Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark interstellar clouds to the formation of planets and the composition of their atmospheres. The initial composition of the ice occurs in the cold, dense regions of molecular clouds before the start of star formation.
Using observational data from the James Webb Space Telescope (JWST), an international team including the Southwest Research Institute, Leiden University and NASA has successfully achieved the darkest image ever of a dense interstellar cloud.
JWST’s 6.5-meter-wide mirror, which offers remarkable spatial resolution and sensitivity optimized for infrared light, enabled the telescope to capture the densest, darkest clouds in the universe for the first time.
These findings have provided new insights into the chemical processes of one of the coldest, darkest regions of the universe, as well as the origins of the molecules that make up the planetary atmospheres by revealing the composition of a virtual treasure chest of ice from the early universe. .
SwRI Research Scientist dr. Danna Qasim, a study co-author, said: “The JWST allowed us to study ice that exists on dust grains in the darkest regions of interstellar molecular clouds. The clouds are so dense that this ice is largely shielded from the harsh radiation of nearby stars, so they are quite pristine. This are the first ices to form and also contain biogenic elements, which are important for life.”
“These observations provide new insights into the chemical processes in one of the coldest, darkest places in the universe to better understand the molecular origins of protoplanetary disks, planetary atmospheres and other objects in the solar system.”
“Most interstellar ice sheets contain very small amounts of elements such as oxygen and sulfur. We are trying to understand the lack of sulfur in interstellar ice.”
“The ice we observed contains only 1% of the sulfur we expect. 99% of that sulfur is locked up elsewhere, and we need to figure out where we can understand how sulfur will eventually be incorporated into the planets that might harbor life.
Scientists also suggested that sulfur may be trapped in reactive minerals such as iron sulfide, which can react with ice to form the observed sulfuric ice.
Qasim said, “Iron sulfide is a highly reactive mineral found in the accretion disks of young stars and samples returned from comets. It is also the most abundant sulfide mineral in lunar rocks.”
“If sulfur is trapped in these minerals, that could explain the low amount of sulfur in interstellar ice, which has implications for where sulfur is stored in our solar system. For example, the atmosphere of Venus has sulfur-containing molecules, where the sulfur could be partly derived from of interstellar inherited minerals.”
- McClure, MK, Rocha, WRM, Pontoppidan, KM et al. An Ice Age JWST inventory of dense molecular cloud ice. Wet Astron (2023). DOI: 10.1038/s41550-022-01875-w