Fragments of a “shooting star” that lit up the night sky over northern Europe last month have been found in a small town in Gloucestershire, England. Astronomers are now examining the 300 grams of rocky material for clues about the origin of life on Earth.
Where did the stuff come from?
A large meteor entered the Earth’s atmosphere at 50,000kph on February 28, its fiery descent appearing as a brilliant fireball flying across the sky. Computer analysis of video recordings of the meteor’s flight allowed scientists to trace its path back into space. This revealed its origin somewhere in the asteroid belt between the orbits of Mars and Jupiter. This contains huge chunks of debris left over from the birth of the solar system around 4.6 billion years ago.
Around 50 tonnes of meteors from the asteroid belt enters the Earth’s atmosphere every day. The vast majority of it is completely incinerated by the frictional heat and buffeting of the descent. Occasionally a decent-sized chunk survives, but rarely is anything found soon after its descent.
So was the discovery just a bit of luck?
Not at all. As well as revealing the origin of the meteorite (the name for meteors that reach the ground), the video recordings also gave scientists details of its trajectory and possible landing site. Within 24 hours the UK Fireball Alliance predicted that some fragments may have landed to the north of Cheltenham in the Cotswolds. A homeowner in the small town of Winchcombe, 10km from Cheltenham, then reported hearing a thud outside and finding a black pile of charred rock on his driveway. Now experts from the UK Natural History Museum, London, have confirmed the fragments are from outer space – the first such discovery in the UK for 30 years.
How important is the discovery?
Tests have shown the Winchcombe meteorite is a very rare type, known as a carbonaceous chondrite. It is the most primitive and pristine matter in the solar system. Making up less than one in 1,000 of all known meteorites, previous specimens have been found to contain organic matter including amino acids, the building-blocks of living organisms.
Having been found so soon after landing, the Winchcombe meteorite is comparable in quality to samples returned by vastly expensive space missions. It is now the focus of an intensive research effort to find out what it can reveal about the early solar system. Dr Ashley King, a member of the NHM research team, described the discovery as “a dream come true”.
What could it tell us about the origin of life?
How life started on Earth is one of the greatest unsolved mysteries. According to one school of thought, the molecules for life originated in the hot and chemically active conditions of the early Earth. However, while experiments attempting to mimic those conditions have created a few biological compounds, they have never produced anything like DNA, the genetic molecule crucial for life. This has led some scientists to claim that life may have been formed elsewhere in the solar system, and travelled to Earth aboard meteorites.
In 1996, Nasa scientists claimed to have found fossilised microbes in a meteorite found in Antarctica. Studies revealed the meteorite had come from Mars. However, the “microbes” are now widely thought to be an illusion. While no one is expecting to find fully-formed life forms in the Winchcombe meteorite, it may contain biological molecules never before seen in such objects.
What happens next?
Researchers are continuing to search the Winchcombe area for more fragments and have asked the public to report anything they think may be part of a meteorite. The response of scientists to such reports has changed dramatically over the years.
Until the 1800s, claims of stones falling from the sky were dismissed and specimens seized to prevent the spread of "superstition". Attitudes only changed after a respected French astronomer confirmed local reports of thousands of stones landing in a village in Normandy on 1803. Meteorites are now recognised for what they are: samples of the early solar system delivered to Earth free of charge.
Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK