If you want to build a habitable planet, ice is a vital ingredient because it is the primary source of several key elements, namely carbon, hydrogen, oxygen, nitrogen, and sulfur (referred to here as NOCs). These elements are essential ingredients of both planetary atmospheres and molecules such as sugars, alcohols, and simple amino acids.
An international group of astronomers using a space telescope James Webb NASA obtained a detailed inventory of the deepest and coldest ices measured to date in the molecular cloud. In addition to simple ice such as water, the team was able to identify the frozen forms of a wide range of molecules, from carbonyl sulfide, ammonia and methane to the simplest, complex organic molecule, methanol. (Researchers consider organic molecules to be complex if they contain six or more atoms.) This is the most complete list to date of the icy ingredients available to build future generations of stars and planets before they heat up as young stars form.
“Our results provide insight into the initial, dark chemical stage of ice formation on interstellar dust, which transforms into the centimeter-sized pebbles from which planets form in disks,” said Melissa McClure, an astronomer at the Leiden Observatory in the US. The Netherlands, who is the principal investigator of the surveillance program and the lead author of the article describing this result. “These observations open a new window into the ways in which the simple and complex molecules necessary to create the building blocks of life are formed.”
In addition to the molecules identified, the team found evidence for molecules more complex than methanol, and while they did not definitively attribute these signals to specific molecules, it is the first evidence that complex molecules form in the icy depths of molecular clouds. before the stars are born
“Our identification of complex organic molecules such as methanol and possibly ethanol also suggests that many star and planetary systems developing in this particular cloud are inheriting molecules in a fairly advanced chemical state,” added Will Rocha, astronomer from the Leiden Observatory, who contributed to the research. before this discovery. “This may mean that the presence of precursor prebiotic molecules in planetary systems is a general result of star formation, rather than a unique feature of our own solar system.”
Astronomers have conducted an inventory of the most deeply embedded ices in the cold molecular cloud to date. They used light from a background star called NIR38 to illuminate a dark cloud called Chamaeleon I. The ice within the cloud absorbed certain wavelengths of infrared light, leaving spectral imprints called absorption lines. These lines show which substances are present in the molecular cloud. These graphs show spectral data from three instruments on the James Webb Space Telescope. In addition to simple ice such as water, the science team was able to identify the frozen forms of a wide range of molecules, from carbon dioxide, ammonia and methane to the simplest complex organic molecule, methanol.Credit: NASA, ESA, CSA and J. Olmsted (STScI)
By discovering sulfur-containing ice carbonyl sulfide, researchers were able to estimate for the first time the amount of sulfur contained in icy prestellar dust particles. Although the measured amount is greater than previously observed, it is still less than the total amount expected in this cloud based on its density. This is also true for other CHONS elements. A key challenge for astronomers is understanding where these elements are hiding: in ice, soot-like materials or rocks. The amount of CHONS in each type of material determines how much of these elements end up in the exoplanet’s atmosphere and how much in their interior.
“The fact that we haven’t seen all the CHONS we expect could indicate that they are locked up in more rocky or carbonaceous materials that we can’t measure,” McClure explained. “This could allow for greater diversity in the basic composition of a terrestrial planet.”
The chemical characterization of the ice was done by studying how starlight from outside the molecular cloud is absorbed by the ice molecules inside the cloud at certain infrared wavelengths visible to the Webb. This process leaves behind chemical fingerprints known as absorption lines, which can be compared to laboratory data to determine which ices (frozen molecules) are present in the molecular cloud. In this study, the team targeted ices buried in a particularly cold, dense and difficult-to-probe region of the Chamaeleon I molecular cloud, a region about 500 light-years from Earth that is currently in the process of forming dozens of young stars.
“We simply wouldn’t be able to observe this ice without Webb,” said Klaus Pontoppidan, a Webb project scientist at the Space Telescope Science Institute in Baltimore, Maryland, who participated in the study. “The ice looks like depressions against the continuous background light of the stars. In such cold and dense regions, much of the light from the background star is blocked, and Webb’s exquisite sensitivity was necessary to detect the starlight and thus identify the ice in the molecular cloud.”
This research is part of the Ice Age Project, one of Webb’s 13 Early Release Science programs . These observations are intended to demonstrate Webb’s observational capabilities and allow the astronomical community to learn how to get the most out of its instruments. The Ice Age team has already planned further observations and hopes to trace the path of the ice from its formation to the icy comet cluster.
“This is just the first in a series of spectral snapshots we’ll get to see how the ice evolves from its initial synthesis to the comet-forming regions of protoplanetary disks,” McClure concluded. “This will tell us what mixture of ices—and therefore what elements—might eventually be delivered to the surface of terrestrial exoplanets or incorporated into the atmospheres of giant gas or ice planets.”
These results were published in the January 23 issue of the journal Nature Astronomy.
The James Webb Space Telescope is the world’s premier space science observatory. Webb will unravel the mysteries of our solar system, peer into distant worlds around other stars, and explore the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners ESA (European Space Agency) and the Canadian Space Agency.
