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6 Posts tagged with the asteroids tag

Some meteorites, called CI chondrites, contain quite a lot of water; more than 15% of their total weight. Scientists have suggested that impacts by meteorites like these could have delivered water to the early Earth. The water in CI chondrites is locked up in minerals produced by aqueous alteration processes on the meteorite’s parent asteroid, billions of years ago. It has been very hard to study these minerals due to their small size, but new work carried out by the Meteorite Group at the Natural History Museum has been able to quantify the abundance of these minerals.


The minerals produced by aqueous alteration (including phyllosilicates, carbonates, sulphides and oxides) are typically less than one micron in size (the width of a human hair is around 100 microns!). They are very important, despite their small size, because they are major carriers of water in meteorites. We need to know how much of a meteorite is made of these minerals in order to fully understand fundamental things such as the physical and chemical conditions of aqueous alteration, and what the original starting mineralogy of asteroids was like.



A CI chondrite being analysed by XRD. For analysis a small chip of a meteorite is powdered before being packed into a sample holder. In the image, the meteorite sample is the slightly grey region within the black sample holder. The X-rays come in from the tube at the right hand side.


The grains in CI chondrites are too small to examine using an optical or electron microscope so we used a technique known as X-ray diffraction (XRD). XRD is a great tool for identifying minerals and determining their abundance in a meteorite sample. We found that the CI chondrites Alais, Orgueil and Ivuna each contain more than 80% phyllosilicates, suggesting that nearly all of the original material in the rock had been transformed by water.


As part of the study we also analysed some unusual CI-like chondrites (Y-82162 and Y-980115) that were found in Antarctica. These meteorites have similar characteristics to the CI chondrites we studied, but also experienced a period of thermal metamorphism (heating) after the aqueous alteration. We found that the phyllosilicates had lost most of their water and had even started to recrystallize back into olivine, a process that requires temperatures above 500°C! The CI-like chondrites are probably from the surface of an asteroid that was heated by a combination of impacts with other asteroids, and radiation from the Sun; however, whether the CI and CI-like chondrites come from the same parent body, remains an open question.



XRD patterns from the CI chondrites Alais, Orgueil and Ivuna. X-rays diffracted from atoms in the minerals are recorded as diffraction peaks. Different minerals produce characteristic diffraction patterns allowing us to identify what phases are in the meteorites. In this work we also used the intensity of the diffraction peaks to determine how much of each mineral is present.


This research has been published in the journal Geochimica et Cosmochimica Acta and can be accessed here.


King AJ, Schofield PF, Howard KT, Russell SS (2015) Modal mineralogy of CI and CI-like chondrites by X-ray diffraction, Geochimica et Cosmochimica Acta, 165:148-160.


It was funded by the Science and Technology Facilities Council (STFC) and NASA.


Last December, Epi Vaccaro (one of our PhD students) and I went to two scientific meetings in Tokyo, Japan. Our aims were to present some of the research that we’ve been doing at the Museum and to meet other scientists who work on similar samples and topics.


First up was the Fifth Symposium on Polar Science at the National Institute of Polar Research (NIPR). Since the early 1960s, the NIPR has used Antarctic stations to carry out research into a wide range of areas including climate, atmospheric science and biology. Fortunately for us, they are also interested in meteorites and, after several 'meteorite hunting'expeditions in the Antarctic, now have one of the largest collections in the world.


I spoke at the meeting (despite a serious case of jetlag!) about differences I have observed between the mineralogy of CI chondrites that were seen to fall to Earth, such as Orgueil, and those that have been recovered from the Antarctic. These CI meteorites are important as they show very similar characteristics to the surfaces of some asteroids that are soon(ish!) to be visited by space missions.



Presentations were temporarily suspended at the NIPR meeting as we watched the launch of the Hayabusa-2 mission.


One of these missions is the Japanese Aerospace Exploration Agency (JAXA) Hayabusa-2 spacecraft, which aims to collect material from a primitive asteroid and return it to Earth. We think that this material will allow us to learn more about water and life in the early solar system.


The samples won’t touch down on Earth until 2020 but the spacecraft was launched (after a few days delay) during our stay in Japan. I think that watching a tiny spacecraft being hurtled into space on the back of a rocket, whilst sitting alongside the people who have invested so much time and energy into the mission, was one of the most tense afternoons of my life!*



Model of the Hayabusa spacecraft at the Japanese Aerospace Exploration Agency (JAXA).


You may have guessed from its name that Hayabusa-2 is actually a follow up to the original Hayabusa spacecraft, which (despite a few bumps along the way) in 2010 became the first ever mission to collect material from an asteroid and bring it back to Earth.


Hayabusa 2014 Symposium at JAXA. The meeting covered diverse subjects such as space weathering and sample curation, and also included a talk by Epi on the challenges of analysing very small samples using non-destructive techniques.



Epi presenting his work at the Hayabusa 2014 Symposium at JAXA.


Sample return missions are challenging and expensive but produce very exciting science, as I witnessed at JAXA. There are limits on what kinds of scientific experiments can be carried out remotely, but returned samples from the asteroid belt will provide a wealth of new information about our solar system’s past.


*You’ll be pleased to hear that the launch was successful and Hayabusa-2 is safely on its way.


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.


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!


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. 



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.



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


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.


Image 1.JPG

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.]


Image 2A.jpg

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.


Image 3A.jpg

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.


Image 4.JPG

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.


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.


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.


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.



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!