Space chemistry

The researchers advanced the understanding of comets and astronomical clouds. The first detailed analysis of infrared emission spectra recorded during 2005’s Deep Impact mission to comet Tempel 1 revealed that comets are made of an assortment of minerals, water, and other inorganic and organic materials (Science 2006, 313, 635). The study provided an unprecedented examination of the chemical nature of comet interiors and will help answer questions regarding the formation and evolution of solar system objects. The spectra included signatures of minerals such as magnesium-rich forsterite and iron-rich fayalite (both of which are in the olivine family); ferrosilite, an iron-rich pyroxene; and nontronite, a smectite clay containing iron, aluminum, and sodium. The spectra also contained signs of other minerals (such as amorphous carbon), polyaromatic hydrocarbons (which are linked to the source of organic material in the solar system), water ice, and metal sulfides.

For the first time, researchers observed in astronomical clouds large amounts of a negatively charged molecule: the hexatriyne anion, or C6H-. Until now, discoveries of compounds in space had been limited to 130 neutral molecules and 14 cations, with nary an anion among them. Detection of an anion in interstellar space overturns a widespread belief that radiation would quickly strip an anion of its extra electron, yielding a radical. The new finding also solves a spectral puzzle, identifying C6H- as the source of a mysterious set of rotational lines discovered in a molecular cloud more than 10 years ago. Observers said the addition of anions to the mix of known molecules in space alters the field of interstellar chemistry.

(Chemical & Engineering News, 2006)