Chemical diversity among comets: Implications for delivery of water and pre-biotic organics to early Earth

Michael J. Mumma

Director, Goddard Center for Astrobiology, and

Senior Scientist, Solar System Exploration Division

NASA Goddard Space Flight Center

Michael.J.Mumma@nasa.gov

Comets are messengers from the early solar system; they contain key information from the time when the planets were forming, and even earlier — some may contain material formed in our natal interstellar cloud. Comets today contain some ices that vaporize at temperatures near absolute zero, demonstrating that their compositions remain largely unchanged after 4.5 billion years. Far from being simple dirty snowballs, the discovery of abundant organic ices such as natural gases (CH₄, C₂H₆), alcohols (CH₃OH), acids (HCOOH), anti-freeze (ethylene glycol), and even embalming fluid (H₂CO) in them shows that comets delivered vast quantities of pre-biotic organic chemicals along with much (most?) water for our oceans, during the first 500 million years of Earth's existence. Did this enable the emergence of life? What are the implications for planetary systems around other stars? I will provide a simplified overview emphasizing how comets are studied, what we are learning, and why these insights are relevant to you.