Christine Chen (STScI) HST - post SM4 Christine Chen (STScI)

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.

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 Direct imaging of extrasolar planets Highest precision transiting planet light curves (constrains planetary albedo) COS WFC3 Broad band reflectance spectroscopy of Mars, outer planets and Kuiper Belt Objects

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).

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).

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 Name Description Wavelength (A) Width (A) F127M H2O/CH4 continuum 1273.64 68.79 F139M H2O/CH4 line 1383.80 64.58 F153M H2O and NH3 1533.31 68.78 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) The dominant type of ice varies with solar distance, from H2O in the satellites of Jupiter and Saturn, to CH4 (Uranus) and CO and N2 (Neptune’s Triton). Additional ices on surfaces of satuellites. The most spectrally active ices are not always the most Abundant. Methane on Pluto was thought to be the dominant constituent but only a small contamination of nitrogen. (Ground based Data suffer from low signal:noise and scattered light background from adjacent planets. 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)

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)

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?

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

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.)