Neutral atmospheric escape in the Solar and extrasolar planetary systems

2018 ◽  
Vol 14 (S345) ◽  
pp. 168-171
Author(s):  
Dmitry V. Bisikalo ◽  
Valery I. Shematovich
Keyword(s):  
Solar System ◽  
Mass Loss ◽  
Planetary Atmospheres ◽  
Space Missions ◽  
Kinetic Approach ◽  
Terrestrial Planets ◽  
Outer Solar System ◽  
Mars Express ◽  
Atmospheric Escape ◽  
Atmospheric Loss

AbstractNew data obtained by space missions to various objects in the Solar system and observations of the outer Solar system and exoplanets by space and ground-based telescopes allowed us to conclude that the atmospheric escape plays an important role in the evolution of the terrestrial planets in the Solar system. We present the recent results of application of the kinetic approach to the problem of neutral escape from planetary atmospheres. As an example, the recent measurements by Mars Express and MAVEN spacecraft are compared with the calculations of neutral escape with the aim to understand the atmospheric loss at Mars. Also the recent calculations of the mass-loss rates of the hot Neptune and Jupiter atmospheres are presented.

scholarly journals Hydrogen Dominated Atmospheres on Terrestrial Mass Planets: Evidence, Origin and Evolution

2020 ◽  
Vol 216 (8) ◽  
Author(s):  
J. E. Owen ◽  
I. F. Shaikhislamov ◽  
H. Lammer ◽  
L. Fossati ◽  
M. L. Khodachenko
Keyword(s):  
Solar System ◽  
Large Population ◽  
High Energy ◽  
Terrestrial Planets ◽  
Important Process ◽  
X Ray ◽  
Origin And Evolution ◽  
Atmospheric Escape ◽  
Low Mass ◽  
High Energy Emission

AbstractThe discovery of thousands of highly irradiated, low-mass, exoplanets has led to the idea that atmospheric escape is an important process that can drive their evolution. Of particular interest is the inference from recent exoplanet detections that there is a large population of low mass planets possessing significant, hydrogen dominated atmospheres, even at masses as low as $\sim 2~\mbox{M}_{\oplus }$ ∼ 2 M ⊕ . The size of these hydrogen dominated atmospheres indicates the envelopes must have been accreted from the natal protoplanetary disc. This inference is in contradiction with the Solar System terrestrial planets, that did not reach their final masses before disc dispersal, and only accreted thin hydrogen dominated atmospheres. In this review, we discuss the evidence for hydrogen dominated atmospheres on terrestrial mass ($\lesssim 2~\mbox{M}_{\oplus }$ ≲ 2 M ⊕ ) planets. We then discuss the possible origins and evolution of these atmospheres with a focus on the role played by hydrodynamic atmospheric escape driven by the stellar high-energy emission (X-ray and EUV; XUV).

scholarly journals Tracing the ingredients for a habitable earth from interstellar space through planet formation

2015 ◽  
Vol 112 (29) ◽  
pp. 8965-8970 ◽  
Author(s):  
Edwin A. Bergin ◽  
Geoffrey A. Blake ◽  
Fred Ciesla ◽  
Marc M. Hirschmann ◽  
Jie Li
Keyword(s):  
Large Scale ◽  
Terrestrial Planets ◽  
Interstellar Space ◽  
Atmospheric Escape ◽  
The Core ◽  
Bulk Silicate Earth ◽  
Thermally Processed ◽  
C And N ◽  
Volatile Loss ◽  
Atmospheric Loss

We use the C/N ratio as a monitor of the delivery of key ingredients of life to nascent terrestrial worlds. Total elemental C and N contents, and their ratio, are examined for the interstellar medium, comets, chondritic meteorites, and terrestrial planets; we include an updated estimate for the bulk silicate Earth (C/N = 49.0 ± 9.3). Using a kinetic model of disk chemistry, and the sublimation/condensation temperatures of primitive molecules, we suggest that organic ices and macromolecular (refractory or carbonaceous dust) organic material are the likely initial C and N carriers. Chemical reactions in the disk can produce nebular C/N ratios of ∼1–12, comparable to those of comets and the low end estimated for planetesimals. An increase of the C/N ratio is traced between volatile-rich pristine bodies and larger volatile-depleted objects subjected to thermal/accretional metamorphism. The C/N ratios of the dominant materials accreted to terrestrial planets should therefore be higher than those seen in carbonaceous chondrites or comets. During planetary formation, we explore scenarios leading to further volatile loss and associated C/N variations owing to core formation and atmospheric escape. Key processes include relative enrichment of nitrogen in the atmosphere and preferential sequestration of carbon by the core. The high C/N bulk silicate Earth ratio therefore is best satisfied by accretion of thermally processed objects followed by large-scale atmospheric loss. These two effects must be more profound if volatile sequestration in the core is effective. The stochastic nature of these processes hints that the surface/atmospheric abundances of biosphere-essential materials will likely be variable.

scholarly journals Losing oceans: The effects of composition on the thermal component of impact-driven atmospheric loss

2020 ◽  
Vol 501 (1) ◽  
pp. 587-595
Author(s):  
John B Biersteker ◽  
Hilke E Schlichting
Keyword(s):  
Noble Gas ◽  
Terrestrial Planet ◽  
Terrestrial Planets ◽  
Thermal Heating ◽  
Atmospheric Escape ◽  
Giant Impacts ◽  
Volatile Loss ◽  
Atmospheric Loss ◽  
The Impact ◽  
Mean Molecular Weight

ABSTRACT The formation of the Solar system’s terrestrial planets concluded with a period of giant impacts. Previous works examining the volatile loss caused by the impact shock in the moon-forming impact find atmospheric losses of at most 20–30 per cent and essentially no loss of oceans. However, giant impacts also result in thermal heating, which can lead to significant atmospheric escape via a Parker-type wind. Here we show that H2O and other high-mean molecular weight outgassed species can be efficiently lost through this thermal wind if present in a hydrogen-dominated atmosphere, substantially altering the final volatile inventory of terrestrial planets. We demonstrate that a giant impact during terrestrial planet formation can remove several Earth oceans’ worth of H2O, and other heavier volatile species, together with a primordial hydrogen-dominated atmosphere. These results may offer an explanation for the observed depletion in Earth’s light noble gas budget and for its depleted xenon inventory, which suggest that Earth underwent significant atmospheric loss by the end of its accretion. Because planetary embryos are massive enough to accrete primordial hydrogen envelopes and because giant impacts are stochastic and occur concurrently with other early atmospheric evolutionary processes, our results suggest a wide diversity in terrestrial planet volatile budgets.

The contribution of Centaur-emitted dust to the interplanetary dust distribution

2019 ◽  
Vol 490 (2) ◽  
pp. 2421-2429 ◽  
Author(s):  
A R Poppe
Keyword(s):  
Solar System ◽  
Mass Loss ◽  
Kuiper Belt ◽  
Interplanetary Dust ◽  
Outer Solar System ◽  
Dust Grains ◽  
Kuiper Belt Objects ◽  
Dust Density ◽  
Outer Planets ◽  
Current Mass

ABSTRACT Interplanetary dust grains originate from a variety of source bodies, including comets, asteroids, and Edgeworth–Kuiper belt objects. Centaurs, generally defined as those objects with orbits that cross the outer planets, have occasionally been observed to exhibit cometary-like outgassing at distances beyond Jupiter, implying that they may be an important source of dust grains in the outer Solar system. Here, we use an interplanetary dust grain dynamics model to study the behaviour and equilibrium distribution of Centaur-emitted interplanetary dust grains. We focus on the five Centaurs with the highest current mass-loss rates: 29P/Schwassmann-Wachmann 1, 166P/2001 T4, 174P/Echeclus, C/2001 M10, and P/2004 A1, which together comprise 98 per cent of the current mass loss from all Centaurs. Our simulations show that Centaur-emitted dust grains with radii s < 2 μm have median lifetimes consistent with Poynting–Robertson (P–R) drag lifetimes, while grains with radii s > 2 μm have median lifetimes much shorter than their P–R drag lifetimes, suggesting that dynamical interactions with the outer planets are effective in scattering larger grains, in analogy to the relatively short lifetimes of Centaurs themselves. Equilibrium density distributions of grains emitted from specific Centaurs show a variety of structure including local maxima in the outer Solar system and azimuthal asymmetries, depending on the orbital elements of the parent Centaur. Finally, we compare the total Centaur interplanetary dust density to dust produced from Edgeworth–Kuiper belt objects, Jupiter-family comets, and Oort cloud comets, and conclude that Centaur-emitted dust may be an important component between 5 and 15 au, contributing approximately 25 per cent of the local interplanetary dust density at Saturn.

scholarly journals EUV irradiation of exoplanet atmospheres occurs on Gyr time-scales

2020 ◽  
Vol 501 (1) ◽  
pp. L28-L32
Author(s):  
George W King ◽  
Peter J Wheatley
Keyword(s):  
Mass Loss ◽  
Time Scales ◽  
High Energy ◽  
Planetary Atmospheres ◽  
X Rays ◽  
X Ray ◽  
Atmospheric Escape ◽  
Euv Emission ◽  
Energy Emission ◽  
High Energy Emission

ABSTRACT Exoplanet atmospheres are known to be vulnerable to mass-loss through irradiation by stellar X-ray and extreme-ultraviolet (EUV) emission. We investigate how this high-energy irradiation varies with time by combining an empirical relation describing stellar X-ray emission with a second relation describing the ratio of solar X-ray to EUV emission. In contrast to assumptions commonly made when modelling atmospheric escape, we find that the decline in stellar EUV emission is much slower than in X-rays, and that the total EUV irradiation of planetary atmospheres is dominated by emission after the saturated phase of high-energy emission (which lasts around 100 Myr after the formation of the star). The EUV spectrum also becomes much softer during this slow decline. Furthermore, we find that the total combined X-ray and EUV emission of stars occurs mostly after the saturated phase. Our results suggest that models of atmospheric escape that focus on the saturated phase of high-energy emission are oversimplified, and when considering the evolution of planetary atmospheres it is necessary to follow EUV-driven escape on Gyr time-scales. This may make it more difficult to use stellar age to separate the effects of photoevaporation and core-powered mass-loss when considering the origin of the planet radius valley.

Magnetic Fields, Atmospheres, and the Connection to Habitability (MACH) – Using Team Science to determine how magnetic fields influence habitability

2021 ◽  
Author(s):  
Dave Brain ◽  
William Peterson ◽  
Ofer Cohen ◽  
Tom Cravens ◽  
Kevin France ◽  
...  
Keyword(s):  
Solar System ◽  
Magnetic Fields ◽  
Giant Planets ◽  
Central Question ◽  
Science Center ◽  
Atmospheric Escape ◽  
The Past ◽  
Terrestrial Magnetosphere ◽  
Global Magnetic Field ◽  
Atmospheric Loss

&lt;p&gt;In order to determine the extent to which a global magnetic field is required for a planet to be habitable at its surface, expertise is required from diverse communities, some of which have diverged from each other over the past several decades. For example, modelers and observers of the terrestrial magnetosphere have limited overlap and interaction with modelers and observers of unmagnetized planets or the giant planets in our solar system. There is relatively limited interaction between any of the above communities and those who study exoplanets, though efforts are increasing to bridge the solar system and exoplanet communities.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We describe a NASA Heliophysics DRIVE Science Center selected to answer the central question of this session: &amp;#8220;Do Habitable Worlds Require Magnetic Fields&amp;#8221;. This Center, named MACH (Magnetic Fields, Atmospheres, and the Connection to Habitability) includes scientists who study atmospheric escape from Earth, unmagnetized planets, and exoplanets. Over the next several years MACH will construct a framework that enables the evaluation of atmospheric loss from an arbitrary rocky planet, given information about the planet and its host star. The MACH Center hosted a community-wide workshop in June 2021 centered around this topic, and is seeking to grow their interactions with interested scientists from relevant disciplines.&lt;/p&gt;

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