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
surface of Mars in the past, and there is mounting evidence that liquid water may still exist underground or on the surface. 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 hides seas of liquid ethane and methane, filled with complex molecules.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
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.
- Do you think it's possible to maintain life on other planets? (Beginner)
- Why search for only Earth-like life on other planets? (Beginner)
- Can life exist on the recently discovered extrasolar planets? (Beginner)
- Is it worthwhile to continue the search for extraterrestrial life? (Beginner)
- Do similar laws of physics throughout the Universe imply that all life must be like life on Earth? (Beginner)
- Would extraterrestrial civilizations know that there is life on Earth? (Beginner)
- Are aliens or UFOs real? (Beginner)
- Did life originate on Earth, or did it come from somewhere else? (Intermediate)
- What is a Dyson Sphere? (Intermediate)
- Have astronomers observed any phenomena that could be produced by extraterrestrial civilizations? (Intermediate)
- Could there be life in the galaxies nearest to the Milky Way? (Intermediate)
- Where is everybody? (Intermediate)
- Why doesn't SETI concentrate its observations to the nearby stars and the solar systems that we are discovering? (Beginner)
- Can I listen to the SETI@home radio signal? (Beginner)
- Why does the SETI project search for radio signals? (Intermediate)
- Wouldn't the vast distances of space distort SETI signals into unintelligeble forms? (Intermediate)
- Which part of the sky did the famous 'wow' signal originate from? (Intermediate)
The Ask an Astronomer team's favorite links about SETI and Extraterrestrial Life:
- SETI@home: You can donate time on your computer to search data from radio telescopes for signals from extraterrestrials!
- Astrobiology at NASA: Learn more about this growing field.
- Astrobiology.com. All sorts of information on astrobiology.
- On the Question of the Mars Meteorite: A nice summary of the debate regarding possible evidence for life on Mars from the meteorite ALH 84001.
How to ask a question?
If you have a question about another area of astronomy, find the topic you're interested in from the archive on the side bar or search using the below search form. If you still can't find what you are looking for, submit your question here.