Intergalactic Beacon


The Asteroid Threat
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 1836 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!
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 15 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

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Read InterStellar Travel                                                               Read The Universe Reality and You

Read Planet Earth where are You?                                             Basic Gravity 101 (easy to understand)

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