Scientists are interested in asteroids because they are representatives of the earliest solar system (Figure 1.4). Eventually asteroids could be mined for rare minerals or for construction projects in space. A few missions have studied asteroids directly. NASAs DAWN mission explored asteroid Vesta in 2011 and 2012 and will visit dwarf planet Ceres in 2015. Click image to the left or use the URL below. URL: The NEAR Shoemaker probe took this photo as it was about to land on 433 Eros in 2001.
kqed asteroid hunters
Thousands of objects, including comets and asteroids, are zooming around our solar system; some could be on a collision course with Earth. QUEST explores how these Near Earth Objects are being tracked and what scientists are saying should be done to prevent a deadly impact. Click image to the left or use the URL below. URL:
the asteroid belt
Hundreds of thousands of asteroids have been discovered in our solar system. They are still being discovered at a rate of about 5,000 new asteroids per month. The majority of the asteroids are found in between the orbits of Mars In 1991, Asteroid 951 Gaspra was the first asteroid photographed at close range. Gaspra is a medium-sized asteroid, mea- suring about 19 by 12 by 11 km (12 by 7.5 by 7 mi). and Jupiter, in a region called the asteroid belt, as shown in Figure 1.2. Although there are many thousands of asteroids in the asteroid belt, their total mass adds up to only about 4% of Earths Moon. The white dots in the figure are asteroids in the main asteroid belt. Other groups of asteroids closer to Jupiter are called the Hildas (orange), the Trojans (green), and the Greeks (also green). Scientists think that the bodies in the asteroid belt formed during the formation of the solar system. The asteroids might have come together to make a single planet, but they were pulled apart by the intense gravity of Jupiter.
More than 4,500 asteroids cross Earths orbit; they are near-Earth asteroids. Between 500 and 1,000 of these are over 1 km in diameter. Any object whose orbit crosses Earths can collide with Earth, and many asteroids do. On average, each year a rock about 5-10 m in diameter hits Earth (Figure 1.3). Since past asteroid impacts have been implicated in mass extinctions, astronomers are always on the lookout for new asteroids, and follow the known near-Earth asteroids closely, so they can predict a possible collision as early as possible. A painting of what an asteroid a few kilometers across might look like as it strikes Earth.
Asteroids are very small, rocky bodies that orbit the Sun. "Asteroid" means "star-like," and in a telescope, asteroids look like points of light, just like stars. Asteroids are irregularly shaped because they do not have enough gravity to become round. They are also too small to maintain an atmosphere, and without internal heat they are not geologically active (Figure 1.1). Collisions with other bodies may break up the asteroid or create craters on its surface. Asteroid impacts have had dramatic impacts on the shaping of the planets, including Earth. Early impacts caused the planets to grow as they cleared their portions of space. An impact with an asteroid about the size of Mars caused fragments of Earth to fly into space and ultimately create the Moon. Asteroid impacts are linked to mass extinctions throughout Earths history.
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an asteroid is
a) a rock and ice body that has a tail near the sun. b) a rounded body with craters on it. --> c) a small rocky body that orbits the sun. d) none of the above
--> a) came together to form the rocky planets. b) came together to form the moon. c) hardly ever venture into the inner solar system. d) all of these.
asteroids are too small to have impacts with other objects so they dont have craters.
a) true --> b) false
we dont know much about asteroids because they are too small for nasa missions to visit them.
a) true --> b) false
a) are mostly found between the orbits of jupiter and saturn. --> b) are still being discovered at a high rate. c) could be added up to equal the mass of a mars-sized planet. d) all of these.
the region where asteroids orbit between mars and jupiter is called ___.
a) the cometary zone b) the near-earth asteroid zone c) the kuiper belt --> d) the asteroid belt
near-earth asteroids can
a) cross earths orbit. b) cause mass extinctions. c) be over 1 km in diameter. --> d) all of the above.
an asteroid the size of mars hit earth sending fragments of earth into space to create the moon.
--> a) true b) false
an asteroid could cause humans to go extinct.
--> a) true b) false
scientists are interested in asteroids because many
a) contain very valuable gemstones. b) contain precious metals. --> c) are representatives of the earliest solar system. d) could have primitive life forms.
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