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https://www.readbyqxmd.com/read/28692303/searching-for-biosignatures-in-exoplanetary-impact-ejecta
#1
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...
July 10, 2017: Astrobiology
https://www.readbyqxmd.com/read/28611223/enhanced-interplanetary-panspermia-in-the-trappist-1-system
#2
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
#3
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
#4
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
#5
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...
April 26, 2017: Astrobiology
https://www.readbyqxmd.com/read/28418704/false-negatives-for-remote-life-detection-on-ocean-bearing-planets-lessons-from-the-early-earth
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
https://www.readbyqxmd.com/read/28230125/seven-temperate-terrestrial-planets-around-the-nearby-ultracool-dwarf-star-trappist-1
#12
Michaël Gillon, Amaury H M J Triaud, Brice-Olivier Demory, Emmanuël Jehin, Eric Agol, Katherine M Deck, Susan M Lederer, Julien de Wit, Artem Burdanov, James G Ingalls, Emeline Bolmont, Jeremy Leconte, Sean N Raymond, Franck Selsis, Martin Turbet, Khalid Barkaoui, Adam Burgasser, Matthew R Burleigh, Sean J Carey, Aleksander Chaushev, Chris M Copperwheat, Laetitia Delrez, Catarina S Fernandes, Daniel L Holdsworth, Enrico J Kotze, Valérie Van Grootel, Yaseen Almleaky, Zouhair Benkhaldoun, Pierre Magain, Didier Queloz
One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star-named TRAPPIST-1-makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities...
February 22, 2017: Nature
https://www.readbyqxmd.com/read/28103105/evolution-of-earth-like-extrasolar-planetary-atmospheres-assessing-the-atmospheres-and-biospheres-of-early-earth-analog-planets-with-a-coupled-atmosphere-biogeochemical-model
#13
S Gebauer, J L Grenfell, J W Stock, R Lehmann, M Godolt, P von Paris, H Rauer
Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models...
January 2017: Astrobiology
https://www.readbyqxmd.com/read/28057962/exoplanetary-atmospheres-chemistry-formation-conditions-and-habitability
#14
Nikku Madhusudhan, Marcelino Agúndez, Julianne I Moses, Yongyun Hu
Characterizing the atmospheres of extrasolar planets is the new frontier in exoplanetary science. The last two decades of exoplanet discoveries have revealed that exoplanets are very common and extremely diverse in their orbital and bulk properties. We now enter a new era as we begin to investigate the chemical diversity of exoplanets, their atmospheric and interior processes, and their formation conditions. Recent developments in the field have led to unprecedented advancements in our understanding of atmospheric chemistry of exoplanets and the implications for their formation conditions...
December 2016: Space Science Reviews
https://www.readbyqxmd.com/read/27973530/detecting-3d-vegetation-structure-with-the-galileo-space-probe-can-a-distant-probe-detect-vegetation-structure-on-earth
#15
Christopher E Doughty, Adam Wolf
Sagan et al. (1993) used the Galileo space probe data and first principles to find evidence of life on Earth. Here we ask whether Sagan et al. (1993) could also have detected whether life on Earth had three-dimensional structure, based on the Galileo space probe data. We reanalyse the data from this probe to see if structured vegetation could have been detected in regions with abundant photosynthetic pigments through the anisotropy of reflected shortwave radiation. We compare changing brightness of the Amazon forest (a region where Sagan et al...
2016: PloS One
https://www.readbyqxmd.com/read/27870585/another-earth-2-0-not-so-fast
#16
Dirk Schulze-Makuch, Edward Guinan
The number of confirmed exoplanets now exceeds 3000, with an additional nearly 5000 exoplanet candidates awaiting confirmation in the NASA Exoplanet Archive ( 2016 ). Nearly weekly we hear about the detection of a new exoplanet similar in mass to Earth and located in the so-called habitable zone around its host star. The excitement is understandable given our desire to find a second Earth. However, the excitement should not lead to an over-interpretation of the findings, because the claim can only be to have some crude similarity to Earth based on a few selected geophysical parameters...
November 2016: Astrobiology
https://www.readbyqxmd.com/read/27792417/the-pale-orange-dot-the-spectrum-and-habitability-of-hazy-archean-earth
#17
Giada Arney, Shawn D Domagal-Goldman, Victoria S Meadows, Eric T Wolf, Edward Schwieterman, Benjamin Charnay, Mark Claire, Eric Hébrard, Melissa G Trainer
Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects...
November 2016: Astrobiology
https://www.readbyqxmd.com/read/27790984/a-population-of-planetary-systems-characterized-by-short-period-earth-sized-planets
#18
Jason H Steffen, Jeffrey L Coughlin
We analyze data from the Quarter 1-17 Data Release 24 (Q1-Q17 DR24) planet candidate catalog from NASA's Kepler mission, specifically comparing systems with single transiting planets to systems with multiple transiting planets, and identify a population of exoplanets with a necessarily distinct system architecture. Such an architecture likely indicates a different branch in their evolutionary past relative to the typical Kepler system. The key feature of these planetary systems is an isolated, Earth-sized planet with a roughly 1-d orbital period...
October 25, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27671635/exoplanet-orbital-eccentricities-derived-from-lamost-kepler-analysis
#19
Ji-Wei Xie, Subo Dong, Zhaohuan Zhu, Daniel Huber, Zheng Zheng, Peter De Cat, Jianning Fu, Hui-Gen Liu, Ali Luo, Yue Wu, Haotong Zhang, Hui Zhang, Ji-Lin Zhou, Zihuang Cao, Yonghui Hou, Yuefei Wang, Yong Zhang
The nearly circular (mean eccentricity [Formula: see text]) and coplanar (mean mutual inclination [Formula: see text]) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ([Formula: see text]). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27661884/design-trade-off-and-proof-of-concept-for-loupe-the-lunar-observatory-for-unresolved-polarimetry-of-earth
#20
H J Hoeijmakers, M L J Arts, F Snik, C U Keller, J M Kuiper
We provide a proof of the technical feasibility of LOUPE, the first integral-field snapshot spectropolarimeter, designed to monitor the reflected flux and polarization spectrum of Earth. These are to be used as benchmark data for the retrieval of biomarkers and atmospheric and surface characteristics from future direct observations of exoplanets. We perform a design trade-off for an implementation in which LOUPE performs snapshot integral-field spectropolarimetry at visible wavelengths. We used off-the-shelf optics to construct a polarization modulator, in which polarization information is encoded into the spectrum as a wavelength-dependent modulation, while spatial resolution is maintained using a micro-lens array...
September 19, 2016: Optics Express
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