"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."
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