For 75 years we have made conventional chemical rockets and recently ion thrusters to take us to other worlds while simultaneously ruining the only ocean&atmosphere worth visiting.
Stop2: Icy outer moons
Stop3: Alfa Centauri - 4.3 light years or 5,879,000,000,000 (trillion) miles.
Keep the air and water on our little spec of dust clean.
The decisions you make today matter. Tomorrows another day.