Suzy B Software 2/Suzy B Software CD-ROM 2 (1994).iso/nasa/asteroid/asteroid.txt

Text File | 1995-05-02 | 7KB | 136 lines

ASTEROID.TXT


 T H E   A S T E R O I D S
 By Carolyn Collins Petersen

Ever meet Hazel Stone?  She's a feisty lady, who's seen it all -- and
some believe -- done it all.  Her stories of The Galactic Overlord
thrill millions of viewers, she's a top-flight space pilot, and she can
beat the pants off anybody (except her grandson, Lowell) at chess.
Nobody would believe that she once took part in the uprising to liberate
Luna -- and, nobody would believe that she once almost died amongst the
asteroids because she forgot to check her oxy bottles.

If you haven't met Hazel yet, she's one of the central figures in
Robert A.  Heinlein's "The Rolling Stones" -- a science fiction book
about a family that roams the solar system in search of adventure.

Part of Hazel's story does indeed take place amongst the asteroids -- a
collection of 100,000 or so rock fragments sometimes referred to as
'the minor planets'.  This belt of tiny worldlets lies mostly between
the orbits of Mars and Jupiter, with a few maverick asteroid groups
making their way out as far as Saturn, and inward toward the orbit of
Earth.

The asteroids have been the subject of many a science fiction story.
Many tales postulate huge mining companies sweeping through the belt,
turning the ore-ridden rocks into metal for spaceships.  Others -- such
as Heinlein's -- turn the Asteroid Belt into a future frontier mining
camp, with feisty, grizzled old prospectors staking their claims on
rotating odd lumps of rock.  Lately, in a kind of "truth is stranger
than fiction" turnabout, asteroids have been linked with dinosaurs and
collisions with Earth.

Mining seems to be a popular pastime in the asteroids of the future --
and while it may seem rather farfetched to even consider the idea,
asteroid mining COULD be done.  Not right now, to be sure, but in some
future decade, scientists and miners could descend on a hapless asteroid
for a spate of assaying.

What is the fascination with these asteroids?  What is it about them
that makes them such a target for mining?  And, why the link with
dinosaurs?

We have no first-hand experience in the asteroid belt, so most of the
information available on the area has come from observations made here
on Earth.

It used to be a common belief that the asteroids were once a planet, a
world which exploded sometime in the misty past of the solar system.
Indeed, the asteroids do orbit an area of the solar system where a
planet WAS predicted to exist by Bode's Law.  (Bode's Law is a
mathematical way to predict the positions of the planets in the solar
system.)  In fact, the search for a planet between the orbits of Mars
and Jupiter led indirectly to the discovery of the asteroids.

The asteroid Ceres was discovered in 1801, and its orbit was confirmed
later that year.  Within the next six years, Pallas, Juno and Vesta were
discovered -- all by astronomers watching carefully for small specks of
light that seemed to move through the sky from night to night.  The
discoverer of Ceres, Giuseppi Piazzi, had been asked to search for the
missing planet -- but intead, was actually looking for comets!

(The honor of naming the asteroids generally have fallen to their
discoverers.  Unfortunately, as more were discovered, hapless
astronomers ran out of operatic heroines, flowers, wives and scientists
after whom they could name their finds.  There are now over 3000
asteroids named, some with such monickers as Gaussia, Washingtonia, and
Rockefellia!)

Asteroids are grouped by the characteristics of their orbits.  These
"families" of asteroids generally move at about the same orbital speed
and inclination.  Observers have identified about 100 families of
asteroids.

Ground-based observations of asteroids have given us some idea of their
sizes and orbital characteristics.  Most of them that we have been able
to measure range in size from 1025 km (635 miles) down to 32 km (19
miles) in diameter.  Undoubtedly there are much smaller particles in the
belt.  It turns out -- based on our estimates of size, and the
relatively small number of asteroids -- that if you glued all the
asteroids together and made them into a planet -- you'd get a world a
bit smaller than Pluto!  It seems that the asteroids were never a planet
-- but more likely a collection of rocky worldlets that never got it
together to make a planet!

While most of the asteroids are so far away that we cannot see them
very well, some few asteroids actually cross the path of the Earth's
orbit. About 1300 of these have been identified so far, and they are
grouped into three families:  the Atens, Apollos and Amors.  Icarus is
one of these asteroids, and passed within 6.4 million kilometers (around
4 million miles) of Earth, in 1967.

It is theoretically possible that an asteroid could hit the Earth.
Indeed, some current theories of dinosaur extinction hinge on the actual
collision of an asteroid with the earth some 65 million years ago.  This
collision could have kicked up a tremendous amount of dust into the
atmosphere, obscuring the Sun and causing a general cooling trend in the
weather.  This cooling trend, if sudden, would have killed off the plant
life on which the dinosaurs lived, thereby killing the dinosaurs.  So
goes the theory.

At the heart of the theory is the element iridium -- which is known to
be abundant in meteorites of asteroid-belt origin.  Iridium is not too
abundant on Earth -- but core samples of the Earth's rock layers show an
iridium-rich layer dated back about 65 million years. Chances of another
asteroid hitting the Earth are fairly slim -- some scientists put it at
3.5 per every million years.

Aside from iridium, most asteroids fall into three categories:

 C, or carbonaceous S, or silicaceous M, or metallic.

The first types are carbonacious chondrites -- stony, carbon-based
bodies.  The Silicaceous types are mostly silicon, with other metals in
smaller amounts.  These are redder and brighter than the others. The
metallic asteroids are mostly iron and nickle, more massive than the
others.  All three types are of interest to scientists studying the
origin and evolution of the solar system.

But, rocky asteroids are not the sole inhabitants of the Belt.  There
are, scientists feel, a great many former comets in orbit out there.
These icy nuclei were probably perturbed from their paths to the Sun by
the gravitational pull of Jupiter.

No doubt all of these different asteroids will be of interest to future
geologists.  Not far behind them will probably be the miners -- who, if
science fiction accounts hold up -- will mine the ore that will build
spaceships, space stations and all of the other tools that we will need
someday to further our own adventures in the outer solar system.  For
now, though, the asteroids remain somewhat enigmatic -- another place to
explore in the planetary neighborhood.