Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and the composition of their atmospheres. The initial ice composition is set in the cold, dense parts of molecular clouds, before the onset of star formation. With the exquisite sensitivity of the James Webb Space Telescope, this critical stage of ice evolution is now accessible for detailed study. Here we show initial results of the Early Release Science programme Ice Age that reveal the rich composition of these dense cloud ices. Weak ice features, including 13CO2, OCN−, 13CO, OCS and complex organic molecule functional groups, are now detected along two pre-stellar lines of sight. The 12CO2 ice profile indicates modest growth of the icy grains. Column densities of the major and minor ice species indicate that ices contribute between 2% and 19% of the bulk budgets of the key C, O, N and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice-rich environment.
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Our raw data are publicly available at the STScI MAST JWST archive. Text files of our enhanced one-dimensional spectra are provided as part of our Early Release Science enabling product deliverables on Zenodo at the following URL: https://doi.org/10.5281/zenodo.7501239.
Dulieu, F. et al. Experimental evidence for water formation on interstellar dust grains by hydrogen and oxygen atoms. Astron. Astrophys. 512, A30 (2010).
Ioppolo, S., Cuppen, H., Romanzin, C., van Dishoeck, E. & Linnartz, H. Laboratory evidence for efficient water formation in interstellar ices. Astrophys. J. 686, 1474 (2008).
Qasim, D. et al. An experimental study of the surface formation of methane in interstellar molecular clouds. Nat. Astron. 4, 781–785 (2020).
Lamberts, T. et al. Methane formation in cold regions from carbon atoms and molecular hydrogen. Astrophys. J. 928, 48 (2022).
Hiraoka, K. et al. Ammonia formation from the reactions of H atoms with N atoms trapped in a solid N2 matrix at 10–30 K. Astrophys. J. 443, 363–370 (1995).
Fedoseev, G., Ioppolo, S. & Linnartz, H. Deuterium enrichment of ammonia produced by surface N + H/D addition reactions at low temperature. Mon. Not. R. Astron. Soc. 446, 449–458 (2015).
Caselli, P., Walmsley, C., Tafalla, M., Dore, L. & Myers, P. CO depletion in the starless cloud core L1544. Astrophys. J. 523, L165 (1999).
Pontoppidan, K. M. Spatial mapping of ices in the Ophiuchus-F core—a direct measurement of CO depletion and the formation of CO2. Astron. Astrophys. 453, L47–L50 (2006).
Watanabe, N. & Kouchi, A. Measurements of conversion rates of CO to CO2 in ultraviolet-induced reaction of D2O(H2O)/CO amorphous ice. Astrophys. J. 567, 651 (2002).
Chuang, K.-J., Fedoseev, G., Ioppolo, S., van Dishoeck, E. & Linnartz, H. H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices—an extended view on complex organic molecule formation. Mon. Not. R. Astron. Soc. 455, 1702–1712 (2016).
Altwegg, K. et al. Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov–Gerasimenko. Sci. Adv. 2, e1600285 (2016).
Ioppolo, S. et al. A non-energetic mechanism for glycine formation in the interstellar medium. Nat. Astron. 5, 197–205 (2021).
Gibb, E. L. et al. Interstellar ice: the Infrared Space Observatory legacy. Astrophys. J. Suppl. Ser. 151, 35 (2004).
Boogert, A. et al. The c2d Spitzer Spectroscopic Survey of ices around low-mass young stellar objects. I. H2O and the 5–8 μm bands. Astrophys. J. 678, 985 (2008).
Aikawa, Y. et al. Akari observations of ice absorption bands towards edge-on young stellar objects. Astron. Astrophys. 538, A57 (2012).
Boogert, A., Gerakines, P. A. & Whittet, D. C. Observations of the icy universe. Annu. Rev. Astron. Astrophys. 53, 541–581 (2015).
Noble, J., Fraser, H., Pontoppidan, K. & Craigon, A. Two-dimensional ice mapping of molecular cores. Mon. Not. R. Astron. Soc. 467, 4753–4762 (2017).
Belloche, A. et al. The end of star formation in Chamaeleon I? A LABOCA census of starless and protostellar cores. Astron. Astrophys. 527, A145 (2011).
Dzib, S. A., Loinard, L., Ortiz-León, G. N., Rodríguez, L. F. & Galli, P. A. Distances and kinematics of Gould Belt star-forming regions with Gaia DR2 results. Astrophys. J. 867, 151 (2018).
Jin, M. et al. Ice Age: chemodynamical modeling of Cha-MMS1 to predict new solid-phase species for detection with JWST. Astrophys. J. 935, 133 (2022).
Jakobsen, P. et al. The near-infrared spectrograph (NIRSpec) on the James Webb Space Telescope—I. overview of the instrument and its capabilities. Astron. Astrophys. 661, A80 (2022).
Greene, T. P. et al. λ = 2.4 to 5 μm spectroscopy with the James Webb Space Telescope NIRCam instrument. J. Astron. Telesc. Instrum. Syst. 3, 035001 (2017).
Rieke, G. H. et al. The mid-infrared instrument for the James Webb Space Telescope, I: introduction. Publ. Astron. Soc. Pac. 127, 584 (2015).
Dartois, E., Noble, J. A., Ysard, N., Demyk, K. & Chabot, M. Influence of grain growth on CO2 ice spectroscopic profiles: modelling for dense cores and disks. Astron. Astrophys. 666, A153 (2022).
Mumma, M. J. & Charnley, S. B. The chemical composition of comets-emerging taxonomies and natal heritage. Annu. Rev. Astron. Astrophys. 49, 471–524 (2011).
Ferrante, R. F., Moore, M. H., Spiliotis, M. M. & Hudson, R. L. Formation of interstellar OCS: radiation chemistry and IR spectra of precursor ices. Astrophys. J. 684, 1210 (2008).
Laas, J. C. & Caselli, P. Modeling sulfur depletion in interstellar clouds. Astron. Astrophys. 624, A108 (2019).
Köhler, M., Jones, A. & Ysard, N. A hidden reservoir of Fe/FeS in interstellar silicates? Astron. Astrophys. 565, L9 (2014).
Calmonte, U. et al. Sulphur-bearing species in the coma of comet 67P/Churyumov–Gerasimenko. Mon. Not. R. Astron. Soc. 462, S253–S273 (2016).
Dartois, E. & d’Hendecourt, L. Search for NH3 ice in cold dust envelopes around YSOs. Astron. Astrophys. 365, 144–156 (2001).
van Scheltinga, J. T., Ligterink, N., Boogert, A., van Dishoeck, E. & Linnartz, H. Infrared spectra of complex organic molecules in astronomically relevant ice matrices—I. acetaldehyde, ethanol, and dimethyl ether. Astron. Astrophys. 611, A35 (2018).
Yang, Y.-L. et al. CORINOS I: JWST/MIRI spectroscopy and imaging of a class 0 protostar IRAS 15398-3359. Astrophys. J. Lett. 941, L13 (2022).
Rachid, M. G. et al. Infrared spectra of complex organic molecules in astronomically relevant ice mixtures. II. Acetone. Astron. Astrophys. 639, A4 (2020).
Goumans, T., Uppal, M. A. & Brown, W. A. Formation of CO2 on a carbonaceous surface: a quantum chemical study. Mon. Not. R. Astron. Soc. 384, 1158–1164 (2008).
Garrod, R. T. & Pauly, T. On the formation of CO2 and other interstellar ices. Astrophys. J. 735, 15 (2011).
Qasim, D. et al. Formation of interstellar methanol ice prior to the heavy CO freeze-out stage. Astron. Astrophys. 612, A83 (2018).
Molpeceres, G. et al. Carbon atom reactivity with amorphous solid water: H2O-catalyzed formation of H2CO. J. Phys. Chem. Lett. 12, 10854–10860 (2021).
Brooke, T., Sellgren, K. & Smith, R. A study of absorption features in the 3 micron spectra of molecular cloud sources with H2O ice bands. Astrophys. J. 459, 209 (1996).
Silsbee, K., Ivlev, A. V., Sipilä, O., Caselli, P. & Zhao, B. Rapid elimination of small dust grains in molecular clouds. Astron. Astrophys. 641, A39 (2020).
Ormel, C., Min, M., Tielens, A., Dominik, C. & Paszun, D. Dust coagulation and fragmentation in molecular clouds—II. The opacity of the dust aggregate size distribution. Astron. Astrophys. 532, A43 (2011).
Horne, K. An optimal extraction algorithm for CCD spectroscopy. Publ. Astron. Soc. Pac. 98, 609 (1986).
Sun, F. et al. First peek with JWST/NIRCam wide-field slitless spectroscopy: serendipitous discovery of a strong [O III]/Hα emitter at z = 6.11. Astrophys. J. Lett. 936, L8 (2022).
Carnall, A. SpectRes: a fast spectral resampling tool in Python. Preprint at https://arxiv.org/abs/1705.05165 (2017).
Boogert, A. et al. Ice and dust in the quiescent medium of isolated dense cores. Astrophys. J. 729, 92 (2011).
Dorschner, J., Begemann, B., Henning, T., Jaeger, C. & Mutschke, H. Steps toward interstellar silicate mineralogy. II. Study of Mg-Fe-silicate glasses of variable composition. Astron. Astrophys. 300, 503 (1995).
Dominik, C., Min, M. & Tazaki, R. Optool: command-line driven tool for creating complex dust opacities. Astrophysics Source Code Library ascl:2104.010 (2021).
Rocha, W. R., Perotti, G., Kristensen, L. E. & Jørgensen, J. K. Fitting infrared ice spectra with genetic modelling algorithms-presenting the eniigma fitting tool. Astron. Astrophys. 654, A158 (2021).
Rocha, W. et al. LIDA—the Leiden ice database for astrochemistry. Astron. Astrophys. 668, A63 (2022).
Pontoppidan, K. M. et al. The c2d Spitzer Spectroscopic Survey of ices around low-mass young stellar objects. II. CO2. Astrophys. J. 678, 1005 (2008).
Cuppen, H., Penteado, E. & Isokoski, K. et al. CO ice mixed with CH3OH: the answer to the non-detection of the 2152 cm−1 band? Mon. Not. R. Astron. Soc. 417, 2809–2816 (2011).
Perotti, G. et al. Linking ice and gas in the Serpens low-mass star-forming region. Astron. Astrophys. 643, A48 (2020).
Öberg, K. I. et al. The c2d Spitzer Spectroscopic Survey of ices around low-mass young stellar objects. III. CH4. Astrophys. J. 678, 1032 (2008).
Pontoppidan, K. et al. A μm VLT spectroscopic survey of embedded young low mass stars I—structure of the CO ice. Astron. Astrophys. 408, 981–1007 (2003).
Öberg, K. I. et al. Effects of CO2 on H2O band profiles and band strengths in mixed H2O:CO2 ices. Astron. Astrophys. 462, 1187–1198 (2007).
Knez, C. et al. Spitzer mid-infrared spectroscopy of ices toward extincted background stars. Astrophys. J. 635, L145 (2005).
Chu, L. E., Hodapp, K. & Boogert, A. Observations of the onset of complex organic molecule formation in interstellar ices. Astrophys. J. 904, 86 (2020).
Hudgins, D., Sandford, S., Allamandola, L. & Tielens, A. Mid-and far-infrared spectroscopy of ices-optical constants and integrated absorbances. Astrophys. J. Suppl. Ser. 86, 713–870 (1993).
Shimonishi, T., Dartois, E., Onaka, T. & Boulanger, F. VLT/ISAAC infrared spectroscopy of embedded high-mass YSOs in the large magellanic cloud: methanol and the 3.47 μm band. Astron. Astrophys. 585, A107 (2016).
Gerakines, P., Schutte, W., Greenberg, J. & van Dishoeck, E. F. The infrared band strengths of H2O, CO and CO2 in laboratory simulations of astrophysical ice mixtures. Astron. Astrophys. 296, 810 (1995).
Ehrenfreund, P., Boogert, A., Gerakines, P., Tielens, A. & van Dishoeck, E. Infrared spectroscopy of interstellar apolar ice analogs. Astron. Astrophys. 328, 649–669 (1997).
Ehrenfreund, P. et al. Laboratory studies of thermally processed H2O–CH3OH–CO2 ice mixtures and their astrophysical implications. Astron. Astrophys. 350, 240–253 (1999).
van Broekhuizen, F., Keane, J. & Schutte, W. A quantitative analysis of OCN− formation in interstellar ice analogs. Astron. Astrophys. 415, 425–436 (2004).
Pendleton, Y., Tielens, A., Tokunaga, A. & Bernstein, M. The interstellar 4.62 micron band. Astrophys. J. 513, 294 (1999).
van Broekhuizen, F., Pontoppidan, K., Fraser, H. & van Dishoeck, E. A 3–5 μm VLT spectroscopic survey of embedded young low mass stars II—solid OCN. Astron. Astrophys. 441, 249–260 (2005).
Noble, J. A. et al. The thermal reactivity of HCN and NH3 in interstellar ice analogues. Mon. Not. R. Astron. Soc. 428, 3262–3273 (2013).
van Broekhuizen, F., Groot, I., Fraser, H., van Dishoeck, E. & Schlemmer, S. Infrared spectroscopy of solid CO–CO2 mixtures and layers. Astron. Astrophys. 451, 723–731 (2006).
Palumbo, M., Tielens, A. & Tokunaga, A. T. Solid carbonyl sulphide (OCS) in W33A. Astrophys. J. 449, 674 (1995).
Palumbo, M., Geballe, T. & Tielens, A. G. Solid carbonyl sulfide (OCS) in dense molecular clouds. Astrophys. J. 479, 839 (1997).
Yarnall, Y. Y. & Hudson, R. L. A new method for measuring infrared band strengths in H2O ices: first results for OCS, H2S, and SO2. Astrophys. J. Lett. 931, L4 (2022).
Rachid, M. G., Rocha, W. & Linnartz, H. Infrared spectra of complex organic molecules in astronomically relevant ice mixtures—V. methyl cyanide (acetonitrile). Astron. Astrophys. 665, A89 (2022).
Gerakines, P. A., Yarnall, Y. Y. & Hudson, R. L. Direct measurements of infrared intensities of HCN and H2O + HCN ices for laboratory and observational astrochemistry. Mon. Not. R. Astron. Soc. 509, 3515–3522 (2022).
de Oliveira, C. A. et al. Herschel view of the large-scale structure in the Chamaeleon dark clouds. Astron. Astrophys. 568, A98 (2014).
André, P. et al. From filamentary clouds to prestellar cores to the stellar IMF: initial highlights from the Herschel Gould Belt Survey. Astron. Astrophys. 518, L102 (2010).
Lacy, J. H., Sneden, C., Kim, H. & Jaffe, D. T. H2, CO, and dust absorption through cold molecular clouds. Astrophys. J. 838, 66 (2017).
Przybilla, N., Nieva, M.-F. & Butler, K. A cosmic abundance standard: chemical homogeneity of the solar neighborhood and the ISM dust-phase composition. Astrophys. J. 688, L103 (2008).
Bouilloud, M. et al. Bibliographic review and new measurements of the infrared band strengths of pure molecules at 25 K: H2O, CO2, CO, CH4, NH3, CH3OH, HCOOH and H2CO. Mon. Not. R. Astron. Soc. 451, 2145–2160 (2015).
Schutte, W. & Khanna, R. Origin of the 6.85 μm band near young stellar objects: the ammonium ion (NH4+) revisited. Astron. Astrophys. 398, 1049–1062 (2003).
Boogert, A., Schutte, W., Helmich, F., Tielens, A. & Wooden, D. Infrared observations and laboratory simulations of interstellar CH4 and SO2. Astron. Astrophys. 317, 929–941 (1997).
Taban, I. M. et al. Stringent upper limits to the solid NH3 abundance towards W33A from near-IR spectroscopy with the Very Large Telescope. Astron. Astrophys. 399, 169 (2003).
Hudson, R. L. & Moore, M. H. Laboratory studies of the formation of methanol and other organic molecules by water+carbon monoxide radiolysis: relevance to comets, icy satellites, and interstellar ices. Icarus 140, 451 (1999).
Rocha, W. R. M. et al. Infrared complex refractive index of astrophysical ices exposed to cosmic rays simulated in the laboratory. Mon. Not. R. Astron. Soc. 464, 754 (2017).
The Ice Age Early Release Science team thanks the support team at STScI (W. Januszewski, B. Sargent, N. Pirzkal and M. Engesser) for their technical suggestions and improvements to the programme since 2017. M.K.M. acknowledges financial support from the Dutch Research Council (NWO; grant VI.Veni.192.241). M.G.R. acknowleges support from the Netherlands Research School for Astronomy (NOVA). S.I., H.L. and E.F.v.D. acknowledge support from the Danish National Research Foundation through the Center of Excellence ‘InterCat’ (grant agreement number DNRF150). E.F.v.D. acknowledges support from ERC grant 101019751 MOLDISK. The research of L.E.K. is supported by a research grant (19127) from VILLUM FONDEN. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (D.C.L.). F.S. acknowledges funding from JWST/NIRCam contract to the University of Arizona, NAS5-02105. A.C.A.B. acknowledges support from the Space Telescope Science Institute for programme JWST-ERS-01309.019. J.E. acknowledges support from the Space Telescope Science Institute for programme JWST-ERS-01309.019. L.E.U.C.’s research was supported by an appointment to the NASA Postdoctoral Program at the NASA Ames Research Center, administered by Oak Ridge Associated Universities under contract with NASA. D.H. is supported by Center for Informatics and Computation in Astronomy (CICA) grant and grant number 110J0353I9 from the Ministry of Education of Taiwan. D.H. acknowledges support from the National Technology and Science Council of Taiwan through grant number 111B3005191. M.N.D. acknowledges the Swiss National Science Foundation (SNSF) Ambizione grant number 180079, the Center for Space and Habitability (CSH) Fellowship, and the IAU Gruber Foundation Fellowship. I.J.-S. acknowledges financial support from grant number PID2019-105552RB-C41 by the Spanish Ministry of Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033. This work was supported by a grant from the Simons Foundation (686302, K.I.Ö.) and an award from the Simons Foundation (321183FY19, K.I.Ö.). J.K.J. acknowledges support from the Independent Research Fund Denmark (grant number 0135-00123B). Z.L.S. acknowledges financial support from the Royal Astronomical Society through the E. A. Milne Travelling Fellowship. J.A.N. and E.D. acknowledge support from French Programme National ‘Physique et Chimie du Milieu Interstellaire’ (PCMI) of the CNRS/INSU with the INC/INP, co-funded by the CEA and the CNES.
The authors declare no competing interests.
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Combined NIRSpec and MIRI/LRS spectrum of the NIR38 source (black), with the ENIIGMA fitting tool model (green). Each component in the fit is colour-coded. Panel a shows the entire range between 2.5 and 13 μm and the residuals of the fit. Panels b-f show a zoom-in of selected ranges corresponding to the major ice components. Small insets show the fit of 12CO2 (Panel b), 13CO2 (Panel c), 13CO (panel d) and CH4 (panel e).
Combined NIRSpec and MIRI/LRS spectrum of the J110621 source (black), with the ENIIGMA fitting tool model (green). Each component in the fit is colour-coded. Panel a shows the entire range between 2.5 and 13 μm and the residuals of the fit. Panels b-f show a zoom-in of selected ranges corresponding to the major ice components. Small insets show the fit of 13CO2 (Panel c), 13CO (panel d) and CH4 (panel e).
Corner plot showing the confidence interval analysis of the coefficients in the linear combination. The grey-scale contours show the differences in the χ2 maps (Δ) which depends on the degree of freedom (ν) and the statistical significance (α). The yellow and red line contours indicate 2 and 3σ confidence intervals. The left and right plots are for NIR38 (AV = 60 mag) and J110621 (AV = 95 mag), respectively. Note that the ice species assigned to w1-w6 is automatically determined and differs between the left and right panels.
Extended Data Fig. 4 Observed absorption profile of the 13CO2 asymmetric stretching, around 4.39 μm, in NIR38 (left panel) and J110621 (right panel).
To demonstrate the ice chemical environment that best reproduces the observed feature peak, the coloured curves show the scaled profiles of 13CO2 in laboratory spectra of the following ice mixtures at 10 K: pure CO2 (blue), H2O:CO2 (orange), CO2:CO (green), and CO2:CH3OH (red). In all the ice mixtures, CO2 is diluted in a ratio of ~ 1:10, with 12CO2/13CO2 ~ 90.
Extended Data Fig. 5 Observed absorption profile of the 13CO stretching, around 4.78 μm, towards NIR38 (left panel) and J110621 (right panel).
The laboratory spectra of pure 13CO ice at 10 K are also shown in blue.
MIRI/LRS spectrum of the two background stars before (black) and after (blue) silicate subtraction. The grey dashed line is the synthetic silicate spectrum used to remove the silicate absorption toward the background stars.
Extended Data Fig. 7 Observed absorption profile of the OCN− feature around 4.62 μm, towards NIR38 (left panel) and J110621 (right panel).
A Gaussian fit using the parameters found in the literature62 is also shown.
Extended Data Fig. 8 Observed absorption profile of the C=O stretching of OCS, around 4.9 μm, towards NIR38 (left panel) and J110621 (right panel).
The coloured curves show the profile of the OCS in laboratory ice spectra of pure OCS(blue), H2O:OCS (orange), and CH3OH:OCS (green), all at 17.5 K.
Extended Data Fig. 9 Optical depths of the AV = 60 mag (NIR38, left) and AV = 95 mag (J110621, right) background sources in the 3.2–3.8 μm (3125 - 2631 cm−1) region.
Top: The red line shows the optical depths of CH3OH laboratory data at 15K scaled for the C–H stretching band around the 3.53 μm feature. Bottom: The blue Gaussian represents the likely NH3 ⋅ H2O component centred at 3.47 μm and the red line again displays the CH3OH laboratory data but both are simultaneously scaled so the sum (in green) fits the data from 3.40-3.65 μm.
Extended Data Fig. 10 Map of the column density distribution in the region inferred from the Herschel far-infrared maps from 70 to 500 μm.
The cyan plus-signs indicate the locations of the Class I protostar Ced 110-IRS4, the Class 0 protostar ChamI-MMS and the clump Cha1-C2 going from the north-east (top-left) to south-west (bottom-right). The yellow box and cross indicate the location of the background stars NIR38 (AV ≈ 60 mag) and J110621 (AV ≈ 95 mag), respectively. The contours indicate increasing H2 column densities in steps of 5 × 1021 cm−2, starting at a value of 5 × 1021 cm−2 for the lowest contour (yellow line).
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McClure, M.K., Rocha, W.R.M., Pontoppidan, K.M. et al. An Ice Age JWST inventory of dense molecular cloud ices. Nat Astron (2023). https://doi.org/10.1038/s41550-022-01875-w