First Study of Photochemical Escape from Proxima Centauri b

2020 ◽  
Author(s):  
Yuni Lee ◽  
Chuanfei Dong
Keyword(s):  
Extreme Environments ◽  
Adaptive Mesh ◽  
Neutral Atmosphere ◽  
M Dwarfs ◽  
Model Framework ◽  
Habitable Zones ◽  
Solar System Bodies ◽  
Mhd Model ◽  
Atmospheric Loss ◽  
First Time

<p>As the upper atmospheres of the ‘habitable’ exoplanets orbiting M-Dwarfs are affected by more extreme environments than what Solar System bodies experience, the observations of such exoplanets raise questions to the mass-loss mechanisms and the sustainability of their atmospheres. For the first time, we examine the loss of neutral atmosphere from Proxima Centauri b (PCb) via photochemical mechanisms and formation processes of resulting exoplanetary hot atomic coronae or exospheres.</p> <p>The study is conducted by utilizing our integrated model framework, which couples our 3D Adaptive Mesh Particle Simulator (AMPS) for planetary exospheres and a 3D multi-species magnetohydrodynamic (MHD) model originally developed for Venus and Mars. The coupling of the two models is achieved in one-way, such that the AMPS code incorporates pre-simulated results by the MHD model as inputs for exosphere simulation. The MHD model describes the ionosphere of the planet self-consistently based on the neutral atmosphere adopted for PCb. All simulations in this study assume a Venus-like condition for the ionosphere and thermosphere of PCb, which is also based on an assumption of the absence of an intrinsic dipole magnetic field. As most of the relevant planetary parameters of PCb are unknown, this study provides one possible interpretation of the atmospheric loss process of PCb as well as other exoplanets similar to PCb, which reside in the Habitable Zones (HZs) of M-Dwarfs, to help our understanding of their habitability.</p> <p> </p>

scholarly journals Oxygen isotopic ratios in Martian water vapour observed by ACS MIR on board the ExoMars Trace Gas Orbiter

2019 ◽  
Vol 630 ◽  
pp. A91 ◽  
Author(s):  
J. Alday ◽  
C. F. Wilson ◽  
P. G. J. Irwin ◽  
K. S. Olsen ◽  
L. Baggio ◽  
...  
Keyword(s):  
Water Vapour ◽  
Atmospheric Chemistry ◽  
Trace Gas ◽  
Oxygen Isotope Ratios ◽  
Infrared Measurements ◽  
History Of ◽  
Oxygen Isotopic ◽  
Atmospheric Loss ◽  
The Impact ◽  
First Time

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

scholarly journals New Infrared Measurements of Magnetic Fields on Cool Stars

1994 ◽  
Vol 154 ◽  
pp. 493-497 ◽  
Author(s):  
Steven H. Saar
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ir Spectra ◽  
Preliminary Analysis ◽  
M Dwarfs ◽  
Pressure Balance ◽  
Infrared Measurements ◽  
Cool Stars ◽  
Rs Cvn Variables ◽  
First Time

I present a preliminary analysis of IR spectra of five K and M dwarfs and two RS CVn variables. Evidence for significant magnetic flux is found on several stars, a number of which are detected for the first time. Field strengths (B) on the RS CVn variables are lower than in the active dwarfs, consistent with the concept of pressure balance limiting B in stellar photospheres. I compare the results with previous measurements.

scholarly journals Exomoons in the Habitable Zones of M Dwarfs

2019 ◽  
Vol 887 (2) ◽  
pp. 261 ◽  
Author(s):  
Héctor Martínez-Rodríguez ◽  
José Antonio Caballero ◽  
Carlos Cifuentes ◽  
Anthony L. Piro ◽  
Rory Barnes
Keyword(s):  
M Dwarfs ◽  
Habitable Zones

scholarly journals CARMENES: M dwarfs and their planets

2015 ◽  
Vol 11 (S320) ◽  
pp. 388-390
Author(s):  
A. Quirrenbach ◽  
P.J. Amado ◽  
J.A. Caballero ◽  
H. Mandel ◽  
R. Mundt ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Spectral Resolution ◽  
M Dwarfs ◽  
Habitable Zones ◽  
Scientific Goal ◽  
New Instrument ◽  
Fabry Perot ◽  
Calar Alto ◽  
Sufficient Precision

AbstractCARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a new instrument currently undergoing commissioning at the 3.5 m telescope of the Calar Alto Observatory. It has been constructed by a consortium of eleven Spanish and German institutions. The scientific goal of the project is a 600-night radial-velocity survey targeting 300 M dwarfs with sufficient precision to detect terrestrial planets in their habitable zones. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope. Both spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a long-term radial velocity precision of 1 m s−1. The wavelength calibration will be done with Th-Ne and U-Ne emission line lamps, and with Fabry-Pérot etalons.

scholarly journals Recovery of pure C-phycoerythrin from a limestone drought tolerant cyanobacterium Nostoc sp. and evaluation of its biological activity

2020 ◽  
pp. 115-128
Author(s):  
Bahareh Nowruzi ◽  
Hossein Fahimi ◽  
Adriana Sturion Lorenzi
Keyword(s):  
Biological Activity ◽  
Antifungal Agents ◽  
Extreme Environments ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Biotechnological Applications ◽  
Drought Tolerant ◽  
Drought Conditions ◽  
Antibacterial And Antifungal ◽  
First Time

Se realizó la caracterización de ficoeritrina de la cepa A5 de Nostoc sp., seguida de investigación de su actividad biológica para aplicaciones biotecnológicas. Para la extracción de ficoeritrina, el uso de tampón acetato (pH 5.1) produjo 65.04 µg mL-1, y se identificó como C-ficoeritrina. Los resultados de su actividad antioxidante sugirieron su acción como un potente eliminador de radicales libres. Además, la C-ficoeritrina de Nostoc mostró una capacidad notable como agente antibacteriano y antifúngico, con estabilidad significativa de hasta 10 días. La glucosa (4 mg mL-1) fue un buen conservante para la C-ficoeritrina a 25 y 4 ºC. Se obtuvo por primera vez una C-ficoeritrina estable de Nostoc sp. en condiciones de sequía en piedra caliza, lo que demuestra la necesidad de estudiar microorganismos de ambientes extremos. The phycoerythrin characterization from Nostoc sp. strain A5 was done, followed by investigation of its biological activity for biotechnological applications. For phycoerythrin extraction, the use of acetate buffer (pH 5.1) resulted in 65.04 µg mL-1, and C-phycoerythrin was identified. Results of its antioxidant activity suggested action as a potent free radical scavenger. In addition, Nostoc's C-phycoerythrin showed noteworthy ability for antibacterial and antifungal agents with significant stability up to 10 days. Glucose (4 mg mL-1) was a good preservative for C-phycoerythrin at 25 and 4 ºC. A stable C-phycoerythrin from Nostoc sp. was obtained for the first time from limestone drought conditions, showing the need of studying microorganisms from extreme environments.

scholarly journals Detection of O2 Produced Abiotically on Habitable but Lifeless Planets around M-dwarfs

2012 ◽  
Vol 8 (S293) ◽  
pp. 39-45 ◽  
Author(s):  
Tong Li ◽  
Feng Tian
Keyword(s):  
Radiative Transfer ◽  
Molecular Oxygen ◽  
Uv Spectra ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Hitran Database ◽  
M Dwarfs ◽  
Near Ir ◽  
Habitable Zones ◽  
Near Ir Range

AbstractHigh atmospheric abundances of oxygen has been widely considered to be a reliable biosignature for life on exoplanets in the habitable zones of all types of stars. Recently it was proposed that the unique UV spectra of observed planet-hosting M dwarfs could lead to the buildup of molecular oxygen in the atmospheres of habitable but lifeless planets around these stars (Tian et al. 2014). However, the detectability of the accumulated O2 was not modeled. In this work we developed a new line by line radiative transfer model based on HITRAN database and used the model to simulate the reflectivity in the visible and near IR range. We show that abiotically produced and maintained O2 in the 0.2% level is observable at 13105 cm−1 (0.76 μm) with the spectra resolution of 70.

scholarly journals Formation of terrestrial planets from planetesimals around M dwarfs

2007 ◽  
Vol 3 (S249) ◽  
pp. 305-308
Author(s):  
Masahiro Ogihara ◽  
Shigeru Ida
Keyword(s):  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
Type I ◽  
M Dwarfs ◽  
Mean Motion Resonances ◽  
Mean Motion ◽  
Habitable Zones ◽  
Pile Up ◽  
Solar Type ◽  
Water Contents

AbstractWe have investigated accretion of terrestrial planets from planetesimals around M dwarfs through N-body simulations including the effect of tidal interaction with disk gas. Because of low luminosity of M dwarfs, habitable zones around them are located near the disk inner edge. Planetary embryos undergo type-I migration and pile up near the disk inner edge. We found that after repeated close scatterings and occasional collisions, three or four planets eventually remain in stable orbits in their mean motion resonances. Furthermore, large amount of water-rich planetesimals rapidly migrate to the terrestrial planet regions from outside of the snow line, so that formed planets in these regions have much more water contents than those around solar-type stars.

scholarly journals Atmospheric Parameters and Luminosities of Nearby M Dwarfs – Estimating Habitable Exoplanet Detectability with the E-ELT

2016 ◽  
Vol 12 (S328) ◽  
pp. 371-373
Author(s):  
Gustavo F. Porto de Mello ◽  
Riano E. Giribaldi ◽  
Diego Lorenzo-Oliveira ◽  
Nathália M. Paes Leme
Keyword(s):  
Spectral Line ◽  
Detailed Analysis ◽  
Atmospheric Parameters ◽  
M Dwarfs ◽  
Habitable Zones ◽  
Pca Method ◽  
Rocky Planets

AbstractWe derive Teff and [Fe/H] for a sample of 72 nearby M-dwarfs with Hipparcos parallaxes and δ < +30. Spectra, acquired at the Observatório do Pico dos Dias, Brazil, have R = 10,000 and S/N ≳ 100 for nearly all targets in the λλ8380-8880 range. Atmospheric parameters were derived from VJHK colors and a system of spectral line indices calibrated against sample stars with interferometric Teff and [Fe/H] from detailed analysis of FGK binary companions. A PCA method of calibration yields internal errors within 70 K and 0.1 dex for Teff and [Fe/H]. For 18 stars we present the first Teff or [Fe/H] derivation in the literature. We compute the star's luminosities, calculate the position of their habitable zones and estimate that, were all of they to harbour rocky planets inside their HZ, 15–20 of these would be detectable by the E-ELT Planetary Camera and Spectrograph.

scholarly journals Screening for Genes Coding for Putative Antitumor Compounds, Antimicrobial and Enzymatic Activities from Haloalkalitolerant and Haloalkaliphilic Bacteria Strains of Algerian Sahara Soils

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Okba Selama ◽  
Gregory C. A. Amos ◽  
Zahia Djenane ◽  
Chiara Borsetto ◽  
Rabah Forar Laidi ◽  
...  
Keyword(s):  
Extreme Environments ◽  
Extreme Environment ◽  
Antibacterial And Antifungal Activities ◽  
Algerian Sahara ◽  
Antitumor Compounds ◽  
Haloalkaliphilic Bacteria ◽  
Novel Bacteria ◽  
Antibacterial And Antifungal ◽  
First Time ◽  
Bacterial Groups

Extreme environments may often contain unusual bacterial groups whose physiology is distinct from those of normal environments. To satisfy the need for new bioactive pharmaceuticals compounds and enzymes, we report here the isolation of novel bacteria from an extreme environment. Thirteen selected haloalkalitolerant and haloalkaliphilic bacteria were isolated from Algerian Sahara Desert soils. These isolates were screened for the presence of genes coding for putative antitumor compounds using PCR based methods. Enzymatic, antibacterial, and antifungal activities were determined by using cultural dependant methods. Several of these isolates are typical of desert and alkaline saline soils, but, in addition, we report for the first time the presence of a potential new member of the genusNocardiawith particular activity against the yeastSaccharomyces cerevisiae. In addition to their haloalkali character, the presence of genes coding for putative antitumor compounds, combined with the antimicrobial activity against a broad range of indicator strains and their enzymatic potential, makes them suitable for biotechnology applications.

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