The subject of extraterrestrial life is one with many more questions than answers: Is there life elsewhere in our solar system? In our galaxy? In other galaxies? How about intelligent life in our solar system/ galaxy/ other galaxies? Is there any chance of communication with other intelligent + communicative life forms? Is direct contact (i.e., visitors, UFOs) possible?

For life to even exist in any form, one needs a variety of factors to occur: one needs a star that can support a suitable rocky planet or moon (all the recent extra solar planet discoveries have raised the estimate of our galaxy's total number of planets), and just the right conditions (temperature, chemistry). Liquid water, and simple and complex organic compounds (the basis for human life), are probably also required to be present. Simple life products must form, and then be given time to evolve without major disruptions to the temperature or chemical conditions over billions of years.

Exploring our solar system has shown that life on other planets in our solar system isn't really possible--with the exception of Mars, Europa and Titan. The current debate regarding the possibility past life on Mars stems from structures resembling primitive bacterial-like growth inside a Martian meteorite (NASA announced this possibility in August 1996, but the results are extremely controversial) and recent evidence that large amounts of water may have existed on Mars' surface. Jupiter's moon Europa may have liquid oceans beneath its icy surface (evidence from the Galileo probe). Saturn's moon Titan has a thick atmosphere containing simple organic compounds and possibly resembles what Earth looked like before life started; NASA's Cassini probe arrives at Saturn in 2004 and will study Titan.

As for communication, we'd need a intelligent civilization that chooses to communicate, via radio waves. Considering the vastness of our galaxy, communication between potential communicative civilizations is hampered by huge distances (hundreds to thousands of light-years inside our galaxy; millions of light-years to other galaxies) and therefore a long time for radio waves to reach their destination.

Spaceship travel would take even longer, and require an unrealistic amount of fuel-- which is why direct contact is pretty much impossible, at least with our current technology. Most UFO sightings can be explained rationally by known airplanes or weather phenomena, or hoaxes (i.e., pie pans + a high-speed camera). However, speculation and sensationalism is fueled by 'Aliens Mutilated My Cattle!'-style-tabloids and other media, including TV shows such as 'The X-Files,' which promise quick and easy (though not necessarily true) answers about extraterrestrial life to people who aren't willing to sit down and study the science surrounding this topic.

Given the communication and visitation issues, the question of 'Are we alone?' therefore may not be easily answered, even if the answer is 'yes.'