Another key amino acid found in space: tryptophan
Astrochemistry is the study of how molecules can form and react in space. Its roots go back to the 19th century, when astronomers like William Wollaston and Joseph von Fraunhofer began to identify atomic elements from the Sun’s spectral lines. But it wasn’t until the last few decades that the field began to mature.
The first identification of a molecule in space was in 1910 during a close approach of Halley’s Comet. The astronomers detected the presence of cyanogen (CN) 2 in the comet’s tail. Also known as poisonous cyanide, the discovery caused a bit of a public panic . Radio astronomers discovered other simple molecules in the 1940s and 1950s, but it was not until 1969 that the more complex molecule of formaldehyde (CH 2 O) was discovered. Formaldehyde is one of the simplest carbohydrates. Since complex carbohydrates are fundamental to life on Earth, this discovery opened the door to the possibility of other organic molecules in space.
Meteorite studies showed the presence of many complex molecules, including amino acids. Amino acids are often referred to as the building blocks of life, as 22 of them are found in DNA and RNA, and living organisms use amino acids to build proteins. But identifying them in space is difficult. The more complex the molecule, the more complex its pattern of spectral lines, making it difficult to distinguish particular molecules.
But thanks to high-resolution spectroscopy, we’ve gotten better. In 2003, astronomers detected the presence of the first amino acid in an interstellar nebula. Glycine (C 2 H 5 NO 2 ) is the simplest stable amino acid and an inhibitory neurotransmitter. It was later observed in the tails of comets and in stellar nurseries, further suggesting that the amino acids of life first formed in space through abiotic processes.
Now another amino acid has been discovered in space. As published in the Monthly Notices of the Royal Astronomical Society , a team of astronomers has discovered C 11 H 12 N 2 O 2 , also known as tryptophan. You probably know it from Thanksgiving dinners and the apocryphal idea that turkey meat makes you sleepy. It is found in various types of meat, as well as plants such as oats and chickpeas. Since humans cannot make tryptophan and we need it to live, it is one of the essential amino acids.
The molecule was identified in the Perseus Molecular Complex, which is a group of molecular clouds and star-forming regions about 1,000 light-years from Earth. Using data from the Spitzer Infrared Telescope, the team identified 20 unique spectral emission lines from tryptophan. It was found in a fairly warm region of a star-forming region, at about 280 Kelvin. This suggests that other amino acids are likely to be found in warm molecular clouds.
