NASA says that life was delivered to Earth on a comet. The NASA Stardust spacecraft flew past Comet 81P/Wild 2 in 2004, collected dust samples on four tiny pieces of aluminum foil, and then returned them to Earth in 2006. It's taken three years for scientists to determine exactly what is on those samples.
After some clever laboratory work, scientists announced the discovery of the amino acid glycine in the comet's dust. Such amino acids are made by mixing organic carbon-containing compounds with water. Zap them with energy by way of commonly available photons, and suddenly you have amino acids, then DNA, and ultimately, people.
Add this discovery to previous finds of amino acids on meteorites, and scientists say this confirms the building blocks of life were delivered to Earth from extraterrestrial travelers such as comets and meteors. And here we were thinking life was delivered to Earth in seven days. So we are stardust after all.