Earth sciences news

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 month a new temporary display featuring some of our foraminiferal specimens and models was placed in the Museum gallery. This features real microfossils on one of our foraminiferal Christmas card slides alongside 20 scale models, part of a set of 120 models generously donated to us last year by Chinese scientist Zheng Shouyi.

Senior Microfossil Curator Steve Stukins admiring some of the specimens and models on display and thinking "this is a much better place for them than the Curator of Micropalaeontology's office!"

As a curator dealing with items generally a millimetre or less in size I have not often been involved in developing exhibits other than to provide images or scale models like the Blaschka glass models of radiolarians. Displaying magnified models is one of the best ways to show the relevance of some of the smallest specimens in the Museum collection, the beauty and composition of foraminifera and to highlight our unseen collections.

This display features one of our most treasured items, a slide with microscopic foraminifera arranged in patterns to spell out the words 'XMAS 1912'.

A festive slide of foraminifera created by Arthur Earland.

This was created by Arthur Earland for his long time collaborator Edward Heron-Allen. A previous blog tells of the sad end to the relationship between these two early 20th Century foraminiferal experts, a story that featured in the Independent under the heading 'shell loving scientists torn apart by mystery woman'.

The slide itself is amazingly beautiful under the microscope and a close up view (see above) is shown on the back board of the exhibit. The naked eye can show the arrangement of the specimens on the slide but cannot really pick out the beauty of the foraminifera. I was at a collections management conference about a year ago where it was suggested that the public feel duped by seeing models rather than real specimens on display. In this instance, the scale models serve to show the beauty as well as to enhance the relevance of the real specimens on display.

Foraminiferal models by Alcide d'Orbigny that also feature in the display.

French scientist d'Orbigny (1802-1857) was the first to recognise that creating models was a good way to show his studies on the foraminifera. These models were created to illustrate the first classification of the foraminifera, a group that at the time were classified as molluscs.

A selection of Zheng Shouyi's models of foraminifera.

Chinese scientist Zheng Shouyi was inspired by d'Orbigny to create models of foraminifera to illustrate her work and to show the beauty of the Foraminifera. Of the 120 models she donated to us in 2014, 20 have been carefully selected for this exhibit. The selection shows a variety of different wall structures, a range of shapes, species for which we have the type specimen as well as some species of planktonic foraminifera relevant to current research at the Museum. Zheng Shouyi is also famous for encouraging and overseeing the production of the world's first foraminiferal sculpture park in Zhongshan, China.

If you are able to pop into the Museum, please come and see this free display. It is situated just after the exit from the dinosaur exhibition on the opposite wall to the dino shop. We can't promise any giant scuptures but I'm sure that you'll agree that these models certainly illustrate the beauty and help to explain the relevance of some of the smallest specimens hidden behind the scenes at the Museum.

The Museum runs an After Hours event called Crime Scene Live that in February featured micropalaeontology curator Steve Stukins.

Micropalaeontological evidence is increasingly being used to solve major crimes. Read on to find out about Steve’s involvement in Crime Scene Live, how our collections could help forensic studies and how our co-worker Haydon Bailey gathered some of the evidence that was key to convicting Soham murderer Ian Huntley.

Botanical or microfossil evidence?

The following image is of modern pollen, so could be described as botanical rather than micropalaeontological evidence.

A variety of modern pollen types similar to the ones investigated at the Crime Scene Live event.

As I mentioned in my post What is micropalaeontology?, distinguishing when something is old enough to become a fossil is difficult, particularly when some modern species are present in the fossil record. The Museum's microfossil collections contain modern species, particularly our recently acquired modern pollen and spores collection, and this collection has enormous potential as a reference for forensic investigations.

What can microfossil evidence tell us?

Because organisms that produce microfossils are present in a wide range of modern and ancient environments and can be recovered from very small samples, they can provide a lot of useful information. Mud or sand recovered from boots or clothing can show where the wearer has been and even the pollen content of cocaine can provide evidence of its origin or where it was mixed.

A scanning electron microscope image of British chalk showing nanofossils.

These details can relate a suspect to a crime scene, relate items to a suspect/victim or crime scene and prove/disprove alibis. Evidence can also show cause of death, for example, diatoms or freshwater algae present in bone marrow can indicate drowning.

Microfossil evidence helps solve the Soham murders

Haydon Bailey, who is working temporarily at the Museum on a project studying our former BP Microfossil Collection, provided some key evidence that convicted Ian Huntley of the Soham murders.

Haydon identified chalk nanofossils on and inside Huntley’s car that were common to the track leading up to the site 30 miles from Soham where the bodies had been dumped. For details about all the scientific evidence used, this article on the Science of the Soham murders is an interesting read.

Members of the public participating in Crime Scene Live activities.

Senior Micropalaeontology Curator Steve Stukins writes about Crime Scene Live at the Museum:

"This special public event gives the audience a chance to become a crime scene investigator for the evening using techniques employed by scientists here at the Museum. People are often surprised that the Museum is involved in forensic work, especially using entomology (insects), botany (plants) and anthropology (analysis of human remains). Crime Scene Live uses all of these disciplines and forms them into an engaging scenario for the visitors to get involved in.

 

Palynology, in most cases pollen, is used quite often in forensics. As pollen is extremely small, abundant and diverse in many environments it can be used to help determine the location of a crime and whether a victim/perpetrator has been in a particular place by understanding the specific pollen signature of the plants in an area.

 

Our jobs as forensic detectives in the Crime Scene Live Event were to determine where a smuggler had been killed, for how long he had been dead and the legitimacy of the protected animals he was thought to be smuggling. I’ll be giving away no more secrets about the evening, other to say that it was a great pleasure to be involved in a thoroughly enjoyable event and the feedback from the visitors was superb."

So if you fancy a bit of murder/mystery then why not come and help micropalaeontology curator Steve Stukins solve the Case of the Murdered Smuggler on 1 May or in October. Details of other Crime Scene Live events scheduled for this year can be found here.