The origin of life on Earth is still somewhat of a mystery. Many different theories have been proposed, and there is no known consensus on which one is correct. Although the Primoridal Soup Theory was proven to be most likely incorrect, other theories are still considered, such as hydrothermal vents and the Panspermia Theory.
The word "Panspermia" comes from the Greek language and means "seeds everywhere". The seeds in this case would not only be the building blocks of life, such as amino acids and monosaccharides, but also small extremophile organisms. The theory states that these "seeds" were dispersed "everywhere" from outer space and most likely came from meteor impacts.
This theory was actually first mentioned by Greek Philosopher Anaxagoras around 500 BC. The next mention of the idea that life came from outer space wasn't until the late 1700s when Benoit de Maillet described the "seeds" being rained down to the oceans from the heavens.
It wasn't until later in the 1800s when the theory really started to pick up steam. Several scientists, including Lord Kelvin, implied that life came to Earth on "stones" from another world which began life on Earth. In 1973, Leslie Orgel and Nobel prize winner Francis Crick published the idea of "directed panspermia", meaning an advanced life form sent life to Earth to fulfill a purpose.
The Panspermia Theory is still supported today by several influential scientists, such as Stephen Hawking. This theory of early life is one of the reasons Hawking urges more space exploration. It is also a point of interest for many organizations trying to contact intelligent life on other planets.
