When humans make it to Mars, they'll be following the trail of the robots that preceded them.
That's the message from the NASA roboticists who today celebrated 10 years of rovers working and exploring on Mars.
Mars rovers Spirit and Opportunity were launched in the summer of 2003 with scientists hoping they'd survive to work on the Martian surface for three months. Spirit, which sent more than 128,000 images of Mars back to Earth, worked for about seven years before it became stuck in soft sand and was abandoned in 2010.
Opportunity, though, is still going strong after 10 long, grueling years on Mars.
And for the last year and a half, Opportunity has been joined by NASA's Mars rover Curiosity in the exploration of Mars' geology and the hunt for evidence that there is or ever was life on the Red Planet.
"There's a relationship between human and robotic science exploration right now," said John Connolly, NASA's acting chief exploration scientist. "The robots we put down on Mars are our avatars right now. They are our eyes, our feet, our hands on the ground that inform us before we get there. Without these robots doing this work, it would be a very risky endeavor getting to Mars."
He added that sending humans to Mars largely depends on the information that robotic rovers and the Mars orbiters send back about the planet's geology, mineral makeup, water reserves and atmosphere.
"The robotic missions on Mars are helping us to handle these big questions," said Connolly.
During a news conference at the Smithsonian National Air and Space Museum in Washington today, Connolly added that Curiosity's discovery of evidence of ancient water flows as well as water in the Martian soil now is the most exciting find NASA has made yet.
"Finding water is like finding gold," said Connolly. "It's the stuff of rocket fuel. It's what astronauts will need. Finding that there are large amounts of water on Mars is the one find that's changed our way of thinking about human exploration of Mars."
NASA hopes to send humans to Mars in the 2030s. But before that happens, the space agency plans to send at least one more rover and more orbiters to lead the way.
John Grunsfeld, a former astronaut and associate administrator of NASA's Science Mission Directorate, said today that Mars has turned out to be a much more complicated planet than previously thought.
"Mars had an environment, some billions of years ago, that could have supported life," he explained. "You could have put a cup in the water and had a nice drink. If you were a microbe, you could have survived in that water. Water. Snow-capped mountains. It was actually a nice place... Why isn't Mars a nice place for human life now? At one time, a space suit wouldn't have been necessary."
That has changed, though.
Today, Mars is a frigid planet with a harsh environment that leaves scientists trying to figure out why it has been losing water, as well as its atmosphere.
It also has scientists trying to figure out how humans will someday work and thrive on the Martian surface.
David Lavery, a program executive with NASA's Solar System Exploration program, pointed out that it's not about robotic exploration versus human exploration. The two are meant to be tied together.
"From someone who builds robots as a career, I can't imagine anything better than human foot prints on Mars," he noted. "Robots are there as precursors. They are tools paving the way. Our long-term real goal is human exploration of the Red Planet. We use robots to get there -- to make that happen."
And Steven Squyres, a Cornell University professor of astronomy and principal investigator for NASA's Mars Exploration Rover mission, said it no longer is hard to imagine the day humans will make it to Mars.
"It just seemed impossibly far away," he said. "Now, when I look at Mars in the sky, it's a totally different feeling. I look at Mars rise in the sky and I think, 'Yah, I know that place. We've all experienced Mars through these rovers. Was there ever life there? We don't have the answer yet, but we're a lot closer than we used to be."
Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin, on Google+ or subscribe to Sharon's RSS feed . Her email address is firstname.lastname@example.org.