Our Cosmic Heritage of Complex Molecules

The evolution of matter in the cosmos includes the production of elements which, over time, produces carbon and other heavy elements needed to form planets and life. The overall physics of the process and the environments in stars where carbon, nitrogen, and oxygen are formed are generally fairly well understood. It is carbon's particular properties of chemical bonding along with its high abundance that make it especially suited as the foundation for life. Over 120 organic molecules are found in interstellar space, and organic phases – some with slight enrichment of one “chiral-enantiomeric” form over the other – are known in meteorites. Delivery of this material to the Earth during formation of the planets was aided by the early presence of Jupiter, whose gravity ensured mixing of materially radially throughout the solar system. In the outer solar system, organic-rich worlds are present and chemistry is evolving there today – Titan is a particularly promising example in this regard. For life as we know it, liquid water is required (though forms of non-Earth life might exist in other liquids), and hence the inferred liquid water environments in Jupiter's moon Europa and Saturn's moon Enceladus are of keen interest along with environments on and within Titan that contain aqueous and non-aqueous liquids.