Energetic ions (galactic cosmic rays, solar wind, energetic solar ions) and UV
photons are believed to significantly contribute to the evolution of solid matter in astrophysical
environments. At the Laboratory for Experimental Astrophysics at INAF-Osservatorio
Astrofisico di Catania samples are exposed to space conditions such as high vacuum, low
temperature (15-300 K), UV irradiation (266 nm and Lyman-alpha at 121.6 nm) and fast ion
bombardment (60-400 keV) and are analyzed in situ by Infrared and Raman spectroscopy.
Ices, carbons and silicates have been processed and analyzed. In addition, extraterrestrial
dust particles (e.g. IDPs, cometary dust particles, and meteorites) have been characterized
by non destructive techniques such as micro-Raman and UV-Vis-IR spectroscopy.
Furthermore, spectra of extraterrestrial samples have been compared to spectra of laboratory
analogues. Here we present some of the most recent results relevant to Astrobiology
and the ongoing upgrade of the experimental set-up

Baratta, G.

OCCHIPINTI, Giovanni

PALUMBO, Maria Elisabetta

Scirè Scappuzzo, C.

STRAZZULLA, Giovanni

OA@INAF - Istituto Nazionale di Astrofisica

2021Publication Year2023-10-26T13:35:27ZAcceptance in OA@INAFAstrobiology studies and extraterrestrial sample analysis at the Laboratory for Experimental Astrophysics - CataniaTitlePALUMBO, Maria Elisabetta; Baratta, G.; OCCHIPINTI, Giovanni; Scirè Scappuzzo, C.; STRAZZULLA, GiovanniAuthorshttp://hdl.handle.net/20.500.12386/34459HandleMEMORIE DELLA SOCIETA ASTRONOMICA ITALIANAJournal92NumberMem. S.A.It. Vol. 92, 158© SAIt 2021 Memorie dellaAstrobiology studies and extraterrestrial sampleanalysis at the Laboratory for ExperimentalAstrophysics - CataniaM.E. Palumbo, G.A. Baratta, G. Occhipinti, C. Scirè, and G. StrazzullaIstituto Nazionale di Astrofisica (INAF) – Osservatorio Astrofisico di Catania, Via SantaSofia 78, I-95123 Catania, Italy; e-mail: maria.palumbo@inaf.itAbstract. Energetic ions (galactic cosmic rays, solar wind, energetic solar ions) and UVphotons are believed to significantly contribute to the evolution of solid matter in astrophys-ical environments. At the Laboratory for Experimental Astrophysics at INAF-OsservatorioAstrofisico di Catania samples are exposed to space conditions such as high vacuum, lowtemperature (15-300 K), UV irradiation (266 nm and Lyman-α at 121.6 nm) and fast ionbombardment (60-400 keV) and are analyzed in situ by Infrared and Raman spectroscopy.Ices, carbons and silicates have been processed and analyzed. In addition, extraterrestrialdust particles (e.g. IDPs, cometary dust particles, and meteorites) have been character-ized by non destructive techniques such as micro-Raman and UV-Vis-IR spectroscopy.Furthermore, spectra of extraterrestrial samples have been compared to spectra of labo-ratory analogues. Here we present some of the most recent results relevant to Astrobiologyand the ongoing upgrade of the experimental set-up.Key words. Astrobiology – Astrochemistry – Methods: laboratory – Techniques: spectro-scopic – Comets: general1. IntroductionMore than 200 molecular species have been de-tected in space1. Molecules are observed in theatmosphere of planets and satellites, on the sur-face of icy bodies, in comets, in the atmosphereof exo-planets and of evolved stars and in theinterstellar medium. The interstellar medium isthe nearly empty space between the stars. Itconsists of gas and dust grains and it is notan uniform environment. There are locations,known as molecular clouds, where the densityis relatively high so that molecules form and1 An updated list is available athttp://www.astrochymist.org/astrochymist ism.htmlare preserved. In molecular clouds, gas phasespecies adhere to the grain surface accretingan ice coating which is referred to as “icygrain mantle”. Molecular clouds are the site ofstar formation and complex organic moleculesformed in these regions have a chance to beincorporated in planets, satellites and cometsformed around a new star.Comets are among the most pristine ob-jects in the Solar System. When a comet fromthe Oort cloud or from the Kuiper belt (i.e., theTNOs region) enters the inner Solar System,the water ice-dominated sublimation at about3 au (astronomical units) or the sublimationof other more volatile species such as CO,Palumbo et al.: Astrobiology studies at INAF-Catania 159Fig. 1. Available instrumentation at the Laboratory for Experimental Astrophysics (INAF-Catania). On the left-hand side the ion source (Danfysik 1080-200). On the right-hand side theultra high vacuum (UHV) chamber (P<10−9 mbar) and the cryostat (15-300 K). The UHV cham-ber fits the sample compartment of the IR spectrometer (Bruker-Vertex 70).CO2, N2, CH4 at much longer heliocentric dis-tances (up to about 25 au) ejects gas and dust.Cometary dust constitutes a fraction of thoseinterplanetary dust particles (IDPs) that havebeen collected in Earth’s atmosphere by air-borne impacting collectors flown at an altitudeof 18-20 km and of those micrometeorites col-lected in Antarctica. The remaining fraction ofIDPs and of the micrometeorites come from as-teroids (e.g. Genge et al. 2008). Finally, IDPscould also have interstellar and planetary ori-gin.One of the key point for the synthesis ofthe first biomonomers is the availability of suit-able precursor organics under primitive Earthconditions. Indeed extraterrestrial organics in-cluded in IDPs and micrometeorites are be-lieved to have provided the precursor materialsto early Earth (e.g. Ruiz-Mirazo et al. 2014).It is largely accepted that solid objects inspace (interstellar grains, comets, interplane-tary dust particles), are continuously exposedto energetic processes such as cosmic ray ir-radiation and UV photolysis. The energy re-leased to the target by fast ions (E∼MeV)and UV photons (E∼10 eV) induces chemi-cal and physical modifications. As an exam-ple, complex organic molecules are formed af-ter ion bombardment and UV photolysis ofice mixtures made of simple molecules (e.g.Öberg et al. 2009; Modica & Palumbo 2010;Kaňuchová et al. 2016; Urso et al. 2017).On the other hand, complex organic moleculestrapped in IDPs and micrometeorites could bedestroyed by galactic cosmic rays (GCRs), so-lar UV photons, and the solar ion populationbefore reaching Earth or other objects in theSolar System.2. Recent resultsMost of the knowledge on the effects of en-ergetic processing on astrophysical relevantanalogs (ices, carbons, and silicates) is basedon laboratory experiments. The Laboratory forExperimental Astrophysics at INAF-Catania(Italy) is fully equipped for these studies.Figure 1 shows part of the available instru-mentations. The main constituents are theultra high vacuum chamber (UHV; P<10−9mbar), the closed-cycle He cryocooler (CTI),the ion implanter (Danfysik 1080-200), amicrowave powered Lyman-alpha resonancelamp (OPTHOS) with a system for “in situ”real-time measurement of the UV photon flux,and a Nd-YAG 266 nm UV laser. Further de-tails on the experimental set up and procedurecan be found in Palumbo et al. (2004) and Ursoet al. (2016).2.1. Formation of complex moleculesSeveral experimental investigations haveshown that “complex” molecules are formed160 Palumbo et al.: Astrobiology studies at INAF-Cataniaafter ion bombardment (E∼keV-MeV) andUV photolysis (mainly Lyman-α) of icemixtures at low temperature (10-30 K). Inparticular, Kaňuchová et al. (2016) and Ursoet al. (2017) have shown that formamide(NH2CHO) is formed after 200 keV protonbombardment of ice (10-20 K) mixturesmade of simple species (i.e. H2O:CH4:N2,H2O:CH4:NH3, CH3OH:N2) along with otherorganic molecules (e.g. HNCO, CH3CHO).After warm up to room temperature mostvolatile species sublimate while a refractoryorganic material stable at room temperatureis left over. The thickness of the residue isabout 10% of the thickness of the initialice sample and it is able to partially trapvolatile species formed at low temperature(e.g. Palumbo et al. 2000; Baratta et al.2015; Urso et al. 2017). Kaňuchová et al.(2016) have shown that formamide formedafter energetic processing of icy mixturescan account for the amount observed in thegas phase in cometary comae and in manycircumstellar regions. Urso et al. (2017)speculate that formamide, tentatively detectedon the surface of comet 67P/Churyumov-Gerasimenko by the Cometary Sampling andComposition (COSAC) mass spectrometer,onboard the Philae lander of the Rosetta mis-sion (Goesmann et al. 2015), is formed afterenergetic ion bombardment of the cometaryice surface.2.2. Analysis of extraterrestrial samplesRaman and infrared spectra of interplanetarydust particles (IDPs), micrometeorites, andcometary particles collected by Stardust mis-sion clearly show the presence of organic ma-terial (Baratta et al. 2004; Sandford et al.2006; Rotundi et al. 2008, 2014; Dartois et al.2018). In fact Raman spectra are dominated bythe D and G bands centered around 1360 and1590 cm−1 respectively, while the IR spectrashow the C-H stretching mode features at about2900 cm−1. The IR spectra of micrometeoriteshave been compared with those of an organicresidue obtained after ion bombardment of icemixtures (Baratta et al. 2015). This compari-son suggests that the organic residue is a goodspectral analog for ultra carbonaceous microm-eteorites. The Raman features of extraterres-trial particles have been compared with that oflaboratory analogs, such as graphite (HOPG),hydrogenated amorphous carbon, and the re-fractory residue obtained after ion bombard-ment of ice mixtures (Rotundi et al. 2008). Ithas been pointed out that the most disorderedamorphous carbon detected by Raman spec-troscopy in some Stardust grains could be in-dicative of ion irradiation of carbon containingices or of pre-existing more ordered carbons.2.3. Evolution in harsh environmentsAs discussed by Baratta et al. (2019), organicrefractory material produced after ion bom-bardment of ice mixtures is representative ofthe organic material present in IDPs and mi-crometeorites. During their journey in the in-terplanetary medium (∼ 105 years), these ma-terials are exposed to GCRs, solar UV pho-tons, and the solar ion population before reach-ing Earth or other objects in the Solar System.Then it is fundamental to investigate its evo-lution under UV irradiation and ion bombard-ment. To this aim organic refractory samplesformed after 200 keV He+ irradiation at 16K of a N2:CH4:CO ice mixture have been ex-posed to the unshielded solar photon radiationoutside the International Space Station (ISS;Baratta et al. 2019) for about 16 months.Taking into account the orbit and the inclina-tion of the ISS, this period is equivalent to2111 hours of perpendicular solar irradiation.Samples have been analyzed before and af-ter exposure by IR transmission spectroscopy.These samples contain, among other species,nitriles and isonitriles as evidenced by a featureat about 2200 cm−1 in the IR spectra. Thesespecies are particularly relevant since they areconsidered key intermediates to form biologi-cally relevant molecules (Kaiser & Balucani2001). Analysis of the samples after exposurehas shown that the nitriles contained in rela-tively large IDPs (>20-30 µm) would have sur-vived in the interplanetary medium; hence theycould have reached prebiotic Earth.Palumbo et al.: Astrobiology studies at INAF-Catania 161Fig. 2. New experimental setup (scale 1:12)composed by a UHV chamber interfaced witha TOF-MS, an IR laser, a UV laser and con-nected to the ion source line by the tube onthe right-hand side. The cryostat is mounted onx, y, z translators and θ rotator. The lasers areplaced on standard optical benches while theUHV chamber and the TOF-MS are mountedon a custom table.3. Ongoing upgrade of theexperimental set-upThe installation of new instrumentation is inprogress at the Laboratory for ExperimentalAstrophysics. This will give us the unique op-portunity to study “in situ” the complex chem-istry induced by ion irradiation and UV pho-tolysis in ice mixtures. In particular the newexperimental set-up will detect molecules “insitu” by a combination of laser desorption,jet cooling and VUV-UV photo-ionization fol-lowed by high resolution mass-spectrometric(TOF-MS) analysis of ices after energetic pro-cessing. This will contribute to understand theorigin of complex molecules which were incor-porated in planets, satellites and comets at thetime of the formation of the Solar System andare believed to be the seeds from which life hasdeveloped on Earth. Figure 2 shows a drawingof the set up in the laboratory. Even if the newsystem is optimized to analyze ice samples af-ter energetic processing, it can also be used toanalyze other samples such as meteorites or ex-traterrestrial particles obtained from sample re-turn missions.Acknowledgements. Astrobiology studies and ex-traterrestrial sample analysis at the Laboratory forExperimental Astrophysics - Catania have beensupported by MIUR program PRIN-2008, theItalian Space Agency contract n. 2013-073-R.0:PSS (Photochemistry on the Space Station), theproject “The Cradle of Life - GENESIS-SKA(General Conditions in Early Planetary Systemsfor the rise of life with SKA)” funded underPRIN-INAF 2016 program, and by the ItalianMinistero dell’Istruzione, dell’Università e dellaRicerca through the grant Progetti Premiali -iALMA.ReferencesBaratta, G. A. et al. 2004, J. RamanSpectroscopy 35, 487Baratta, G. A. et al. 2015, Planetary and SpaceScience 118, 211Baratta, G. A. et al. 2019, Astrobiology 19,1018Dartois, E. et al. 2018, Astronomy &Astrophysics 609, A65Genge, M. J. et al. 2008, Meteoritics &Planetary Science 43, 497Goesmann, F. et al. 2015, Science 349,aab06891Kaiser, R. & Balucani, N., 2001, Acc. Chem.Res. 34, 699Kaňuchová, Z. et al. 2016, Astronomy &Astrophysics 585, A155Modica, P., & Palumbo, M. E., 2010,Astronomy & Astrophysics 519, A22Öberg, K. et al. 2009, Astronomy &Astrophysics 504, 891Palumbo, M. E., et al. 2000, ApJ 534, 801Palumbo, M. E., et al. 2004, Adv. Space Res.33, 49Rotundi, A. et al. 2008, Meteoritics &Planetary Science 43, 367Rotundi, A. et al. 2014, Meteoritics &Planetary Science 49, 550Ruiz-Mirazo, K. et al. 2014, Chem Rev 114,285Sandford, S. et al. 2006, Science 314, 1720Urso, R. G. et al. 2016, Astronomy &Astrophysics 594, A80Urso, R. G. et al. 2017, Phys. Chem. Chem.Phys. 19, 21759

Astrobiology studies and extraterrestrial sample analysis at the Laboratory for Experimental Astrophysics - Catania

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Astrobiology studies and extraterrestrial sample analysis at the Laboratory for Experimental Astrophysics - Catania

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