Earlier explorers seemed to be very hard on native populations. Very often someone was decimated, by smallpox, or measles, or something.

Personally, I think the precautions are frustrating - expensive, time-consuming and slow down what I'd like to see happen NOW.

And, as everyone points out, why take a chance in a matter which could be catastrophic? If we are so concerned Man may disappear from this solar system we are already thinking of ways to spread, it seems to make sense we last here as long as possible.

The odds that something on Mars could be very hard on Earth organisms must be about that of an asteroid slamming into Keokuk, and folks are more than willing to see that doesn't happen.

Arf