>Bacteria/microscopic
Meh
>Alien biosphere with vegetation
Yes.
>Alien biosphere with non-sapient life
Mega YES.
>Alien biosphere with sapient life at a higher tech level
They found us, in which case we're boned
>Alien biosphere with sapient life at a lower tech level
Pic related

>>16719749 (OP)
you won't even leave your mom's basement, how in the hell do you expect to join the army and kill aliens?