January 23, 2023

Ices are a necessary component if you want to create a planet that is habitable because they are the primary source of several essential elements, including carbon, hydrogen, oxygen, nitrogen, and sulfur (referred to here as CHONS). These substances play a significant role in the composition of simple amino acids, sugars, and alcohols as well as planetary atmospheres.

An extensive inventory of the deepest, coldest ices ever observed in a molecular cloud has been compiled by an international team of astronomers using NASA's James Webb Space Telescope. The team was able to recognize frozen versions of a variety of compounds, including carbonyl sulfide, ammonia, and methane as well as the most basic complex organic molecule, methanol, in addition to simple ices like water. (The researchers defined complex organic compounds as those with six or more atoms.) This is the most thorough inventory to date of the ice building blocks that can be used to create stars and planets in the future, before they are heated during the formation of newborn stars.

Melissa McClure, an astronomer at Leiden Observatory in the Netherlands and the principal investigator of the observing program as well as the lead author of the paper describing this result, said that "our results provide insights into the initial, dark chemistry stage of the formation of ice on the interstellar dust grains that will grow into the centimeter-sized pebbles from which planets form in disks." These findings "provide a new window into the production paths for the simple and complex molecules required to produce the fundamental constituents of life."

The scientists also discovered evidence for molecules more complicated than methanol. Although they were unable to identify these signals with certainty, this establishes for the first time that complex molecules originate in the frigid depths of molecular clouds prior to the formation of stars.

Will Rocha, an astronomer at Leiden Observatory who contributed to this discovery, continued, "Our identification of complex organic molecules, like methanol and possibly ethanol, also suggests that many star and planetary systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state. This would indicate that the presence of precursors to prebiotic chemicals in planetary systems is a typical outcome of star formation rather than a peculiarity of our solar system.

The researchers were able to determine the amount of sulfur buried in icy pre-stellar dust grains for the first time by spotting the sulfur-bearing ice carbonyl sulfide. Despite being greater than previously seen, the amount detected is still less than the total amount that, given this cloud's density, should be present. This also applies to the other CHONS components. Understanding whether these components are buried in ice, soot-like substances, or rocks is a major difficulty for astronomers. How much of these elements wind up in exoplanet atmospheres and how much of them end up in their interiors depends on the amount of CHONS in each type of material.

Source - NASA