Meteorites are rocks that have arrived on Earth from outer space – they originate from planetary bodies in the asteroid belt, from the Moon and even from Mars. These samples are critically important to scientists to study the geology, chemistry and age of different planetary bodies, helping us to understand the origin and evolution of the Earth’s place in the Solar System. Meteorites fall all over the Earth – we currently have about 56,000 samples in our collection, most of which, some 35,000 stones have been collected in Antarctica by science teams from the USA, Japan, China, Italy, Belgium, South Korea and Europe.
Why do we go to Antarctica? Antarctica is a special environment that is ideal for meteorite searching. The meteorites are well preserved in the cold dry icy environment, they do not break up as quickly as they would if they fell in a hot or wet climate. Meteorites are also relatively easy to spot as they are dark rocks that stand out the white ice and often look very different from any surrounding local geology. Most importantly, there is a natural concentration mechanism that transports meteorites within icy glaciers to collection zones along mountain ranges. This makes it easier for scientists to go to a field site and know that they will be able to collect many meteorites by only visiting a few places. When it is cold and difficult to do fieldwork this helps makes meteorite collection missions more productive for finding lots of samples!
How do you do fieldwork in Antarctica? We camp in tents on the ice for a field season of 4 to 6 weeks in small teams of 2 to 8 people. The field sites are normally a long way from the main science bases scattered across Antarctica, so you have to take everything with you including food, power supply, safety equipment and field kit. There is a lot of logistical planning work to get everyone into and out of the field safely, a little bit like a space mission! You need good weather to search so that you can do fieldwork safely – when it is cloudy all the shadows and surface definition is removed which makes it unsafe to travel as you can’t easily see crevasses and steep slopes, and when it is very windy it is too cold to work. When the weather is bad like this all you can do is sit in your tent and wait for things to improve.
How do you search for meteorites in Antarctica? We search for meteorites by either driving around on snowmobiles and finding black rocks sitting on blue ice (areas of ice that is moving incredibly slowly), or we walk around in areas where there are lots of rocks in places called glacial moraines (rocky debris left behind by glaciers) and try and pick out any meteorites hiding among the terrestrial rock. Meteorites typically have a black crust on their outside surface, formed when the rock’s surface melted a little as it came down through Earth’s atmosphere. They have other properties such as being magnetic and having a different surface texture that make them stand out from other types of Earth rocks. You have to learn what you are looking for and train your eyes to spot the difference in appearance. When someone spots an interesting looking rock on the ice they jump off their skidoo, check it is a meteorite, and then wave their arms to call the other people over to come and help collect it. The meteorite is photographed, its logged its location and carefully put it into a special collection bag ready to send back to the lab.
Once the meteorites are collected, stored safely and sent back to laboratories scientists can review what types of samples have been collected – have they been lucky enough to find a piece of Mars, a piece of the Moon’s farside, or an asteroid that has never been sampled before? Then scientists, including those of us in the Isotope Geochemistry and Cosmochemistry Group at the University of Manchester, have the opportunity to study the meteorites to test our ideas about how the planets formed and have been changed through the last 4.56 billion years of Solar System history.