Nasa boffins are designing a spaceship fuelled by antimatter to carry men to Mars.
It is the stuff of science fiction and one of the most potent and dangerous materials in the universe. But scientists say they will only need a fraction of an ounce of it to fly to the Red Planet in days.
The danger comes because when antimatter and normal matter meet, they are both destroyed in a massive flash.
The explosion releases deadly gamma rays which can tear apart molecules of anything nearby – including human flesh and bones.
But that flash also releases an incredible amount of power which will drive the spaceship at fantastic speeds.
A team at the Nasa Institute for Advanced Concepts in Atlanta is working on designing an antimatter engine that can produce gamma rays that are 400 times weaker than usual.
They say that will protect the ship and its crew.
If the studies are successful, the fuel will be used to fly the first US manned flight to the Red Planet, the Mars Reference Mission around 2030.
Previous plans had been to use a nuclear reactor for an engine but there were fears that an explosion on launch could spread radio active material into the atmosphere.
Antimatter produced using positrons is safer and cleaner – plus it could get the astronauts to Mars in as little as 45 days.
This is a lot shorter than the six month journey taken for unmanned probes and would expose the crew to less radiation from the Sun on the way.
Expert Dr Gerald Smith said: “The most significant advantage is more safety. A positron spacecraft would release a flash of gamma-rays if it exploded, but they would be gone in an instant.”