If humanity is to conquer the red planet, they need to be able to cross the gulf of space as quickly as possible. Otherwise future colonists may suffer from health problems such as bone loss and muscle fatigue when en route towards Mars.
However, if a future antimatter engine can be built, then those future threats could be eliminated, if not at least reduced.
(Red Orbit) Antimatter is sometimes called the mirror image of normal matter because while it looks just like ordinary matter, some properties are reversed. For example, normal electrons, the familiar particles that carry electric current in everything from cell phones to plasma TVs, have a negative electric charge. Anti-electrons have a positive charge, so scientists dubbed them "positrons".
When antimatter meets matter, both annihilate in a flash of energy. This complete conversion to energy is what makes antimatter so powerful. Even the nuclear reactions that power atomic bombs come in a distant second, with only about three percent of their mass converted to energy.
Unlike the nuclear powered space craft, a "positron" powered ship would be safer and more efficient. Many scientists have opted towards a nuclear powered craft in order to reduce time while in flight. However, reactors can be complex and a slight error could spell doom for all on board--especially during a launch.
(Red Orbit) If a rocket carrying a nuclear reactor explodes, it could release radioactive particles into the atmosphere. "Our positron spacecraft would release a flash of gamma-rays if it exploded, but the gamma rays would be gone in an instant. There would be no radioactive particles to drift on the wind. The flash would also be confined to a relatively small area.
The danger zone would be about a kilometer (about a half-mile) around the spacecraft. An ordinary large chemically-powered rocket has a danger zone of about the same size, due to the big fireball that would result from its explosion," said Smith.
Currently the price for assembling 10 milligrams of anti-matter is around $250 million. This price could be reduced through research as well as technology, and is probably less expensive than chemical rockets which cost around $10,000 per pound.
This would probably be easier to develop than a safe nuclear reactor and may be a preferable choice amongst astronauts--since no one probably enjoys riding with a nuclear device strapped to their back.