Do you think alien beings exist somewhere in the universe? It seems like Mars, our closest neighbor, has inspired the most science fiction as the place where aliens are most likely to come from. Recent Mars probes (探测) have shown us that there is no life on that planet—at least not now. But that does not mean that life does not exist elsewhere—after all, the universe is really big. A lot of scientific research is going on in the search for "extraterrestrial life".
Think about it—why should the seven billion people on this little planet be the only living beings in the universe? It would, in fact, seem reasonable that this is not the case. So scientific research in this matter is based around the idea of finding other planets that have environments that can support life —environments similar to the Earth. The search is on for the evidence of the existence, or earlier existence of life: from very wise beings to simple organisms.
So far, there have been a number of theories as to which planetary bodies may have an atmosphere that can support such life and therefore deserve closer attention. As for places within our own Milky Way Galaxy, it has been assumed over the decades that Mars and Venus, as well as some of the moons of Jupiter and Saturn, may have been hosts for life. Now, as technologies have improved and we can obtain measurements of the composition of the atmosphere on extra-solar planets, the chances of finding "alien" life forms are increasing.
There has been a theory that some of the planets in the habitable zone of the red dwarf star Gliese 581 may be able to support life. In 2007, scientists discovered exoplanet Gliese 581c—and felt that its atmosphere was most suitable for supporting life. But further research revealed that it would not. Now, attention has been turned to Gliese 581d, at the outer edge of the star's habitable zone. The main standards for deciding whether a planetary body can be life-supporting are atmospheric conditions which allow the existence of water. Gliese 581 is about 20.4 light years away from the Earth, so even if life does exist there, the distance would mean that communication would be unlikely.
Having said this—who says alien life forms (if they exist) need water?
