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Meteorites

7 Posts tagged with the planetary_science tag
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We’re delighted to announce the start of a new meteorites project called Shooting Stars @ the Natural History Museum that aims to observe meteors over the UK.

 

Meteors (also known as shooting stars) are dust and rocks from space that generate a bright trail in the sky as they pass through the atmosphere. When a piece of rock enters Earth’s atmosphere it is moving very quickly (11 – 70km per second). As it falls to Earth the friction from the air causes it to glow and disintegrate. A very bright meteor is called a fireball. If the fireball is large enough (usually >1m), some of the rock may survive the fall and land on the Earth’s surface, which is when it becomes known as a meteorite.

 

Meteorites record 4.5 billion years of solar system history, but we rarely know where exactly in the solar system they came from. We think most are from asteroids, and some may even be from comets. One way to confirm this is to know a meteorite’s original orbit, which can be estimated if its fireball is witnessed from multiple locations. However, out of a collection of ~50,000 meteorites worldwide, fewer than 10 have been observed falling to Earth in enough detail to accurately calculate their orbit.

 

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My desk is getting crowded but we now have everything we need to start watching the skies!

 

To increase the chances of seeing a meteorite while it is falling to Earth, a number of digital camera networks, dedicated to detecting meteors and fireballs, have been set up around the world. Some use highly sophisticated cameras and software, whilst others are more low-tech affairs.

 

Our Shooting Stars project will contribute to these networks by using two CCTV cameras to search for meteor fireballs above the UK. One camera will be placed on the roof of the Natural History Museum in South Kensington, and the second will be located at our Tring site to avoid the effects of light pollution in central London.

 

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Our new toy! This is one of the CCTV cameras that we will use to search for meteors and fireballs above the UK.

 

Over the last few months we have received almost daily deliveries of cameras, lenses, cables and computers. We’re hoping to have the first camera built and ready for testing in the next couple of weeks, so check back here and keep an eye on our twitter account for the latest updates.

 

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A fish-eye lens will be attached to the camera to give us a wide-angle view of the night sky.

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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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Next week is the Annual Meeting of the Meteoritical Society. This year it is being held in Morocco by scientists from Hassan II University of Casablanca. All of us in the Museum’s meteorite research team are heading out to Casablanca on Sunday for a week of presentations, discussions, networking and a great chance to explore some of Morocco.

 

epi.jpgThe Moroccan Atlas Mountains. A great place to go meteorite hunting! (Image credit: E. Vaccaro)

 

Many meteorites have been found in Morocco, including the Martian meteorite Tissint, so this is a very appropriate place for hundreds of meteorite-lovers to convene (the organisers have even named the conference meeting rooms after meteorites!).

 

Morocco has an abundance of meteorites because it is largely desert, and deserts are excellent places to look for odd, dark coloured rocks from space. Most of the meteorites found in this region are given the designation NWA (for North West Africa) as it is not always known exactly where they fell before they were passed on to collectors and institutions by meteorite dealers. 

 

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Museum scientist Dr Caroline Smith holds the Tissint meteorite. It is now the largest Martian meteorite in the Natural History Museum collections.

 

Museum research being presented at the meeting includes:

  • Professor Sara Russell on the new carbonaceous chondrite, Jbilet Winselwan.
  • Dr Caroline Smith on planning for Mars sample return missions.
  • Dr Penny Wozniakiewicz on collecting and identifying micrometeorites.
  • Dr Ashley King on fine-grained rims in CM chondrites.
  • Dr Jennifer Claydon on the Al-Mg system in chondrules.
  • Dr Natasha Stephen on mapping Martian meteorites.
  • PhD student Epifanio Vaccaro on characterising primitive meteorite matrix.
  • PhD student Natasha Almeida on using CT to study the interiors of meteorites.

 

We hope to keep you updated on the Meteoritical Society Meeting via our blog and our Twitter account @NHM_Meteorites.

 

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And here's what one of our PhD students, Epi, got up to on his last time in Morocco! (Image credit: E Vaccaro)

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Museum scientists Ashley King and Anton Kearsley have co-authored an article published in Science on 14 August 2014 on the first laboratory analysis of interstellar dust grains.


Have you ever wondered what exists beyond the solar system? Most people think space is empty, but in actual fact the vast regions between the stars, the interstellar medium, is full of tiny dust grains. Until recently the only way to study this dust was to use telescopes and we knew very little about its size, composition and structure. However, a new study has now described the first successful laboratory analysis of dust grains from outside the solar system.

 

The interstellar dust was returned to Earth by NASA’s Stardust mission. Launched in 1999, the spacecraft had a collector made of aerogel bricks (the lightest solid material on Earth) in a frame made of aluminium. This was specially designed to preserve materials impacting into it at very high speeds (faster than 6 km/s). One side of the collector was used to capture materials from the comet Wild 2, the other to capture interstellar dust passing through the solar system. The sample-return capsule arrived safely back on Earth in 2006 and, following initial analysis of the comet grains, work began on the interstellar side.

 

er_capsule_ground.jpgThe Stardust sample-return capsule landed in the Utah desert on 16 January 2006. The capsule was transported to Johnson Space Centre, Houston to be opened in a clean facility (Image courtesy NASA/JPL-Caltech).


The study reports the findings of a 6 year collaborative effort between 66 scientists (including myself and Anton Kearsley at the Museum) working in 36 laboratories in 7 countries. The team also received help from >30,000 members of the public who identified impacts tracks by searching through thousands of digital microscope images as part of the citizen science program Stardust@home.

 

It turned out that most of the impact tracks and craters were caused by debris from the spacecraft or dust from within the solar system. However, 7 grains are likely to be of interstellar origin and, using the experience gained from examination of the comet particles, the team developed methods for extracting, handling and analysing the precious interstellar samples, finding some unexpected results along the way!

Picture2.jpgTiny dust particles impacting into the collector (about the size of a tennis racket) produced tracks in the aerogel (right) and craters in the Al-foils (Image courtesy NASA/JPL-Caltech).


The interstellar grains are very small, typically weighing a picogram (a millionth of a millionth of a gramme) or less, and have different compositions and structures. One of the biggest discoveries is that the grains have at least partly crystalline structures, which is surprising as most people thought that the crystallinity should be destroyed in interstellar space by irradiation.

 

Sample-return missions such as Stardust are therefore allowing us to answer big questions about the formation and evolution of galaxies and solar systems by studying minute amounts of material in the laboratory. The Science paper has just hit the headlines today but, hopefully, there's a lot more to come in this story.

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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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Hi all! Natasha here again, raring to tell you all about a most excellent trip that I’ve recently returned from. It was my first experience of the US and boy was it a good ‘un. Killing two birds with one Texan stone, I first went on a short course on geological applications for computed tomography (CT) in Austin, and then on to Houston for a visit to the NASA Johnson Space Center.

 

Micro-CT is a remarkable (and pretty novel) technique that uses X-rays to image specimens in three-dimensions, giving us a non-destructive way to see what’s inside. I use it to look at extraterrestrial material, but the scanner at the Museum gets used for all sorts! Sometime I'll do a more detailed post that goes into the physics of it all, but for now, back to the Lone Star State.

 

So my experience can be summed up in three words – humid, delicious and rocky! Everything is bigger in Texas. The cars (read pick-up trucks), the cakes, the personalities! Arriving into 40°C heat in Austin, my glasses immediately steamed up. After a short shuttle bus to the hotel, I was excited to meet my roommate for the duration of the course, a lovely PhD student studying drill cores with CT at the University of Florida.

 

Course on CT scanning

 

The short course was run by the High Resolution X-Ray CT Facility at the Jackson School of Geosciences (UTCT) in the University of Texas at Austin. This fantastic lab has been doing pioneering work in the geological applications of CT for almost 20 years. As well as getting a very helpful tutorial on their in-house software and talks on successful projects they have done, we also had the opportunity for a tour around the labs. UTCT has two CT scanners, which are optimised for different sizes and types of sample, including one instrument with detectors on microscope objectives. This means they can sort of ‘zoom in’ to features inside the specimen and get very high resolution images! Luckily they also have air conditioning in the lab otherwise I’m sure I’d have passed out from the heat!

 

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Ryan in the computer lab, learning how to use Blob3D.

 

That evening, all the course delegates were invited to a marvellous barbeque at the course director’s house, with home-smoked brisket, and my first Texan ribs! As well as enjoying dinner, I was dinner for certain unwelcome party guests… I left that night with about forty mosquito bites! 

 

Tuesday and Wednesday were likewise spent in workshops and tutorials on both CT hardware and software. One of the most important and useful aspects of attending the course was the chance to spend time with other rock-minded people, to share ideas on how to tackle problems or artefacts in the data, and to make contacts for future collaboration or discussion. We also managed to sneak in a couple of World Cup games along with a quick craft beer tasting walk through the city!

 

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Congress Bridge in Austin and the crowds awaiting the awakening of the million or so bats that live underneath.

 

Oh, and to continue the gastronomic theme, I tried a chimichanga, Detroit-style pizza, possibly the best pulled pork sandwich I’ve ever had, and breakfast burritos. Mostly yum!   

 

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This is a chimichanga, a deep fried burrito, soaked in cheese. Can’t say this one went down well!

 

As if often the case when you’re having fun, the days passed quickly, and it was soon time to leave Austin. I headed on to Houston for the next stage of the trip.

 

A trip to NASA

 

The Johnson Space Center is NASA’s base for human spaceflight training and flight control, and houses their Astromaterials Research and Exploration Science department. This means that all the astronauts are based there, and all the Apollo samples, Antarctic meteorites and samples collected during the Stardust and Genesis missions are kept there! It is possibly the most awesome facility that I could ever imagine.

 

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The Space Shuttle Endeavour flying over the Johnson Space Center on a Boeing 747 carrier aircraft. Copyright NASA.

 

The key reason I went to NASA was to visit Ryan Zeigler, the Apollo Sample Curator. Ryan is responsible for looking after all the rocks, soils and cores brought back by the Apollo astronauts on the six missions that landed on the Moon. Back in February, he brought four of these samples, from Apollo 14, 15 and 16, to the Museum, and we CT scanned them here together in the Imaging and Analysis Centre.

 

We haven’t written up the results yet, but all four scans were very interesting, showing different textures and inclusions. One of the most exciting finds was that of a very large clast of basalt in an Apollo 16 breccia (a rock made up of fragments of other rocks or minerals). Below is a visualisation I made of the CT data, which shows the outline of the sample and where the clast is located inside (the green mass). This kind of image is invaluable for curators who would like to know exactly where to slice into the rock to expose features of interest for science. The sample is about ten centimetres across.

 

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A visualisation of the location of a basalt clast within an Apollo 16 breccia, made using the Drishti program.

 

Blimey, that’s a long post already and I’ve barely got on to the coolest stuff that I saw and the rocks that I got to hold! I’ll leave it there for now but check back soon, as I’ll be doing another post all about the Lunar and Meteorite Laboratories! Here’s a taster:

 

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A lunar basalt, collected by Apollo 11. The only rock to have been brought from the Moon then taken back into space for a trip on the International Space Station.

 

Lastly, if you’re ever in Texas, check out the ribs at Rudy’s!

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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…