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The Wow! signal computer printout.
The "Wow!" Signal. On August 15, 1977, a radio telescope called Big Ear, at Ohio State University, was searching the sky for a signal from an extaterrestrial intelligence. As Jerry Ehman read the printout of the night's observations, he noticed a surprisingly strong and brief signal. He circled it, and wrote "Wow!" in the margin. The little blip would go down in history as the "Wow! signal."

SETI astronomers are fairly confident that this signal did not come from a source on Earth, and that the signal is artificial. However, the signal may have come from some manmade object in space.

Despite continued observations, no more signals have been received from that part of the sky.

The Search for Extra-Terrestrial Intelligence and Life in the Universe

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

Searching for Messages from Alien Civilizations

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

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.

The Ask an Astronomer team's favorite links about SETI and Extraterrestrial Life:

Previously asked questions about SETI and Extraterrestrial Life:

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