scholarly journals Detectability of biosignatures on LHS 1140 b

2021 ◽  
Author(s):  
Fabian Wunderlich ◽  
Markus Scheucher ◽  
John Lee Grenfell ◽  
Franz Schreier ◽  
Clara Sousa-Silva ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Spectral Feature ◽  
Absorption Feature ◽  
M Dwarfs ◽  
Surface Conditions ◽  
Mixing Ratios ◽  
Molecular Features ◽  
James Webb Space Telescope ◽  
Surface Mixing ◽  
Near Future

<p>Rocky extrasolar planets orbiting M dwarfs are prime targets in the search for habitable surface conditions and biosignatures with near-future telescopes like the James Webb Space Telescope (JWST) and the Extremely Large Telescope (ELT). Even for the closest known targets the capabilities to characterize Earth-like or CO<sub>2</sub>-dominated atmospheres with JWST or ELT might still be limited to a few molecules such as CO<sub>2</sub> or CH<sub>4</sub>. Hence it would be difficult to draw conclusions on the surface conditions and potential habitability of these planets. In clear H<sub>2</sub>-He atmospheres the molecular features in transmission spectra could be much larger and hence potential biosignatures might be detectable.</p><p>In this study, we investigate the detectability of the potential biosignatures NH<sub>3</sub>, PH<sub>3</sub>, CH<sub>3</sub>Cl, and N<sub>2</sub>O, assuming different H<sub>2</sub>-He atmospheres for the habitable zone super-Earth LHS 1140 b. Recent observations of the atmosphere of LHS 1140 b suggest that the planet might hold a clear H<sub>2</sub>-dominated atmosphere and might show an absorption feature around 1.4 µm due to H<sub>2</sub>O or CH<sub>4</sub> absorption. Here we use the coupled convective-climate-photochemistry model 1D-TERRA to simulate H<sub>2</sub> atmospheres of LHS 1140 b with different amounts of CH<sub>4</sub> and assuming that the planet has an ocean and a biosphere.</p><p>The destruction of the potential biosignatures NH<sub>3</sub>, PH<sub>3</sub>, CH<sub>3</sub>Cl, and N<sub>2</sub>O shows a weak dependence on the concentrations of CH<sub>4</sub>. For weak abundances of CH<sub>4</sub> only 5 to 10 transits are required to detect these molecules with JWST or ELT. However, for CH<sub>4</sub> surface mixing ratios of a few percent only NH<sub>3</sub> and N<sub>2</sub>O might be detectable with less than 10 transits. A scenario with large abundances of CH<sub>4</sub> is consistent with the spectral feature at 1.4 µm and such an atmosphere might allow habitable surface temperatures. If this spectral feature at 1.4 µm originates from H<sub>2</sub>O absorption, the planet is likely not habitable at the surface.</p>

scholarly journals Characterization and mapping of hematite ore mineral classes using hyperspectral remote sensing technique: a case study from Bailadila iron ore mining region

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Ibrahim Shaik ◽  
S. K. Begum ◽  
P. V. Nagamani ◽  
Narayan Kayet
Keyword(s):  
Infrared Absorption ◽  
Near Infrared ◽  
Spectral Feature ◽  
Absorption Feature ◽  
X Ray ◽  
Remote Sensing Technique ◽  
Ore Minerals ◽  
Feature Fitting ◽  
Hematite Ore

AbstractThe study demonstrates a methodology for mapping various hematite ore classes based on their reflectance and absorption spectra, using Hyperion satellite imagery. Substantial validation is carried out, using the spectral feature fitting technique, with the field spectra measured over the Bailadila hill range in Chhattisgarh State in India. The results of the study showed a good correlation between the concentration of iron oxide with the depth of the near-infrared absorption feature (R2 = 0.843) and the width of the near-infrared absorption feature (R2 = 0.812) through different empirical models, with a root-mean-square error (RMSE) between < 0.317 and < 0.409. The overall accuracy of the study is 88.2% with a Kappa coefficient value of 0.81. Geochemical analysis and X-ray fluorescence (XRF) of field ore samples are performed to ensure different classes of hematite ore minerals. Results showed a high content of Fe > 60 wt% in most of the hematite ore samples, except banded hematite quartzite (BHQ) (< 47 wt%).

scholarly journals Assessment of Tropospheric Concentrations of NO2 from the TROPOMI/Sentinel-5 Precursor for the Estimation of Long-Term Exposure to Surface NO2 over South Korea

2021 ◽  
Vol 13 (10) ◽  
pp. 1877
Author(s):  
Ukkyo Jeong ◽  
Hyunkee Hong
Keyword(s):  
South Korea ◽  
Spatial Resolution ◽  
Atmospheric Composition ◽  
Mixing Ratio ◽  
Mean Values ◽  
Mixing Ratios ◽  
Tropospheric No2 ◽  
Korean Ministry ◽  
Surface Mixing ◽  
Rural Sites

Since April 2018, the TROPOspheric Monitoring Instrument (TROPOMI) has provided data on tropospheric NO2 column concentrations (CTROPOMI) with unprecedented spatial resolution. This study aims to assess the capability of TROPOMI to acquire high spatial resolution data regarding surface NO2 mixing ratios. In general, the instrument effectively detected major and moderate sources of NO2 over South Korea with a clear weekday–weekend distinction. We compared the CTROPOMI with surface NO2 mixing ratio measurements from an extensive ground-based network over South Korea operated by the Korean Ministry of Environment (SKME; more than 570 sites), for 2019. Spatiotemporally collocated CTROPOMI and SKME showed a moderate correlation (correlation coefficient, r = 0.67), whereas their annual mean values at each site showed a higher correlation (r = 0.84). The CTROPOMI and SKME were well correlated around the Seoul metropolitan area, where significant amounts of NO2 prevailed throughout the year, whereas they showed lower correlation at rural sites. We converted the tropospheric NO2 from TROPOMI to the surface mixing ratio (STROPOMI) using the EAC4 (ECMWF Atmospheric Composition Reanalysis 4) profile shape, for quantitative comparison with the SKME. The estimated STROPOMI generally underestimated the in-situ value obtained, SKME (slope = 0.64), as reported in previous studies.

Atmospheric dynamics of tidally synchronized extrasolar planets

2008 ◽  
Vol 366 (1884) ◽  
pp. 4477-4488 ◽  
Author(s):  
James Y.-K Cho
Keyword(s):  
Temperature Distribution ◽  
Solar System ◽  
Flow Pattern ◽  
Extrasolar Planets ◽  
Atmospheric Dynamics ◽  
Reliable Interpretation ◽  
Near Future ◽  
Theoretical Issues

Tidally synchronized planets present a new opportunity for enriching our understanding of atmospheric dynamics on planets. Subject to an unusual forcing arrangement (steady irradiation on the same side of the planet throughout its orbit), the dynamics on these planets may be unlike that on any of the Solar System planets. Characterizing the flow pattern and temperature distribution on the extrasolar planets is necessary for reliable interpretation of data currently being collected, as well as for guiding future observations. In this paper, several fundamental concepts from atmospheric dynamics, likely to be central for characterization, are discussed. Theoretical issues that need to be addressed in the near future are also highlighted.

scholarly journals Historical greenhouse gas concentrations

2016 ◽  
Author(s):  
Malte Meinshausen ◽  
Elisabeth Vogel ◽  
Alexander Nauels ◽  
Katja Lorbacher ◽  
Nicolai Meinshausen ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gas ◽  
Radiative Forcing ◽  
Sulfur Hexafluoride ◽  
Climate Model ◽  
Future Climate Change ◽  
Large Set ◽  
Mixing Ratios ◽  
Surface Mixing ◽  
Cooling Effects

Abstract. Atmospheric greenhouse gas concentrations are at unprecedented, record-high levels compared to pre-industrial reconstructions over the last 800,000 years. Those elevated greenhouse gas concentrations warm the planet and together with net cooling effects by aerosols, they are the reason of observed climate change over the past 150 years. An accurate representation of those concentrations is hence important to understand and model recent and future climate change. So far, community efforts to create composite datasets with seasonal and latitudinal information have focused on marine boundary layer conditions and recent trends since 1980s. Here, we provide consolidated data sets of historical atmospheric (volume) mixing ratios of 43 greenhouse gases specifically for the purpose of climate model runs. The presented datasets are based on AGAGE and NOAA networks and a large set of literature studies. In contrast to previous intercomparisons, the new datasets are latitudinally resolved, and include seasonality over the period between year 0 to 2014. We assimilate data for CO2, methane (CH4) and nitrous oxide (N2O), 5 chlorofluorocarbons (CFCs), 3 hydrochlorofluorocarbons (HCFCs), 16 hydrofluorocarbons (HFCs), 3 halons, methyl bromide (CH3Br), 3 perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen triflouride (NF3) and sulfuryl fluoride (SO2F2). We estimate 1850 annual and global mean surface mixing ratios of CO2 at 284.3 ppmv, CH4 at 808.2 ppbv and N2O at 273.0 ppbv and quantify the seasonal and hemispheric gradients of surface mixing ratios. Compared to earlier intercomparisons, the stronger implied radiative forcing in the northern hemisphere winter (due to the latitudinal gradient and seasonality) may help to improve the skill of climate models to reproduce past climate and thereby reduce uncertainty in future projections.

scholarly journals The Hubble PanCET program: Transit and Eclipse Spectroscopy of the Hot-Jupiter WASP-74b

2021 ◽  
Vol 162 (6) ◽  
pp. 271
Author(s):  
Guangwei Fu ◽  
Drake Deming ◽  
Erin May ◽  
Kevin Stevenson ◽  
David K. Sing ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Hubble Space Telescope ◽  
Absorption Feature ◽  
Spectral Library ◽  
Data Set ◽  
Space Telescope ◽  
Methane Absorption ◽  
James Webb Space Telescope ◽  
Hot Jupiter

Abstract Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results.

Incorporation and evaluation of the CRI v2.2 chemical mechanism in UKESM1: An alternative mechanism with updated isoprene chemistry for investigating the influence of BVOCs on atmospheric composition and climate. 

2021 ◽  
Author(s):  
James Weber ◽  
Scott Archer-Nicholls ◽  
N. Luke Abraham ◽  
Youngsub M. Shin ◽  
Thomas Bannan ◽  
...  
Keyword(s):  
Peroxy Radical ◽  
Tropospheric Chemistry ◽  
Chemical Mechanism ◽  
Atmospheric Composition ◽  
Radiation Budget ◽  
Alternative Mechanism ◽  
Mixing Ratios ◽  
The United Kingdom ◽  
Surface Mixing ◽  
Phase Chemistry

&lt;p&gt;We present the first incorporation and evaluation of the Common Representative Intermediates version 2.2 chemistry mechanism, CRI v2.2, for use in the United Kingdom Earth System Model (UKESM1). Tuned against the MCM v3.3.1, the CRI v2.2 mechanism builds on the previous CRI version, CRI v2.1, in UKESM1 (Archer-Nicholls et al., 2020) by updating isoprene chemistry and offers a more comprehensive description of tropospheric chemistry than the standard chemistry mechanism STRAT-TROP (ST).&lt;/p&gt;&lt;p&gt;&lt;span&gt;CRI v2.2 adds state-of-the-art isoprene chemistry with the introduction of HO&lt;/span&gt;&lt;sub&gt;&lt;span&gt;x&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;-recycling via the isoprene peroxy radical isomerisation pathway, &lt;/span&gt;&lt;span&gt;making UKESM1 one of the first CMIP6 models to include this important chemistry. &lt;/span&gt;&lt;span&gt;HO&lt;/span&gt;&lt;sub&gt;&lt;span&gt;x&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;-recycling has noticeable effects on oxidants in regions with large emissions of biogenic volatile organic compounds (BVOCs). Low altitude OH in tropical forested regions increases by 75-150% relative to ST, reducing the existing model low bias compared to observations. Consequently, isoprene surface mixing ratios decrease considerably (25-40%), significantly improving the model high bias relative to ST. Methane lifetime decreases by 2% and tropospheric ozone burden increases by 4%. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;Aerosol processes also differ between CRI v2.2 and ST, resulting in changes to the size and number distributions. Relative to ST, CRI v2.2 simulates an 8% decrease in the sulphate aerosol burden with 20% decreases in the nucleation and Aitken modes. By contrast, the secondary organic aerosol (SOA) nucleation mode burden increases by 11%. Globally, the average nucleation and Aitken mode aerosol number concentrations decrease by 20%.&lt;/p&gt;&lt;p&gt;The differences in aerosol and gas phase chemistry between CRI v2.2 and ST are likely to have impacts on the radiation budget. We plan to use CRI v2.2 and ST to investigate the influence that the chemical mechanism has on the simulated chemistry-climate feedbacks from BVOCs. In addition, CRI v2.2 will serve as the basis for the addition of a scheme describing the formation of highly oxygenated organic molecules (HOMs) from BVOCs, facilitating a semi-explicit mechanism for new particle formation from organic species.&lt;/p&gt;

scholarly journals Properties of sub-Neptune atmospheres: TOI-270 system

2020 ◽  
Vol 495 (1) ◽  
pp. 962-970
Author(s):  
J Chouqar ◽  
Z Benkhaldoun ◽  
A Jabiri ◽  
J Lustig-Yaeger ◽  
A Soubkiou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Signal To Noise Ratio ◽  
Spectral Features ◽  
Transmission Spectra ◽  
Infrared Transmission ◽  
Signal To Noise ◽  
Space Telescope ◽  
Molecular Features ◽  
James Webb Space Telescope ◽  
Mean Molecular Weight

ABSTRACT We investigate the potential for the James Webb Space Telescope (JWST) to detect and characterize the atmospheres of the sub-Neptunian exoplanets in the TOI-270 system. Sub-Neptunes are considered more likely to be water worlds than gas dwarfs. We model their atmospheres using three atmospheric compositions – two examples of hydrogen-dominated atmospheres and a water-dominated atmosphere. We then simulate the infrared transmission spectra of these atmospheres for JWST instrument modes optimized for transit observation of exoplanet atmospheres: NIRISS, NIRSpec, and MIRI. We then predict the observability of each exoplanet’s atmosphere. TOI-270c and d are excellent targets for detecting atmospheres with JWST transmission spectroscopy, requiring only 1 transit observation with NIRISS, NIRSpec, and MIRI; higher signal-to-noise ratio can be obtained for a clear H-rich atmosphere. Fewer than three transits with NIRISS and NIRSpec may be enough to reveal molecular features. Water-dominated atmospheres require more transits. Water spectral features in water-dominated atmospheres may be detectable with NIRISS in two or three transits. We find that the detection of spectral features in a cloudy, H-rich atmosphere does not require integrations as long as those required for the water-dominated atmosphere, which is consistent with the differences in atmospheric mean molecular weight. TOI-270c and d could be prime targets for JWST transit observations of sub-Neptune atmospheres. These results provide useful predictions for observers who may propose to use JWST to detect and characterize the TOI-270 planet atmospheres.

scholarly journals Single-photon laser-induced fluorescence detection of nitric oxide at sub-parts-per-trillion mixing ratios

2020 ◽  
Vol 13 (5) ◽  
pp. 2425-2439 ◽  
Author(s):  
Andrew W. Rollins ◽  
Pamela S. Rickly ◽  
Ru-Shan Gao ◽  
Thomas B. Ryerson ◽  
Steven S. Brown ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Detection Limit ◽  
Fluorescence Detection ◽  
Narrow Band ◽  
Single Photon ◽  
Spectral Feature ◽  
Laser Induced Fluorescence ◽  
Mixing Ratios ◽  
Laser Induced Fluorescence Detection ◽  
Direct Measurements

Abstract. We describe a newly developed single-photon laser-induced fluorescence sensor for measurements of nitric oxide (NO) in the atmosphere. Rapid tuning of a narrow-band laser on and off of a rotationally resolved NO spectral feature near 215 nm and detection of the red-shifted fluorescence provides for interference-free direct measurements of NO with a detection limit of 1 part per trillion by volume (pptv) for 1 s of integration, or 0.3 pptv for 10 s of integration. Uncertainty in the sensitivity of the instrument is typically ±6–9 %, with no known interferences. Uncertainty in the zero of the detector is shown to be <0.2 pptv. The instrument was deployed on the NASA DC-8 aircraft during the NASA/NOAA FIREX-AQ experiment (Fire Influence on Regional to Global Environments Experiment – Air Quality) during July–September 2019 and provided more than 140 h of NO measurements over 22 flights, demonstrating the ability of this instrument to operate routinely and autonomously. Comparisons with a seasoned chemiluminescence sensor during FIREX-AQ in a variety of chemical environments provides validation and confidence in the accuracy of this technique.

scholarly journals Future Directions for Radial-Velocity Research

1999 ◽  
Vol 170 ◽  
pp. 401-409
Author(s):  
David W. Latham
Keyword(s):  
Radial Velocity ◽  
Extrasolar Planets ◽  
Space Missions ◽  
Galactic Structure ◽  
M Dwarfs ◽  
Future Directions ◽  
The Status ◽  
The Impact

AbstractI review the status of ground-based radial-velocity searches for extrasolar planets and speculate about the new results that can be expected in this field over the coming years. Then I review the plans for astrometric space missions and speculate about the impact that these missions will have on ground-based radial-velocity work, citing the specific examples of extra-solar planet research, the mass-luminosity relation for M dwarfs and metal-poor stars, and Galactic structure and evolution.

scholarly journals The habitability of stagnant-lid Earths around dwarf stars

2019 ◽  
Vol 625 ◽  
pp. A12 ◽  
Author(s):  
Mareike Godolt ◽  
Nicola Tosi ◽  
Barbara Stracke ◽  
John Lee Grenfell ◽  
Thomas Ruedas ◽  
...  
Keyword(s):  
Water Loss ◽  
Main Sequence ◽  
Extrasolar Planets ◽  
Water Reservoir ◽  
Habitable Zone ◽  
High Luminosity ◽  
Dwarf Stars ◽  
Surface Conditions ◽  
M Dwarf Stars ◽  
M Dwarf

Context. The habitability of a planet depends on various factors, such as the delivery of water during its formation, the co-evolution of the interior and the atmosphere, and the stellar irradiation which changes in time. Aims. Since an unknown number of rocky extrasolar planets may operate in a one-plate convective regime, i.e. without plate tectonics, our aim is to understand the conditions under which planets in such a stagnant-lid regime may support habitable surface conditions. Understanding the interaction of the planetary interior and outgassing of volatiles in combination with the evolution of the host star is crucial to determining the potential habitability. M-dwarf stars in particular possess a high-luminosity pre-main sequence phase that endangers the habitability of planets around them via water loss. We therefore explore the potential of secondary outgassing from the planetary interior to rebuild a water reservoir allowing for habitability at a later stage. Methods. We compute the boundaries of the habitable zone around M-, K-, G-, and F-dwarf stars using a 1D cloud-free radiative-convective climate model accounting for the outgassing history of CO2 and H2O from an interior evolution and outgassing model for different interior compositions and stellar luminosity evolutions. Results. The outer edge of the habitable zone strongly depends on the amount of CO2 outgassed from the interior, while the inner edge is mainly determined via the stellar irradiation, as soon as a sufficiently large water reservoir has been outgassed. A build-up of a secondary surface and atmospheric water reservoir for planets around M-dwarf stars is possible even after severe water loss during the high-luminosity pre-main sequence phase as long as some water has been retained within the mantle. For small mantle water reservoirs, between 62 and 125 ppm, a time delay in outgassing from the interior permits such a secondary water reservoir build-up especially for early and mid-M dwarfs because their pre-main sequence lifetimes are shorter than the outgassing timescale. Conclusions. We show that Earth-like stagnant-lid planets allow for habitable surface conditions within a continuous habitable zone that is dependent on interior composition. Secondary outgassing from the interior may allow for habitability of planets around M-dwarf stars after severe water loss during the high-luminosity pre-main sequence phase by rebuilding a surface water reservoir.

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