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NASA’s Webb Discovers Ethanol and Other Icy Ingredients for Potential Worlds.

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On March 13, 2024, this article was updated to provide clarification on the presence of chemicals around IRAS 2A and their significance in the early stages of our solar system’s development. Margaritas, vinegar, and ant stings may seem unrelated, but they share common chemical components identified by NASA’s James Webb Space Telescope around two young protostars, IRAS 2A and IRAS 23385.

While planets have yet to form around these stars, the molecules detected, including ethanol and possibly acetic acid, are vital building blocks for potentially habitable worlds. Utilizing Webb’s Mid-Infrared Instrument (MIRI), an international team of astronomers identified various icy compounds rich in complex organic molecules, expanding upon previous detections in cold, dark molecular clouds.

The Parallel Field: MIRI Image Reveals Insights into Protostar IRAS 23385.


This image at a wavelength of 15 microns was taken by MIRI (the Mid-Infrared Instrument) on NASA’s James Webb Space Telescope, of a region near the protostar known as IRAS 23385.

Captured at a wavelength of 15 microns, this image was produced by the Mid-Infrared Instrument (MIRI) aboard NASA’s James Webb Space Telescope, showcasing a region adjacent to the protostar designated as IRAS 23385. While IRAS 2A remains unseen in this specific image, both it and IRAS 23385 served as focal points for a recent collaborative research endeavor conducted by an international team of astronomers. Their study, facilitated by Webb’s advanced capabilities, unveiled the presence of crucial ingredients necessary for the formation of potentially habitable worlds within early-stage protostars, even before the inception of planetary bodies.

Contribution of complex organic molecules (COMes) in the protostellar evolution.

Team leader Will Rocha from Leiden University in the Netherlands emphasized the significance of this discovery, stating, “This finding contributes to one of the long-standing questions in astrochemistry: What is the origin of complex organic molecules, or COMs, in space? Are they made in the gas phase or in ices? The detection of COMs in ices suggests that solid-phase chemical reactions on the surfaces of cold dust grains can build complex kinds of molecules.

Previously, various COMs, including those identified in the solid phase during this research, had been detected in the warm gas phase. However, this recent revelation suggests that they likely originate from the sublimation of ices—directly transitioning from a solid to a gas without becoming a liquid. Therefore, the detection of COMs in ices offers astronomers newfound hope for a deeper understanding of the origins of other, potentially larger molecules present in the vast expanses of space.

Scientists are eager to investigate the extent to which these complex organic molecules (COMs) are transported to planets during later stages of protostellar evolution. It is believed that COMs in cold ices are more readily transported from molecular clouds to planet-forming disks compared to their warmer, gaseous counterparts. These icy COMs have the potential to be incorporated into comets and asteroids, which could subsequently collide with developing planets, potentially providing the necessary ingredients for life to thrive.

Additionally, the science team identified simpler molecules alongside COMs, including formic acid (known for its role in ant stings), methane, formaldehyde, and sulfur dioxide. Research indicates that sulfur-containing compounds such as sulfur dioxide likely played a significant role in driving metabolic reactions on early Earth, highlighting the potential importance of these molecules in the emergence of life.

Webb detects icy complex organic molecules and ions.

Complex organic molecules (COMs) are frequently detected in the gas phase and are believed to primarily form on icy grains. However, unambiguous detections of COMs larger than CH3OH in ices have yet to be reported. The James Webb Space Telescope (JWST) now offers unprecedented opportunities to delve into this topic further, thanks to its remarkable capabilities within the infrared (IR) spectral range. With its high sensitivity and spectral resolution in the critical 5–10 µm range, which is the fingerprint region of oxygen-bearing COMs, JWST enables detailed investigations that were previously unattainable.

As part of the JWST Observations of Young protoStars (JOYS+) program, over 30 protostars are currently under observation using the Medium Resolution Spectrograph (MRS) of the Mid-IR Instrument (MIRI). This study aims to comprehensively explore the signatures of COMs in ices in both low- and high-mass protostars: NGC 1333 IRAS 2A and IRAS 23385+6053, respectively.

Methods: The analysis began with global continuum and silicate subtractions of the MIRI-MRS spectra, followed by a local continuum subtraction in the optical depth scale around the 6.8 to 8.6 µm range, known as the ice COM fingerprint region. Different approaches for the local continuum and silicate subtraction were explored. Subsequently, observational data were fitted with a diverse sample of available IR laboratory ice spectra using the ENIIGMA fitting tool, a genetic algorithm-based code. This tool not only identifies the best fit between lab data and observations but also conducts statistical analyses to derive confidence intervals and quantify fit degeneracy.

Results: The study reports the best fits for spectral ranges between 6.8 and 8.6 µm in NGC 1333 IRAS 2A and IRAS 23385+6053, revealing signatures from simple molecules, COMs, and negative ions. The analysis indicates the necessity of ten chemical species to accurately reproduce the astronomical data. The prominent feature in this range (7.7 µm) is primarily attributed to CH4, with contributions from SO2 and OCN−. Strong detections of COMs, such as CH3CHO, CH3CH2OH, and CH3OCHO, are supported by multiple bands, along with a probable detection of CH3COOH.

The study also suggests that these COMs are likely formed on icy grains based on ice column density ratios. Furthermore, ice abundances in NGC 1333 IRAS 2A show a notable correlation with those in comet 67P/GC, supporting the idea of inherited cometary COMs from early protostellar phases.

Conclusions: The high-quality JWST (MIRI-MRS) spectra provide compelling evidence for the presence of COMs in interstellar ices, reinforcing the solid-state origin of these species in star-forming regions. The correlation between ice abundances in comet 67P and NGC 1333 IRAS 2A suggests a significant inheritance of cometary COMs from early protostellar phases.

Complex organic molecules are shown in this IRAS 2A.

 


Webb’s MIRI detects complex organic molecules in interstellar ices around protostars.

Utilizing NASA’s James Webb Space Telescope’s Mid-Infrared Instrument (MIRI), researchers have discerned an array of complex organic molecules within interstellar ices enveloping two protostars. Among these molecules, pivotal for the formation of potentially habitable worlds, are ethanol, formic acid, methane, and probably acetic acid, all in solid form. This discovery emerged from the examination of two nascent protostars, IRAS 2A and IRAS 23385, both at such early stages of development that planetary formation has yet to commence.

This research has been accepted for publication in the journal Astronomy & Astrophysics.

There are similarities in the early stages of our solar system.

Of particular significance is the investigation of IRAS 2A, identified as a low-mass protostar, which bears resemblance to the early stages of our solar system. The chemicals detected around IRAS 2A may have been present during the nascent phases of our own solar system and subsequently transported to the primitive Earth. Ewine van Dishoeck of Leiden University, a coordinator of the science program, noted, “All of these molecules can become part of comets and asteroids and eventually new planetary systems when the icy material is transported inward to the planet-forming disk as the protostellar system evolves.
The team anticipates further exploration of this astrochemical pathway with additional data from the James Webb Observations of Young ProtoStars (JOYS+) program in the coming years.These observations were conducted under the JOYS+ program. The team dedicates these findings to Harold Linnartz, a member who unexpectedly passed away in December 2023, shortly after the acceptance of this paper.

NASA’s Webb Discovers Ethanol and Other Icy Ingredients for Potential Worlds.

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