scholarly journals Characterization of extrasolar terrestrial planets from diurnal photometric variability

Nature ◽  
2001 ◽  
Vol 412 (6850) ◽  
pp. 885-887 ◽  
Author(s):  
E. B. Ford ◽  
S. Seager ◽  
E. L. Turner
Keyword(s):  
Terrestrial Planets ◽  
Photometric Variability

Impact-induced hydrothermal dissolution in pyroxene: Petrographic and geochemical characterization of basalt-dominated polymict impact breccias from the Vargeão Dome, Brazil

2021 ◽  
Author(s):  
Jennifer Epstein ◽  
Lidia Pittarello ◽  
Álvaro P. Crósta ◽  
Christian Koeberl
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Fluids ◽  
Terrestrial Planets ◽  
Impact Structure ◽  
Impact Event ◽  
Southern Brazil ◽  
Geochemical Characterization ◽  
Heterogeneous Nature ◽  
The Impact

ABSTRACT Constraints on impact-related hydrothermal alteration are important to enable the reconstruction of the possible processes affecting the surface of other terrestrial planets, such as Mars. Terrestrial impact structures excavated in basaltic targets provide the opportunity for analog studies. In Brazil, seven impact structures have been confirmed so far. Three of them, Vargeão Dome, Vista Alegre, and Cerro do Jarau, were formed in the same basaltic province belonging to the Paraná Basin, and they have several common characteristics. Oxidized basaltic breccias locally containing sandstone clasts occur in all these structures. In this work, selected samples of such breccias from the Vargeão Dome impact structure in southern Brazil were petrographically and geochemically investigated to further constrain the effects of the postimpact hydrothermal alteration. The breccia matrix shows typical oxidation effects induced by postimpact hydrothermal fluids, which highlight its heterogeneous nature, related to the impact event, and mixing components from different pre-impact stratigraphic formations. The detection of partially dissolved exsolution lamellae in pyroxene and of related alteration products constrains the effects of hydrothermal alteration in the basalts of the Vargeão Dome, which could serve as a terrestrial analog for planetary studies.

scholarly journals The Virtual Planetary Laboratory: Towards Characterization of Extrasolar Terrestrial Planets

2004 ◽  
Vol 213 ◽  
pp. 129-138
Author(s):  
Victoria Meadows ◽  
David Crisp
Keyword(s):  
Extrasolar Planets ◽  
Terrestrial Planet ◽  
Remotely Sensed ◽  
Search Strategies ◽  
Early Earth ◽  
Terrestrial Planets ◽  
Research Project ◽  
Modeling Tools ◽  
Remotely Sense

NASA and ESA are currently undertaking mission studies for space-based observatories designed to search for life on other worlds. To optimize the designs of these missions, and to ultimately interpret the data sent back by them, we need to recognize habitable worlds and to discriminate between planets with and without life based only on remotely-sensed information. This paper provides an overview of the characteristics we would look for on an extrasolar terrestrial planet that might indicate habitability or the presence of life. It also describes a new NASA Astrobiology Institute research project to develop an innovative suite of modeling tools to simulate the environments and spectra of extrasolar planets. These modeling tools will constitute a Virtual Planetary Laboratory, which will be used to explore the plausible range of atmospheric compositions and globally-averaged spectra for early Earth and for plausible terrestrial planets both with and without life. Products of this research will provide an improved basis for recommending spacecraft and instrument characteristics, as well as search strategies required to remotely sense the signs of life in the atmosphere or on the surface of another world.

scholarly journals Retrieving magma composition from TIR spectra: implications for terrestrial planets investigations

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alessandro Pisello ◽  
Francesco P. Vetere ◽  
Matteo Bisolfati ◽  
Alessandro Maturilli ◽  
Daniele Morgavi ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Degree Of Polymerization ◽  
Snake River Plain ◽  
Reflectance Spectra ◽  
Snake River ◽  
Terrestrial Planets ◽  
Vulcano Island ◽  
End Members ◽  
River Plain

Abstract Emissivity and reflectance spectra have been investigated on two series of silicate glasses, having compositions belonging to alkaline and subalkaline series, covering the most common terrestrial igneous rocks. Glasses were synthesized starting from natural end-members outcropping at Vulcano Island (Aeolian Islands, Italy) and on Snake River Plain (USA). Results show that the shift of the spectra, by taking Christiansen feature (CF) as a reference point, is correlated with SiO2 content, the SCFM factor and/or the degree of polymerization state via the NBO/T and temperature. The more evolved is the composition, the more polymerized the structure, the shorter the wavelength at which CF is observable. CF shift is also dependent on temperature. The shape of the spectra discriminates alkaline character, and it is related to the evolution of Qn structural units. Vulcano alkaline series show larger amount of Q4 and Q3 species even for mafic samples compared to the subalkaline Snake River Plain series. Our results provide new and robust insights for the geochemical characterization of volcanic rocks by remote sensing, with the outlook to infer origin of magmas both on Earth as well as on terrestrial planets or rocky bodies, from emissivity and reflectance spectra.

scholarly journals A multiplanet system of super-Earths orbiting the brightest red dwarf star GJ 887

Science ◽  
2020 ◽  
Vol 368 (6498) ◽  
pp. 1477-1481 ◽  
Author(s):  
S. V. Jeffers ◽  
S. Dreizler ◽  
J. R. Barnes ◽  
C. A. Haswell ◽  
R. P. Nelson ◽  
...  
Keyword(s):  
Solar System ◽  
Equilibrium Temperature ◽  
The Sun ◽  
Habitable Zone ◽  
Dwarf Star ◽  
Velocity Measurements ◽  
Detailed Characterization ◽  
Photometric Variability ◽  
Orbital Periods

The closet exoplanets to the Sun provide opportunities for detailed characterization of planets outside the Solar System. We report the discovery, using radial velocity measurements, of a compact multiplanet system of super-Earth exoplanets orbiting the nearby red dwarf star GJ 887. The two planets have orbital periods of 9.3 and 21.8 days. Assuming an Earth-like albedo, the equilibrium temperature of the 21.8-day planet is ~350 kelvin. The planets are interior to, but close to the inner edge of, the liquid-water habitable zone. We also detect an unconfirmed signal with a period of ~50 days, which could correspond to a third super-Earth in a more temperate orbit. Our observations show that GJ 887 has photometric variability below 500 parts per million, which is unusually quiet for a red dwarf.

scholarly journals Hurricanes on tidally locked terrestrial planets: fixed surface temperature experiments

2020 ◽  
Vol 643 ◽  
pp. A37
Author(s):  
Mingyu Yan ◽  
Jun Yang
Keyword(s):  
Surface Temperature ◽  
Circulation Model ◽  
Terrestrial Planets ◽  
Habitable Zone ◽  
M Dwarfs ◽  
Planetary Rotation ◽  
The Mean ◽  
Global Atmospheric Circulation ◽  
Mean Molecular Weight

Aims. In this work, we study the presence of hurricanes on exoplanets. Tidally locked terrestrial planets around M dwarfs are the main targets of space missions looking to discover habitable exoplanets. The question of whether hurricanes can form on this kind of planet is important for determining their climate and habitability. Methods. Using a high-resolution global atmospheric circulation model, we investigated whether there are hurricanes on tidally locked terrestrial planets under fixed surface temperatures (TS). The relevant effects of the planetary rotation rate, surface temperature, and bulk atmospheric compositions were examined. Results. We find that hurricanes can form on the planets but not on all of them. For planets near the inner edge of the habitable zone of late M dwarfs, there are more numerous and stronger hurricanes on both day and night sides. For planets in the middle and outer ranges of the habitable zone, the possibility of hurricane formation is low or even close to zero, as has been suggested in recent studies. Earth-based hurricane theories are applicable to tidally locked planets only when the atmospheric compositions are similar to that of Earth. However, if the background atmosphere is lighter than H2O, hurricanes can hardly be produced because convection is always inhibited due to the effect of the mean molecular weight, similarly to the case of Saturn. These results have broad implications on the precipitation, ocean mixing, climate, and atmospheric characterization of tidally locked planets. Finally, A test with a coupled slab ocean and an Earth-like atmosphere in a tide-locked orbit of ten Earth days demonstrates that there are also hurricanes present in the experiment.

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

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