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https://www.readbyqxmd.com/read/29148825/on-the-growth-and-detectability-of-land-plants-on-habitable-planets-around-m-dwarfs
#1
Duo Cui, Feng Tian, Yuwei Wang, Changshen Li, Chaoqing Yu, Le Yu
One signature of life on Earth is the vegetation red edge (VRE) feature of land plants, a dramatic change of reflectivity at wavelength near 0.7 μm. Potentially habitable planets around M dwarfs are tidally locked, which can limit the distribution of land plants. In this study, we used a biogeochemical model to investigate the distribution of land plants on potentially habitable planets around M dwarfs driven by climate data produced in a general circulation model (GCM). When considering the effects of clouds, the observation time needed for VRE detection on nearby p = 1 exoplanets around nearby M dwarfs is on the order of days using a 25 m(2) telescope if a large continent faces Earth during observations...
November 17, 2017: Astrobiology
https://www.readbyqxmd.com/read/29142018/terahertz-dictating-the-frequency-of-life-do-macromolecular-vibrational-modes-impose-thermal-limitations-on-terrestrial-life
#2
Kieran Hand, Edwin Yates
Conditions on exoplanets include elevated temperatures and pressures. The response of carbon-based biological macromolecules to such conditions is then relevant to the viability of life. The capacity of proteins and ribozymes to catalyse reactions or bind receptors, and nucleic acids to convey information, depends on them sampling different conformational states. These are determined by macromolecular vibrational states, or phonon modes, accessible using terahertz (THz: 10(12)Hz) absorption spectroscopy. THz spectra of biological macromolecules exhibit broad absorption at approximately 6 THz (equating to approx...
November 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/29097693/atmospheric-beacons-of-life-from-exoplanets-around-g-and-k-stars
#3
Vladimir S Airapetian, Charles H Jackman, Martin Mlynczak, William Danchi, Linda Hunt
The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments...
November 2, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29041743/ultrafast-laser-inscription-in-zblan-integrated-optics-chips-for-mid-ir-beam-combination-in-astronomical-interferometry
#4
Jan Tepper, Lucas Labadie, Simon Gross, Alexander Arriola, Stefano Minardi, Romina Diener, Michael J Withford
Astronomical interferometry is a unique technique that allows observation with angular resolutions on the milliarcsec scale by combining the light of several apertures hundreds of meters apart. The PIONIER and GRAVITY instruments at the Very Large Telescope Interferometer have demonstrated that silica-based integrated optics (IO) provide a small-scale and highly stable solution for the interferometric beam combination process. Yet, important science cases such as exoplanet hunting or the spectroscopic characterization of exoplanetary atmospheres are favorable for observation in the mid-IR, namely the atmospheric windows L and L' band (3-4 µm), a wavelength range that is not covered by conventional silica-based IO...
August 21, 2017: Optics Express
https://www.readbyqxmd.com/read/29041252/large-format-platinum-silicide-microwave-kinetic-inductance-detectors-for-optical-to-near-ir-astronomy
#5
P Szypryt, S R Meeker, G Coiffard, N Fruitwala, B Bumble, G Ulbricht, A B Walter, M Daal, C Bockstiegel, G Collura, N Zobrist, I Lipartito, B A Mazin
We have fabricated and characterized 10,000 and 20,440 pixel Microwave Kinetic Inductance Detector (MKID) arrays for the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). These instruments are designed to sit behind adaptive optics systems with the goal of directly imaging exoplanets in a 800-1400 nm band. Previous large optical and near-IR MKID arrays were fabricated using substoichiometric titanium nitride (TiN) on a silicon substrate. These arrays, however, suffered from severe non-uniformities in the TiN critical temperature, causing resonances to shift away from their designed values and lowering usable detector yield...
October 16, 2017: Optics Express
https://www.readbyqxmd.com/read/28905896/detection-of-titanium-oxide-in-the-atmosphere-of-a-hot-jupiter
#6
Elyar Sedaghati, Henri M J Boffin, Ryan J MacDonald, Siddharth Gandhi, Nikku Madhusudhan, Neale P Gibson, Mahmoudreza Oshagh, Antonio Claret, Heike Rauer
As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements-such as hydrogen, oxygen, carbon, sodium and potassium-have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive...
September 13, 2017: Nature
https://www.readbyqxmd.com/read/28790357/red-edge-position-of-habitable-exoplanets-around-m-dwarfs
#7
Kenji Takizawa, Jun Minagawa, Motohide Tamura, Nobuhiko Kusakabe, Norio Narita
One of the possible signs of life on distant habitable exoplanets is the red-edge, which is a rise in the reflectivity of planets between visible and near-infrared (NIR) wavelengths. Previous studies suggested the possibility that the red-edge position for habitable exoplanets around M-dwarfs may be shifted to a longer wavelength than that for Earth. We investigated plausible red-edge position in terms of the light environment during the course of the evolution of phototrophs. We show that phototrophs on M-dwarf habitable exoplanets may use visible light when they first evolve in the ocean and when they first colonize the land...
August 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28770846/an-ultrahot-gas-giant-exoplanet-with-a-stratosphere
#8
Thomas M Evans, David K Sing, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R Wakeford, Drake Deming, Mark S Marley, David S Amundsen, Gilda E Ballester, Joanna K Barstow, Lotfi Ben-Jaffel, Vincent Bourrier, Lars A Buchhave, Ofer Cohen, David Ehrenreich, Antonio García Muñoz, Gregory W Henry, Heather Knutson, Panayotis Lavvas, Alain Lecavelier des Etangs, Nikole K Lewis, Mercedes López-Morales, Avi M Mandell, Jorge Sanz-Forcada, Pascal Tremblin, Roxana Lupu
Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum. Conversely, if there is a stratosphere-where temperature increases with altitude-these molecular features will be observed in emission. It has been suggested that stratospheres could form in highly irradiated exoplanets, but the extent to which this occurs is unresolved both theoretically and observationally...
August 2, 2017: Nature
https://www.readbyqxmd.com/read/28770834/astronomy-ozone-like-layer-in-an-exoplanet-atmosphere
#9
Kevin Heng
No abstract text is available yet for this article.
August 2, 2017: Nature
https://www.readbyqxmd.com/read/28692303/searching-for-biosignatures-in-exoplanetary-impact-ejecta
#10
Gianni Cataldi, Alexis Brandeker, Philippe Thébault, Kelsi Singer, Engy Ahmed, Bernard L de Vries, Anna Neubeck, Göran Olofsson
With the number of confirmed rocky exoplanets increasing steadily, their characterization and the search for exoplanetary biospheres are becoming increasingly urgent issues in astrobiology. To date, most efforts have concentrated on the study of exoplanetary atmospheres. Instead, we aim to investigate the possibility of characterizing an exoplanet (in terms of habitability, geology, presence of life, etc.) by studying material ejected from the surface during an impact event. For a number of impact scenarios, we estimate the escaping mass and assess its subsequent collisional evolution in a circumstellar orbit, assuming a Sun-like host star...
August 2017: Astrobiology
https://www.readbyqxmd.com/read/28611223/enhanced-interplanetary-panspermia-in-the-trappist-1-system
#11
Manasvi Lingam, Abraham Loeb
We present a simple model for estimating the probability of interplanetary panspermia in the recently discovered system of seven planets orbiting the ultracool dwarf star TRAPPIST-1 and find that panspermia is potentially orders of magnitude more likely to occur in the TRAPPIST-1 system compared with the Earth-to-Mars case. As a consequence, we argue that the probability of abiogenesis is enhanced on the TRAPPIST-1 planets compared with the solar system. By adopting models from theoretical ecology, we show that the number of species transferred and the number of life-bearing planets are also likely to be higher because of the increased rates of immigration...
June 27, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28495748/hat-p-26b-a-neptune-mass-exoplanet-with-a-well-constrained-heavy-element-abundance
#12
Hannah R Wakeford, David K Sing, Tiffany Kataria, Drake Deming, Nikolay Nikolov, Eric D Lopez, Pascal Tremblin, David S Amundsen, Nikole K Lewis, Avi M Mandell, Jonathan J Fortney, Heather Knutson, Björn Benneke, Thomas M Evans
A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted a detailed atmospheric study of the transiting Neptune-mass exoplanet HAT-P-26b. We detected prominent H2O absorption bands with a maximum base-to-peak amplitude of 525 parts per million in the transmission spectrum...
May 12, 2017: Science
https://www.readbyqxmd.com/read/28495725/how-much-water-is-in-that-exoplanet
#13
EDITORIAL
Keith T Smith
No abstract text is available yet for this article.
May 12, 2017: Science
https://www.readbyqxmd.com/read/28443722/reflections-on-o2-as-a-biosignature-in-exoplanetary-atmospheres
#14
Victoria S Meadows
Oxygenic photosynthesis is Earth's dominant metabolism, having evolved to harvest the largest expected energy source at the surface of most terrestrial habitable zone planets. Using CO2 and H2O-molecules that are expected to be abundant and widespread on habitable terrestrial planets-oxygenic photosynthesis is plausible as a significant planetary process with a global impact. Photosynthetic O2 has long been considered particularly robust as a sign of life on a habitable exoplanet, due to the lack of known "false positives"-geological or photochemical processes that could also produce large quantities of stable O2...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/28418704/false-negatives-for-remote-life-detection-on-ocean-bearing-planets-lessons-from-the-early-earth
#15
Christopher T Reinhard, Stephanie L Olson, Edward W Schwieterman, Timothy W Lyons
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere...
April 2017: Astrobiology
https://www.readbyqxmd.com/read/28408771/was-venus-the-first-habitable-world-of-our-solar-system
#16
M J Way, Anthony D Del Genio, Nancy Y Kiang, Linda E Sohl, David H Grinspoon, Igor Aleinov, Maxwell Kelley, Thomas Clune
Present-day Venus is an inhospitable place with surface temperatures approaching 750K and an atmosphere 90 times as thick as Earth's. Billions of years ago the picture may have been very different. We have created a suite of 3-D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 Gya, present-day Venus orbital parameters, an ocean volume consistent with current theory, and an atmospheric composition estimated for early Venus. Using these parameters we find that such a world could have had moderate temperatures if Venus had a rotation period slower than ~16 Earth days, despite an incident solar flux 46-70% higher than Earth receives...
August 28, 2016: Geophysical Research Letters
https://www.readbyqxmd.com/read/28383497/evo-seti-a-mathematical-tool-for-cladistics-evolution-and-seti
#17
Claudio Maccone
The discovery of new exoplanets makes us wonder where each new exoplanet stands along its way to develop life as we know it on Earth. Our Evo-SETI Theory is a mathematical way to face this problem. We describe cladistics and evolution by virtue of a few statistical equations based on lognormal probability density functions (pdf) in the time. We call b-lognormal a lognormal pdf starting at instant b (birth). Then, the lifetime of any living being becomes a suitable b-lognormal in the time. Next, our "Peak-Locus Theorem" translates cladistics: each species created by evolution is a b-lognormal whose peak lies on the exponentially growing number of living species...
April 6, 2017: Life
https://www.readbyqxmd.com/read/28282216/remote-sensing-of-potential-biosignatures-from-rocky-liquid-or-icy-exo-planetary-surfaces
#18
Olivier Poch, Joachim Frey, Isabel Roditi, Antoine Pommerol, Bernhard Jost, Nicolas Thomas
To detect signs of life by remote sensing on objects of our Solar System and on exoplanets, the characterization of light scattered by surface life material could complement possible clues given by the atmospheric composition. We reviewed the reflectance spectra of a broad selection of major biomolecules that constitute terrestrial carbon-based life from 0.4 to 2.4 μm, and we discuss their detectability through atmospheric spectral windows. Biomolecule features in the near-infrared (0.8-2.4 μm) will likely be obscured by water spectral features and some atmospheric gases...
March 2017: Astrobiology
https://www.readbyqxmd.com/read/28257111/a-cubesat-payload-for-exoplanet-detection
#19
Marcella Iuzzolino, Domenico Accardo, Giancarlo Rufino, Ernesto Oliva, Andrea Tozzi, Pietro Schipani
The search for undiscovered planets outside the solar system is a scientific topic that is rapidly spreading into the astrophysical and engineering communities. In this framework, the design of an innovative payload to detect exoplanets from a nano-sized space platform, like a 3U cubesat, is presented. The selected detection method is photometric transit, and the payload aims to detect flux decrements down to ~0.01% with a precision of 12 ppm. The payload design is also aimed at false positive recognition. The solution consists of a four-facets pyramid on the top of the payload, to allow for measurement redundancy and low-resolution spectral dispersion of the star images...
March 2, 2017: Sensors
https://www.readbyqxmd.com/read/28241521/fabrication-tolerant-chalcogenide-mid-infrared-multimode-interference-coupler-design-with-applications-for-bracewell-nulling-interferometry
#20
Harry-Dean Kenchington Goldsmith, Nick Cvetojevic, Michael Ireland, Stephen Madden
Understanding exoplanet formation and finding potentially habitable exoplanets is vital to an enhanced understanding of the universe. The use of nulling interferometry to strongly attenuate the central star's light provides the opportunity to see objects closer to the star than ever before. Given that exoplanets are usually warm, the 4 µm Mid-Infrared region is advantageous for such observations. The key performance parameters for a nulling interferometer are the extinction ratio it can attain and how well that is maintained across the operational bandwidth...
February 20, 2017: Optics Express
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