HST post SM4

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HST - post SM4

• Christine Chen (STScI)

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HST SM4 Science that Addresses Astrobiology
Roadmap Goals

• Characterize extrasolar giant planets (e.g.
  measure orbital distance, planetary mass, radius,
  albedo) and constrain models for planet formation
• Path-find techniques to search for
  astrobiologically relevant molecules (e.g. H2O,
  O2) in atmospheres of extrasolar terrestrial
  planets
• Characterize the early evolution of the solar
  system to understand the environment in which
  life arose on Earth and whether that evolutionary
  path is common for extrasolar planetary systems.

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Post-SM4 Capabilities

• Serving Mission 4 is currently scheduled for May
  2009
• Cycle 17 GO observations will begin 3-4 months
  after repair mission
• STIS
• Multi-wavelength transiting planet light curve
• Transiting planet atmospheric characterization
  (e.g. Na)
• Extended atmospheres around transiting planets
  (Ly ?)
• Debris disk atomic gas studies
• Circumstellar disk scattered light imaging
• NICMOS
• Primary tool for detecting molecules in
  transiting planet atmospheres at NIR H2O, CH4,
  NH3, CO, CO2
• Circumstellar disk scattered light imaging
  (coronagraphy and polarimetry)
• ACS
• Circumstellar disk scattered light imaging
• Direct imaging of extrasolar planets
• Highest precision transiting planet light curves
  (constrains planetary albedo)
• COS
• Extended atmospheres around transiting planets
  (Ly ?)
• Debris disk atomic gas studies
• WFC3

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Direct Imaging of Exoplanets

• Multi-epoch coronagraphic ACS observations have
  been used to image directly a point source
  orbiting Fomalhaut at the inner edge of the dusty
  disk ring. The putative planet is 2 orders of
  magnitude brighter than planetary atmosphere
  models predict.

ACS 0.6 ?m coronagraphic image of Fomalhaut. The
yellow ellipse has a semimajor axis of 30 AU that
corresponds to the orbit of Neptune in our solar
system. The planet appears to be located at 115
AU (Kalas et al. 2008).
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Exoplanet Atmosphere Characterization

• HST ACS and NICMOS (in conjunction with Spitzer
  IRAC and MIPS) photometry have already been used
  to characterize the composition of exoplanet
  atmospheres. These studies are pathfinding
  techniques for searching for water on habitable
  planets.

Simulated infrared spectrum of transiting Hot
Jupiter HD 189733b with HST (ACS, NICMOS) and
Spitzer (IRAC and MIPS) data overlaid (Tinetti
Beaulieu 2008).
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KBO Composition

• Medium band WFC3 IR filters are optimized to
  search for water, methane and ammonia and can be
  used to determine the ice composition of small
  bodies in the outer solar system

Keck NIRSPEC spectrum of Quaor with models
assuming water ice and a dark red continuum (top)
and a best fit model using water ice, continuum,
methane, and ethane (Schaller Brown 2008)
Keck NIRC spectra of 2003 EL61 and its
collisional family with model spectrum of pure
water ice shown at the top and best fits using
water ice and continuum overlaid (Barkume, Brown
Schaller 2008)
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Organics in Debris Disks?

• The debris disk around HR 4796 may be composed
  of organics although, silicates may also be
  consistent with the current data (Li et al.
  2008). ACS, STIS and NICMOS will provide
  spectro-photometry of more sources to determine
  grain composition via scattered light.

Inferred dust scattering coefficients for HR
4796A (at STIS and NICMOS wavelengths) can be
reproduced using Tholins (Debes, Weinberger
Schneider 2008)
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Gas Abundance in Exoplanetary Systems

• FUSE/STIS observations of atomic gas along the
  line of sight toward ? Pictoris show that the
  carbon abundance is anomalously high (Roberge et
  al. 2006). Does the high carbon abundance
  indicate preferential outgassing of carbonaceous
  species in young solar systems?

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Unique HST Capabilities

• Premier high contrast imaging facility
• Access to astrobiologically relevant atoms and
  molecules (CHON,H2,CO)
• Probing the star/disk interactions with high
  energy photons

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Water on Mars

• WFC3 Medium band 1.4 ?m filter, designed to
  search for water vapor. For Mars, WFC3 may
  measure atmospheric water with a spatial
  resolution of a few tens of km.

Water in Martian rocks as revealed by WFPC2 (left
panel) and NICMOS (right panel) observations. The
bluer shade along the edges of the Martian disk
in the left panel is due to atmospheric haze and
water ice clouds. The large reddish region in the
right panel identifies an area of water-rich
minerals known as Mare Acidalium (J. Bell, J.
Maki, M. Wolff and NASA.)