The distance from Earth to Mars ranges from 33.9 million to 249 million miles. It might also be measured in the minutes it takes light to flit between the two planets, the months it takes a spaceship to travel there, or the millenniums in which people have pointed toward the sky, their imaginations on fire.
Tonight, if all goes well, a NASA spacecraft will touch down on Mars for the first time in more than four years when the Phoenix Mars Lander alights on the Red Planet's frigid northern polar region. And though we've long given up on encountering hostile telepathic humanoids there (sorry, Ray Bradbury), scientists are still excited about what they might find. Phoenix is set to dig deep into ice that could be the remains of an ancient sea - and might hold carbon-based organic material, a component of all known life.
There are always those who decry such projects as a waste of money that would be better spent on less-glamorous earthbound pursuits such as health care and national defense. And at a cost of $457 million to travel 422 million miles, Phoenix does make your Hummer look like a bargain, even with gas at $4 a gallon.
Then why explore Mars? Because humans have always gazed up at night and thought, "What's out there?" - and we are fortunate to live to see that question begin to be answered. Because extraterrestrial adventures inspire wonder in children, stir interest in science for adults and awaken national pride among nearly all Americans.
Critics who carp about the expense are missing the larger point: A great nation should be able to provide the necessities of government and nourish a spirit of adventure. If we sometimes fail at the former, that is no reason to abandon the latter.