07/19/2012 01:57 pm ET

Mars Rover Curiosity Risks: NASA Scientists Say Successful Mission Not Assured (PHOTOS)

In less than two weeks, NASA's hyper-sophisticated, car-sized Mars rover Curiosity will touch down on the Red Planet to begin two years of scientific discovery.

If all goes well, that is. And yet some of the scientists behind the audacious mission--whose do-or-die landing sequence has been called seven minutes of terror--aren't taking success for granted.

"Those seven minutes are the most challenging part of this entire mission... For the landing to succeed, hundreds of events will need to go right, many with split-second timing and all controlled autonomously by the spacecraft. We've done all we can think of to succeed. We expect to get Curiosity safely onto the ground, but there is no guarantee. The risks are real." -- Pete Theisinger, JPL's Mars Science Laboratory project manager, said in a written statement.

"Are we terrified? I think we're confident in what we've designed... But we're all human. Everything we've worked for -- the scientific discoveries, the proven engineering, the contributions we make toward future NASA missions -- it all lies on the other side of those seven minutes." -- Ashwin R. Vasavada, JPL scientist, told the Los Angeles Times.

"The Curiosity landing is the hardest NASA mission ever attempted in the history of robotic planetary exploration." -- John Grunsfeld, associate administrator for NASA's Science Mission Directorate at NASA headquarters in Washington, D.C., said in a written statement.

“I think we all feel this incredible sense of pressure on MSL to do something grand and profound... I think it’s going to be thrilling.” -- John Grotzinger, a NASA scientist who’s working on the mission, told McClatchy Newspapers, referring to the Mars Science Laboratory division of NASA.

“If you look at the scorecard, Earth is doing less than 50 percent; less than 50 percent of Earth’s missions to Mars have been successful." -- Doug McCuistion, a former U.S. fighter pilot and NASA's Mars exploration director, said at the Farnborough Airshow south of London.

Is NASA playing up the rover mission's risks to keep expectations down? Maybe that's not a bad idea. In addition to many glorious successes, America's space agency has tasted its share of failure (even beyond the fatal tragedies of an early Apollo mission and the space shuttle disasters).

Keep clicking on the photos below to see some of the most embarrassing "black eyes" NASA and other nation's space agencies have endured.

Space Agencies' Most Embarrassing Moments