Good opinion piece on MSNBC about what it would cost to return to the moon and to go to Mars. There are some absurd numbers (like $1 trillion) being batted around out there that have no basis in reality. Until you decide what the goals are, you can't design the hardware. You can't even begin to estimate the timeframe or the cost.

Estimates vary greatly. Many analysts say a manned mission to Mars would cost anywhere from $50 billion to $250 billion. Others, like Robert Zubrin of the Mars Society advocacy group, think it could be done for as little as $30 billion if bureaucracy is limited.

If one assumes a NASA-led $100 billion effort and a launch target of 2024, that would be $5 billion per year if we start funding the project now. That's one-third of NASA's present annual budget. Not outlandish, not impossible, and not with any significant impact on other governmental programs.

Again, other countries will be willing to share the cost of the grandest mission ever, if we ask them to.