Parallel Session P12: 1545-1730, Tuesday 13th April 2010
Water in the Solar System and Beyond
This session aims to cut across some of the traditional subject areas in astrobiology, bringing people together to consider the origin, distribution and action of water in the galaxy. Topics covered will span the range from water in the Solar System – i.e. the Moon, Mars and asteroids, and icy bodies (e.g. comets, Europa) – to exoplanetary atmospheres.
- Monica Grady (Open University)
|13 April, 15:45||The Densities of Kuiper Belt Objects|
Pedro Lacerda (Queen's University Belfast)
|13 April, 16:00||The Main-Belt Comets: Long-lived Ice in the Inner Solar System|
Henry Hsieh (Queens University Belfast)
|13 April, 16:15||The Frequency and Composition of Water-Rich Extrasolar Asteroids|
Jay Farihi (University of Leicester)
|13 April, 16:30||Characterisation of exoplanetary atmospheres|
Ingo Waldmann (UCL)
|13 April, 16:45||Nightside Pollution of Exoplanet Transit Depths|
David Kipping (Harvard-Smithsonian Center for Astrophysics)
|13 April, 17:00||Observations and modelling of water vapour lines in the Herschel SPIRE FTS spectrum of the luminous red-supergiant, VY Canis Majoris|
Mikako Matsuura (University College London)
|13 April, 17:15||Amasing Water|
Anita Richards (JBCA, University of Manchester)
The Densities of Kuiper Belt Objects
Queen's University Belfast
13 April, 15:45
The cold Kuiper belt objects (KBOs) are believed to contain a significant fraction of volatiles in the form of ice. The few density estimates that have been secured support this idea. KBO bulk densities can be constrained in binaries, if the size (albedo) known, or from lightcurve data (spin period and photometric range) under the assumption that the objects are near hydrostatic equilibrium. One of the major science goals of the Herschel key programme to study KBOs will be to measure the albedos of roughly 25 binary KBOs and estimate the system densities. To this date, most of the useful density estimates have come from lightcurve analysis. I will outline what is currently known about KBO densities, including estimates obtained using the most recent lightcurve data. I will discuss possible trends between density and other physical properties and what those might be telling us about the water content and interior structure of KBOs.
The Main-Belt Comets: Long-lived Ice in the Inner Solar System
Queens University Belfast
13 April, 16:00
The main-belt comets are a newly-identified class of small bodies in our solar system which have the orbits of main-belt asteroids but exhibit cometary activity in the form of dust tails or comae, indicating the presence of sublimating ice. Since their discovery in 2006, they have drawn interest due to the unexpected presence of icy bodies on stable (i.e. long-lived) inner solar system orbits, their implications for solar system formation, and their astrobiological significance as a possible primordial terrestrial water source. I will detail the advances made in the study of these unusual objects since their discovery, discuss the many outstanding questions that still remain, and consider their role in our understanding of the origin and past and present distribution of water in the solar system.
The Frequency and Composition of Water-Rich Extrasolar Asteroids
Farihi, Jay, M. A. Barstow, S. Redfield, P. Dufour, N. C. Hambly
University of Leicester
13 April, 16:15
The interstellar medium is no longer a viable physical model for the origin of heavy elements seen in cool white dwarfs. Instead, ongoing Spitzer and ground-based studies of a large number of single, metal-enriched stars have demonstrated the source of the pollution must be circumstellar. Where detected, the geometry of the dust and (heavy element) gas disks orbiting contaminated white dwarfs are consistent with tidally disrupted asteroid analogs, a hypothesis which also accounts for the volatile-poor, rocky composition of the photospheric metals and circumstellar debris. Tantalizingly, a handful of these polluted white dwarfs appear to contain excess hydrogen, an indication that the destroyed minor (or major) planet carried internal water.
I will describe the evidence for such water-rich extrasolar asteroids, and the ongoing work to confirm this hypothesis by searching for oxygen in excess of that expected from mineral oxides as commonly found in the inner Solar System. The confirmation of water in extrasolar, terrestrial planetary bodies will constrain the frequency of environments favorable to habitable planet formation and may indicate that habitats suitable to extremophiles are common in the Galaxy.
Characterisation of exoplanetary atmospheres
13 April, 16:30
Among the 400-plus exoplanets discovered to date, an ever-growing sample of the transiting variety present themselves as good targets for further characterisation. Using transmission (when the planet eclipses its host star) and emission (the day-side thermal emission of the exoplanet) spectroscopy it is possible to study the atmospheric compositions of these so-called "hot Jupiters" in more and more detail. The feasibility of such measurements has been demonstrated with great success using Spitzer and HST in the recent years. Most notable are the detections of molecular species such as water, methane, carbon monoxide and dioxide in the near infra-red for a variety of planets. These detections allow us to build up an intricate picture of the atmospheric compositions and dynamics present. At the end of the Spitzer cold-phase, a gap in space-based observatories in the near- to mid-infra-red has emerged, calling for increased efforts in ground-based techniques. With the detection of methane in fluorescence, in the L-band, on HD 189733b, it has been shown that such measurements using medium-sized telescopes on the ground are feasible. At this conference, I will give an overview of what has been done from the space and ground, what we have learned from these observations, and how to build upon our results in future developments.
Nightside Pollution of Exoplanet Transit Depths
Kipping, David, G. Tinetti
Harvard-Smithsonian Center for Astrophysics
13 April, 16:45
Hot-Jupiter exoplanets have been discovered to exhibit significant thermal emission from their dayside but efficient circulation implies similar emission signals from the nightside too. This emission acts as a self-blend and attenuates transit depths, particularly at mid-infrared wavelengths. The effect is shown to cause changes in the Spitzer-measured transit depths at the 1-sigma level for the case of HD 189733b. We explore how the nightside pollution effect alters the interpretation of exoplanet spectra, with emphasis on the signature of water, and also present methods for accounting for this attenuation.
Observations and modelling of water vapour lines in the Herschel SPIRE FTS spectrum of the luminous red-supergiant, VY Canis Majoris
Matsuura, Mikako, Mikako Matsuura (UCL), Jeremy A. Yates (UCL), Michael J. Barlow (UCL), Dugan Witherick (UCL), Roger Wesson (UCL), E. T. Polehampton (RAL), Bruce M. Swinyard (RAL), and the Herschel MESS Key project consortium (P.I. M.A.T. Groenewegen)
University College London
13 April, 17:00
Water vapour is commonly found in the atmospheres of oxygen-rich red giants and supergiants. The Herschel Space Observatory has carried out a spectral survey of luminous M-supergiant VY Canis Majoris in the far-infrared and submillimetre. In particular, the 200-670 micron region has been explored for the first time using the SPIRE (Spectral and Photometric Imaging Receiver) Fourier Transfer Spectrometer (FTS). We present the SPIRE FTS observations, together with non-local thermodynamic equilibrium SMMOL modelling of the far-infrared water-vapour lines, dominant coolants in the outflows from such stars.
JBCA, University of Manchester
13 April, 17:15
The water molecule is one of the few known to produce natural, cosmic masers. These can attain extaordinary brightness temperatures (1017K) which allows their positions and velocities to be measured with spatial and spectral resolutions of milli-arcsec and tens of m/s, using radio interferometers such as e-MERLIN. Masers from water (and its daughter, the hydroxyl radical) are found in environments from comets to discs orbiting AGN. I will concentrate on the use of water masers to measure the kinematics of molecular gas and shocks in star-forming regions. Looking ahead, ALMA will image both maser and thermal water (sub-)mm lines, potentially exciting indicators of differentiation in proto-planetary discs.