Asteroids are less pristine than comets because they have often withstood heating and exposure to liquid water. But these effects can create dramatic up-to-date organic complexity. Scientists have known for decades that meteorites called chondrites, which come from asteroids, contain an astonishing variety of organic molecules. The Murchison meteorite, which fell in Australia in 1969, contains over 96 different amino acids. Life only uses about 20. Osiris-Rex and Hayabusa2 confirmed that the asteroids Bennu and Ryugu are as convoluted as these meteorites. At least some of this complexity appears to have arisen before the appearance of the asteroids themselves: A preliminary analysis Bennu samples suggest that it preserved organic matter, including polycyclic aromatic hydrocarbons, from the protoplanetary disk.
Chemistry of life?
Organic molecules on early Earth have achieved a up-to-date, extraordinary escalate in complexity. They They organized themselves somehow into something alive. Some hypotheses for the origin of life on Earth include a starter kit of organic material from space. For example, the “PAH world” hypothesis assumes a primordial soup stage in which polycyclic aromatic hydrocarbons dominated. The first genetic molecules emerged from this suspension.
Overall, understanding how convoluted organic substances form in space and end up on planets can give us a better idea of whether life has arisen on other worlds as well. If the raw materials for life on Earth originated in the interstellar medium, the material of life should be found everywhere in the universe.
For now, such ideas remain largely untestable. But because life itself represents a up-to-date level of organic complexity, astrobiologists are looking for convoluted organic substances as a possible biosignature, or sign of life, on other worlds in our solar system.
The European Space Agency’s Juice mission is already on its way to explore Jupiter and three of its icy moons, and NASA’s Europa Clipper mission launched in October towards one of those moons, Europa. Both will employ onboard instruments to search the atmosphere for organic molecules, similar to Dragonfly’s future mission to Saturn’s moon Titan.
However, determining whether a given organic molecule is a given is challenging is a biosignature or not. If scientists could find sufficiently convoluted organic molecular assemblies, it would be enough to convince at least some researchers that we have found life on another world. But as comets and asteroids show, the inanimate world is itself convoluted. Compounds considered biosignatures have been discovered in dead rocks, such as dimethyl sulfide, which Hänni’s team recently identified on 67P.