Spa Day for MeteoritesPosted on 22-01-2018 by Becky Desjardins
When a meteorite is more pampered than you...
The chemical makeup of meteorites falls into one of three classes. Stony, stony-iron, and iron. Most of the meteorites that fall are stoney in composition, but iron meteorites are found more frequently. This is for a number of reasons: first of all, the intense heat that a meteorite is exposed to as it enters the earth’s atmosphere causes it to melt. Iron meteorites are more resistant to this heat than stony meteorites which therefore sometimes completely melt away. Also, this melting gives an iron meteorite a distinctive shape which makes it obvious that they are unusual, even to a lay person. So, they are spotted more easily. In addition, iron meteorites are more resistant to weathering on earth than stony or stoney iron, so more likely to stay in the spot where they land for hundreds of years without alteration from rain, sun and snow.
Many meteorites in museum collections have interesting stories about the years before they came to be in museums. Because they are so heavy, they are perfect for use as an anvil, or a door stop, or, in one case, a counter balance to hold down the stand on a basketball net. Iron meteorites are thought to frequently come from asteroids: they are the broken up bits that split off after the asteroid had a collision with another object. But still much is unknown.
Photo: one of the two iron meteroties from Naturalis: the 'Canyon Diablo", was found in Arizone USA. Picture by Becky Desjardins.
In the Naturalis collections, we have two large iron meteorites. Because they are primarily made up of heavy metals, they rust when exposed to air. To protect them from rusting, they have to be smeared with white vaseline (acid free vaseline) to keep them from coming in contact with air. We do this once a year. Recently it was time for the annual “meteorite spa day”, where we take them out of their storage boxes and give them a vaseline massage.
Giving an meteorite a massage is not very difficult, as you can imagine. But what is a little tricky, is the fact that these meteorites are very, very heavy! I don’t know how much Naturalis’ weigh in kilograms, but with the smaller of the two, which is about the size of a basketball, it takes 3 of us to move it (and even then we can’t pick it up, we just roll it around). So, what we do is gently tip the box on its side and then roll the meteorite onto a blanket and flip it around as we rub it all over with vaseline. After that, we have to maneuver it back into the box.
In the last 200 years, 6 meteorites have been recovered in the Netherlands. Astronomers estimate that on average every 3 years a meteorite lands in the Netherlands, though unfortunately they are not always found. Sometimes they fall into the water, or are buried in the soft soil on impact, or become so small from the heat of atmospheric entry that they cannot be recovered. The most recent meteorite that fell in the Netherlands landed in January 2017 in Broek in Waterland. This stony meteorite smashed into the roof of a garden shed when it fell to earth. As most meteorites are believed to come from broken asteroids, crashing through a roof was the end of a journey that undoubtedly started, as the saying goes: A long time ago in a galaxy far far away”.....
Langbroek, Marco 1 July 2017. Sat TrackCam Leiden blog.