research efforts in the field of astrobiology

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research efforts in the field of astrobiology
University of Aarhus

• Steen Brøndsted Nielsen, Lars Andersen, Liv
  Hornekær, David Field
• Department of Physics and Astronomy

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University of Aarhus
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Areas of Research

• Fundamental physico-chemical interactions of
  radiation and electrons with molecules and
  spontaneous molecular processes on surfaces
• Systems chosen are of special interest in biology
  and in astrophysics, including the formation and
  survival of biomolecules in space and on the
  early Earth or Mars

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Specific areas of research

• Radiation damage to isolated biomolecular systems
• Photoexcitation dynamics of bio-chromophores
• Molecular Astrophysics on Surfaces
• Cold electron interactions with molecules

Me!
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What facilities do we have available?

• Synchrotron Radiation we have a SR storage ring
  at Aarhus, ASTRID

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ASTRID
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What facilities do we have available?

• Synchrotron Radiation we have a SR storage ring
  at Aarhus, ASTRID
• We use SR for Circular Dichroism and biomolecule
  damage studies
• SR is also used for making very cold electron
  beams for electron-molecule interaction studies

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ELISA Electrostatic Storage Ring for ions at
Aarhus
http//www.isa.au.dk/facilities/elisa/elisa.html
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ELISA
maximum energy of ion beam 22 keV/charge storage
time seconds to minutes
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Experiments using ELISA

• damage to isolated biomolecular systems,
  involving DNA and RNA nucleotides and peptides
  under the influence of low energy electrons and
  UV light.
• These experiments investigate the primary events
  associated with radiation damage in a harsh
  environment relevant to the early Earth.
• Steen Brøndsted Nielsen and Lars Andersen

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More experiments using ELISA (and femtosecond
lasers)

• the electronic structure of macromolecular ions,
  in particular bio-chromophores
• energy conversion processes after photoexcitation
  (e.g. in Green Fluorescent Protein with 238
  aminoacids European Physical Journal D, 20 597
  (2002)
• see also http//www.biophysj.org/cgi/content/f
  ull/92/1/201
• Influence of the solvent on the absorption
  characteristics of isolated biomolecular ions
• Lars Andersen

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Circular Dichroism using ASTRID Synchrotron
Radiation

• Circular Dichroism is the difference in
  absorption between left and right hand circularly
  polarised light in chiral molecules
• Experiments shed light on the electronic coupling
  between nucleobases when DNA is excited by VUV
• Relevant to the survival of DNA strands under the
  VUV stress associated with the Earth before the
  formation of an ozone layer.
• Steen Brøndsted Nielsen

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Molecular Astrophysics on Surfaces

• Molecular Hydrogen formation on amorphous
  solid water
• Molecular Hydrogen formation on carbonaceous
  surfaces
• The influence of surface morphology on molecule
  formation surface with pores or a smooth surface
• Interaction of atomic species (H, N, O) with
  Polycyclic Aromatic Hydrocarbons
• Liv Hornekær

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Dust around protostars

• dust grains made of Mg, Fe silicates and
  graphitic composites 1 of total mass of gas
• particle size large molecule (tens of Å) to
  microns, with many more small dust particles than
  large (n(M)M-2.3)
• temperature 10K but can be higher
• coated with a cocktail of molecules CO, H2O, NH3,
  CO2, methanol etc.
• dust is primarily formed in red supergiants and
  giant stars and distributed around the Galaxy

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Liv is studying surface reactions on interstellar
dust grains
H
O
C
N
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Techniques available

• Scanning Tunnelling Microscopy (STM)
• temperature programmed desorption
• laser desorption techniques
• time-of-flight and internal energy measurements
  of products (e.g. H2)

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H-Dimers on Graphite a Scanning Tunneling
Microscope image
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Cold electron interactions

• Using the ASTRID synchrotron storage ring we
  create very high resolution electron beams with
  an energy spread of 1-2 meV, using an Argon
  photoionization source.
• Cold electron beams are guided onto solid
  material and their interaction with these solids
  is studied.

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Electron induced reactions
H
O
C
N
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• Cold electron interactions with solids is a new
  topic
• The processes which we study are relevant to the
  fate of ices in the interstellar medium
• Cold electron induced synthesis could be a key to
  understanding the formation of prebiotic
  molecules in space, such as the 70-80 amino-acids
  extracted from the Murchison meteorite
• NH3 CH3COOH ? glycine via an electron induced
  mechanism?
• David Field

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This telescope will transform our knowledge of
molecular species in the interstellar medium. For
example, if glycine and other aminoacids are in
the gas phase, we will find them.
Atacama Large Milllimetre Array ALMA
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OMC1 scale 0.15 pc
We can study very young stars in the Orion
Molecular Cloud (OMC1) and discover what were the
physical conditions prevailing at the time of the
formation of the Sun and our planetary system
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What can we see when we look at protostellar
zones?

• Dust obscures protostars you cannot see them in
  the visible region of the spectrum
• look in the infrared e.g. at 2 microns (and at
  longer wavelengths)
• 2 micron emission of vibrationally excited
  hydrogen is a beacon of star formation
• one can see gas bursting out of protostars and
  smashing into the surrounding material with
  velocities of 5 to 50 km/s

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Hot hydrogen in the Orion molecular cloud
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Star formation in Orion a fast outflow from a
protostar is a beacon of star formation
extensive chemical processing at high temperature
in shocks material blasted off the surface of
dust, reacts in the gas phase and redeposited on
dust
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• material re-deposited after the shock cools from
  several thousand K to 10K (1-2 years)
• chemically processed material is reprocessed on
  dust grain surfaces by cold electrons these may
  be very active in inducing chemistry already
  mentioned
• chemical processing also by UV photons if
  majority of the dust is not completely shielded
  from light by other dust

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Specific areas

• Radiation damage to isolated biomolecular systems
• Photoexcitation dynamics of bio-chromophores
• Molecular Astrophysics on Surfaces
• Cold electron interactions with molecules
• The emphasis is strongly on fundamental
  physics and chemistry processes of relevance to
  the evolution of biology