Formation and evolution of a complex organic molecule : from interstellar ices to asteroids

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1 Formation and evolution of a complex organic molecule : from interstellar ices to asteroids V. Vinogradoff, S. Bernard, Duvernay F., C. Le Guillou, Chiavassa T., L. Remusat

2 Molecules in Interstellar ices H 2 O, CO, CO 2, CH 3 OH, H 2 CO H 3 Gibb et al., The Astrophysical Journal, Simple molecules observed in interstellar ices A.C.A. Boogert and P. Ehrenfreund, ASP Conference Series, 2004.

3 Organic matter in chondrites IOM (75-90%) SOM (10-25%) Remusat, 2015 Derenne & Robert, 2010 Evidence of hydrothermal alteration in chondrites : modification of the organic matter? Le Guillou et al., 2014

4 Goal? Relationship between ices and asteroids?

5 The HMT molecule Characterized in interstellar ice analogue residues Up to 60%wt of the residue H 2 O / CH 3 OH / H 3 / CO / CO 2 ice analogue: photolysed at 20 K and warmed to room temperature Hexamethyltetramine (HMT) COO - H 4 + amide HMT HMT HMT never observed in the ISM, nor in meteorites J.E. Bowey, MRAS, 298, 1998 esters G.M. Muñoz-Caro et al., ature, 2002, 416, M.P. Bernstein et al., ature, 2002, 416, mechanism formation in ices? -initial molecule in the OM in meteorites? What is its modifications during hydrothermal alteration?

6 Experimental investigations? Interstellar ice evolution: Formation of complex organic molecules in ices From simple molecules (3-5 atoms) to HMT (22 atoms)

7 Interstellar ice evolution ( Reactivity in Iterstellar Grains) Gas mixture cryogenerator 4 K- 800 K FTIR spectrometer mass spectrometer Gas inlet Ice mixture Pressure inside 10-9 mbar 2 gas lines H 2 plasma source Simulation of ISM energetic processes Experiments and detection of products followed by infrared and mass spectrometers «ices» (H 2 O, CO, CO 2, CH 3 OH, H 2 CO H 3 ) VUV Irradiation Warming Warming Refractory compounds (10 K-200 K) (200 K-300 K)

8 Interstellar ice evolution: the case of HMT UV irradiation process: 25 K H 2 O / CH 3 OH / H 3 10:1:1 hν 25 K CH 3 OH + H 3 + H 2 O VUV 10 K Vinogradoff et al., A&A, 530, 2011 Vinogradoff et al. A&A, 551, 2013 After warming, HMT in observed in the residue HMT is not formed after the irradiation process Thermal process? Main Products H 2 CO, HCOOH Oberg,A&A, 504, 2009

9 Interstellar ice evolution: the case of HMT Thermal process: 10 K to 210 K H 2 CO + H 3 Δ 70 K H 2 CH 2 OH Δ 210 K gaz x HMT Bossa et al. The Astrophysical Journal, 707, 2009 Is formic acid key molecule? (main product of the irradation process)

10 Interstellar ice evolution: the case of HMT Thermal process: 10 K to 330 K H 2 CO/ H 3 /HCOOH 1:6:1 H 2 CO H 3 HCOOH Δ Δ HMT FTIR spectrum of an H 2 CO/H 3 HCOOH 1:6:1, ice mixture 10 K (a), 170 K (b), 240 K (c) and 330 K (d). HMT is formed only by thermal process Vinogradoff et al., Astronomy & Astrophysics, 2011,530.

11 Interstellar ice evolution: the case of HMT Importance of the thermal processes G Assuming a warming rate of 1 K for 100 years Ice H 3 + H 2 CO HCOOH+H 2 O Kinetical extrapolation kj.mol kj.mol kj.mol -1 H 2 CH 2 OH HCOOH HCOO - TMTH HMT Time (Years) Temperature (K) HMT and precursors could be used as thermometer in ISM HMT is likely a molecule accreted in asteroids Vinogradoff, Rimola et al.., Phys.Chem.Chem.Phys, 2012,14. Vinogradoff et al. A&A, 551, 2013

12 Experimental investigations? Interstellar ice evolution: Formation of complex organic molecules in ices

13 Experimental investigations? Interstellar ice evolution: Formation of complex organic molecules in ices Asteroid evolution: Hydrothermal alteration of interstellar molecule The case of HMT

14 Asteroids evolution: the case of HMT Hydrothermal alteration experiments 1) Product 2) autoclave 3) Glove box under 2 4) Stove at 150 C + Water ph 10 After different duration, up to 31 days 5) Treatment for analysis 6) Analyses -GC-MS -FTIR -XAES-STXM (synchrotron based)

15 Asteroids evolution: the case of HMT Hydrothermal alteration experiments 99 %wt of soluble compounds Mainly nitrogen aromatic compounds > atomes 22 atoms 1%wt of insoluble compound Macromolecule > 100 atomes *Brearley 2006 Vinogradoff et al, in prepapration

16 Asteroids evolution: the case of HMT X-ray Absorption XAES analysis of organic compounds in the solution Carbon edge 0 day 2 days 7 days 20 days 31 days Liquide phase HMT under hydrothermal alteration, 150 C, ph 10 C=C C=O/ C= COOH/ COH 2 C-H C- CH-O CH- X-ray Absorption itrogen edge C= aromatics -C=O (amides) -C=/ -=C aromatics 0,7 M C=C- (pyrrole) ev ev Fast transformation of HMT o more evolution after 20 days

17 Asteroids evolution: the case of HMT GC-MS analysis Diversity of soluble compounds Polymers of imidazole, pyrazine and pyridine complex molecules ->m/z=254 Me3 Large diversity of soluble organic molecules formed, o more HMT after 20 days

18 Asteroids evolution: the case of HMT The Insoluble organic matter formed from HMT (<1 wt.%), formed from 7 days FTIR IR of IOM HMT 31 days νc=o-h/ νc=o-h 2 νc=c /C= δch 2 δch 3 νc-c/ C-/ C-O XAES-carbon edge Carbon edge IOMs Absorbance H/ OH νch 3 νch 2 νc=o X-ray Absorption 7 jrs 20 jrs 31 jrs Wavenumbers (cm -1 ) -Complex macromolecule ev -no evolution once formed

19 Where do we stand?? H/ OH CH 2 C=C /C= C=O-H/ C=O-H CH 2 Absorbance C=O IOM HMT IOM Paris Wavenumber (cm -1 ) Similiar molecules from meteorites 2% nitrogen aromatic cycles 2% amides/amines HMT IOM compared to Paris IOM, similar features but not all SO.

20 Ices to Asteroids: take home message -Organic evolution in ices is the first stage to form complex organic molecules Thermal process has to be closely investigated Potential link between organic in ices and organic in Asteroids, but : -High impact of hydrothermal alteration in organics HMT totally decomposed in less than 20 days Formation of a IOM (clues for SOM and IOM origins in Meteorites) Thank you!

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22 STXM = Scanning Transmission X-ray Microscopy Synchroton radiation - Spatial Resolution: ~25 nm - Spectral Resolution: 0.1eV Monochromatic X-ray at a single energy E Absorption (Beer Lambert) Inner shell electronic excitation and ionization (K-edge) The energy of the edge is specific of the chemical element Courtesy S. Bernard

23 STXM = Scanning Transmission X-ray MICROSCOPY Synchroton radiation - Spatial Resolution: ~25 nm - Spectral Resolution: 0.1eV Spectromicroscopy= Both spectroscopy and MICROSCOPY at high spatial resolution 20 nm OH 2 objects: one rich in aromatics, the other in carboxylic groups C=O Absorption ev ev ev Energy (ev) XAES spectra Aromatics absorb STXM images Carboxylics absorb Image contrast = Differential absorption of X-rays depending on speciation STXM = Organic Geochemistry at the nanoscale

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