Assuming there is habitable double exoplanet. Each body has roughly the same mass as Earth One body is habitable and inhabited by little green men. The other body is not inhabited by little green men and in fact little green men cannot survive there without support, however it too has relatively dense atmosphere.

Now, assume the little green men develop rocketry and travel to the other body is naturally one of their priorities. Also assume their civilization abhors suicide. Assuming the little green men posses similar technology to what is available on Earth today would manned mission to the other body be possible?