Murchison
A stone that fell on an Australian town in 1969, packed with the chemical building blocks of life.
Key facts
- Type
- Carbonaceous chondrite (CM2)
- Fell or found
- Fell (witnessed)
- Year
- 1969 (28 September)
- Country
- Australia
- Mass
- more than 100 kg recovered
- Official name
- Murchison
On a Sunday morning, 28 September 1969, residents of the small town of Murchison in Victoria, Australia, heard loud booms and saw a fireball break into pieces, leaving a trail of smoke. Dark stones fell over an area of more than ten square kilometres around the town. Many were collected within days, and in total more than 100 kilograms were recovered. People who handled the fresh stones noticed something odd: some of them gave off a smell like methylated spirits.
That smell was a clue. Murchison was a carbonaceous chondrite, a type of meteorite rich in carbon compounds, and it would become one of the most studied rocks in the world.
A watery asteroid
Murchison belongs to the CM group of carbonaceous chondrites. The number 2 in its classification, CM2, tells scientists that its parent asteroid was once soaked in liquid water. Early in the Solar System's history, ice inside the asteroid melted, perhaps warmed by radioactive elements, and the water reacted with the rock, turning many of its minerals into clays. Murchison still contains water locked inside those minerals, along with around 2 per cent carbon, much of it in complex organic molecules.
Amino acids from space
Amino acids are the molecules that living things link together to make proteins. Within about a year of the fall, scientists analysing Murchison found amino acids, and over the years more than 70 different kinds have been identified. Crucially, the evidence shows they came from space rather than from contamination on Earth. Many of them are types that life on Earth does not use at all. Their chemical make-up, including the proportions of heavier forms of carbon and nitrogen, differs from that of earthly biology. Life on Earth uses almost exclusively 'left-handed' amino acids, while Murchison's amino acids are much more evenly balanced between left- and right-handed forms, although some show a small excess of left-handed forms, a finding that has fascinated scientists studying how life's preference arose.
Later studies found other ingredients for life, including some of the nucleobases used in genetic molecules, such as uracil. A study published in 2010 using extremely sensitive instruments suggested Murchison contains more than 14,000 different molecular compositions, and potentially millions of distinct organic compounds.
None of this means that Murchison contains life or fossils. These molecules were made by ordinary chemistry, not biology. What they show is that the raw materials for life were being made naturally in space and were delivered to the young Earth by meteorites.
Older than the Sun
Murchison also contains tiny presolar grains, specks of dust that formed around other stars before our Sun was born and survived the formation of the Solar System. In 2020 researchers reported that some silicon carbide grains from Murchison may have spent hundreds of millions of years, and in some cases more than a billion years, in interstellar space before being incorporated into the meteorite, making them some of the oldest solid material ever studied.
Why it matters
Murchison is a cornerstone of research into the origin of life. Because it was a witnessed fall that was collected quickly, its organic chemistry can be studied with confidence. Its findings shape how scientists think about asteroid sample-return missions, which have brought back material from carbonaceous asteroids and compared it with meteorites like Murchison. Specimens are held in many collections, including in Australian museums.
It is also a reminder of why meteorites should be handled carefully. Every touch adds a little of Earth's own chemistry. Collectors and scientists store precious samples in clean containers and handle them with gloves, so that the story they tell is the meteorite's own.
Did you know?
Some people who handled the fresh stones said they smelled like methylated spirits.
More than 70 different amino acids have been identified in Murchison, many of them not used by life on Earth.
Murchison contains presolar grains, dust that formed around other stars before the Sun existed.