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Meteorites

4 Posts tagged with the solar_system tag
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A guest post by Helena Bates, undergraduate student at Imperial College London.


This summer I had the opportunity to work alongside scientists in the Mineral and Planetary Science Division at the Natural History Museum on a project sponsored by the Paneth Trust, a scheme which offers bursaries to undergraduates so that they can do a summer internship in fields relating to meteoritics.

 

The project I joined was led by Ashley King and involved investigating minerals that were created by aqueous alteration in CI and CM carbonaceous chondrites. These types of meteorites have had almost all of their original material altered by water into fine-grained clay type minerals, which are so small they cannot be easily studied by looking through a microscope. Instead, we used a process called X-ray diffraction to identify mineral components. When a small beam of X-rays is focused on the sample it produces a diffraction-pattern unique to the minerals present.

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Ashley and I are busy using the X-ray diffractometer.

 

Usually this process involves grinding up a sample of a meteorite, and any information about where in the meteorite a certain mineral is located is lost. However, the alteration that the meteorite experienced was probably not uniform so knowledge of the distribution of aqueous alteration minerals is important. If we can see where the alteration took place within the meteorite this can help us put constraints on the role of water in the early solar system and perhaps even see how the water moved through the sample! So rather than grinding up samples we carried out X-ray diffraction on thin sections of meteorites.

 

We looked at a total of 4 meteorites, all of which were found in Antarctica and on loan to us from NASA and JAXA. They were; Y-82162, a CI chondrite, LAP 02277 and MIL 07689, both of which were CM1 chondrites, and MCY 05231, a CM1/2.

 

HBimage1.jpgA thin section of meteorite LAP 02277 with dots showing where X-ray diffraction patterns were collected.


For each meteorite we produced maps of various minerals that are produced by reactions with water, including phyllosilicates, iron oxides and carbonates. These maps give us spatial information about where some minerals are located in relation to others. Obviously this is just the beginning of the technique, but it is easy to see how this can be taken further to produce larger maps which can show how water moved through the sample. This will help us understand the role of water during the formation of asteroids, 4.6 billion years ago.

 

Thank you so much to everyone at the Natural History Museum, especially Ashley King, who let me help with his research, and thank you to the Paneth Trust for helping fund this internship – it was an incredible experience!

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As well as keeping you informed about our research we're going to use this blog to let you know more about our meteorite collection, especially the ones that aren't currently out on display.

 

All of us in the meteorite group are off to Casablanca, Morocco in September to present our research at the Annual Meeting of the Meteoritical Society (... more on that nearer the time). At the meeting there is going to be a special session about a very important meteorite called Orgueil.

 

It is 150 years since Orgueil was seen to fall in southern France (n.b. all meteorites are named after the place where they fell or were found so this one was seen to land near its namesake). We have several pieces of Orgueil, kept in the meteorite curation facility at the Museum.

 

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Me in the meteorite curation area. Most of our meteorites are kept in drawers like this.

 

Orgueil is important because it is part of a rare group of meteorites called CI chondrites. There are only five known CI chondrite 'falls' and Orgueil is by far the biggest, weighing 14 kg. We only have a total of about 7 kg of the other four CI chondrites so they are all very precious.

 

[A quick diversion into terminology - when meteorites are seen to fall and land we call them 'falls'. If a meteorite is found but no one saw it fall then it is called a 'find'. Falls are more valuable to scientists because they can be recovered more quickly and so are less likely to experience contamination or chemical alteration during their time on Earth.]

 

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A piece of Orgueil from our collection. All our meteorites have a unique number so that they can be identified.

 

When scientists analysed the chemistry of the CI chondrites they found that they are almost identical to the composition of the Sun. We think the chemistry of the Sun has stayed pretty much the same since it formed over 4.5 billion years ago and that the Sun contains over 99% of the mass in the Solar System.

 

This means that the Sun is very representative of the material that was present in the early Solar System; however it is very difficult to sample for what are probably obvious reasons. The compositions of other planets and many asteroids have been changed over time by chemical and physical processes so they are no longer representative of the early Solar System. As the CI chondrites are chemically very similar to the Sun we can study them to learn more about what the material in the Solar System was like when it formed 4.5 billion years ago.

 

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Different analytical techniques require different sample preparation. Here we have Orgueil "three ways": a disk (left) for infra-red analyses, powder (back-right) for x-ray diffraction analyses and chips (front-right) that can be polished for scanning electron microscopy.

 

Another of the CI chondrites, Alais, also fell in France about 50 years before Orgueil. Alais was found in 1806, just three years after one of the first scientific reports of a meteorite fall.

 

The report was written by Biot, a member of the French Academy of Science, and convinced the scientific community that meteorites were extra-terrestrial (apparently it was a much more exciting read than an earlier report by the German physicist, Ernst Chladni). Before this time meteorites were thought to be terrestrial rocks that had been struck by lightning, or rocks ejected from volcanoes. If Biot's work had not been published it is likely Alais would have been thrown away because it was initially thought to be fossilised peat.

 

The other three CI chondrite falls fell in the 20th century and are called Tonk, Ivuna and Revelstoke. The biggest piece of Ivuna is kept in our collection. It has been stored in a nitrogen atmosphere for the past twenty to thirty years. This protects it from the Earth's environment.

 

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We have the largest piece of Ivuna in a public collection anywhere. It is kept in a nitrogen environment to protect it from the Earth's atmosphere.

 

CI chondrites like Orgueil and Ivuna are also important as they contain organic material. This consists of molecules of carbon and hydrogen with some oxygen, nitrogen and sulphur. All this carbon makes the CI chondrites very black in colour - and perhaps easily mistaken for fossilised peat. They also contain a lot of water (up to 20%). One of our post-doctoral researchers, Ashley, is studying the mineralogy of Orgueil and other meteorites like it to find out more about water in the Solar System.

 

That the CI chondrites contain organic material and water is interesting because you need both these things in order for life to survive, and some people think that the building blocks for life on Earth could have been delivered by meteorites or comets. But - and it's a big but - you do not need life in order to have organic material and water, so they in themselves are not evidence of life coming from outer space.

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If you’ve read Jenny’s post you’ll be familiar with our research group. This week I’m going to tell you a bit about my job - I’m Ashley, a research scientist at the Museum investigating water in meteorites.

 

We all know that water is vital to sustaining life on Earth, but where did it come from? One suggestion is that it arrived here from asteroids and comets early in the Earth’s history. Meteorites can contain nearly 20% water and we study these to try and better understand the history of water in the solar system.

 

Recently, a group of us visited the Diamond Light Source (DLS) to carry out experiments on some meteorites. Diamond is the UK’s synchrotron facility and is used by many different scientists to study anything from dinosaur bones to new medicines. It works by accelerating electrons close to the speed of light to produce bright beams of electromagnetic radiation. These beams can be up to 10 million times brighter than the Sun.

 

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Here I am using the data collected to make a map of water-bearing minerals in the Murchison meteorite.

 

During our visit we used a beam of infrared light. Infrared light can be used for many things (like controlling your TV using a remote control); we used it to map the location of water in meteorites. We focused the beam to a very small spot so that we could study the meteorites on a very small scale.

 

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Nat keeps the infra-red detector cold by topping it up with liquid nitrogen. This had to be done every 7 hours.

 

Synchrotrons are now becoming a very popular choice for scientists carrying out experiments. They operate 24 hours a day, 7 days a week, they can be set up to carry out lots of different experiments and they generate huge amounts of data in a very short time. This means that synchrotrons are used to study some of the most important topics in science. Unfortunately it also means that the time for your experiment is limited and you often have to work for several days with very little sleep, which has been known to lead to the occasional nap on job!

 

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Searching for water in meteorites is hard work…

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Hello! I’m Jenny, a research scientist studying meteorites at the Natural History Museum. My work focuses on the timing of heating events in the early solar system, but more on that another time…

 

I’m part of a group of researchers, curators and PhD students who study meteorites and other extraterrestrial materials in the Museum’s Earth Sciences department. We study these rocks – using various laboratory techniques – so that we can better understand the formation of the solar system.

 

The Museum is a great place to carry out this research as its meteorite collection is one of the finest in the world; containing almost 5,000 pieces of 2,000 individual meteorites. Most of these come from asteroids, but we also have meteorites from the Moon and Mars. Our collection also includes objects formed during meteorites impacts.

 

We’ve decided to start this blog so that we can communicate our research to you and provide a more in depth look at the Museum’s meteorite collection. As it’s our first post I’ll give a few examples of why our research matters and how it gives important insights into the world and space around us.

 

  • The solar system formed about four and a half billion years ago. We know this from studying meteorites like this one, called Allende. It contains a component that is rich in calcium and aluminium (called calcium-aluminium inclusions or CAIs). These CAIs are the oldest solar system materials.

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This is a stone from the Allende meteorite. The white part is a calcium aluminium inclusion (we call them CAIs). These CAIs are thought to be the first solid material to form in the solar system.

 

  • There has not been a sample return mission to Mars yet so, for now, the only pieces of Mars available for scientific study on Earth are meteorites. These meteorites help us understand the volcanic processes that occurred on another planet. We are lucky enough to have a large (1.1 kg) piece of a martian meteorite called Tissint on display in the Vault gallery.

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The largest piece of the martian meteorite, Tissint. We keep it in a container called a dessicator to protect it from Earth's environment.


  • Meteorites contain a lot of water! You might think that asteroids are very dry objects, but in some meteorites up to 20% of their weight is made up of water. These meteorites are called carbonaceous chondrites as they contain organic carbon – this also makes them look very black in colour, as you can see in the photo of the Ivuna meteorite, below. Their chemical composition is very similar to the Sun, which means they preserve the most primitive solar system materials, unchanged for over four and a half billion years.

 

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This is a piece of the Ivuna meteorite. It looks very dark, almost black, because it contains a lot of carbon.


I hope you found that information interesting! I, along with the rest of the meteorite group, will use this blog to tell you more about our collection. We will also write about our individual research (what we hope to achieve, what lab techniques we use, conferences we attend), the curation of meteorites and our outreach activities. Check back soon for more!