Greetings  young  Earthlings.    This  article  is not meant to scare you but to
inform you of the facts about the asteroid threat to planet Earth.  All advanced
civilizations  have  asteroid  defenses,  as  Earth  will someday in the future.
Perhaps you, my young Earthling friends, will be  the  ones  to  deploy  Earth's
first  asteroid defenses so Study Hard and stay in School! Let us begin with the
location of the large majority of asteroids.  You may  already  know  from  your
science  classes the main Asteroid Belt lies between Mars and Jupiter at average
distances  of  2.1  to  3.3  astronomical  units  (AU)  (195,300,000  miles   to
306,900,000  miles)  from  the  Sun.    From  my article on the Planets you will
remember that an astronomical unit, abbreviated as AU, is a convenient  unit  of
measure  that  scientists  use when talking about the huge distances involved in
the solar system.  One AU is equal to 93 million  miles  which  is  the  average
distance  between  the Earth and the Sun.  If you clicked the above link you now
realize that the Cassini Spacecraft, (shown at the top of the picture), and  all
other spacecraft sent to the outer planets must pass through this Asteroid Belt.
The blue line is Cassini's course on its way to Saturn.  Asteroids are chunks of
rock  or  iron  or a combination of both.  They may be rubble left over from the
formation of our solar system or the remains of small planets that  collided  or
were torn apart by the gravity of giant Jupiter and Mars.  Though most asteroids
remain in the belt some are drawn inward toward Earth and the inner planets.




Please Click all underlined Links for pictures like the above.  The
Dark Blue Line was Cassini's course on its way to Planet Saturn.
The Home Page has the link to the Cassini SpaceCraft Web Site.
Cassini is still in orbit around Planet Saturn and has Great
Pictures of Saturn's Rings and Moons!


We will begin with Ceres the largest known asteroid.  Ceres is NOT a  threat  to
planet  Earth  thank  goodness! Asteroid Ceres is estimated to contain more than
one third of the total mass of all other asteroids combined! Ceres is  also  the
First  asteroid  to  be discovered.  Near the end of the 18th century scientists
became aware of the regular spacing of the planets in the  inner  solar  system,
with a gap between Mars and Jupiter, where they expected to find another planet.



On January 1, 1801, the Sicilian  astronomer  Giuseppe  Piazzi  at  the  Palermo
Observatory  discovered a moving object in the region.  Scientists of the period
first thought Ceres was the missing planet but determined it was too small to be
a  planet.  As more objects were discovered in this region, they became known as
Asteroids or Minor Planets.  Ceres orbits the sun once  every  4.6  years  at  a
distance of 414 million kilometers (257 million miles), and it spins on its axis
once every nine hours.  Although Ceres has been observed for 200 years there  is
still  a  debate  about  its  exact size.  Recently an international team led by
scientists at the Southwest Research Institute (SwRI) observed  Ceres  with  the
Hubble  Space  Telescope  (HST)  at  ultraviolet  wavelengths using a resolution
higher than previously attained.  The high-resolution images allowed the team to
refine  measurements  of  Ceres  and  indicate  that  the  asteroid  is slightly
flattened, with a diameter ranging from  930  to  970  kilometers  (578  to  603
miles).  The team plans to do even more with a new instrument to be installed on
HST next year.



My Favorite Spacecraft Galileo, that  was  orbiting  Jupiter,  took  some  great
images  of  the asteroids Gaspra and Ida in 1991 and 1993 respectively, while on
its way to Jupiter.  Gaspra  is  roughly  17  kilometers  (10  miles)  long,  10
kilometers  (6  miles)  wide and Gaspra rotates once in roughly 7 hours.  Ida is
the first asteroid discovered  to  have  a  natural  satellite.   The  Image  of
Asteroid  243 Ida  and its moon, Dactyl, taken by Galileo in June 1994 is really
cool.  Analysis of the images show  that  Ida  is  58  kilometers  long  and  23
kilometers  wide  (36  x  14  miles).  Dactyl is about 56 miles from Ida in this
shot.  Dactyl is approximately egg-shaped, measuring  about  1.2  x  1.4  x  1.6
kilometers 0.75  x  0.87 x 1 mile.

Asteroid 243 Ida & moon Dactyl

Image Credit: NASA/JPL       Image Addition Date: 1996-01-29

This color picture is made from images  taken  by  the  imaging  system  on  the
Galileo  spacecraft about 14 minutes before its closest approach to asteroid 243
Ida on August 28,  1993.   The  range  from  the  spacecraft  was  about  10,500
kilometers  (6,500 miles).  The images used are from the sequence in which Ida's
moon was originally discovered;  the  moon  is  visible  to  the  right  of  the
asteroid.   This picture is made from images through the 4100-angstrom (violet),
7560 A (infrared) and 9680 A (infrared) filters.  The color is 'enhanced' in the
sense  that  the  CCD  camera is sensitive to near infrared wavelengths of light
beyond human vision; a 'natural' color picture of  this  asteroid  would  appear
mostly  gray.    Shadings in the image indicate changes in illumination angle on
the many steep slopes of this irregular body as well as subtle color  variations
due to differences in the physical state and composition of the soil (regolith).


Asteroid 951 Gaspra
Image Credit: NASA/JPL		Image Addition Date: 1996-02-01
Please Click all underlined Links for pictures like the above. 

Original Caption Released with Image:
This picture of asteroid 951 Gaspra is a mosaic  of  two  images  taken  by  the
Galileo  spacecraft  from  a  range  of  5,300 kilometers (3,300 miles), some 10
minutes before closest approach on October 29, 1991.  The Sun  is  shining  from
the right; phase angle is 50 degrees.  The resolution, about 54 meters/pixel, is
the highest for the Gaspra encounter and is about three times better  than  that
in  the  view  released  in  November  1991.  Additional images of Gaspra remain
stored on Galileo's tape recorder, awaiting playback in November.  Gaspra is  an
irregular  body  with  dimensions  about  19  x 12 x 11 kilometers (12 x 7.5 x 7
miles).  The portion illuminated in this view is about 18 kilometers (11  miles)
from lower left to upper right.  The north pole is located at upper left; Gaspra
rotates counterclockwise every 7 hours.  The large concavity on the lower  right
limb  is  about  6  kilometers  (3.7  miles) across, the prominent crater on the
terminator, center left, about 1.5 kilometers (1 mile).  A striking  feature  of
Gaspra's  surface  is  the  abundance  of small craters.  More than 600 craters,
100-500 meters (330-1650 feet) in diameter are visible here.  The number of such
small  craters  compared  to  larger  ones  is  much greater for Gaspra than for
previously studied bodies of comparable size such as  the  satellites  of  Mars.
Gaspra's  very  irregular  shape  suggests  that the asteroid was derived from a
larger body by nearly catastrophic collisions.  Consistent with such  a  history
is  the  prominence  of  groove-like  linear features, believed to be related to
fractures.  These linear depressions, 100-300 meters wide  and  tens  of  meters
deep,  are  in two crossing groups with slightly different morphology, one group
wider and more pitted than the other.  Grooves had previously been seen only  on
Mars's moon Phobos, but were predicted for asteroids as well.  Gaspra also shows
variety of enigmatic curved depressions and ridges in  the terminator  region at
left.    The  Galileo  project,  whose primary mission is the exploration of the
Jupiter system in 1995-97, is managed for NASA's Office  of  Space  Science  and
Applications by the Jet Propulsion Laboratory. PHAs updated 7-15-2023.

From the Orbits  of Gaspra and Ida you can  see they are no threat to Our Earth.
However there are many asteroids that do present a threat to Earth and they  are
called "Potentially Hazardous Asteroids (PHAs)".  There are currently 2344 known
PHAs and more will be discovered in the coming months.  One of the  most  famous
asteroids  of  recent  times  is  asteroid  "433  Eros"  which  was photographed
extensively by the NEAR Spacecraft a few  years  ago.   NEAR  became  the  first
spacecraft  in history to land on an asteroid when it landed on Eros.  Visit the
NEAR Home Page for pictures and movies.  Eros was discovered in August  1898  by
Carl  Gustav  Witt.    It was the first asteroid found to travel almost entirely
within the orbit of Mars.  Now from the Orbit of asteroid Eros you  can  see  it
comes very close to Mars and Earth during its trip around the Sun! Eros actually
cuts across the orbit of Mars twice, and at its closest approach it is less than
23  million km (14 million miles) from the Earth.  Based on the latest estimates
I am aware of, Eros has a chance of being a threat about 1 million years  or  so
into  the  future.   Well at least we will not be here for that encounter and by
then planet Earth should have a great asteroid defense!


Asteroid Eros

One  of my Favorite Sites is the "Near Earth Objects" site, where they help keep
up on the PHAs and other cool stuff.  You  can  also  check  the  orbit  of  any
asteroid  or comet as you have seen from the above orbit captures.  You can also
check on any date in the future or past and see where your favorite Asteroid  or
Comet  is along its orbit.  Another PHA is asteroid 2001 WL15 which is currently
opposite  the  Sun from Earth and  201,810,000 miles or  (2.17 AU)  away.   From
the orbit sketch you can see that WL 15 also cuts across the orbit of Mars twice
and comes very  close  to  Earth  Orbit.   Another  PHA  (Potentially  Hazardous
Asteroid) is 2001 WN5 which is now far from Earth at 291,834,000 miles or (3.138
AU) away.  From the orbit sketch for WN5 you can see that it  cuts  across  both
the  orbit of Mars and the orbit of Earth twice! You can see why asteroid WN5 is
a threat to Earth! When you get to the "Near Earth Objects" site, just click  on
"Orbit  Diagrams".    You can type in the name of any asteroid or comet and then
press enter to see the orbit.  You can rotate and zoom in and out with  ease  as
well  as  change  the date to future or past time periods.  Scroll down a little
and you will see a list of the PHAs including the ones we just talked about  and
you can just click one from the list to see its orbit displayed.

Asteroid Apophis, a new PHA discovered in 2004, is going to have  a  VERY  CLOSE
encounter with Planet Earth in 2029.  It will be closer than anything Earthlings
have ever seen before!!!! Asteroid Apophis will  come  within  18,000  miles  of
Planet  Earth on April 13th, 2029! Yes it is on Friday the 13th of that year and
it will finally get the Human Race to start building a  REAL  Asteroid  Defense.
By  the  way  we have Satellites orbiting at 22,000 miles, and it will be closer
than they are to Earth! I am sure the Pentagon will be scrambling to  get  there
Satellites  out  of the way! You can visit the Near Earth objects Site and watch
the approach of the asteroid! When you arrive at the Site just click  on  "Orbit
Diagrams" and then just type: Apophis in the Name Box and press Enter.  You will
see the diagram of the orbit of Apophis and its position on  the  current  date.
Now  click  the Date Box and when the pop up date box appears change the date to
January and the the year to 2029 so you can see where Earth and  Apophis  are  a
few months before the close encounter! Then click OK.  Now click the >> to watch
the encounter! Just click the II control to stop the action.  You  can  back  up
using  the  <<  key until just a few days before the encounter and then watch in
slow motion by using the >I key.  You can zoom in or  tilt  any  way  you  want.
Enjoy my young Earthling Friends and be thankful its just a close encounter.  If
Apophis passes through what scientists call the Keyhole, (the  perfect  distance
from  Earth), then Apophis will be caught by  Earth's Gravity and  come back and
hit Earth in 2036.  We do not expect this to happen though.

My time  on  Planet
Earth  grows  short so I will not be here to see Apophis make its close approach
but you will be  here to watch the show Earthlings!  I will be on my way home to
the Whirlpool Galaxy to continue my Sage Training, and then be assigned to a new
post some where in the Universe.


Earth's technology of today for Asteroid Defense is in the primitive stage so we
need to devote LOTs more Money and people  to find all the PHAs that cross Earth
Orbit.  In the case of  Asteroid  Apophis we have 8 years  warning of the danger
and can take action.  However, we may not have a long warning period before each
encounter with an  approaching Asteroid.  If the Asteroid is discovered too late
for us to prevent a hit on Earth, all we could do is try to evacuate the area of
impact!   Now you see why I am so insistent about building up  our defenses NOW!
The  Nuclear Weapons  of the  USA and Russia  only have fuel  to reach low Earth
orbit briefly and then the warhead falls to the target.  These  missiles do  NOT
have fuel to attack  an incoming comet or asteroid far from Earth where it might
be possible to  deflect the asteroid or comet.  Only  rockets like those used to
land on the moon even have a chance of intercepting  a comet or asteroid if they
are modified!!!!   The best asteroid defense is an energy field shield or highly
advanced Beam Weapons.   Earth has some knowledge  of  Beam Weapons now but they
need lots more research  and development time before deployment.   In the future
Earth will have  a permanent  Moon Base and at least  2 "Real Space Stations" in
orbit which will make it unlikely that an  Asteroid Strike can destroy the Human
Race like it did the Dinosaurs 65 million years ago!   Asteroid Apophis is NOT a
Dooms Day extinction event Asteroid, but Apophis could knock out a Moderate size
city.   All the people of Earth must unite and work together against this threat
or we will suffer the fate of the Dinosaurs!

Stay in School and Study Hard my young Earthling Friends, and you  can  one  day
join  the  search  or  maybe even help build the first Real Asteroid Defense for
planet Earth.  Asteroids and Comets are a much  greater  threat  to  Earth  than
UFOs!  Asteroid Apophis is reminding us of that!

May the Force be with you my Earthling Friends.  Live Long and Prosper!   May HE
whom the winds fear Light your path and Guide your steps as  you journey through
this life.

			 Written by: The Galactic Sage