In either case, using a rover or orbiter, monitoring changing events on the surface is difficult, if not altogether impossible.

Since that was altogether impossible, he decided to believe in reincarnation.

He also imagined their unlikely but still not altogether impossible meeting.

You know that it is not altogether impossible.

Anything in the shape of mist or cloud would be altogether impossible at this height.

"If they should mate, which is not altogether impossible?"

Type and longevity are much harder, but not altogether impossible to cost.

Looking at the shelves now it didn't seem altogether impossible.

It seems to be altogether impossible that the bounty could ever contribute to lower the price of grain.

Nor could it be argued that the thing was altogether impossible.