Frequently Asked Questions
In this section we'd like to answer some
frequently asked questions concerning meteorites.
If you don't find your question here, feel free to
contact us - it's our pleasure to provide you with
additional information!
What is a meteorite?
A meteorite is an actual piece of
extra-terrestrial matter that has reached the
surface of our planet, Earth. Sometimes the term
"meteorite" is confused with two related terms -
"meteoroid" and "meteor". A meteoroid is a small
object that orbits the Sun near the Earth - the
precursor of a meteorite before it enters the
atmosphere. Upon entering the Earth's atmosphere,
it produces a bright streak of light in the sky, a
phenomenon known as a "shooting star", or a
"meteor". However, most meteors do not produce any
meteorites because they stem from tiny particles
burning up completely in the atmosphere. Only
larger chunks of matter finally make it to the
ground, producing extremely bright meteors known
as "fireballs", or "bolides". >> top...
Where do meteorites come from?
Most meteorites have their origin in the asteroid
belt, a region between Mars and Jupiter, where
many thousands of large and small asteroids orbit
the Sun. Through collisions and gravitational
forces, pieces of these asteroids are sometimes
pulled into an Earth-crossing orbit, finally
reaching the ground in the form of a meteorite.
However, some rare types of meteorites have proven
to have different origins. Today, we know of
several meteorites that are pieces of the Moon and
the planet Mars. Some other rare meteorites are
suspected to have a cometary origin. For further
information, have a look at our Origins
page. >>
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How do we know that some
meteorites are from the Moon?
When it comes to lunar meteorites, the answer is
easy: we have been to the Moon, and we have
returned samples for comparison. Chemical and
mineral compositions, isotope ratios, and textures
of lunar meteorites, are similar to those of
samples collected on the Moon during the Apollo
and Luna missions. Taken together, these
characteristics differ from those of any other
type of meteorite or terrestrial rock, so that we
can say for sure: Yes, these meteorites are
genuine
lunar rocks. >>
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How do we know that some
meteorites are from Mars?
When it comes to Martian meteorites, we haven't
returned any samples thus far. However, the Viking
and Pathfinder probes have provided enough data to
justify this conclusion. Some Martian meteorites
were found to contain trapped gas-inclusions that
perfectly match the composition of the Martian
atmosphere, but are distinct from our own. Several
other characteristics are consistent with a
Martian origin for these rare meteorites - have a
look at our
Mars meteorite page. >> top...
What are meteorites composed
of?
The most common meteorites from the asteroid belt
are stony meteorites, called chondrites, which are
primarily composed of olivine, different types of
pyroxene, and nickel-iron metal. Their mineral
compositions have remained more or less unaltered
since the time of the formation of our solar
system, and hence, they can be regarded as genuine
primordial matter. Other, less common, meteorite
types were subjected to a process of
differentiation, a fact that is reflected in their
mineral compositions. Their parent bodies
developed a nickel-iron core, a stony-iron mantle,
and a stony crust. Hence, meteorites that stem
from the core of a differentiated asteroid are
composed of different alloys of nickel-iron, and
they are usually referred to as iron meteorites.
Meteorites from the mantle of a differentiated
asteroid often have a stony-iron compostion, while
those from the crust have stony compositions,
often resembling terrestrial rocks. Have a look at
our
Classification section for additional
information. >>
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