SPACE SCIENCE 8: NEAR-EARTH OBJECTS

NEAR-EARTH OBJECTS (NEOs) Near-Earth objects (NEOs) are asteroids or comets with sizes ranging from meters to tens of kilometers that orbit the Sun and whose orbits come close to that of Earth's. Of the more than 600, 000 known asteroids in our Solar System, almost are NEOs. Near-Earth objects (NEOs) are asteroids or comets with sizes ranging from meters to tens of kilometers that orbit the Sun and whose orbits come close to that of Earth's. Of the more than 600, 000 known asteroids in our Solar System, almost are NEOs.

COMETS COMET A comet is an icy body that releases gas or dust. They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs. Comets contain dust, ice, carbon dioxide, ammonia, methane and more. COMET A comet is an icy body that releases gas or dust. They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs. Comets contain dust, ice, carbon dioxide, ammonia, methane and more.

COMETS

ASTEROIDS ASTEROID a small rocky body orbiting the sun. Large numbers of these, ranging in size from nearly 600 miles (1,000 km) across (Ceres) to dust particles, are found (as the asteroid belt ) especially between the orbits of Mars and Jupiter, though some have more eccentric orbits, and a few pass close to the earth or enter the atmosphere as meteors. ASTEROID a small rocky body orbiting the sun. Large numbers of these, ranging in size from nearly 600 miles (1,000 km) across (Ceres) to dust particles, are found (as the asteroid belt ) especially between the orbits of Mars and Jupiter, though some have more eccentric orbits, and a few pass close to the earth or enter the atmosphere as meteors.

COMETS VS. ASTEROIDS

COMETS AND ASTEROIDS In addition, asteroids usually come from the Asteroid Belt, some may originate from other parts of the solar system. While a comet or asteroid orbits the Sun, some parts may break off from the comet or asteroid. These fragments are called “meteoroids.” Comets, asteroids, or their fragments come from very distant places within and beyond the Solar System.

IMPACT CRATERS What causes an impact crater? An impact crater is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteor) with the surface. What causes an impact crater? An impact crater is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteor) with the surface.

What is Kuiper Belt? Kuiper Belt is a region of the solar system beyond the orbit of Neptune, believed to contain many comets, asteroids, and other small bodies made largely of ice.

What is Oort Cloud? The Oort Cloud is an extended shell of icy objects that exist in the outermost reaches of the solar system. It is named after astronomer Jan Oort, who first theorized its existence. The Oort Cloud is roughly spherical, and is the origin of most of the long-period comets that have been observed. The Oort Cloud is an extended shell of icy objects that exist in the outermost reaches of the solar system. It is named after astronomer Jan Oort, who first theorized its existence. The Oort Cloud is roughly spherical, and is the origin of most of the long-period comets that have been observed.

METEOROID, METEOR, METEORITE

METEOROID A meteoroid is a fragment from a comet, an asteroid, Moon, or even Mars that orbits around the Sun, following the orbit of its parent or source. A comet or an asteroid may break apart while orbiting the Sun. When this happens, the fragments from comets or asteroids still orbit the same path as their mother comet or asteroid. These smaller fragments are called meteoroids Meteoroids can come from comets, asteroids, the Moon, and Mars A meteoroid is a fragment from a comet, an asteroid, Moon, or even Mars that orbits around the Sun, following the orbit of its parent or source. A comet or an asteroid may break apart while orbiting the Sun. When this happens, the fragments from comets or asteroids still orbit the same path as their mother comet or asteroid. These smaller fragments are called meteoroids Meteoroids can come from comets, asteroids, the Moon, and Mars

METEOR A meteor is observed when a meteoroid passes through Earth’s atmosphere and burns up in the process. When viewed from Earth, a meteor moves fast while a comet moves slow. Also, a comet is very difficult to see with an unaided eye due to its distance from Earth. A meteor is more readily seen on a cloudless night. A meteor is observed when a meteoroid passes through Earth’s atmosphere and burns up in the process. When viewed from Earth, a meteor moves fast while a comet moves slow. Also, a comet is very difficult to see with an unaided eye due to its distance from Earth. A meteor is more readily seen on a cloudless night.

METEOR SHOWER A meteor shower is an annual light phenomena characterized by many meteors appearing in the sky in a short period of time.

Why does a meteor shower occur? A meteor shower happens when Earth passes through the orbit of a comet (or an asteroid) where fragments are dust remain in orbit and orbits the Sun as well while Earth goes around the Sun. Since there are more dust and fragments, there are more meteoroids that may burn up in Earth’s atmosphere as Earth passes the orbit of the parent comet or asteroid. A meteor shower happens when Earth passes through the orbit of a comet (or an asteroid) where fragments are dust remain in orbit and orbits the Sun as well while Earth goes around the Sun. Since there are more dust and fragments, there are more meteoroids that may burn up in Earth’s atmosphere as Earth passes the orbit of the parent comet or asteroid.

Why does it seem that meteors during a meteor shower appear to come from only one point in the sky? The meteors in a meteor shower seem to come from one point in the sky because they are travelling in parallel paths with the same velocity.

METEORITE A meteorite is a solid piece of debris from a source such as an asteroid or a comet, which originates in outer space and survives its impact with the Earth's surface. It is called a meteoroid before its impact. A meteorite's size can range from small to extremely large. A meteorite is a solid piece of debris from a source such as an asteroid or a comet, which originates in outer space and survives its impact with the Earth's surface. It is called a meteoroid before its impact. A meteorite's size can range from small to extremely large.

METEORITE Meteorites are of important to scientists in studying the occurrence of different elements and compounds on Earth. This information is in turn important in studying our mineral resources which is an important in any country. Three Types of Meteorites: 1.Stony 2.Stony-Iron 3.Iron Meteorites are of important to scientists in studying the occurrence of different elements and compounds on Earth. This information is in turn important in studying our mineral resources which is an important in any country. Three Types of Meteorites: 1.Stony 2.Stony-Iron 3.Iron

ALVAREZ HYPOTHESIS Proposed by Luis and Walter Alvarez They proposed that an asteroid with approximately 10 kilometers in diameter made impact with Earth 65 million years ago. They thought that the impact caused materials to be thrown up in air, thus blocking sunlight, and bringing about a period of winter long enough to cause a mass extinction of plants, and animals including the dinosaurs. Proposed by Luis and Walter Alvarez They proposed that an asteroid with approximately 10 kilometers in diameter made impact with Earth 65 million years ago. They thought that the impact caused materials to be thrown up in air, thus blocking sunlight, and bringing about a period of winter long enough to cause a mass extinction of plants, and animals including the dinosaurs.

ALVAREZ HYPOTHESIS There was one thing missing from the "Alvarez hypothesis": an impact crater or site. The Alvarez's had shown that the meteorite had to be 10km in diameter which would have created a ~ km wide crater. T he Alvarez had failed to find any craters that would have matched the age or the size. Ten years later, Alan K. Hildebrand and Glen Penfield found it. They discovered the Chicxulub crater site in the Yucatan Peninsula and dated it to be around 65 Ma. The discovery of the impact site, along with debris in the sedimentary record in North America, provided the proverbial "smoking gun" and much needed credibility to the "Alvarez hypothesis." There was one thing missing from the "Alvarez hypothesis": an impact crater or site. The Alvarez's had shown that the meteorite had to be 10km in diameter which would have created a ~ km wide crater. T he Alvarez had failed to find any craters that would have matched the age or the size. Ten years later, Alan K. Hildebrand and Glen Penfield found it. They discovered the Chicxulub crater site in the Yucatan Peninsula and dated it to be around 65 Ma. The discovery of the impact site, along with debris in the sedimentary record in North America, provided the proverbial "smoking gun" and much needed credibility to the "Alvarez hypothesis."

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