“Can lightning strike upwards?” and “What is the wettest place in the world?” BBC Click Radio presenter Gareth Mitchell answers life's big questions
The Moon could be harbouring enormous reserves of a future nuclear fuel known as helium-3. Today, nuclear power stations work using ‘nuclear fission’ where the nuclei at the centre of big, heavy atoms are split apart, releasing energy in the process. But fission generates hazardous radioactive waste.
‘Nuclear fusion’, on the other hand, involves joining together lighter nuclei such as hydrogen. The hydrogen is heated to temperatures of millions of degrees, welding the atoms together and churning out energy.
Such temperatures would melt through any solid container. So the hydrogen is held in place using a magnetic field. This is possible because the nuclei are electrically charged. However, most fusion reactions give out additional particles, called neutrons. These are electrically neutral and so slip through the magnetic field and escape. Neutron radiation can be deadly.
But there’s one kind of fusion reaction that gives off no neutrons – fusing helium-3 (helium that’s had one neutron particle removed from its nucleus) with deuterium (hydrogen that’s had a neutron added). Helium-3 is rare on Earth, but is thought to exist in abundance on the Moon – deposited there over billions of years by the solar wind streaming outwards from the Sun.
In 2006, Russian scientists announced plans to try and mine helium-3 from lunar soil.
Professor John Lewis, of the University of Arizona, believes the copious amount of iron locked away in near-Earth asteroids make them a tantalising target for future space mining missions. He points out that the asteroid 3554 Amun alone could harbour iron and nickel deposits worth around $6 trillion. The practicalities of getting this material back to Earth have yet to be addressed.
However, one possibility is that they might not need to be returned at all, but rather could be used in situ for constructing spacecraft in space – thus also saving on the colossal fuel expense needed to propel the completed craft out of Earth’s gravitational field.
Platinum and other precious metals are abundant on some asteroids. Asteroid 3554 Amun is believed to be home to platinum deposits with a value of around $12 trillion – that’s approximately half a million tonnes of the stuff. And this would be much easier to haul back to Earth than the same cash value of a bulky, less-precious commodity such as iron. But don’t be greedy. Platinum is valuable because it’s rare – only a few hundred tonnes of it are mined annually on Earth. But suddenly adding several thousand times this quantity to the world supply could saturate the market somewhat, leading to a sharp downturn in prices.
It’s the most potent energy source known. Annihilating just a half of a gram of matter and antimatter unleashes the same energy given out by the bomb that flattened Hiroshima. But there’s a catch. The world’s particle accelerator labs currently turn out just 10 billionths of a gram of antimatter per year, at a total cost of around $600,000. However, scientist James Bickford, of the Draper Laboratory in Massachusetts, believes nearly four tonnes of antimatter drifts naturally into our Solar System every year – much of which he says will be snagged by the magnetic field of Jupiter, from where it could be scooped up by a suitably equipped spacecraft.