Do you think NASA will find signs of life on any other planets within your lifetime?
The holy grail for astrobiologists is to find and study an [extraterrestrial] form of life. In the case of Mars, it would be wonderfully exciting to find life there, but it would be great to find something that was not too related to Earth life. We ought to have the capability within the next 25 years to drill below the surface of Mars. If we're really lucky, it will be some serendipitous discovery that I can't anticipate. How could drilling on Mars lead to identifying life there?
The plan is to take rocks and bring them back to Earth for analysis. We won't know if there's life until we can get it back to Earth. We have an obligation to protect the Earth from contamination from Mars, so they will be treated as if they have alien life and will be isolated and studied so they won't have contamination from Earth. How likely is it that extraterrestrial life would be related to Earth life?
If the life had an independent origin, it's not going to be similar to us. That would be the most exciting origin. In the case of Mars, however, 4 billion years ago, the climates of Earth and Mars were very similar, and we know there was an exchange of rocks [between the two planets] because it's still happening today. If the climates were similar, it's possible that if life started on one, it would spread to the other. [Since Earth's first life-forms might have originated on Mars,] it's possible that we are Martians, which is a fascinating idea.