Astrobiologia J.R. Brucato INAF-Arcetri Astrophysical
Observatory, Firenze Italy [email protected] Workshop
Planetologia ASI 3-4 June 2014
Slide 2
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
Slide 3
DUST GaseousLiquidSolid AtmosphereOceansSurfaces
Slide 4
Titanium dioxide Photochemistry AnataseRutile h e-e- 3.2 eV h
e-e- 3.0 eV
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).
Slide 9
Surface catalysis Eley-Rideal Desorption Reaction Adsorption 1
2 3 Langmuir-Hinshelwood Adsorption Reaction Desorption Diffusion 1
2 3 4 Surface catalysis allow molecules formation that are not
possible in the gas phase. It open pathways for the chemical
evolution in space.
Slide 10
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
Slide 11
The formation of water can follow hydrogenation of both O and O
2 pathways.
Slide 12
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)
Slide 13
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
Slide 14
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
Slide 15
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
Slide 16
Cytosine on MgO Invariance of the C=O stretching frequency pH
10 Interpretation of spectroscopic features Face-to-face
configuration
Slide 17
Slide 18
ADENINE
Slide 19
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 0.0008
%), confirming the high intrinsic photostability of such
molecules.
Slide 20
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
Slide 21
ESA CV M3, 21 J AN. 2014 4a. How do organics in primitive NEAs
relate to life on Earth ? The origin of life on Earth remains one
of humankinds important unanswered questions Eros, NEAR mission
(JHU/APL)
Slide 22
ESA CV M3, 21 J AN. 2014 4a. How do organics in primitive NEAs
relate to life on Earth ? The origin of life on Earth remains one
of humankinds important unanswered questions Eros, NEAR mission
(JHU/APL) Early Earths chemistry
Slide 23
ESA CV M3, 21 J AN. 2014 4a. 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 humankinds important unanswered
questions Early Earths chemistry
Slide 24
ESA CV M3, 21 J AN. 2014 Ehrenfreund et al. 2001 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.
Slide 25
ESA CV M3, 21 J AN. 2014 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
Slide 26
ESA CV M3, 21 J AN. 2014 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 (AHearn 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 ?
