Meteoroids Asteroids Comets 6 th Grade Earth Science

Meteoroids Asteroids Comets 6 th Grade Earth Science 2006

Comets Comet Collision A dark ring on Jupiter caused by comet Shoemaker-Levy 9 You can think of a comet as a “dirty snowball” about the size of an Earth mountain. Comets are chunks of ice and dust whose orbits are usually very long, narrow ellipses.

ØComets are very fragile ØThey contain lots of frozen water, frozen methane, and carbon dioxide. ØThese frozen compounds act to hold the comet together

Its believed that comets carried to Earth the waters that compose its oceans, seas, lakes, and rivers.

Today these waters support life on Earth and help carve Earth’s many shapes.

Comets orbit the sun in highly elliptical orbits. Because their orbits are so elliptical, few of them pass near Earth. They can usually then be seen only briefly.

The sun's corona produces a stream of particles called the solar wind. Solar wind pushes the gas from a comet away from the sun. Gas and dust form the comet's tail. The tail looks like hair; in fact, the name comet means “longhaired star” in Greek.

A comet's tail can be hundreds of millions of kilometers long and stretch across most of the sky. The material is stretched out very thinly, however, so there isn't much mass in a comet tail.

WHERE COMETS ORIGINATE Oort Cloud: a cloud of rocks and dust that surrounds our solar system. It contains long -period comets with orbital periods of over 200 years and up to 30 million years. It was named for Jan H. Oort, who proposed its existence in 1950. It is hypothesized that the Oort cloud is responsible for the periodic mass extinctions on Earth.

Kuiper Belt: A region beyond Neptune in which at least 70, small objects orbit. This belt is located from 30 to 50 AU’s and was discovered in 1992. It contains Short-Period comets with orbital periods under 200 years such as Halley; s comet. It was named for the Dutch-American astronomer Gerald P. Kuiper, who predicted its existence in 1951.

SOME MAJOR COMETS HALLEY'S COMET Halley's comet is a periodic comet (made of frozen gas and dust), that orbits around the sun. Its earliest-recorded sighting was in 240 B. C. in China, but Edmund Halley was the first person to recognize that it was periodic. It was last seen in 1986 and will be seen next in the year 2061; its period is 76 years. When the Earth passes through Halley's comet's orbit (twice each year), its detritus causes the meteor showers the Eta Aquarids and the Orionids.

SHOEMAKER-LEVY 9 (SL-9) was a short-period comet that was discovered by Eugene and Carolyn Shoemaker and David H. Levy. As the comet passed close by Jupiter, Jupiter's gravitational forces broke the comet apart. Fragments of the comet collided with Jupiter for six days during July, 1994, An SL-9 impact site on Jupiter, July causing huge fireballs in 6, 1994. Photo by Hubble Space Jupiter's atmosphere that Telescope. were visible from Earth.

COMET LINEAR Comet LINEAR [designated C/1999 S 4 (LINEAR)] was a comet that broke apart when it approached the Sun. The comet's icy core disintegrated as it passed close to the Sun (its perihelion) in July 2000. The Sun's intense heat had more to do with this comet's break -up than the Sun's gravitational forces. HALE-BOPP COMET Hale Bopp (designated C/1995 O 1) is a periodic comet that orbits around the sun. Its earliest-recorded sighting was on July 23, 1995. It was independently discovered by Alan Hale (of New Mexico) and Thomas Bopp (of Arizona), both amateur astronomers. This comet has a diameter of about 40 km; it's rotation rate is 11. 4 hours. It was last seen in 1997 and will be seen next in the year 4377; its period is 2380 years.

SOME COMETS About 600 comets have been observed. About a dozen comets are discovered each year. Most comets have very long periods (over 200 years). Period (years) A Few Comets Discovered Biela 1772 1852 broken up 6. 62 Encke 1786 1997 2000 3. 28 Faye 1843 1991 1999 7. 34 Hale-Bopp July 23, 1995 1997 4377 2380 Halley 240 B. C. 1986 2061 76. 00 Hyakutake January 30, 1996 31, 496 29, 500 Kohoutek March 7, 1973 76, 973 75, 000 Swift. Tuttle aka Kegler (responsible for the Perseids meteor shower) Wild 2/Comet 81 P Last Visit Next Visit July 16, 1862 (Kegler first seen in 1737) 1992 2126 January 6, 1978 (by Paul Wild) - - about 130 6. 39 years

Meteoroids

A meteoroid is a chunk of rock or dust in space. Meteoroids usually come from comets or asteroids. Comets leave dust behind as they move through the solar system.

If a meteoroid falls into the Earth's atmosphere, it will begin to heat up and start to glow. This is called a meteor. If you have ever seen a "falling star", you were actually seeing a meteor. Most of the original object burns up before it strikes the surface of the Earth.

So, a Meteor is a streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere.

Any leftover part of a meteor that does strike the Earth is called a meteorite. A meteorite can make a hole, or crater, in the ground when it hits it. The larger the meteorite, the bigger the hole.

Meteoroids Chunk of rock or dust in space If it enters Earth’s atmosphere Creating a streak of light it’s Called a Meteor If it strikes the ground it’s Called a Meteorite

Asteroids

Asteroids, are “space rocks” that are too small and too numerous to be considered fullfledged planets. Asteroids visited by spacecraft. Some can reach to over 250 km across

Some asteroids can reach up to 250 km in diameter and even have their own satellites as shown in this picture.

Asteroids represent material left over from the formation of the solar system and represent material that never coalesced into a planet. If the estimated total mass of all asteroids was gathered into a single object, the object would be less than half the diameter of the Moon.

If the estimated total mass of all asteroids was gathered into a single object, the object would be less than half the diameter of the Moon

Most asteroids revolve around the sun between the orbits of Mars and Jupiter. This region of the solar system, shown in the illustration below, is known as the asteroid belt.

Near Earth Asteroids Near Earth asteroids are asteroids that travel to within 1. 3 AU (195 million kilometers/121 million miles) of the Sun. There are over 250 near Earth asteroids known and they are classified into three groups; §Amor: crosses the orbit of Mars, does not cross orbit of Earth. §Apollo: Crosses Earth’s orbit, orbital period greater than one year. §Aten: crosses Earth’s orbit, orbital period less than one year. Most near Earth asteroids are believed to be asteroids that were knocked out of the asteroid belt by collisions with other asteroids and/or by the gravitational forces of Jupiter. How Big? The largest known near Earth asteroid is 1036 Ganymed with a diameter of nearly 41 kilometers (25. 5 miles). Scientists are working to identify near Earth asteroids with diameters of 1 kilometer (0. 6 mile) or more that may pose a danger of colliding with the Earth.

How Near? In 1989, an asteroid 0. 4 kilometers (0. 25 miles) wide traveling 74, 000 km/hr (46, 000 m/hr) came within 640, 000 kilometers (400, 000 miles) of the Earth. The closest approach recorded was on Dec. 9, 1994 when a near Earth asteroid came within 0. 0007 AU (103, 500 km/64, 200 mi) of the Earth. [The mean distance between the Earth and the Moon is 0. 0026 AU (384, 400 km/239, 000 mi)]. In June 2002, an asteroid passed about 120, 000 km (74, 000 mi) from the Earth. Asteroid 2002 NY 40 was photographed passing near the Earth on August 15 and 16, 2002. At its closest approach it passed about 524, 000 km (326, 000 mi. ) from the Earth. 235 K Quicktime Movie Courtesy National Optical Astronomy Observatory, Tucson, AZ.

Hayabusa is Japan's asteroid sample return mission. The journey to collect pieces from asteroid Itokawa will take about 17 months. The spacecraft will remain with the asteroid for about three months before heading back to Earth. The sample return capsule will detach from the spacecraft and plunge through Earth's atmosphere. After re-entry, the container will parachute to Earth where it can be brought to a lab for study. It landed on the asteroid in Oct. 2005 and will return to Earth in June 2007.

It’s theorized that dinosaurs along with 70% of all life on Earth became extinct when an asteroid struck Earth 65 million years ago.

It made a crater 200 kilometers in diameter near the Yucatan Peninsula of Mexico. The explosion almost certainly raised trillions of tons of dust into the atmosphere, blocking the light from the sun for months. Debris from the explosion probably started huge fires that destroyed much of Earth's forests and grass.

Impact Structures listed by Name Current total number of confirmed impact structures: 172 CRATER NAME LOCATION LATITU DE LONGITUD E DIAMETER (km) Age (Ma)* EXPO SED DRILLE D Acraman South Australia, Australia S 32° 1' E 135° 27' 90 ~ 590 Y N Ames Oklahoma, U. S. A. N 36° 15' W 98° 12' 16 470 ± 30 N Y Amguid Algeria N 26° 5' E 4° 23' 0. 45 < 0. 1 Y N Aorounga Chad, Africa N 19° 6' E 19° 15' 12. 6 < 345 Y N Aouelloul Mauritania N 20° 15' W 12° 41' 0. 39 3. 0 ± 0. 3 Y N Araguainha Brazil S 16° 47' W 52° 59' 40 244. 40 ± 3. 25 Y N Arkenu 1 Libya N 22° 4' E 23° 45' 6. 8 < 140 Y N Arkenu 2 Libya N 22° 4' E 23° 45' 10 < 140 Y N Avak Alaska, U. S. A. N 71° 15' W 156° 38' 12 100 ± 5 N Y B. P. Structure Libya N 25° 19' E 24° 20' 2 < 120 Y N Barringer Arizona, U. S. A. N 35° 2' W 111° 1' 1. 186 0. 049 ± 0. 003 Y Y Beaverhead Montana, U. S. A. N 44° 36' W 113° 0' 60 ~ 600 Y N Beyenchime-Salaatin Russia N 71° 0' E 121° 40' 8 40 ± 20 Y N Bigach Kazakhstan N 48° 34' E 82° 1' 8 5± 3 Y Y Boltysh Ukraine N 48° 45' E 32° 10' 24 65. 17 ± 0. 64 N Y Bosumtwi Ghana N 6° 30' W 1° 25' 10. 5 1. 07 Y N Boxhole Northern Territory, Australia S 22° 37' E 135° 12' 0. 17 . 0540 ± 0. 0015 Y N Brent Ontario, Canada N 46° 5' W 78° 29' 3. 8 396 ± 20* N Y Calvin Michigan, USA N 41° 50' W 85° 57' 8. 5 450 ± 10 N Y Campo Del Cielo Argentina S 27° 38' W 61° 42' 0. 05

The End (is coming…. . ? )