Echoes of ancient Earth: Further proof that the Moon was created by massive collision
Steve Connor is the Science Editor of The Independent. He has won many awards for his journalism, including five-times winner of the prestigious British science writers’ award; the David Perlman Award of the American Geophysical Union; twice commended as specialist journalist of the year in the UK Press Awards; UK health journalist of the year and a special merit award of the European School of Oncology for his investigative journalism. He has a degree in zoology from the University of Oxford and has a special interest in genetics and medical science, human evolution and origins, climate change and the environment.
Monday 09 June 2014
The idea that the Moon was created after a massive cosmic collision between a Mars-sized object and the primordial Earth some 4.5bn years ago has received its second boost in less than a week.
Scientists have detected the chemical signature of the ancient Earth, as it was before the collision took place, in material found deep within the planet’s mantle, which separates the Earth’s molten iron core from the surface crust.
Last week, a separate team of researchers found the chemical signature of the ancient object itself, known as Theia, within lunar rock samples brought back to earth by the Apollo missions 40 years ago.
The second piece of evidence comes from a study of unexplained ratios of chemical isotopes in deep mantle rock which scientists believe are the signature of the primordial Earth before it was hit by Theia.
The collision would have generated enough energy to melt the entire planet but the researchers believe that although material would have vaporised on the side of impact, some of the planet remained solid and intact on the opposite hemisphere.
“The energy released by the impact between the Earth and Theia would have been huge, certainly enough to melt the whole planet. But we believe that the impact energy was not evenly distributed throughout the ancient Earth,” said Professor Sujoy Mukhopadhyay of Harvard University.
“This means that a major part of the impacted hemisphere would probably have been completely vaporised, but the opposite hemisphere would have been partly shielded and would not have undergone complete melting,” Professor Mukhopadhyay.
The study found that isotope ratios of the gases neon and helium differed significantly depending on whether they came from the shallow mantle or the deeper mantle of the Earth – which indicates a different origin.
“This implies that the last giant impact did not completely mix the mantle and there was not a whole mantle-magma ocean,” Professor Mukhopadhyay said.
“If the theory is proven correct, then we may be seeing echoes of the ancient Earth, from a time before the collision,” he said.
Another piece of evidence comes from the analysis of xenon gas isotopes, which result from from the slow radioactive decay of iodine gas. This suggests that the formation of the more ancient part of the mantle came within the first 100m years of the Earth’s origins – thereby putting a possible date on the impact with Theia.
Most computer models of the collision suggest that between 70 and 90 per cent of the material making up the Moon comes from the original Theia, with the remaining 10 or 30 per cent coming from terrestrial debris flung out from Earth during the glancing blow of the impact.
Professor Richard Carlson of the Carnegie Institute in Washington, past president of the Geochemical Society, said: “This exciting result is adding to the observational evidence that important aspects of Earth’s composition were established during the violent birth of the planet and is providing a new look at the physical processes by which this can occur.”
The research was presented to the Goldschmidt conference in Sacramento, California.
- 1 Five-year-old Iris Grace is raising awareness of autism through her extraordinary paintings
- 2 Car tax disc changes: Two days to go - and they affect you much more than just not displaying a piece of paper
- 3 The Simpsons death: Creator Al Jean would 'kill himself' before character like Homer or Lisa
- 4 British man raped while urinating in bushes at Oktoberfest beer festival in Germany
- 5 A teacher speaks out: 'I'm effectively being forced out of a career that I wanted to love'
Five-year-old Iris Grace is raising awareness of autism through her extraordinary paintings
Car tax disc changes: Two days to go - and they affect you much more than just not displaying a piece of paper
Isis an hour away from Baghdad - with no sign of Iraq army being able to make a successful counter-attack
British man raped while urinating in bushes at Oktoberfest beer festival in Germany
George Clooney and Amal Alamuddin wedding: The famous congratulate actor and human rights lawyer after Venice nuptials
Isis, we are told, is a 'clear and dangerous threat to our way of life'. I’m sorry, but I just don’t buy it
Exclusive: 'Putin's Russia has been my biggest regret,' says Nato's outgoing Secretary General
'Women, walk wherever you want' posters taken down in Stamford Hill following 'unacceptable' signs separating men and women
There’s no excuse for Dave Lee Travis’s behaviour, but we need to keep a sense of proportion
Mark Reckless becomes second Tory MP to defect to Ukip in a month
Should gay sex be illegal? 16% of Britons think so
- < Previous
- Next >
£60000 - £75000 per annum: Sauce Recruitment: This is a busy and varied role w...
£21000 - £35000 per annum: Randstad Education Cambridge: Maths teacher require...
£21500 - £31500 per day: Randstad Education Chelmsford: Would you like to work...
£330 - £350 Per Day: Clearwater People Solutions Ltd: Our client based in Lond...