Sixty-three years ago, Italian physicist Enrico Fermi asked, "Where is everybody?" The question was of cosmic proportions.
While there are many ufologists and those who believe that there are other living beings in other parts of the universe, there are those who don't believe in UFOs and aliens.
According to a study about the "Prevalence of Earth-size planets orbiting Sun-like stars" reported by PNAS.org, there are many planets that have potential to support life. The nearest, according to the study, is "just 12 light-years away."
Experts in the field say that a generation ago, it was unthinkable to believe that aliens exist. Today, however, there are so many theories about extraterrestrials, alleged UFO sightings, alien conquest and even alien biochemistry.
Although there are no proven signs of intelligence elsewhere in the galaxy, there are numerous sightings of alleged UFOs dating to the 16th century, according to researchers making the issue a rather mind-boggling one.
In March 2011, Richard Hoover, a scientist from NASA, claimed that he found evidence of microbes in meteorites while scanning a piece of the said meteorites. According to Mr Hoover, the microbes resemble the make-up of tiny unicellular algae.
Reaction from other scientists varied from being skeptical to dismissive, but other researchers say, according to Space.com, that the study was done thoroughly. It is however too soon to say that life exists in other parts of the galaxy.
Viking Landers in 1976 "proved" that there are lurking microorganisms on Martian soil. While the interpretation was not widely accepted, it is still one of the closest pieces of evidence that life exists elsewhere in the universe.
In the year 2001, Sir Arthur C. Clarke made the headlines by claiming that Mars had vegetation. While the science community scoffed at the author, he firmly stood by his claim saying, "Something is actually moving and changing with the seasons that suggests, at least, vegetation."
Researchers also say that a key ingredient for life was more abundant in early Mars than on Earth in the same time period. The chemical ingredient in question is phosphate which, according to experts, is the backbone of DNA.
Other researchers say, however, that even if phosphate is available, it does not necessarily follow that there is life on Mars.