The popular claim that space tastes like raspberries and smells like rum has been circulating for over fifteen years, but the actual story behind the finding is more intriguing than the simplified version. The detection of ethyl formate, a molecule with a chemical formula of C2H5OCHO, in a specific dust cloud at the center of the Milky Way, sparked this claim. However, the story is far more fascinating than the one that has been repeated ad nauseam.
Ethyl formate, while responsible for the flavor of raspberries and carrying a faint rum-like scent on Earth, is not the exotic find it was made out to be. The molecule is one of approximately fifty detected in the Sagittarius B2(N) cloud, which is far too thin to be tasted by human sensory standards. The cloud, located near the galactic center, is one of the largest molecular clouds in the galaxy and has been a consistent source of new molecular discoveries for decades. The goal of the survey was to find the building blocks of life, not to determine the taste of space.
The detection of ethyl formate was significant, but the discovery of n-propyl cyanide, a twelve-atom molecule with a branched structure, was more scientifically important. This molecule demonstrated that the structural complexity required for amino acids could be assembled in the cold, low-density environment of an interstellar cloud. The science press, however, focused on the raspberry flavor, which is chemically more complicated than the popular framing suggests. The dominant compound responsible for the raspberry flavor, raspberry ketone, has not been detected in Sagittarius B2 or anywhere else in the interstellar medium.
The claim that space tastes like raspberries reduces a finding about one specific dust cloud to a claim about space in general. The actual smell of low-earth orbit, according to astronauts, is closer to a welding shop than a fruit bowl. The smell is produced by ionized oxygen atoms from the upper atmosphere bonding to materials on the exterior of spacesuits, releasing a distinctive metallic odour. The chemistry behind this is not fully understood, but it is not related to the raspberry or rum scent.
The Belloche detection of ethyl formate and n-propyl cyanide was scientifically important because it demonstrated that complex organic molecules with the kind of branched structures characteristic of biological compounds can form in the interstellar medium under cold, low-density conditions. The implication is that the chemistry of life is not unique to planetary surfaces, and the kinds of molecules that life on Earth uses to build itself can be assembled by the slow physics of interstellar space. The next stage of complexity, which Belloche and others continue to search for, is the detection of the amino acids themselves.
The question of whether the chemistry of life can occur in interstellar space is one of the most important open questions in astrobiology. If amino acids and other biological precursors are routinely produced in molecular clouds before stars form, then every star that forms in such a cloud, including the Sun, would have inherited a starting inventory of organic chemistry from the cloud it formed in. This would substantially change the picture of how Earth got its first organic molecules and how common life-relevant chemistry might be in other planetary systems.
The Belloche detection of ethyl formate and n-propyl cyanide is one step in answering that question. Each detection of a new and more complex molecule in Sagittarius B2 narrows the gap between the chemistry that interstellar space has been confirmed to produce and the chemistry that biological life requires. The underlying research continues at the same telescopes, in the same molecular cloud, with the same patient methods, moving in the right direction towards understanding the origins of life.
