As a further token of friendship, they allow humans to visit their home planet via ten-year "exchange groups".

Then they'd broadcast until a new molehole was latched on-giving the USS a whole new Samothrace, in a solar system humans had never visited.

This section addresses questions about whether humans should visit Mars at all, especially, whether they should visit the Mars surface.

Its course has been suggested as the route that the first humans to visit Britain took.

There are signs that humans visit it occasionally.

He asked how she had come to be there, at the most remote place humans had ever visited.

No reason is given why humans have not visited other galaxies, which would seem to be within range of the hyperspace drive.

But that hardly means the first humans to visit Mars will have nothing to fear.

Pups, a few months old, were plentiful and unconcerned by our presence; humans rarely visit these islands and pose no threat to the once threatened, but now protected, species.

Only when we were starting bad toward Quicksilver did I pause to attempt to appreciate the fact that I could die in a place no humans had ever visited.