If we find life on a different planet we should not colonise it beause:
Firstly, there may be life on some planets like some of the moons of Saturn and Jupiter. If Mars isn’t in our reach at the moment, then Jupiter and Saturn are going to be impossible to reach. This would not risk but kill so many people trying to get there. People have lost contact with Earth by going to the moon, no where near Jupiter or Saturn. One time, the astonought lost connection when it was about to land on the moon. Sometimes, peoples DNA and genes change. Secondly, if their is any life, they might not be welcoming towards us, they might not want us on their planet or imprison/ kill us. Finally, it would take alot of training and money to send all of us into space and safley arrived. Some people won't want to leave earth as it's their home. Their might not be enough recources so some familes may have to be left on Earth.