We have the ability to perform both ultraviolet (UV) photolysis (primarily Lyman‐α photons, average E ≈ 10.2 eV per photon) and ion irradiation (protons, E = 0.8 MeV) in the same experimental setup, with ices created under identical conditions. Here we present recent results on the UV and ion processing of ice mixtures at 18 K of the composition H 2 O + CO 2 + CH 3 OH (1:1:1) and H 2 O + CO 2 + CH 4 (1:1:1). H 2 O, CH 3 OH, CH 4 , and CO 2 are all major components of ices in most astrophysical environments (whether interstellar, cometary, or planetary). Identifications and formation rates of products were measured. Results for photolyzed and irradiated ices are contrasted. We find that similar chemical products are observed in both cases and that rates of formation are equivalent for most of the major products.
We have the unique ability to perform ultraviolet photolysis (∼ 10 eV photon−1) and ion irradiation (0.8 MeV p+) in the same experimental set-up, with ices created under identical conditions. We present experiments that show the formation of carbonic acid (H2CO3) from H2O:CO2 ice mixtures exposed to either UV photons or high-energy protons. CO and CO3 were also formed in these experiments. Results show that while H2CO3 is readily formed by p+ bombardment, its formation by UV photolysis is limited by the penetration of UV photons into the ice. H2CO3 production pathways are investigated. Intrinsic IR band strengths are determined for eight IR features of H2CO3. Implications for ices found in various astrophysical environments are discussed.
We present searches for gas-phase CO2 features in the ISO-SWS infrared spectra of four deeply embedded massive young stars, which all show strong solid CO2 absorption. The abundance of gas-phase CO2 is at most 2 10 7 with respect to H2, and is less than 5% of that in the solid phase. This is in strong contrast to CO, which is a factor of 10-100 more abundant in the gas than in solid form in these objects. The gas/solid state ratios of CO2 ,C O and H 2O are discussed in terms of the physical and chemical state of the clouds.
Abstract Infrared (IR) spectral features of interstellar and solar system ices have been attributed to solid organic and inorganic compounds for over 50 yr, but in many cases the laboratory IR data needed to fully quantify such work have never been published, forcing researchers to rely on assumptions about gas- or liquid-phase measurements to interpret data for ices. Here, we report the first mid-IR intensity measurements for isocyanic acid (HNCO) ices that are free of such assumptions, providing new results for use by both observational and laboratory astrochemists. We also report similar new IR data for both formaldehyde (H 2 CO) and formic acid (HCOOH), which have been discussed in the astrochemical literature for decades, but again without adequate laboratory data to help quantify observational results. Densities and refractive indices of HNCO, H 2 CO, and HCOOH as amorphous ices also are reported. Two applications of the new H 2 CO work are presented, the first vapor-pressure measurements of solid H 2 CO, along with an enthalpy of sublimation, at 100 to 109 K and a set of IR intensities of H 2 CO in H 2 O + H 2 CO ices. Band strengths, absorption coefficients, and optical constants are calculated for all three compounds. Extensive comparisons are made to older results, which are not recommended for future use.
Comets are time capsules from the birth of our Solar System that record pre-solar history, the initial stages of planet formation, and the sources of prebiotic organics and volatiles for the origin of life. These capsules can only be opened in laboratories on Earth. CAESAR (Comet Astrobiology Exploration Sample Return)’s sample analysis objectives are to understand the nature of Solar System starting materials and how these components came together to form planets and give rise to life. Examination of these comet nucleus surface samples in laboratories around the world will also provide ground truth to remote observations of the innumerable icy bodies of the Solar System.
