Meteorite (n): A mass of stone or metal that has reached the earth
from outer space. Meteor (n): A transient fiery streak in the sky produced by a
meteoroid passing through the earth's atmosphere. Meteoroid (n): A small body traveling through space.
Where Do Meteorites Come From?
Since there are many kinds of meteorites, they may come from different
extraterrestrial objects Here are a few things scientists study to
determine the source of meteorites:
They compare them to rocks collected on the Moon and observed by space
craft on Mars. A few meteorites resemble these rocks.
They observe the orientation of crystals in meteorites to determine if
they solidified in a strong gravitational field. Strong gravity will
result in more oriented crystals. This has allowed scientists to infer
that some very rare types of meteorites come from Mars--apparently blasted
off the surface of that planet by a meteorite impact.
They analyze the light reflected from meteorites--a fancy analysis of
color--and compare it to light reflected from meteorite specimens found on
Earth. This has allowed scientists to determine that the most likely
source for most meteorites is the Asteroid Belt between Jupiter and Mars.
How Did Meteorites Get from Asteroids to the Earth?
The short answer - is that Asteroids bump into each other. Pieces break
off or the orbit may be changed. Asteroids can only stay in certain
orbits. Once their course is deflected, the gravity of the planet Jupiter
can fling asteroids or fragments out of the Asteroid Belt and into an
orbit that crosses the orbit of the Earth. Once this happens, there is a
chance of collision--and a chance of a meteorite hitting the Earth. Chondrules--the First Rocks
Scientists have hypothesized that the first solid matter was dust--tiny
mineral grains that solidified from the gases that proceeded them at the
beginning of the universe. The dust clumped together. Perhaps electrical
charges or gravitational attraction made this happen. The clumps melted.
We are uncertain of the reasons for the melting. Heat from star systems
may have caused it--or radioactivity in the clumps themselves. (Billions
of years ago, matter was far more radioactive. Because of their age
meteorites are among the least radioactive rocks known.) When the clumps
melted, small spheres were formed. These are chondrules.
Origins of Particular Meteorite Types
Chondrules floating in space eventually clumped together again, this time
with other chondrules and the cosmic dust. The result was chondrite parent
bodies--we know them as asteroids or planets. Iron and Stony Iron Meteorite Parents
The clumping together of the larger material, like the initial clumping,
had the effect of concentrating the radio activity and resulting heat.
Parts of the rock melted. The heavier material--metallic iron and nickel
settled by gravity to the center of the forming mini-planet. This is the
parent for iron meteorites. Outside of the iron, a mixture of iron and
other minerals formed the parents of stony-iron meteorites. The process is
called differentiation. Achondrite Parents
By the theory, the melting and differentiation would also result in
lighter rocks. These would be like the lava we see emerging from volcanoes
on Earth. They would form the parents for achondrites
How Old Are Meteorites?
If meteorites formed from dust from the early universe, then we would
expect them to be very old. Indeed, this is what we find. Scientists have
used radiometric dating to measure the ages of meteorites. The results
show ages of around 4,500,000,000 years--about seven hundred million years
older than the oldest rocks on Earth.
Meteorite Classification Table
Chondrites Stony Meteorites are characterized by chondrules
--small spheres (average diameter= 1 mm) of formerly melted
minerals that have come together with other mineral matter to form
a solid rock. Chondrites are believed to be among the oldest rocks
in the solar system. 85.7 percent of meteorite falls are
Irons (structural classification)
These meteorites are made of a crystalline iron-nickel
alloy . Scientists believe that they resemble the outer core
of the Earth. Widmanstatten bands are a crystal form. 5.7
percent of meteorite falls are irons.
Irons (Chemical Classification)
A second scheme for classifying iron meteorites is by their
chemistry. The determining factors are groupings of meteorites
with similar ratios of trace elements to nickel. Generally, the
higher the Roman numeral of the classification, the lower the
concentration of trace elements. The casual observer cannot see
this as one can with the Widmanstatten bandwidth that is the
determining factor for structural classification. Chemical
classification is important because it suggests that certain iron
meteorites share a common origin or were formed under similar
These meteorites are mixtures of iron-nickel
alloy and non-metallic mineral matter. Scientists believe
that they are like the material that would be found where the
Earth's core meets the mantle. 1.5 percent of meteorite
falls are stony irons.
Space is dry and that is how you should keep your meteorites. Remember
that no matter where you live there is moisture in the air. Your
meteorites are especially likely to absorb that moisture if they contain
chloride (salt) or change temperature. Changes in temperature can cause
condensation like that you will find on a cold can of soda. When salt
cakes, it is drawing moisture out of the air. If your meteorite has any
salt in it it will draw moisture out of the air. Moisture and salt can
damage a meteorite very quickly.
To protect your meteorites you should do the following:
Keep your meteorites dry--that means keep them in dry air.
Keep your meteorites at a constant temperature.
Use cleaning and coatings, as appropriate, to protect your
Keep your Meteorites Dry
Here is a list of things that you can do to keep your meteorites dry:
Live in a dry place (this is not fool-proof by any means!)
Never seal your meteorite in a plastic bag
Keep your collection in desiccated containers.
Use Cleaning and Coating to Protect Your Specimens
Any iron that is left out is likely to be handled--you should assume by
sweaty hands. For this reason, you need to clean your specimen
periodically. I recommend that you use anhydrous alcohol.
The next step is to coat the specimen. I coat natural irons with Rust
Guardit, a spray on wax coating. Some people use Sheath which is a
petroleum distillate like WD40. I have used WD40 as well, but I don't
prefer it because they add water to it For etched irons, heat the specimen
to 200º F (95º C) and apply "Rig" grease. After the specimen cools, wipe
off the excess grease.
If a stony meteorite is susceptible to rust, my policy is to keep it dry.
I keep it in a box with desiccant. If any stone is handled much, it is a
good idea to clean it with alcohol. I do not use any coating on stones as
I believe that coatings interfere with observation of the natural
If you collect meteorites, it is inevitable that some specimens will be
damaged or deteriorate. Most often the damage can be repaired and further
damaged can be stopped or slowed. Damage to most specimens can be related
to two things: Rust and chloride (salt). Rust is the symptom, chloride is
the disease. Both need to be removed. Removing Rust
Most often rust can be removed with a little elbow grease and a steel wire
brush. Use anhydrous (or 95%) alcohol to do your washing. Alternatively,
you can use a petroleum distillate rust 'remover'. Sheath or WD40 are
examples. On etched surfaces or bare metal surfaces that have lots of
cracks, you might want to try phosphoric acid. Naval Jelly is one brand of
phosphoric acid rust remover. After you use the acid, be sure to clean it
all off using alcohol or distilled water. Etched irons will have to be
re-polished and etched.
Here is a process recommended by Steve Schoner (American Meteorite Survey,email@example.com):
The real problem with rusting in meteorites is chlorine. Rinsing the
meteorite with water, (tap water) should never be done if any of these
treatments is used. For some reason, meteorite irons have an affinity for
chlorine, and it is chlorine that is the main cause of rusting.
Often it comes to the surface of cut or wire brushed irons as little dark
brown or green blebs of fluid. What this is is FeCl2, FeCl3, or even
NiCl2, or NiCl3 (in much smaller amounts). Ferric and Ferrous Chloride
(FeCl2 & FeCl3) are hydroscopic substances, that is they have an
affinity for moisture just as a desiccant does. Then once the water is
present and these are in solution, the Chlorine is free to bond to other
iron atoms attacking it so that it will combine with oxygen, producing
iron oxide. Once a thick coat of rust develops, then the "bleeding" stops
and the meteorite becomes more or less stable. Some though, will continue
to rust till they actually fall apart.
At one time the iron and nickel chlorides in meteorites were described as
"Lawrenceite" after the mineralogist that first identified it. It was
thought at the the the time that they were present in the meteorite before
it fell to earth, but it was later found that it was a substance that
formed in the meteorite from reactions between terrestrial groundwater and
The trick to stop this rusting is to get rid of the chlorine. Fortunately,
a good long soak in alcohol will dissolve iron-nickel chlorides, but I
have found a much better way.
Soak the affected specimen in a strong solution of distilled water 50%;
isopropyl alcohol 30%, and sodium hydroxide (lye) 20%. The percentages are
When mixing the sodium hydroxide crystals in this solution be very careful
as it gets hot. Also it is caustic, and if gets on the skin will burn just
as badly as if it were an acid.
Use stainless steel containers.
Put the meteorite in the solution and let it soak for a few days to a
week. If the solution gets tainted so that it looks rusty then you might
want to replace the solution sooner than a week. Pour out the solution,
and clean the surface of you meteorite. This solution is strong enough to
strip most irons of their varnish coatings, but I recommend that it is
done beforehand. You will notice after this first soak that there are big
blobs of gelatinous rust on the iron surface. Some of these will be green
but most will be dark brown. This is Fe0H and nigh, both are like jelly in
water but when exposed to air expel their hydrogen and become solid iron
an nickel oxides.
The chlorine that caused the rusting is now in the solution as NaCl,
(salt) having exchanged places with the iron atoms in the meteorite for
the Na (sodium) in the caustic solution. Chlorine has a greater attraction
for sodium than iron, so that is why this solution works better than just
keeping air and moisture away from the meteorite.
Get rid of the chlorine, and you get rid of the problem.
I stumbled upon this process over 20 years ago, and have used it with
great success to treat some of the most stubborn rusting meteorites in my
collection, including Brenham and more recently Lamont, which is a
mesosiderite. Lamont is a very unusual olivine rich meteorite, maybe a
link between the Lodranites and the mesosiderites, but unfortunately it is
a prolific ruster. Soaking my 900 gram end piece six times over six weeks
has seemed to cure it, as it is now on my shelf with no varnish coating
and not a speck of rust on its cut surface.
With pallasites, the crystals tend to pop out. But if you are very, very
patient, and like puzzles, you can clean the places where they were, then
re-insert them with super-glue. Then after everything is together
re-finish the surface so that it looks good as new.
Iron meteorites will, however have to be re-polished, and etched. And be
sure to use only distilled water so as not to re-infect your meteorite
with chlorine which is the primary cause of the progressive rusting of our
specimens in the first place.
This solution can also be used in electrolysis-- a much more aggressive
method of removing chlorine from iron. This is done for the preservation
of iron artifacts that are recovered from shipwrecks. It is more involved
and it does work.
Meteorite Finds and Falls before 1972
Total Enstatite Chondrites
Total Bronzite Chondrites
Total Hypersthene Chondrites
Total All Chondrites
Total Stony Irons
Many numbers in this table are estimates and others are dated.