Webb Enters the Frozen Heart of Molecular Cloud Unveils Pre-Stellar Ice Chemistry's Dark Side

Webb Enters the Frozen Heart of Molecular Cloud Unveils Pre-Stellar Ice Chemistry's Dark Side ...

Fengwu Sun (Steward Observatory), Zak Smith (The Open University), IceAge ERS Team, Image Processing: M. Zamani (ESA/Webb)

An international team of astronomers using NASA's James Webb Space Telescope has announced the discovery of diverse ices in the darkest areas of a cold molecular cloud measured to date. This result allows astronomers to investigate simple icy molecules that will be incorporated into future exoplanets, while opening a new window on the origin of more complex molecules that are the first steps toward life's building blocks.

Fengwu Sun (Steward Observatory), Zak Smith (The Open University), IceAge ERS Team, Image Processing: M. Zamani (ESA/Webb)

Ices are a vital component of any habitable planet because they are the main source of several key elements — carbon, hydrogen, oxygen, and sulfur (referred to here as CHONS). These elements are also important components in both planetary atmospheres and simple amino acids.

The most comprehensive census to date of the icy components required to create future generations of stars and planets, using NASA's James Webb Space Telescope[1]

Melissa McClure, an astronomer at the Leiden Observatory in the Netherlands, has been involved in the initial, dark chemistry phase of the formation of ice on interstellar dust grains that will grow into centimeter-sized pebbles from which planets form in disks, and the lead author of the paper detailing this finding.

NASA, ESA, CSA, and M. Zamani (ESA/Webb) are denoted on the image in white. F. Sun (Steward Observatory), Z. Smith (Open University), and the Ice Age ERS Team

The team also discovered evidence for other substances that are different from methanol, and, although they did not assign these signals to specific molecules, this is the first time that complex molecules exist in the icy depths of molecular clouds before stars.

"Our identification of complex organic molecules, such as methanol and perhaps ethanol, suggests that the many star and planetary systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state," said Will Rocha, an astronomer at the Leiden Observatory who contributed to this discovery. "This may suggest that the presence of precursors to prebiotic molecules in planetary systems is a common result of star formation, rather than a unique feature of our own solar system."

For the first time, researchers were able to estimate the amount of sulfur embedded in icy pre-stellar dust grains. This is also true for other CHONS elements, such as ices, soot-like materials, or rocks.

"The fact that we haven't seen all of the CHONS we expect might indicate that they're locked up in more rocky or sooty materials that we are unable to quantify," said McClure. "This might allow for a greater diversity in the bulk composition of terrestrial planets."

The upper-left panel depicts the background star's brightness versus wavelength, and highlights weaker spectral features of less abundant ice sheets. Photo credit: NASA, ESA, CSA, Joseph Olmsted (STScI), and Melissa McClure (Leiden Observatory)

The team focused on ices buried in a particularly cold, dense, and difficult-to-investigate region of the Chamaeleon I molecular cloud. Thousands of young stars are currently living in this region.

Klaus Pontoppidan, a Webb project scientist at the Space Telescope Science Institute in Baltimore, Maryland, explained that "the ices show up as dips against a continuum of background starlight." "Webb's exceptional sensitivity was required to detect the starlight and hence identify the ices in the molecular cloud."

The Ice Age project is a part of Webb's 13 Early Release Science programs. These observations are intended to demonstrate Webb's observation capabilities and to enable the astronomical community to learn how to utilize its instruments correctly. The Ice Age team is planning further observations, and is hoping to track the evolution of ices through the assemblage of icy comets.

"This is just the first of a series of spectral snapshots we will obtain to examine how the ices evolve from their initial synthesis to the protoplanetary disks' comet-forming regions," said McClure. "This will reveal which ices — and therefore which elements — may be delivered to terrestrial exoplanets or integrated into giant gas or ice planets' atmospheres."

The following findings were published in the Nature Astronomy issue on January 23.


M. K. McClure, W. R. M. Rocha, K. M. Pontoppidan, J. A. Noble, J. J. Perotti, D. Qasim, M. G. Rachid, Z. L. Smith, Fengwu Sun, Tracy L. Beck, A. C. A. Boogert, W. A. Brown, P. Caselli, S. E. Charnley, M. C. Garrod, J. K. J

The James Webb Space Telescope is the world's leading space science observatory. Webb will explore the world's hidden bodies, look beyond the far distant worlds around other stars, and explore the universe's mysterious structures and origins.

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