Astrobiologia J.R. Brucato INAF-Arcetri Astrophysical Observatory, Firenze Italy Workshop Planetologia ASI 3-4 June 2014

The role of minerals and metal oxides on prebiotic processes. A general overview Minerals can accumulate the prebiotic precursors (concentration effect) Minerals can act as catalytic environments, reducing the activation energy for the formation of products Minerals can tune the selectivity of prebiotic syntheses Minerals may act as a template Minerals are benign environments to preserve newly formed biomolecules from degradation

DUST GaseousLiquidSolid AtmosphereOceansSurfaces

Titanium dioxide Photochemistry AnataseRutile h e-e- 3.2 eV h e-e- 3.0 eV

Mineral PowderPhotons Energy dose (mW*s=J) Exp. : Anatase BG Photons2.7 Exp. : Anatase FG Photons2.7 Exp. : Rutile Photons1.8 Exp. : Mix Rutile + Anatase Photons1.5 Exp. : Formamide Photons1.5 BG= Big grains >500 nm FG= Fine grains<100 nm Monochromatic Irradiation 3.2 eV, ± 2.14 nm INFN – DAFNE Synchrotron facility

Anatase > 500 nm Anatase < 100 nm Biogenic Carboxylic Acids TiO 2 Rutile Lactic acidGlycolic acidPyruvic acid Succinic acid Malic acid Oxalacetic acid Ketoglutaric acid Fumaric acid

H + O 2  HO 2  H 2 O 2  H 2 O + OH  H 2 O H H H H 1) (Ioppolo et al. 2008, 2010) O + O 2  O 3  O 2 + OH  H 2 O + H HH2H2 2) (Tielens & Hagen 1982) H + O  OH  H 2 O H (Dulieu et al. 2010) 3) Some argues that species formed by these exotermic reactions will immediately desorb (Paoupular 2005). However, models predicts that most (99.1%) of OH and H 2 O formed remain on surfaces (Cupper and Herbst 2007).

Surface catalysis Eley-Rideal Desorption Reaction Adsorption Langmuir-Hinshelwood Adsorption Reaction Desorption Diffusion Surface catalysis allow molecules formation that are not possible in the gas phase. It open pathways for the chemical evolution in space.

Desorption peaks for various species after D and O co- exposure. From bottom to top: 10 min, 15 min, 22.5 min, 30 min, 45 min, 60 min and 90 min. Ed=390 meV Ed=400 meV Ed=430 meV Ed=170 meV

The formation of water can follow hydrogenation of both O and O 2 pathways.

Mars soil analogues Natrolite Fayalite Forsterite Enstatite Ferrosilite Jadeite Diopsite Augite Serpentine Apatite arsenate Pyrrhotite Troilite Pyrite Oxides Kaolinite Smectite Montmorillonite Nontronite Illite Albite Andesite Labradorite Anorthite Bytownite Oligoclase Anorthoclase Oligoclase Labradorite Nepheline Biomarkers ExtantExtinctMeteoritic ATP Cyclic AMP Pyrimidine base Purine base DNA Nicotinamide Quinones ATP Synthase Phytane LPS Squalene Generic Isoprenoid Pristane Phytane Tetramethyl benzenes Fatty Acids Quaternary carbon alkane Napthalene Generic amino acid Isovaline Generic aromatic carboxylic acid Biomarker Selection  Expectation of detection in Martian soils (likelihood of preservation and likelihood of existence)

Some Facts Minerals: pivotal role in the prebiotic evolution of complex chemical systems by AdenineHypoxanthine Cytosine Uracil Study the photochemistry and the photophysics of nucleobases in the presence of mineral matrices, to investigate both the survivability when exposed to Mars surface and the physical and chemical processes occurring in extraterrestrial environments. mediating the effects of electromagnetic radiation influencing the photostability of bio-molecules catalyzing important chemical reactions protecting molecules against degradation

IR-spectroscopy studies of nucleobase-mineral complexes To better understand, at molecular level, the kind of interactions between nucleobases and minerals, IR-spectroscopy studies were carried out, using the diffuse reflectance infrared Fourier transform spectroscopy technique (DRIFTS) Adenine adsorbed onto MgO IR bands are NOT observed Adenine adsorbed onto forsterite Detectable IR bands

Interpretation of spectroscopic features Adenine on MgO Low frequency shift (-22 cm -1 ) of the Q 7 vibrational mode: N 3 C 4 str, C 5 C 6 str pH ≈ 10 Distorted nearly planar arrangement

Cytosine on MgO Invariance of the C=O stretching frequency pH ≈ 10 Interpretation of spectroscopic features Face-to-face configuration

ADENINE

Cytosine and hypoxanthine have a greater photostability, both pure and adsorbed on MgO and forsterite. For adenine and uracil degradation was observed both pure and adsorbed onto MgO and forsterite. Minerals make degradation faster and more probable (the half-lifetimes of degradation decrease and the degradation cross sections increase), but do not promote the formation of new species. Comparing the measured cross sections with the molecular dimensions, a rather low probability of interaction between UV radiation and nucleobases was estimated (between 0.07 % and %), confirming the high intrinsic photostability of such molecules.

Analyses of organic compounds that could be responsible for the origin of life on Earth; Discovery primitive materials preserved during Solar System formation; Understanding evolutionary processes occurred during the Solar System lifetime. Development of Sample Return technologies suitable for future exploration: Sampling mechanism, Earth return vehicle, re-entry capsule. Development of robotic systems able to make use of SR resources for human exploration. Development of Curation Centers for analyses, delivery and storage of ET samples. Sample Return mission opens new perspectives Educational Return Public-Outreach

ESA CV M3, 21 J AN a. How do organics in primitive NEAs relate to life on Earth ? The origin of life on Earth remains one of humankind’s important unanswered questions Eros, NEAR mission (JHU/APL)

ESA CV M3, 21 J AN a. How do organics in primitive NEAs relate to life on Earth ? The origin of life on Earth remains one of humankind’s important unanswered questions Eros, NEAR mission (JHU/APL) Early Earth’s chemistry

ESA CV M3, 21 J AN a. How do organics in primitive NEAs relate to life on Earth ? Extraterrestrial delivery via small bodies seeded the young Earth during in its early history: precursor material for life ? Organics from space The origin of life on Earth remains one of humankind’s important unanswered questions Early Earth’s chemistry

ESA CV M3, 21 J AN Ehrenfreund et al Interstellar and circumstellar regions : ~ 180 molecules are detected and many carbon allotropes …. Insights into cosmic carbon chemistry Carbonaceous meteorites contain: macromolecular carbon, biomolecules, hydrocarbons, nanoglobules… MarcoPolo-R-like mission will permit analysis of a unique sample of abiotic organic chemistry as it was in the Solar System shortly before the onset of life.

ESA CV M3, 21 J AN How do volatiles (H, C, N…) in primitive NEAs relate to the atmosphere and oceans on Earth ? What are the compositions of asteroids ? Only measurements are from meteorites – possibility of terrestrial contamination Are comets/asteroids the origin of terrestrial water and atmosphere ? Marty, 2012 Sun (Genesis) Busemann et al. 2006

ESA CV M3, 21 J AN A comet-asteroid continuum? The computed water/rock ratio in meteorites (representative of asteroids?) is up to 1 (Clayton 1984, Young et al. 2002) The observed water/rock ratio of Comet Tempel 1 is 1 (A’Hearn et al. 2005) Clays in meteorite 200 nm Deep impact on Tempel1 6 km NASA/JPL-Caltech/UMD What is the difference between a water-rich asteroid & a dust-rich comet ?

ESA CV M3, 21 J AN

THANKS