The aliens then stocked the area with all manner of Earth life over the following several millennia.

At least some of these machines had chambers suited to Earth life, and could take individuals inside them for extended periods.

At this temperature range, the only Earth life that could exist on the planet would be thermophiles.

Mars is one of the few places in our solar system where life similar to Earth life may be able to survive.

"And if there were, it might after all be built on the same plan as is Earth life."

Again, this can't be a unique trait of Earth life.

There was a whole biosphere down here, gen-enged from Earth life.

The Earth life had adapted with a vigor which was much too great.

Nothing on the aliens made for easy analogues with Earth life.

There, scientists would have to artificially sustain any Earth life.