation and shifted mysteriously off-center.
Scientists speculate that the dynamo generating the magnetic
disturbance is not a deep central core, like the earth's, but a
spherical shell of liquid located near the surface of the planet.
The real star of Voyager's last picture show, though, was
Triton, the largest and strangest of Neptune's eight moons. Images
pieced together last week revealed in detail a complex and dynamic
body. Parts of Triton's surface are glazed brightly with pinkish
ice, while others are pockmarked like a ripened cantaloupe. Using
3-D imaging computers to zoom in for a closer look, scientists saw
steep mountains and rugged cliffs, deep pools of dark, oozing
material and vast oceans of slush.
Struggling to make sense of the bizarre landscape, Laurence
Soderblom of the U.S. Geological Survey put forward a "crazy idea"
that was just wild enough to ring true. The key to Triton's strange
geology may be the kind of volcanic activity that takes place when
surface temperatures reach -400 degrees F. At that temperature,
gaseous nitrogen would freeze as hard as rock. But 60 ft. to 100
ft. below the surface, tidal pressures could transform the solid
nitrogen into a viscous fluid that could rise through faults and
erupt explosively at the surface, spewing gas and icy debris 20
miles into the air. If true, Soderblom's theory would make Triton
only the third celestial body known to have active volcanoes --
after earth and Jupiter's moon Io.
Its grand tour of four planets complete, Voyager 2, like its
sister craft Voyager 1, followed a trajectory beyond the solar
system. If all goes well, the aging robot should reach the
heliopause before its fuel runs out and its instruments fall
silent, around the year 2012. But even then it will drift on,
approaching Barnard's star in 6,500 years and passing Sirius, the
brightest star visible from earth, in 296036. Searching for words
to close the final Voyager 2 press conference, mission chief Stone
chose lines from T.S. Eliot:
Not fare well,
But fare forward, voyagers.