I wouldn't call a slow migration that has no written record on the same scale as the exploration of the new world.

>Indians had no trouble crisscrossing America

Well yeah there weren't any human infectious illness where... there aren't any humans.

This video explains the history of man kind's infectious illness very well https://www.youtube.com/watch?v=JEYh5WACqEk

And Europeans had no trouble crossing Europe.

A single smallpox laden explorer would have started a plague in the Americas and a single native American would likely have died of one of the many plagues in Europe that Europeans had grown up with (and still often died from).

The problem of safety is not always placed on the explorer, sometimes the explorer is the danger to his environment.

The point is that entire classes of extremely common diseases in Europe basically didn't exist in all or most of the Americas, and many of those diseases spread very easily once even a handful of people had carried them across the ocean.

Gah, you're right. I read it as we mustn't... rather than there aren't any so we can't. My mistake.

1- Probably but not certainly, and a little caution (say, 100 more years of remote sensing exploration as technology improves) will go a long way.

2- I'm not so anthropocentric as to think that the only value in the universe is human value. It's not our universe; we're an infinitesimal fraction of it. Other life has inhabited earth for billions of years, and maybe other places too. The terrestrial or extraterrestrial environments have value for existing and future life, regardless of whether that is human life. And most of life isn't human, and won't be in the future either.

It doesn't need to be alive to be beautiful. There is great peace and beauty in empty places. Mars has grand and majestic vistas: canyons and plains, dunes and mountains. Reducing it in your mind to a lifeless rock obscures the awe and wonder. It is the opposite of appreciation, it makes the idea small in you, worthless and not deserving of respect.