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
a 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.
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 1853 known
PHAs and more will be discovered in the coming years. 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!
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 12 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
Written by: The Galactic Sage