IT'S A typical day in 2035, engineer Josh Richards is out in the garden tending his tomatoes and potatoes.

The only quirky thing is that Richards might be gardening on Mars.

He is one of 100 remaining astronaut candidates, some of whom will be selected by global organisation Mars One to establish a human colony on the Red Planet by 2032.

"As soon as we get there we want to become Earth-independent which means growing our own food as much as possible," Richards said.

"Most of the research Mars One has done to date is about ... growing food in mock Mars dirt (regolith).

Richards said even moon soil was capable of growing things and Mars soil was better than moon soil.

As for that key ingredient for life - water: "We're almost certain there's water on Mars," he said.

"We actually suspect there's flowing water on Mars in different areas.

"The atmospheric pressure on Mars isn't enough for it to stay flowing for very long but there's particular salts in the soil - that are actually quite toxic to us - that allow for that soil to carry water, so that water can flow."

Richards, a former engineer and physicist who went on to became a stand-up comedian, is passionate about discovering the universe.

"It's going to be an amazing experience all round, even if the whole thing fell apart tomorrow, the world's a better place because we are trying to do something interesting," he said.

Richards said the current pool of 100 astronaut hopefuls would be cut back through group testing processes to a group of about 12-24.

"They're the people who will start full-time training - about 14 years' worth of training," he said.

"Mars One will try to maintain a pool of people that are training, then they select individuals to form teams to go.

"Every 26 months when Earth and Mars line up there'll be another crew ready to go."

Richards said if he makes the first launch in 2031, he'll turn 46 in space.

He said his desire to go to Mars was not about abandoning a doomed Earth.

"There are things we need to change (about) the way we are living here on Earth.

"By going to Mars and living in a positive sense, trying to explore, to learn more about the Universe, we can set a great example for how to live back here on Earth," he said.

He'd better hope he's right.

If he's chosen, his trip to Mars is one-way only - there's no return rocket.