Is There Life on Other Planets?
Most scientists believe that, yes, there may be life on other planets.
What scientists look for when searching for alien life are stars that are similar to our sun, and planets that show evidence of water, an atmosphere that contains oxygen or methane, and a planet that is neither too far nor too close to its sun. Scientists believe that water is a necessary component of life, so a planet with none cannot support life (at least not life as we know it).
In our solar system, the planet most similar to ours is Mars, however, scientists have not found evidence that life exists there, or that it ever did. There is evidence that there was once water on Mars, however, there doesn't seem to be any water on Mars now. Mars does have a lot of water ice at the polar caps, but the temperature on Mars at the poles is too cold for this ice to melt. At Mars equator it does get to a comfortable daytime temperature that is slightly above 60 °F (16°C) but there isn't ice or water at the equator and Mars equator gets very cold during the nighttime, below -200 °F (-129 °C). This means that any life that might be inclined to form during the daytime would probably not survive the night. Scientists are still investigating whether or not life ever existed on Mars.
Scientists are also investigating whether or not some of the moons of Jupiter and Saturn are capable of supporting life, such as Jupiter's moon Europa, for example. The planets Jupiter and Saturn themselves certainly don't seem capable of supporting life.
The Drake Equation
Scientists sometimes use the Drake equation (developed by Frank Drake) to calculate the probability that other technology-using life exists in the Universe.
N = R*fpneflfifcfL
- R* = the number of stars similar to our sun present in the Milky Way Galaxy
- fp = the number of sun-like stars in the Milky Way that have planets in orbit around them
- ne = the number of planets that have conditions capable of supporting life
- fl = the number of planets that actually have life
- fi = the number of planets that have intelligent life capable of using technology
- fc = the number of civilizations that have actually developed technology
- fL = the lenth of time that a civilization has been using technology and how long they will continue to do so
You can plug different numbers into this equation to determine the likelihood that there is other technology-using life present in the Universe. However, this equation doesn't predict whether or not there is life, or even intelligent life, somewhere else besides Earth. It only predicts whether or not technology-using life is present. For example, I would consider an animal, such as a dog or a cat, intelligent life. However, they wouldn't be capable of using technology.
Why is there a focus on technology-using civilizations in the Drake equation? The reason is that Frank Drake and other scientists have tried listening for radio frequencies produced by alien life forms. For example, the SETI Institute listens for radio frequencies produced by alien civilizations. If there is life on another planet, but the inhabitants are not using radio technology, then scientists won't find them using this method.
You can even participate in the SETI program. To do this go to SETI@home to sign up. If you choose to participate and sign up, you'll get a free screensaver and program to download on your home computer. This program uses your Internet connection to download, run, and analyze data from a radio telescope. Once your computer has analyzed the data the information gets sent back to SETI@home.
If Alien Life Exists Do We Really Want To Find Them?
The answer to that question depends on who you ask. If we find another civilization capable of using technology it is possible that they may be more advanced than we are. Depending on their nature, making contact may or may not be a good idea.
It is also possible that life on another world could be so different from us that we may not even be able to recognize it as life even if we do find it.