CHARACTERIZATION OF EXOGENOUS ORGANIC MATTER ON THE GANYMEDE SURFACE.

1
CHARACTERIZATION OF EXOGENOUS ORGANIC MATTER ON
THE GANYMEDE SURFACE.

• M. A. Zaitsev1, M. V. Gerasimov1, E. N.
  Safonova1, M. A. Ivanova2, C. A. Lorenz2, A. V.
  Korochantsev2, Yu. P. Dikov3,1
• 1Space Research Institute (IKI),
• 2Vernadsky Institute of Geochemistry and
  Analytical Chemistry (GEOKHI)
• 3Institute of Geology of Ore Deposits,
  Petrography, Mineralogy and Geochemistry (IGEM)

International Colloquium and Workshop "Ganymede
Lander scientific goals and experiments
IKI, Moscow, 06.03.2013
2

• What is the Habitability of the Ganymede Ocean?
• What Organic Compounds (OC) and Biomarkers are
  Present in the Ocean?
• What is the Signature of the Ocean Organics in
  the Surface Ice?

3
Cratered terrain of the Ganymede
4
Dynamics of exogenous (OC) and endogenous (OC)
organic compounds
Impacts of meteorites and comets
OC
crack
5
Important questions to answer

• What is the proportion between endogenous and
  exogenous OC in the upper 1 m layer of surface
  ice (available for analysis by a lander)?
• How to discriminate endogenous OC from exogenous?

6
Delivery of biologically important OC by
meteorites.
Numerous studies of Murchison by different
researches had revealed a complex mixture of
large and small organic chemicals, including
amino acids, sugar related compounds, carboxylic
acids and nucleobases (Botta Bada, 2002).

• Given the different isomers for organic molecules
  with the same composition Murchison should
  contain several million different carbon-,
  hydrogen-, nitrogen-, oxygen-, and sulfur-based
  organic chemicals (Philippe Schmitt-Kopplin et
  al. (PNAS, 2010, 107, no. 7, 27632768).
• What is the fate of OC during impact processing?

7

• Composition of endogenous OC is unknown
• Composition of OC in falling bodies can be
  characterized by OC in meteorites of different
  classes
• Hypervelocity impact-induced modification of OC
  can be simulated in laboratory
• The aim of the work
• Characterization of OC in carbonaceous chondrites
  of different types and to investigate
  modification trends of these OC during simulated
  impact-induced high-temperature processing.

8
Experiment

• Samples
• carbonaceous chondrites Murchison (CM2) and
  Kainsaz (CO3)
• starting meteorites - selection of fresh pieces
  (20 mg) and their powdering
• condensed material (20 mg) collected after
  simulated impact-induced evaporation by means of
  a pulse laser
• Extraction of OC
• thermodesorption at 460?/pyrolysis at 900?
• Analysis of OC
• collection of OC in a cold trap at liquid
  nitrogen temperature, then pulse heating to
  250-300? and transfer of volatile species to
  GC-MS

9
Typical chromatogram of thermodesorption products
of Murchison at 460? and mass-spectra of some OC
1
2
5
2
3
4
6
3
4
1
5
6
8
7
8
7
(1) - CO2, (2)-isobutene, (3)-benzene, (4)
thiophene, (5) toluene, (6)-methyl thiophene,
(7) n-dodecane, (8) n-tridecane
10
OC in the products of thermodesorption of
Murchison
Results of identification Results of identification Results of identification Abun-dance,
Classes of OC Subclasses of OC Groups of compounds and individual substances Abun-dance,
Hydro-carbons Alkanes gt C10 N-dodecane (C12H26), n-tridecane (C13H28), , n-tetradecane (C14H230), , ?-pentadecane (C15H32), structural isomers of ?11-?19 alkanes. Main components are n-alkanes ?11-?18 56,5
Hydro-carbons Unsaturated hydrocarbons Isobutene (C4H8), isomers of ?6-?10 alkenes , ?4-?7 alkadyenes, alkynes 3,3
Hydro-carbons Alicyclic hydrocarbons Isomerides of alkylcyclopropanes, cyclopentene (C5H8), alkylcyclopentenes, alkylcyclohexanes, decahydronaphthalene derivatives 1,2
Hydro-carbons Benzene and aklylbenzenes Benzene (?6H6), toluene (?7H8), xylene (?8H10), styrene (?8H8), cumene (?9H12), cymenes (?10H14), trimethylbenzenes (?9H12), alkylbenzenes containig ?4lt?7 side chains 20,4
Hydro-carbons Naphthalene, its derivatives and other aromatics Naphthalene (?10H8), methylnaphthalenes (?11H10), dimethylnaphthalenes (?12H12) 9,1
O-containing compounds Carbonyl compounds Aldehydes acetaldehyde (CH3CHO) and others, cetones acetone (?3H6O) and others. 2,2
O-containing compounds Other O-containing compounds Alcohols, furan (?4H4O) and its derivatives 2,4
S- containing compounds - Thiophene (?4H4S) and alkylthiophenes with ?2gtC4 side chains, benzothiophene, dimethyldisulfide CH3S-SCH3 4,0
N-containing compounds - Nitriles (acetonitrile CH3CN, benzonitrile C6H5CN), pyridine (C5H5N) and its derivatives 0,9
Total Total Total 100
11
Comparison of abundances of different subclasses
of OC in products of thermodesorption at 460? of
Murchison and Kainsaz
12
Comparison of products which are produced during
pyrolysis (at 900?) of Murchison and Kainsaz
meteorites
Components and groups of components Murchison Kainsaz
CO2
SO2 -
Methylmercaptane CH3SH -
Isoprene (?5H8) -
Acetonitrile (CH3CN) -
Benzene (?6H6)
Toluene (C7H8)
Xylenes and other alkylbenzenes
Naphthalene (?10H8)
Alkanes gtC10
13
SummaryWe have measured 200 organic compounds
in products of thermodesorption (460º?) of
Murchison (CM2) and Kainsaz (CO3) carbonaceous
chondrites. Some biochemically important
compounds (e.g. amino acids) were not targeted in
this step of investigation.OC are qualitatively
similar in composition for both Murchison and
Kainsaz, though Murchison has higher abundance
and diversity of OC rather than Kainsaz. This is
consistent with the higher metamorphic
temperatures of the Kainsaz (45329ºC) compared
to the Murchison (9665 º?) which resulted in
depletion of volatile organics. Organic
sulfides (methylmercaptane and dimethylsulfide)
were measured in the Murchison thermodesorption
products but were absent for Kainsaz. This
observation may indicate the absence of sulfide
and disulfide bridges in the Kainsaz OC, which
bounds fragments of high-molecular OC (result of
high metamorphic temperatures). Such OC as
acetonitrile and isoprene were also absent in the
Kainsaz pyrolysis products contrary to that of
the Murchison and are probably lost due to
defragmentation of kerogen during thermal
metamorphism. Based on the pyrolysis results,
high-molecular polymerized OC (kerogen) of the
carbonaceous chondrites can be characterized as
blocks of high-condensed aromatic structures with
functional groups, which are bound by
hydrocarbon- and sulfur-containing bridges.
14
Comparison of abundances of different subclasses
of OC in products of thermodesorption at 460? of
Kainsaz and the condensate from its
impact-simulated high-temperature vaporization
15

• Main characteristics of high-temperature products
  of impact-simulated vaporization of Murchison and
  Kainsaz
• high qualitative similarity of OC in starting
  meteorites and in their experimentally produced
  condensates
• high abundance of CO2 and SO2
• higher concentration of acetonitrile, furan group
  compounds, various thiophene derivatives,
  compared to starting meteorites thermodesorption
  products

16

• Conclusions
• endogenous OC delivered to the Ganymede surface
  by falling meteorites can be represented by a
  wide diversity of hydrocarbons, O-, S-, and N-
  containing compounds
• being fragmented from a high-condensed
  kerogen-like material, OC can be presented by a
  sufficiently complex molecules
• biologically important molecules like amino acids
  and nucleobases can be also delivered by
  carbonaceous chondrites/comets
• impact-induced high-temperature processing of
  meteoritic material does not change qualitatively
  the pattern of delivered OC
• we need to elaborate composition- and isotope-
  based criteria to discriminate between endogenous
  and exogenous OC
• try to find fresh ices to avoid exogenous
  contamination.