Table 3 - uploaded by Hajime Kawahara
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Future radial velocity, astrometric and direct imaging surveys will find
nearby Earth-sized planets within the habitable zone (HZ) in the near future.
How can we search for water and oxygen in those non-transiting planets? We
propose a combination of high-dispersion spectroscopy and coronagraphic
techniques as a method to detect molecular lines in...
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Citations
... The requirement of high-contrast imaging may be loosened when a starlight suppression instrument is combined with the high-dispersion spectroscopy (R>100,000) where individual lines are resolved (Sparks & Ford 2002;Riaud & Schneider 2007;Kawahara et al. 2014;Snellen et al. 2015). The Doppler shift of the planetary spectral lines from those from starlight and from Earth's atmosphere allows for the efficient separation between the planetary component and other contaminations, and the cross-correlation of a large number of lines with template spectra can increase the signal-to-noise ratio of the detection. ...
... However, temperate Earth-sized planets are too faint for this method alone to succeed. Several work (Kawahara & Hirano 2014;Snellen et al. 2015;Wang et al. 2017) have investigated the potential of the combination of high contrast imaging and high-resolution spectrograph, and showed that molecular signatures of Earth-like planets around late-type stars may be detected with high-contrast imaging instruments that achieve ~10-5-10-4 contrast (~improved by a factor of 10 3 than otherwise required) when combined with high-resolution spectrograph. ...
We provide an overview of the prospects for biosignature detection and general characterization of temperate Earth-sized planets. We review planned space-based missions and ground-based projects as well as the basic methods they will employ, and summarize which exoplanet properties will become observable as these new facilities come on line. The observational strategies depend on whether the planets are transiting or not as well as on the spectral type of the host star. There is a reasonable expectation that the first constraints on spectroscopic features of atmospheres will be obtained before 2030. Successful initial characterization of a few nearby targets will be an important touchstone toward a more detailed scrutiny and/or a larger survey to address statistical questions such as the occurrence rate of habitable environments. The broad outlook which this paper presents may help develop a framework to evaluate the possibility of biospheres based on the observables, and consider new methodologies to characterize exoplanets of astrobiological interest.
... Some of these observations could serve as precursors for better spectral techniques in detecting Earth-like habitable planets (e.g. Kawahara and Hirano, 2015 ) and screening astronomical spectra from common telluric contaminations. From the presence experiment, it thus appears that both telluric contamination and planetary desiccation could be responsible in giving flawed spectral data while studying habitability ( Carter et al., 1992 ). ...
Red clays of Central Indian Basin (CIB) under influence of trace of Rodriguez Triple Junction exhibited chemoautotrophy, low temperature hydrothermal alterations and photoautotrophic potential. Seamount flank TVBC-08, hosting such signatures revealed dominance of aerobic anoxygenic phototroph Erythrobac-ter , with 93% of total 454 pyrosequencing tags. Subsequently, enrichments for both aerobic (Erythrobacter) and anaerobic anoxygenic phototrophs (green and purple sulphur bacteria) under red and white LED light illumination, with average irradiance 30.66 W m −2 , were attempted for three red-clay sediment cores. Successful enrichments were obtained after incubation for c.a. 120 days at 4 °± 2 °C and 25 °± 2 °C, representing ambient psychrophilic and low temperature hydrothermal alteration conditions respectively. During hydrothermal cooling, a microbial succession from anaerobic chemolithotrophy to oxygenic photoau-totrophy through anaerobic/aerobic anoxygenic phototrophic microbes is indicated. Spectral absorbance patterns of the methanol extracted cell pellets showed peaks corresponding to metal sulphide precipi-tations, the Soret band of chlorosome absorbance by photosystem II and absence of peaks at Qy transition band. Dendritic nano-structures of metal sulphides are common in these sediments and are comparable with other sulphidic paleo-marine Martian analogues. Significant blue and redshifts have been observed for the experimental samples relative to the un-inoculated medium. These observations indicate the propensity of metal-sulphide deposits contributing to chemiluminiscence supporting the growth of phototrophs at least partially, in the otherwise dark abyss. The effects of other geothermal heat and light sources are also under further consideration. The potential of phototrophic microbial cells to exhibit Doppler shift in absorbance patterns is significant towards understanding planetary microbial habitability. Planetary desiccation could considerably influence Doppler effects and consequently spectral detection techniques exo-planetary microbial life.
