In 1971, the American space probe "Mariner Nine" blasted off from Cape Kennedy, Florida, on a journey to Mars.

CNN: News Almanac

If any bacteria have survived the decontamination and the journey to Mars, they could cast doubt on whatever the rover might find.

BBC: New age of exploration in the hunt for extreme life

But Mr Aldrin disagreed with the view that astronauts should test capabilities for a long-duration flight on the Moon before attempting a journey to Mars.

BBC: Moon astronauts urge Mars mission

"We're better prepared for a journey to Mars now than we were when we sent men to the moon in the 1960s, " Zubrin told CNN.

CNN: Life on Mars?

The aim of the 17 month-long Mars500 project was to study the physical and psychological effects that the much longer journey to Mars might have on future astronauts.

BBC: Sleep problems could jeopardise future missions to Mars

While Earth orbit is vital, keep in mind that visionaries like Elon Musk have in mind a human journey to Mars to look for signs of water and life.

WHITEHOUSE: Space Community Leaders on Historic Berthing of Dragon to the International Space Station | The White House

That number includes the cost of the actual Mars probe and its launch, as well as the cost of the NASA crew handling its journey to Mars for almost a year before it started transmitting.

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The radiation exposure from a Mars journey is similar to getting a full-body CT scan every five or six days, said lead researcher Cary Zeitlin of the Southwest Research Institute in Boulder, Colo.

NPR: Astronauts Face Radiation Threat On Long Mars Trip

Last November, the Mars probe Curiosity began its months-long journey to the red planet.

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