What is a meteorite?
A meteorite is a piece of space rock that has landed on Earth after travelling throughout the Solar System. Meteorites are the oldest rocks in existence, created right back when the Solar System formed. Because of this, they can offer a direct look into the past, and can help us answer many of the questions we have about how solar systems form.
As a meteorite enters the atmosphere, it begins to burn up due to the speed it is travelling at. Depending on its composition, it can appear to be one of many colours. This burning meteorite streaking through the sky is what we call a fireball.
Meteorites can come in just about any size, ranging from the size of a grain of dust to about 100 meters across. Larger meteorites often break up into many smaller fragments upon their descent to Earth’s surface.
Images captured by the network can give information about the speed, direction and impact location of a fireball travelling through Earth’s atmosphere. By analysing this information, models can be made using software to trace a meteorite’s orbit back.
Meteorites have the potential to show us how the Solar System formed and evolved, coming from the very first bodies to be created. They act as a snapshot in time, holding the minerals that came from their parent bodies and are unchanged as they hurtle towards Earth. Studying a meteorite’s composition and tracing its orbit can therefore tell us about what type of body in the Solar System it came from and give us information about the composition of the early solar system that we otherwise wouldn’t be able to discover.
Sending spacecraft on asteroid sample return missions to collect space rocks can cost billions of dollars and take many years. The DFN complements these endeavors using cameras to track where meteorites will land to get ‘free samples’ from a number of different asteroids that come with a way to calculate their orbit. By combining the mineral data with the orbital data we can then create a geological map of the solar system.
Iron meteorites are made up of pure nickel and iron metals and are thought to originate from within the metallic cores of asteroids. Iron meteorites fall very rarely, but are easier to find because they can survive re-entry relatively intact, are very resistant to weathering and look very different to normal rocks, having more of a melted appearance.
Stony meteorites are largely made of rock but can also contain small amounts of iron. This category is split up into chondrites and achondrites.
Chondrites are the most common type of meteorite. They are made up of circular mineral blobs called chondrules that formed in space billions of years ago and became clumped together over the years. They are the oldest rocks that we know of and have not been altered or changed since their formation, and so are an important type of meteorite to study to learn more about how the solar system and planets formed.
Achondrites are meteorites that contain minerals which have been melted, changed and altered since they were formed, which makes them different to chondrites. This process of change happens because they are formed on bodies with enough mass to support a molten interior. These can include large asteroids, the Moon and even Mars. Achondrites are much younger than chondrites and have a variety of different textures and mineral compositions which can teach us about the formation history of their parent body.
Stony-Iron meteorites are made up of almost even amounts of metallic and rocky material. They are thought to have formed by mixing between metal cores and the rocky magmas within asteroids.This makes them extremely rare because there is only a small region inside asteroids where metallic and stony material can mix. There are two types of stony-iron meteorites; pallasites and mesosiderites
Pallasites are mostly metallic, however also contain large, translucent crystals of olivine. They come from the boundary between the metallic core of an asteroid and the surrounding rocky magma which makes them very rare but extremely interesting. They are some of the most visually striking meteorite specimens ever discovered.
Mesosiderites are composed of even amounts of metallic elements and sillicate minerals. Unlike pallasites, the crystals within mesosiderites are made of pale silicate minerals and are not very large, giving the meteorite a speckled and irregular appearance. Because of the presence of silicate minerals and the small size of the crystals, scientists believe that mesosiderites probably form when magma mixes with the core during a collision.
Currently the Desert Fireball Network has tracked and recovered four meteorites.
The first was the Bunburra Rockhole meteorite in 2007, followed by the Mason Gully meteorite in 2010 and the Murrili meteorite in 2016. The most recent meteorite recovered is the Dingle Dell meteorite which was found on 31st October 2016. As these meteorites were photographed by the camera network before impact, the researchers were able to use the data to work out their orbits. This is a massive achievement as out of the nearly 1100 meteorite falls (a meteorite that has been sighted falling and recovered), only about 25 have known orbits– 4 of which have been contributed by the Desert Fireball Network.
The Fireballs in the Sky citizen science program were winners of the 2016 Australian Museum Eureka Prize for Innovation in Citizen Science, and also winners of the 2016 Chevron Science Engagement Initiative of the Year award.
In 2015 the initiative won the National iAward for Education and the Best Community Engagement Award for Excellence in Collaboration, Business and Higher Education Round Table.
To find meteorites, the Desert Fireball Network uses a camera network that stretches across the Australian outback. These cameras, housed within small ‘observatories’ take long exposure pictures of the night sky and these images are sent back to the team to be analysed. If an image of a meteorite is captured from three cameras, its location can be found through a method called triangulation, and calculations of its speed and direction of travel using specialised software. Using all this information the impact site can be determined, allowing the DFN team to head out to find it.
Fireballs in the Sky invites everyone to learn about the science behind meteorites and get involved with the project. By downloading the Fireballs in the Sky app, you can report a sighting of a fireball to help our researchers collect data, view sightings by other users, and see information about upcoming meteor showers. You can also keep up to date with our research on this website, Facebook and Twitter.
Meteoroids enter the earth’s atmosphere at very high speeds, ranging from 11 km/sec to 72 km/sec.
Comets are small clumps of dust and ice with eccentric (circular or elliptical) orbits. Comets spend most of their lifetimes in the outer solar system but periodically fly close to the Sun.
As a comet gets closer to the sun, solar radiation melts the ice on the surface. Once the ice has melted an atmosphere of water vapour and other gases forms. This is called a Coma. As the gets even closer to the sun, solar winds exert a force upon the coma to form a distinctive comet tail.
The solid core of a comet is called the nucleus and is actually rather small, with the largest being only 60 kilometres across (the biggest asteroids are up to 500 kilometres wide). However, the comet tails can stretch over thousands of kilometres. Some tails can even become longer than the distance between the Earth and the Sun.
When you witness a single ‘shooting star’ you would have seen a lone meteoroid entering the Earth’s atmosphere and burning up. Meteor showers are associated with a parent comet that crossed the Earth’s orbit. The dust and meteorites left behind in the comet’s tail burn up in the earth’s atmosphere and create a spectacular phenomena. Comets have regular orbits meaning that meteor showers occur at regular times every year. For example, the Orionid meteor shower which regularly peaks in October is made of debris from Halley’s Comet.
Asteroids are large rocks that have accreted together over millennia but never became large enough to form into a planet. They can come in a variety of shapes and sizes from as small as ten metres to hundreds of kilometres across.
It is estimated that nearly two million asteroids exist in the main asteroid belt between Mars and Jupiter, but there are other asteroid groups such as the Jupiter Trojans that orbit next to Jupiter and near Earth asteroids which orbit closer to the Earth.
C-Type or carbonaceous asteroids are the most common type of asteroid. The materials inside C-type asteroids are incredibly old and represent the primitive materials which may have been around since the formation of the Sun.
S-Type or stony asteroids are made of stony minerals such as silicates but can have a variety of compositions, including iron and magnesium bearing minerals.
M-type or metallic asteroids are incredibly dense asteroids with high concentrations of nickel and iron. They are thought to be the broken iron cores of larger asteroids which have been torn apart by ancient collisions.
Aboriginal culture is massively diverse with over 400 different language groups in different regions of Australia. Different cultural groups have formed their own explanations of the sky and these have different meanings and importance. While not every story is the same across the country, some stories are common to many different Aboriginal groups.
Meteors have been seen as omens, tools, beginnings, endings, weapons and rewards. Shooting stars were seen by some as ‘fiery demon eyes’ and were omens for death and disease.
While many attempts have been made previously to track and recover meteorites elsewhere using a sky survey facility, the environments were not ideal for recovery.
The Australian Desert Fireball Network aims to utilise the unique environment of the Australian outback which makes it easier for researchers to photograph and recover meteorites. The DFN is set up in the Nullarbor Desert and surrounds where the sky is clear almost all year round, and the ground is flat, white limestone.
The Nullarbor is an ideal location for the DFN because there is little human or animal activity to disturb the meteorites and the pale white landscape makes it easy to spot the darker meteorites once they have landed. These unique conditions make tracking and recovery much easier.
The cameras use an assortment of 3D printed parts to streamline the production process and reduce costs. To protect against extreme weather the cameras are housed within a waterproof container with an inbuilt fan cooling system to protect the camera during the day.
In Australia, ownership is dependent on the state in which the meteorite is found or falls. In four states (WA, SA, NT, and Tas) meteorites are required to be housed in an official state repository (i.e. The state’s museum).
In Western Australia, South Australia, Tasmania and the Northern Territory, the law states that meteorites found (or observed to fall) belong to the State, and the Trustees of the state’s museum become the custodians.
In Queensland, Victoria and New South Wales, there are no specific laws covering the ownership of meteorites. The meteorite is generally the property of the landowner. If the land is government owned, then the meteorite is the property of the government and will go to the local state museum.
A meteoroid is a rock that is travelling through space. As it travels through the Earth’s atmosphere and burns up giving off light, it is called a meteor. If the rock survives and hits the surface of the Earth, it is called a meteorite.
The DFN team involves specialists from multiple disciplines including geologists, planetary scientists, astrophysicists, petrologists, mineralogists, mechatronic engineers, software engineers and science communicators.
The DFN is a collaborative effort between Imperial College, London, Ondrejov Observatory in the Czech Republic, Curtin University in Western Australia and the Western Australian Museum.