Panspermia is said to be one of the possible ways for evolution of life on Earth. The theory of panspermia suggests that life did not originate on Earth, but instead came from space. The possibility that life originated here on Earth, but was supplemented by space-derived microorganisms also cannot be ruled out. Another variant of panspermia, “neopanspermia” refers to the contemporary arrival of life from space. The idea that life originated from space has a long history, while the theory of neopanspermia is relatively new. However, the entire concept of panspermia, in its modern guise is based on the seminal work of Sir Fred Hoyle and Chandra Wickramasinghe. Until recently most of the work on panspermia has been theoretical. However, there is now laboratory evidence to support the view that microbes can be transferred across the cosmos, and which suggests that, at this moment, life is entering the Earth’s atmosphere from space.
The engineers also determined that cleanliness would make or break this mission. The slightest dust in the spacecraft could also scatter light to the detector, and such scattering had to kept to about 10 photons per pixel per second from the nearby Earth (which is putting out about 10^20 photons per second per pixel, a huge, huge number). This required keeping particle contamination (dust) to something under 200 parts/million, which is very clean even for a clean room used to building delicate spacecraft.