This question was suggested by Itty2Bitty
"What do you think would be humanity's reaction to the discovery of extraterrestrial life?"
Itty2Bitty: I believe this could be a bad thing, honestly. There are many conspiracy theories on how they are already here but look exactly like us, but I'll save that conversation for another time. The deciding factors for how we would react include: Are they hostile? Why have we just now discovered them; is it because they mean to take over earth or cause harm? Also, Humans already have problems with race, as is, we are way more accepting in this day and age, but if we find out there's a separate race out there, humans would undoubtedly be in an uproar; we may have segregation again or the Extraterrestrial life may go higher up in status than us and we may become slaves or pets. It also depends on if you Believe in God or not-I believe in Jesus and even though I am not trying to push my religion on someone, It's one of those questions of 'Who created extraterrestrial life? Something good or something evil?' It has also been stated that Humans will automatically fear and deny something they don't understand, protests and riots may break out, and more crime could break out. Mainly because Humans would automatically assume this is a bad thing, that other life forms are evil. What happens if there's breeding between humans and extraterrestrial life forms? Like the idea of Nephilim, what would the result be? Something good or Evil? In the end things may turn out for the good, but I believe in the beginning after this discovery...Chaos would ensue.
Ibis: Hm. To answer this, I'm going to assume that we happen to find them on another planet, not that they come down from the sky in a glimmering spaceship in order to either interact with us intelligently, or to simply murder us.
So, assuming that someone's telescope, space craft, or any sort of technology/invention that is meant to be used in space(camera's, rover's, etc.), happens to take a few images of extraterrestrial life forms(which could be something extremely simple, or something brilliantly complex), then I would assume that the higher government officials and groups would be the first alerted. After they conducted and partook in various meetings, they would probably try to gain as much information about the species as they possibly could, including trying to get people out there to explore. In addition, they would most likely send information(such as photographs, information about the living conditions on the planet, etc.) to acclaimed scientists in order for them to try and deduct as much they can, assuming no one can be sent out to meet the aliens.
After all that(and after they were sure the information wasn't fake), they would probably send out some sort of logical, yet scanty, information pertaining to the discovery of a new life form. Of course, given this exciting piece of news, the media would go absolutely insane, resulting in a lot of overall elation among the human race; there might be talk of the end of the world, of moving to that planet, and, of course, the possibility of other life forms. After awhile, as people start to lose interest, and as the scientists and astronauts(along with others) find no more real evidence, the fact that we discovered new life will probably fade away, becoming something that only those in NASA and such will keep working at for various reasons (like finding new planets for people to inhabit).
Of course, there is always the off chance that some neon green, giant eyed creatures with large, oval heads will descend from a red sky in their Frisbee-shaped spaceship, offering us garbled words of peace and awkward hand gestures. Or they could just show up in the sky, leave some creepy message, and hang around for three days before beginning an attack for world domination. Or they can be caramel colored wrinkly things that enjoy chocolate peanut butter candy and have magical healing powers(and a fascination with phones).
Well, I suppose we'll just have to wait and see.