Natural History Museum (2)

BIMS visit to the Natural History Museum, London

Early in September 2008, members of BIMS were given the opportunity to visit the NHM, London. We were hosted by Dr Caroline Smith, Curator of Meteorites, who kindly agreed to allow us behind the scenes access to the national collection. The museum curates some of the most famous and scientifically important meteorites in the world; as with all museums, for reasons of space most of the collection cannot be put on public display. We took a trip into the depths of the building…

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The main mass of the Appley Bridge meteorite, an LL6 which landed in Lancashire in 1914. Weight is about 8.5kg.

A large fragment of the famous Barwell ‘Christmas’ meteorite. Barwell, an L5, fell to earth in Leicestershire on Christmas Eve, 1965. Most was recovered very quickly, meaning a beautiful fresh fusion crust was preserved. This example has very nice contraction cracks which unfortunately aren’t visible in the photo. There was also a large (2 – 3cm) oval inclusion, possibly some HED material.

In case the piece above isn’t quite what the scientific staff are after, there’s a drawer full of other stones, slices and fragments of Barwell.

One of my personal favourites is Cold Bokkeveld, a CM2 which fell in Cape Province, South Africa in 1838. (I have a small piece in my personal collection). The total weight is only 5.2kg, MetBase lists the NHM as having 1.1kg. This isn’t quite that much, but it’s still a big piece of a very rare stone.

A drawer with specimens of assorted carbonaceous chondrites – including quite a lot of Mokoia, which fell in New Zealand in 1908. The TKW is only 4.5kg, only a few hundred grams ever left New Zealand. This fall is like hens’ teeth for collectors!

Mark Ford with the main mass of Launton, another impossible-to-get-hold-of British fall. It struck Earth in 1830, in Oxfordshire. The total weight is just over a kilo. It’s an L6.

The rest of Launton.

Murchison isn’t a particularly rare meteorite, with a known weight of over 100kg. This piece is unusual in that it’s remarkably fresh and has been sealed for most of its curation. There is a powerful odour from the organic volatiles when the lid is removed from its container.

Murchison fell in Victoria, Australia in 1969.

A drawer containing many specimens of L’Aigle, an important historical meteorite. Over 3,000 stones fell in a shower in 1803 in Normandy. At that time, there was fierce debate about the origin and nature of meteorites. Following an investigation by the French Academy of Science, they concluded that the combination of physical and witness evidence clearly showed that rocks really did fall from the sky. L’Aigle was a turning point in the understanding of meteorites, although it didn’t completely settle the argument.

Another important French meteorite, Orgueil fell in 1864. It’s scientifically important as a very primitive CI class chondrite, and historically important too – although for different reasons to L’Aigle. It was the subject of a famous hoax.

Two large pieces of Parnallee, an LL3.6 which fell in India in 1857. Parnallee is appreciated for having a beautiful internal texture and appearance. The total weight is 77kg, and most of it is at the NHM.

The museum also, naturally, holds many iron- and stony-iron meteorites. Here is a large Canyon Diablo with beautiful regmaglypts. This piece is on display in the dinosaur hall – I’m sure you can guess why…

Mincy was found in Missouri in 1857. It’s a lovely mesosiderite with a total weight of about 90kg.

A huge chunk of the mesosiderite Estherville.

 

Mark holding a piece of Nakhla weighing perhaps 150g. Nakhla has several claims to fame. It’s quite a small mass, with only about 10kg known. It was observed to fall in Egypt in 1911, and is alleged to have struck and killed a dog. But most important of all, it’s been shown to be one of the very rare meteorites which originated from Mars.

A closer view…

…and a shot of the beautiful shiny, black fusion crust. This forms as the rock heats up and the surface melts in the earth’s atmosphere. Sometimes small ‘rivulets’ of molten rock flow around the surface, and are locked in place when the rock cools. These are called flow lines, and are clearly seen in the photo above.

All our visitors from space don’t crash in sound and fury. Some are so small that they slow down in the atmosphere, and then drift downwards at a leisurely pace, eventually coming to rest on land or sea. If they land in the sea, they accumulate on the sea bed, and someone with a magnet, a microscope, and a high degree of patience can identify and seperate out the extra-terrestrial wheat from the chaff.

This is exactly what was done with material dredged from the sea bed by the Challenger Expedition in the 1870s, and these are some of the original spherules produced by that mission. Incidentally, the space shuttle Challenger was named after ths ship used on the expedition.

This is one of the museum’s newest and proudest acquisitions – the main mass of the CI1 meteorite Ivuna. Ivuna fell in Tanzania in 1938, and represents some of the most primitive material in the solar system. Only 700g was ever recovered. The museum paid a substantial sum for this specimen, and the story generated strong interest in the national media.
(If you’re still looking, it’s the black object between the two white bars! All the rest is temporary packaging designed to maintain a stable, oxygen-free, dry, protective atmosphere until the specimen can be more permanently housed).

Tektites!

Tektites are not meteorites. Most scientists now believe that they are pieces of the earth’s crust which were thrown into space as a result of a meteorite impact. The molten rock solidified as it re-entered the atmosphere, and many of these tektites form into characteristic shapes through rotation or tumbling.
Here are a few from the museum’s collection.

Although not strictly considered a tektite, LDG (Libyan desert glass) is believed to have formed in a similar fashion, as a result of an impact or atmospheric explosion turning desert sand into glass. It has long been prized for jewelery.  We were shown this particularly nice piece.

LDG is beautiful under normal lighting, but hold it up and illuminate from behind…

…and the delicate texture and inclusions become visible.