A latter-day Jules Verne has devised a plan to make a journey to the centre of the Earth using a nuclear explosion and millions of tons of molten iron.
David Stevenson, from the California Institute of Technology in Pasadena, wants to send a scientific probe to the Earth's core to take seismic measurements that can be beamed back to the surface for analysis.
His suggestion, outlined in a letter to the journal Nature, is being treated seriously by the wider scientific community, which has long complained that it knows more about deep space than the Earth's inner workings.
The probe, launched with the help of a megaton-sized explosion to create a crack in the Earth's crust and lubricated by the molten iron, could reach the Earth's core in less than a week, Dr Stevenson said.
He estimates that the crack would propagate downwards at a speed of about five metres per second to allow the slug of hot metal carrying the grapefruit-sized probe to be propelled by gravity.
"Planetary missions have enhanced our understanding of the Solar System, but no comparable exploratory effort has been directed towards the Earth's interior, where equally fascinating scientific issues are waiting to be investigated," Dr Stevenson said. "We live on the Earth's surface, which divides what is above from what is below ... the part below is crammed with interesting stuff and is mostly unknown, despite its proximity to us."
Although space probes have reached the furthest planets, the deepest drill holes into the ground have penetrated no more than about 6.2 miles into the Earth's crust – a tiny fraction of its total depth.
"This proposal is modest compared with the space programme, and may seem unrealistic only because little effort has been devoted to it. The time has come for action," Dr Stevenson said. The use of a nuclear device to generate a crack – which would close up once the slug of molten iron and its probe passed through – was totally feasible.
He said that a nuclear device of a capability within the range of those currently stockpiled was all that was needed. "The technological challenge of initiating the crack should be less than that posed by the Manhattan Project," Dr Stevenson said.
The main problem is the volume of molten iron needed. Dr Stevenson said it would amount to the total output of all the world's iron foundries working flat out for at least an hour and, possibly, a week.
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