SETI and Extraterrestrial Life

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One of the most profound questions that we humans ask ourselves is: Are we alone in the Universe?

Searching for Messages from Alien Civilizations

The Arecibo message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16 November 1974. (Credit: Arne Nordmann)Credit: Arne Nordmann

The Arecibo Message. The Arecibo message was broadcast into space a single time via frequency modulated radio waves at a ceremony to mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16 November 1974. See the details of the message here.
We cannot travel to different solar systems, and, though many people seem to believe that UFOs are spaceships visiting from other planets, most astronomers believe that the chances of a visit from an alien are slim to none.

However, since the invention of the radio, humans have been broadcasting signals into outer space. Other civilizations in our Galaxy might be doing the same. They might even be deliberately sending out signals to find other civilizations. Someone out there may even be beaming a signal directly at the Earth.

With our current technology, the chances of us finding a signal are fairly bleak. There are currently no nationally-funded programs searching for signals from other civilizations, but the SETI Institute continues the search, using private donations.

Life in our Solar System

Front view of antennas of the Allen Telescope Array, a radio telescope for combined radio astronomy and SETI (search for extraterrestrial intelligence) research being built by the University of California at Berkeley, outside San Francisco. The first phase, consisting of 42 6-meter dish antennas shown here, was completed in 2007. Eventually it will have 350 antennas. This type of antenna is called an offset Gregorian design. The incoming radio waves are reflected by the large parabolic dish onto a secondary parabolic reflector in front of the dish, and then into a feed horn. A metal shroud along the bottom of the secondary reflector shields the antenna from ground noise. It covers the frequency range from 0.5 to 11.2 GHz. (Credit: Colby Gutierrez-Kraybill)Credit: Colby Gutierrez-Kraybill

Allen Telescope Array. Front view of antennas of the Allen Telescope Array, a radio telescope for combined radio astronomy and SETI (search for extraterrestrial intelligence) research being built by the University of California at Berkeley, outside San Francisco. The first phase, consisting of 42 6-meter dish antennas shown here, was completed in 2007. Eventually it will have 350 antennas. This type of antenna is called an offset Gregorian design. The incoming radio waves are reflected by the large parabolic dish onto a secondary parabolic reflector in front of the dish, and then into a feed horn. A metal shroud along the bottom of the secondary reflector shields the antenna from ground noise. It covers the frequency range from 0.5 to 11.2 GHz.
Even if we cannot find intelligent life from distant stars, we might find simple forms of life right in our own backyard. There are several places in our Solar System where liquid water might be present. There are signs that liquid water flowed on the surface of Mars in the past, and there is mounting evidence that liquid water may still exist underground. Some astronomers think there is liquid water to be found among the larger satellites of Jupiter, under Europa's icy surface, even deep within Ganymede and Callisto. Where there is liquid water, there is the possibility of life. Some even speculate about life on Titan, a frigid moon of Saturn. It may be too cold for liquid water to exist, but Titan's cloudy methane atmosphere may hide a sea of liquid ethane, filled with complex molecules.

If extraterrestrial life exists in our Solar System, it is probably no more advanced than bacteria. In recent years, biologists have discovered bacteria on Earth living in conditions that were once thought too hostile for life, for example in Antarctic ice, in super-hot ocean vents, and in rock deep in the Earth. These types of bacteria are called extremophiles, because they love extreme conditions like heat or acidity or saltiness. Because of the quantity and variety of extremophiles found on Earth, astrobiologists are hopeful that we may find life even in harsh environments on other planets and moons.

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