Saturn has its famous rings and Jupiter is the granddaddy of the solar system, but no planet has entranced earthlings quite like Mars.
Humans have launched 40 spacecraft to the Red Planet, lured by the prospect that life might once have existed in what is now dry rocks and sand. The latest machine to make the journey is NASA'sMars Science Laboratory, a hulking, souped-up lab-on-wheels that will plunge toward the Martian surface Sunday.
But even as excitement builds, some wonder: Is Mars exploration a good investment?
It certainly doesn't come cheap. It's hard to calculate a total price tag, but over the 48 years that NASA has been launching missions to Mars, Americans have spent a significant sum. The Viking missions alone cost nearly $1 billion — in 1970s dollars. The twin rovers Spirit and Opportunity cost a total of about $1 billion to build and operate as well.
Curiosity, as the Mars Science Laboratory rover is known, is over budget at $2.5 billion.
Some in the federal government have suggested it's time to roll back the spending. President Obama's fiscal plan for 2013 would cut NASA's funds for Mars exploration from $587 million to $360 million.
Proponents insist Mars science is vital for the U.S. More visits to our next-door neighbor could answer lingering questions about Earth's history, reinforce U.S. prestige and get more children interested in science.
It also could bring humanity closer to answering the ultimate question: Are we alone in the universe?
"It's the search for the meaning of life," said Alden Munson, a senior fellow at the Potomac Institute for Policy Studies, a science and technology think tank based in Arlington, Va.Some experts question the wisdom of focusing so intently on a single planet. Jupiter's moon Europa, which is covered with an ice-encrusted ocean, could have the potential to harbor life; Saturn's moon Titan, rich in organic chemistry, might as well.
"It's like the person who loses their keys and only looks for them below the streetlight," said David Jewitt, a planetary scientist at UCLA who studies comets.