Download Q: What are meteorites? A: Meteorites are rocky-metallic

Q: What are meteorites?
A: Meteorites are rocky-metallic fragments of solar system objects
that, on colliding with the earth, survive their passage through the
atmosphere and wind up on the surface of the earth. They were
ejected by violent by collisions and put into orbits that eventually
caused them to collide with earth.
Tags: meteorites
Q: Where do meteorites come from?
A: Almost all meteorites are fragments of asteroids. Asteroids
frequently collide with one another. The relatively small masses of
asteroids allow some of the fragments to escape the asteroid’s gravity
and go into orbits that will eventually result in a collision with earth. In
some cases, the orbit of a meteorite can be determined and shown to
have originated in the asteroid belt located between Mars and Jupiter. Some few meteorites are fragments of glancing collisions involving more
massive solar system objects such as the moon, or, in rare cases, Mars. The greater mass of these objects makes it much less likely that
fragments of their surfaces can escape to become meteorites. The
rocks brought back by Apollo missions to the moon have been analyzed
extensively. They differ from earth rocks and from meteorites that are
fragments of asteroids in very distinct ways. A small percentage, but still
a large number of meteorites have chemical compositions that identify
them as moon rocks. We know something of the chemical
composition of the surface of Mars through robotic missions. About
two dozen meteorites have chemical compositions that rule out the
earth, asteroids, or the moon as points of origin and are consistent with
what we know of Mars’s surface. The clinching evidence that they are
Martian rocks is that the analysis of gas trapped within some of them is
identical with the composition of Mars’s atmosphere.
Tags: meteorites
Q: What is the difference between meteorites and meteors?
A: They are similar in that both are the result of the earth colliding
with meteoroids, that is, space debris too small to be seen before the
collision. Meteoroids enter the earth’s atmosphere with speeds in the
tens of thousands of miles per hour, generating tremendous heat due to
friction. If the mass of the meteoroid is sufficient, it will survive the trip
through the atmosphere and land on the earth’s surface. In this case, it
is called a meteorite. Otherwise it completely evaporates before
reaching the surface and is known as a meteor. Meteors are sometimes
referred to as shooting stars, but, of course, they have nothing to do
with stars. Another difference between meteors and meteorites is that
the origin of most meteorites is fragments of asteroids, while most
meteors are debris from comets. Thus meteor showers occur when
the earth passes through the orbit of a comet.
Tags: meteorites, meteors
Q: What is the difference between meteorites and meteors? A: They are similar in that both are the result of the earth colliding
with meteoroids, that is, space debris too small to be seen before the
collision. Meteoroids enter the earth’s atmosphere with speeds in the
tens of thousands of miles per hour, generating tremendous heat due to
friction. If the mass of the meteoroid is sufficient, it will survive the trip
through the atmosphere and land on the earth’s surface. In this case, it
is called a meteorite. Otherwise it completely evaporates before
reaching the surface and is known as a meteor. Meteors are sometimes
referred to as shooting stars, but, of course, they have nothing to do
with stars. Another difference between meteors and meteorites is that
the origin of most meteorites is fragments of asteroids, while most
meteors are debris from comets. Thus meteor showers occur when
the earth passes through the orbit of a comet.
Tags: meteorites, meteors
Q: Why do meteors produce a streak of light across the night sky?
A: Many people believe that the light is coming from the meteor itself. However, this is not true. As it passes through the atmosphere, it
knocks electrons out of the molecules of the atmosphere; that is, it
ionizes the atmosphere. This is followed by recombination to form
neutral atoms and molecules with the emission of light. When you see
a streak of light in the night sky, you are not looking at the object itself
but rather the path of its motion through the atmosphere.
Tags: emission spectra, meteors
Q: I have heard that the earth accumulates something like three
hundred tons of material from outer space per day! Where does this
come from? Wouldn’t this have some noticeable effect if the earth is
billions of years old?
A: Actually, it would not. The added mass comes mostly from
micrometeorites, that is, debris from space so small that it is brought to
rest almost immediately in its collision with the earth’s atmosphere. Thus, it doesn’t generate the heat necessary to evaporate it. Over long
periods of time it drifts down through the atmosphere, landing on earth
(hence the name micrometeorite). The mass of the earth is about 6 x
1024 kg, which would weigh 6.8 x 1021 tons. Over a period of 4.6 billion
years, three hundred tons per day would only be about 5 x 1014 tons, or
one part in 1.4 x 107, a negligible fraction.
Tags: micrometeorites