Preserving Meteorites
By Philip Bagnall

Hunting down or simply buying a meteorite is just half the battle - you've then got to keep it. Here's how...

The second a meteorite enters the atmosphere it begins to decay. While we on Earth regard our thin envelope of gases as essential to the ecosystem, to a meteorite it is a totally hostile environment. Our water-laden air can destroy a meteorite in just a few years, while vegetative growth can penetrate even the most robust meteorites causing all sorts of problems.

To prevent natural damage to a meteorite certain preservation techniques can be employed. These methods will not stop decay completely, but will slow it down to an acceptable rate. No matter what methods are used, preservation is largely a compromise short of returning the meteorite to its original environment - space.

Ideally, preservation should begin the moment a meteorite hits the ground. In practice, this is rarely achieved. More often, meteorites are only found after some considerable time during which it has begun to weather.

If you are fortunate enough to be near the site of a fall then there are a number of things you can do. Having sought the permission of the land owner to examine the meteorite you should take a few measurements and then photograph the meteorite where it fell, placing a ruler or some everyday object next to it to give some idea of scale. The object should then be wrapped in foil or, preferably, placed in a Teflon bag and sent to a local natural history museum for examination, providing they have an adequate geology department, or to a national museum - such as the Smithsonian or British Museum - if they have not. Newly fallen meteorites should be preserved only by professionals who have the expert knowledge and equipment to carry out such work.

Old meteorites (i.e. those that have been on Earth for some time) can usually be cleaned and preserved by amateurs without fear of doing more damage to the meteorite than the environment already has done.

The three most common problems associated with weathered meteorites are dust (mainly in hot, dry regions), clay or mud (in damp areas) and vegetative growth (in almost any region). Each causes its own problems and has its own solutions.

Dust is usually the easiest to remove requiring a soft camel-hair brush or a can of compressed air, both of which are available from photographic shops. However, where a meteorite has spent some considerable time in a dusty environment, the dust can become compacted and difficult to remove, especially if there has been a little rainfall at some stage. It is then a case of having to coax out the ingrained dust with a sharp instrument without damaging the meteorite further. It is best to spend quite a while doing this - rushing the job will undoubtedly result in scratching.

Clay and mud can be removed with a hard brush (I use a shoe polish brush - without the shoe polish!) though thick layers may require immersion in water or vinegar. Don't leave the meteorite in the liquid too long: keep checking every 10 minutes or so by rubbing the mud with your fingers. As soon as you are through to the meteorite you should take it out of the liquid and wash it in distilled water, or place it in an alcohol bath for two or three days. The meteorite should then be dried in a warm room preferably above a radiator. Placing it in a box with air vents in the side will allow moisture to escape without much dust settling on the meteorite.

Vegetation can be a real nuisance. If the growth is simply clinging to the surface of the meteorite then it can usually be removed in the same way as clay or mud. However, some plant life will send roots deep into any fissures and, if left untreated, can crack open the meteorite, or cause considerable internal damage. You can kill off the growth, and its roots, by using a systemic weed killer. After a week or so the plant will die and crumble away. Roots can occasionally be removed with tweezers, but not always - although they will sometimes dry out to a fine dust and fall out of the fissure.The real problem, however, is that you don't know how much internal damage has been done by either the plant or the weed killer. If the plant has introduced moisture into the meteorite then it could be rotting away from the inside, so it is best to treat the meteorite to an alcohol bath for a couple of days.

All iron meteorites, and some stones that have iron flecks and inclusions, will rust through time. The first signs are a red, brown or yellowish discoloration of the specimen. In stones a halo may appear around the metallic flecks. You can remove rust with oxalic or tartaric acid, sodium citrate or sodium hydro_sulphate. Small stains are best treated with a cotton ball soaked in a solution of one part sodium citrate in five or six parts water. Leave the ball on the affected area for 10-20 minutes. After treatment for rust the meteorite should be bathed in alcohol. You can reduce the risk of rusting be spraying cut surfaces with a good quality lacquer.

Now, before certain professional meteoriticists have apoplectic attacks, I will qualify that statement. If the meteorite is scientifically valuable (e.g. a rare or unique type) then, firstly, some of the specimen should be deposited with a museum or university that undertakes meteorite research. Lacquers will protect meteorites from the sort of damage that can occur when the object is on public display, but they can also cause problems from a chemical viewpoint, corrupting the composition and structure of the meteorite. If some of the specimen has been given to the professionals for research then your commitment to meteoritics will have been fulfilled.

What many professionals do not appear to realize, is that a meteorite in a private collection is subject to the sort of damage that does not occur in museum and university labs. Consider a meteorite that is proudly displayed on someone's window ledge, mantle-piece, display cabinet or whatever. The first thing that happens is that the cat comes along and rubs its forehead on the object to claim it. Apart from its scent, its fur is also deposited on the specimen. Then it knocks it over onto the floor where it picks up dust and carpet mites. Your four-year old daughter then tells the cat off for being so naughty and picks the meteorite up for you with her sticky hands that have heaven-knows-what on them. Unless the cut surface has been lacquered then you have got problems.

The second point is that most meteorites in private collections are not scientifically valuable and have been studied to death. If they weren't salvaged by the collector then they would still be lying in a field somewhere weathering away. Whatever the views of people like the Rev. Pillinger, who preaches that no meteorite should be in a private collection, I have never been able to see the value of a pile of rust in the middle of a field in Kazakhstan.

Meteorites are often difficult to locate and expensive to buy, so spending a little time on their preservation will pay dividends in the long run.