What do you think the Aliens are like on Europa and do you think Mars used to have a human like civilisation in the past or maybe Venus??

Europa may well have some type of intelligent life on it. It has the right resources.
I think there is a fairly good chance Mars used to have life on it. It has extremely high levels of atmospheric radiation mixed with Uranium and Thorium isotopes that are likely due to the aftermath of huge nuclear explosions on Mars.