In 2008 Dr. Edgar Mitchell of the Apollo 14 mission clearly stated that intelligent life does exist on other planets. Methane gas detected on Mars in January of 2009 suggests that life might be present there. Although that life would most likely include simple bacteria or single celled organisms, the idea that any life exists on a neighboring planet further promotes the idea that more complex organisms might exist on planets outside our solar system.
Surprisingly, stories such as these often go unnoticed by the general public. They are relegated to small blurbs in the Science and Technology sections of major newspapers or websites while further discussion is generally found only in publications specifically geared toward science or space exploration.
The SETI (Search for Extraterrestrial Intelligence) Organization firmly states on their website (http://www.seti.org/Page.aspx?pid=1241) that should they have success in detecting the presence of intelligent alien life, their findings will be made known to the public. However, if past behaviors are indeed the best indication of future behaviors, there will be neither public outcry nor celebration. Few people will be aware of the event at all and many of those who are aware will take little interest in it. That being said, some people will be deeply affected and the societal implications concerning these particular individuals or groups of individuals will be great.
If SETI were to have success, those who have an active interest in extraterrestrial life might feel a sense of triumph. Their beliefs would be validated and skeptics would be hard-pressed to argue the findings of a scientific institution once endorsed by NASA itself.
They might also feel some disappointment. The goal of SETI is to detect optical and auditory transmissions from space. These will not necessarily be easily translated into specific messages. Though the presence of alien life would be confirmed, it is not likely that we would be aware of their reasons for making themselves known - at least not right away.
The deeply religious might have difficulty coming to terms with the existence of extraterrestrial life as this would be contradictory to the various creation theories associated with such widely practiced religions as Christianity, Judaism, and Islam. Some might discount a SETI success as a fluke or a hoax, while others might accept it as truth, but struggle with the spiritual implications. It is not likely that many would abandon their faith altogether, but some might feel that the concept of creationism would have to be altered somehow to include the creation of entities beyond our world.
The Scientific Community
Certainly a SETI success would be quite inspiring for the scientific community. Organizations such as SETI would most likely intensify their efforts and those who fund their research would be more willing to donate money to the cause. Governmental organizations the world wide might engage in a competition similar to the 'Space Race' of the 20th Century.
The General Public
If the general public did, in fact, take interest in news of a SETI success, they would most likely feel one of two emotions: fear or hope or a mixture of both.
Fear would occur as a natural response to facing the unknown. Since a laser beam or radio transmission cannot necessarily be put into words, how would we know that the intelligent life we have discovered (or that has discovered us) is of a benevolent nature?
Hope would come from the knowledge that there exist beings with the technological advancement to contact us in the first place. The idea that they have such a degree of intelligence might be enough to allay our misgivings. Of course this is all speculation, but considering the turmoil with which we are regularly faced, it is a definite possibility that alien contact would inspire hope for the future of mankind.