The report of liquid water on Mars, and the increased probability that life will be found on the planet, reminded me of this old article hoping humans are alone in the universe because the alternative is too terrifying. The search of extraterrestrial intelligence (SETI) has been going on for decades will no success. Why?
We're Too Dumb
They Killed Themselves
Great Filter theory mentioned by Nick Bostrom. Any civilization that achieves interstellar travel would have to be both aggressively expansionist and an aggressive user of resources. Aggressive species are, necessarily, warrior species. Like humanity, a dominate warrior species will likely develop weapons capable of destroying their planet's ecosystem. Likewise, rapacious consumption of resources can deplete the planet and collapse the civilization before space travel can be achieved.
God Zaps Them
Gamma Ray bursts. When a star goes supernova it releases a beam of gamma rays that, quite literally, will fry any planet in its path. Gamma rays travel at the speed of light, there is no seeing it coming. Estimates are they happened in the Milky Way some 5,000 times since the Earth was formed. It is suggested a gamma ray burst struck the Earth 450 million years ago causing a mass extinction.
Reptilian shape-shifting extraterrestrials are among us now and Barack Obama is their king.