Organic chemistry in space and the search for life in our Solar System

One of the most fascinating questions in planetary science is how life originated on Earth and whether life exists beyond Earth. Carbonaceous compounds in the gas and solid state, refractory and icy are identified by astronomical observations in our Solar System, and distant galaxies. Among them are a large number of molecules that are essential in prebiotic chemistry and used in contemporary biochemistry on Earth. Life on Earth originated approximately 3.5 billion years ago and has adapted to nearly every explored environment. What was chemical raw materials available for life to develop? Small Solar System bodies hold clues to processes that formed our Solar System and probably contributed carbonaceous molecules and volatiles during the heavy bombardment phase to the young planets. This process may have contributed to life’s origin on Earth. Space missions that investigate the composition of comets and asteroids and in particular their organic content provide major opportunities to determine the prebiotic reservoirs available to the early Earth and Mars. Recently, the Comet rendezvous mission Rosetta has monitored the evolution of comet 67P/Churyumov-Gerasimenko during its approach to the Sun and observed numerous volatiles and complex organic compound on the cometary surface and in the coma. Several asteroid sample return missions are currently operational such as JAXA’s Hayabusa-2 which was launched in 2014 and will return samples to Earth in 2020. Hayabusa-2 also carried the German-French landing module MASCOT (mobile asteroid surface scout) that provided during the 17 hours of intensive scientific exploration new insights into the structure and composition of the asteroid Ryugu.

A fleet of robotic space missions currently targets planets and moons in order to assess their habitability and to seek biosignatures of simple extraterrestrial life beyond Earth. Prime targets in the outer Solar System include moons that may harbor internal oceans such as Europa, Enceladus, and Titan. Life may have emerged during habitable periods on Mars and remains may still be preserved in the subsurface, evaporite deposits, caves or polar regions. On Mars, a combination of solar ultraviolet radiation and oxidation processes are destructive to organic material and life on and close to the surface. However, the progress and the revolutionary quality and quantity of data on “extreme life” on Earth have transformed our view of habitability. In 2020, ESA’s ExoMars program will launch the Rosalind Franklin Rover and landing platform, and drill for the first time 2m deep into the Martian subsurface. Mars is still the central object of interest for habitability studies and life detection beyond Earth, paving the way for returned samples and human exploration.

Knowledge on the evolution of organic material in space environment such as their photochemistry and preservation potential are crucial to advance life detection strategies and instrument development. This Cassini lecture will review the evolution of organic matter in space including recent observations, space missions and laboratory research and discuss the science and technology preparation necessary for robotic and human exploration efforts investigating habitability and biosignatures in our Solar System.