Europa is the sixth moon of Jupiter and has been discovered by Galileo in 1610. It’s very possible that at that time, life has been swimming around in the subsurface ocean Europa almost certainly contains. For those 400 years, it’s entirely possible that extraterrestrial life has been around, but we just have not known it. This is as intriguing a reason as any to go there right now.
The surface of Europa is the smoothest in the entire Solar System, which supports the concept that there is a water ocean beneath it. There are very few craters but one of note is that the Pwyll crater, whose bright white look again implies the presence of water below the surface. When it comes nearer to Jupiter the gravitational pull is raised, which slightly stretches the planet out, and once it goes farther away in its own orbit, Europa returns to its spherical shape. Additionally it is an excellent example of gravitational energy turning to kinetic energy, which in turn becomes heat energy.
There have been many probes which have visited Mars in the hope of locating present or past life. It’s very unlikely to harbor any sorts of life now, although its chances of having played host to microorganisms in the past is still quite good. However, there is nothing as persuasive as a liquid water ocean to hold extraterrestrial life in the present day. As you read this guide, weird and amazing creatures could be swimming around the deathly cold seas of Europa, or parked around some hydrothermal vent (as we see in the ocean depths on our own planet Earth). It’s because of this that we must go to Europa, not within twenty, not over ten, but when possible. A robotic probe could be sent within five decades.
A robotic probe would need to carry substantial power on board, maybe by atomic fission. It would need to melt through the good ice crust that’s at least ten kilometres thick, and then release a probe which could swim through the cold oceans and transmit information back to earth.
Unfortunately, a plan known as the Jupiter Icy Moons Orbiter was shelved five decades back, and funding cuts have seen a string of false starts at the search for life on Europa. If we are to discover extraterrestrial life any time soon, this has to change.