Manned Mars mission: Rx for problems?

(CNN) -- Scientists have been sending spacecraft to Mars for a quarter of a century, but a manned mission so far remains the stuff of Hollywood movies.

VIDEO CNN's Miles O'Brien has more on possible medical problems on a mission to Mars (July 18) Play video (QuickTime, Real or Windows Media)

Sending astronauts to the red planet would pose numerous risks. Mechanical problems could handicap the vessel, or natural phenomena could have an unexpected effect on the mission. Another concern: medical problems among the crew during the lengthy flight.

How could NASA or another space agency adequately prepare for a medical emergency on such a long mission? CNN's Miles O'Brien examines the issue.