DALLAS—Speaking from his home in Dallas, former president George W. Bush told reporters Tuesday that when he's not busy giving lectures or writing his memoirs, he spends most of his spare time working on the manned mission to Mars he proposed in January 2004.

Bush goes over some of the statistics on surviving in a prolonged low-light environment.

"This is genuinely important to me," said Bush, looking over sketches of potential rocket systems he had drawn up while waiting for his oil to be changed at a service station earlier this week. "I wasn't kidding when I announced a plan to get us to Mars, by God, and I intend to finish what I started. That's why I try to carve out a little time before lunch and after dinner to work on this important interplanetary initiative."

"It's a big project," Bush added. "Lots of little details to work out."

While in 2004 many critics suggested Bush's call for a mission to Mars was little more than political theater, the 43rd president has called those claims "ridiculous." Bush said he has spent many hours scouring the web for information about space travel and Mars, in addition to checking out "a bunch" of books on the subject from the local library and regularly e-mailing contacts he still has at NASA to ask their advice on his plan.

He also frequently watches the PBS program Nova.

"It's the first thing I think of when I wake up after having some breakfast and doing the crossword," Bush said. "Ask anyone: Whenever I have a spare minute, I'm always thinking about how to put astronauts on the surface of Mars."

The former president believes the journey from Earth to Mars will be feasible, although fraught with peril.

"And Laura knows not to bother me on Saturday afternoons when I don't have a speaking engagement or a golf match to go to," Bush added. "That's my Mars time."

Working from the makeshift basement office he refers to as "Mission Control 2," Bush said he has grappled with some of the major issues surrounding a manned mission to Mars. For months he's been jotting down notes about how zero gravity would affect the bone density and muscle mass of the crew, and he spends about five minutes during his morning jog each day coming up with ideas for safely storing a year's worth of onboard oxygen.

Sometimes, Bush said, potential solutions come not when he's reading about the Red Planet's inhospitable surface conditions on Wikipedia or brainstorming shuttle names through free-association exercises, but when he's not thinking about the historic 34- million-mile voyage at all.

"Just last week, I was out in the garden tending to the tomatoes when it hit me: The astronauts should grow their own food to eat on their spaceship," Bush said. "I'm not saying I have all the specifics down just yet, but how the astronauts going to Mars will eat is at least one thing the next president won't have to worry about."

Bush recently started a blog devoted entirely to his thoughts about setting up a permanent colony on Mars. To achieve this, he writes on MarsUSA.blogspot.com, the astronauts will need to bring materials for building a sustainable base on the planet, and be able to convert water in the Martian soil into hydrogen and oxygen for the trip home.

"That's just common sense," Bush said. "All the science-fiction writers know that."

Bush admitted that he didn't have as much time as he would like to devote to the mission, but assured reporters he would never give up on something so important. While the challenges may seem insurmountable, he said, the greatest hope for man to achieve the incredible goal of landing on the surface of Mars lies in exploiting as-yet undiscovered technologies to overcome the incredibly daunting physical distances involved.

"I'm pretty busy right now, but when I get a spare 30 minutes, I'm going to start working on that," Bush said while flipping through a copy of Scientific American. "I'll have my friend Jerry from down the road come over and crunch some of the numbers for me. He's good with computers."