CAPE CANAVERAL, Fla. -- With NASA planning to land on Mars 30 years from now, the space agency has begun to ponder some of the thorny ethical dilemmas posed by deep-space exploration.

Such as: If an astronaut were to die during a three-year mission to Mars and back, what would the other crew members do with the body?

And just when should the plug be pulled on a critically ill astronaut who is using up precious oxygen?

Also, should NASA use DNA testing to weed out astronauts who might get a disease on a long flight?

Some of these questions are outlined in a NASA document obtained by The Associated Press through a Freedom of Information Act request.

NASA doctors and scientists, with help from outside bioethicists and medical experts, hope to answer many of these questions over the next several years.

One topic that's evidently too hot to handle: Sex in space. It's not mentioned in the document and has long been almost a taboo topic at NASA, even with the prospect of extended space travel by men and women together.