Asteroids, Comets, Meteorites
Asteroids
Asteroids are rocky fragments left over from the formation
of the system about 4.6 billion years ago. Most asteroids orbit around the sun
during a belt between Mars and Jupiter. Scientists think that there are
probably many asteroids, ranging widely in size from many kilometers wide to a
kilometer wide.
Occasionally, the orbital paths of asteroids are influenced
by the gravitational pull of the planets, causing their paths to change.
Scientists believe that lost asteroids or fragments from previous collisions
have crashed into Earth in the past, playing an important role in the evolution
of our planet.
Comets
Comets are relatively small, fragile, irregularly shaped
bodies and, like asteroids, remain from the system formation process. Comets,
however, are icy balls of earth that form within the external system. The icy
surface is encrusted with dust, sand and particles from space.
Many comets have elliptical orbits that traverse the orbits
of the planets, bringing them to the edge of the sun and then away, often
beyond Pluto. The farthest comets can take 30 million years to finish an
orbit. Comets with smaller orbital paths can take just 200 years to orbit the
sun, making them more predictable.
When they get away from the sun, comets are very cold and
icy balls of earth. As they get closer to the sun, their surfaces begin to heat
up and the volatile materials vaporize. Vaporization gases carry small grains
of dust, which form a gas and mud environment and can appear as a bright tail
when viewed from Earth.
Scientists believe that comet impacts played a role in
Earth's evolution billions of years ago. One theory suggests that comets
carried a quantity of water and a scattering of organic molecules to the first
Earth.
Near-Earth Objects
Some asteroids and comets follow orbital paths that take
them much closer to the sun, and therefore to Earth, than usual. If the focus
of a comet or asteroid brings it closer to 1.3 astronomical units from the sun,
we call it a near-Earth object. Near-Earth objects can provide the raw materials
necessary for future interplanetary exploration. Some should even be fairly
easy to land for future explorations.
Potentially dangerous objects
A relatively small number of near-Earth objects pass close
enough to Earth and are large enough to warrant close observation. This is
because the gravitational pull of the planets could, over time, cause an
object's orbital path to evolve into an orbit that crosses Earth.
Potentially dangerous asteroids are approximately 150 meters
(almost 500 feet) or larger, approximately twice as large because the Statue of
Liberty is tall. They are approaching Earth's orbit at 7.5 million kilometers
(about 4.6 million miles). In comparison, when Mars and Earth are at their
closest point, they are about 53 million kilometers (about 33 million miles)
apart. Potentially dangerous comets also unusually reach the edge of the Earth.
Knowing the dimensions, shape, mass, composition and
structure of these objects helps determine the simplest thanks to deflecting
one, in case it has a path that threatens Earth.
Meteorites and Meteorites
As they travel through space, asteroids sometimes collide
with each other and cut smaller fragments. Kites throw dust as they roam the
system. These "breaks" end in numerous small particles and fragments,
called meteoroids, that orbit around the sun.
- Fireballs are larger meteorites, ranging in size anywhere from a basketball to a Volkswagen. They also make very impressive sky displays, as they forced an entry of fragments and passed through Earth's atmosphere.
- Some meteorites survive passage through Earth's atmosphere and hit the bottom. These are called meteorites.
Some facts about Asteroids, Comets and Meteorites.
- Sometimes asteroids collide with each other. When this happens, thousands of tiny pieces chip at the asteroids. These little pieces are called meteorites. Meteorites travel through space and are rarely caught by a planet's gravitational pull. Meteors enter Earth's atmosphere daily. Most of them spend, but if they land on Earth, they are called meteorites.
- Most meteorites are small, but the largest have landed in cars or houses, causing damage.
- In 2013, in the Russia area, Chelyabinsk was called a meteorite over 20 m wide exploded in midair. The big blast wave damaged thousands of buildings and injured more than 1,500 people. Luckily for the people of Chelyabinsk, the meteorite exploded in midair and bottomed out and exploded, if it had, it might have depleted the city.
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