What environmetal characteristics would be necessary for a human to survive on a nother planet?

Answer 1

A good, constant and fresh supply of water, atmosphere similar to earth's, which is about 78% oxygen, 21% nitrogen, .98% inert (not chemically active) argon and small amounts of other types of gases. The temperature of the air can go up to about 35 degrees C.

Trees, animals and micro organisms to decompose dead matter and regulate the gases of the air. These will also provide food supply, granted that humans have the necessary tools to hunt.

And gravity. Gravity is pretty important.

Answer 2

Well instead of worrying about that you should worry about how we will genetically engineer people for the other planets.

Answer 3

an atmosphere with the perfect consistency of gases  apropriate for human survival (oxygen, nitrogen, helium, etc.) also a layer of ozone and water

distance from the sun and solidity are also improtant!