Hypothetically, if there are aliens:
Some scientists are saying that if there are aliens, some are far more advanced than us, and that they have been for hundreds or thousands of years. Humans are now curious of what's out there, and we're not even that advanced yet. We've been sending devices/machines to Mars. Let's be honest, if we only have the technology to go to Mars and walk its surface to find out more about the planet, we would. And MAYBE we will reach that level of technology--decades or hundreds of years from now--but the point is, intelligent creatures are curious.
This is a silly example, but just so we could determine if there's any logic for aliens to visit our planet: Let's say there are trees and animals in Mars. Let's say it's just like Earth, but there are no intelligent life forms yet--OR there are apes and small tribes of homo sapiens, but they're not that advanced or civilized yet; and we have the right technology to go there. Because the environment is just like Earth, it's safe for humans. In this scenario, I'm certain that scientists/experts will be sent to Mars. Perhaps rich people would go there just for vacation. If we've determined that it is a safe place, I know I would go there if I were rich. How cool would surfing on a different planet be. We may even help the locals if we think we need to.
Next: Let's just say aliens haven't visited us yet. Do they exist? Some scientists have claimed that there's a 99% chance we're not alone. In my opinion, if we are alone, wow, we must be very special. Billions and billions of other planets, and yet, only one planet sustains life. Another silly example, but that's like saying, "Trees grow in New York, but not in the rest of the planet." Trees grow in other parts of the planet as well because, just like New York, other places are capable of growing trees. Having said that, if there are planets out there that are capable of sustaining life (perfect location from its sun), they will sustain life because they are capable of sustaining life. Science is universal, it doesn't care what people think; it just does what it does when it's supposed to. I'm no expert, but with the right combination of elements, a process can be completed--2 parts Hydrogen and 1 part Oxygen will ALWAYS be H2O/Water. If a planet undergoes the same process that Earth has undergone, it will sustain life. Earth is not the oldest planet.
But just like we can't say that there are aliens, we also can't say that there aren't. Science and even the odds say that there are, but without solid scientific proof, everything remains hypothetical.
