All 5 genetic letters of DNA and RNA discovered in 4.5B-year-old asteroid

aurareturn • today at 12:31 PM

  The discovery of all five nucleobases on Ryugu suggests the molecular ingredients of life may have been already forming in space billions of years ago. Asteroids may have helped deliver those ingredients to the early Earth – making the origin of life part of a much larger cosmic chemical story.

Why do we think that Earth needed those ingredients from asteroids when the same rocks formed Earth - thus, giving Earth everything it needs without asteroids?