But we almost came close to destroying earth with atomic bombs several times , I mean surely it cant be that hard. Yes we can devote some of our efforts towards making earth a better place to live, but we will always have problems here on earth, every now and then adventure will do us good.
We can release all our nuclear bombs then multiply that by a factor of a billion...it won't do didley squat.
Our destruction is primarily focused on the delicate biosphere, because it is sensitive to small changes. Thats relatively easy to alter and mess with. Harsh environments really aren't moved by our actions. In short, we excel at fucking up places that are nice to live in. Don't mistake that for genuis.
The hard work is making making harsh places nice to live in, ie Terraforming but that's beyond our ability at least for a few hundred millenia. To get there faster we need all the brains we can get to be working on the problem. As of right now building snapchat filters is number one human priority. Building facebook stories, making financial derivatives is close second. Very far away from space exploration...