Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSeismicity on Tidally Active Solid-Surface Worlds
73
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Tidal interactions between planets or stars and the bodies that orbit them dissipate energy in their interiors. The energy dissipated drives internal heating and a fraction of that energy will be released as seismic energy. Here we formalize a model to describe the tidally-driven seismic activity on planetary bodies based on tidal dissipation.
rate research
Read More
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. Using a high-resolution global atmospheric circulation model, we investigated whether there are hurricanes on tidally locked terrestrial planets under fixed surface temperatures. The relevant effects of the planetary rotation rate, surface temperature, and bulk atmospheric compositions were examined. 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.
We investigate modons on tidally synchronised extrasolar planets. Modons are highly dynamic, coherent flow structures composed of a pair of storms with opposite signs of vorticity. They are important because they divert flows on the large-scale; and, powered by the intense irradiation from the host star, they are planetary-scale sized and exhibit quasi-periodic life-cycles -- chaotically moving around the planet, breaking and reforming many times over long durations (e.g. thousands of planet days). Additionally, modons transport and mix planetary-scale patches of hot and cold air around the planet, leading to high-amplitude and quasi-periodic signatures in the disc-averaged temperature flux. Hence, they induce variations of the hot spot longitude to either side of the planets sub-stellar point -- consistent with observations at different epoch. The variability behaviour in our simulations broadly underscores the importance of accurately capturing vortex dynamics in extrasolar planet atmosphere modelling, particularly in understanding current observations.
Using a shallow water model with time-dependent forcing we show that the peak of an exoplanet thermal phase curve is, in general, offset from secondary eclipse when the planet is rotating. That is, the planetary hot-spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset is a function of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady-state in the reference frame of the moving forcing. The model is an extension of the well studied Matsuno-Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planets surface) exceeds that of the gravity waves then the hotspot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wavespeed of the system the hottest point can lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.
To be habitable, a world (planet or moon) does not need to be located in the stellar habitable zone (HZ), and worlds in the HZ are not necessarily habitable. Here, we illustrate how tidal heating can render terrestrial or icy worlds habitable beyond the stellar HZ. Scientists have developed a language that neglects the possible existence of worlds that offer more benign environments to life than Earth does. We call these objects superhabitable and discuss in which contexts this term could be used, that is to say, which worlds tend to be more habitable than Earth. In an appendix, we show why the principle of mediocracy cannot be used to logically explain why Earth should be a particularly habitable planet or why other inhabited worlds should be Earth-like. Superhabitable worlds must be considered for future follow-up observations of signs of extraterrestrial life. Considering a range of physical effects, we conclude that they will tend to be slightly older and more massive than Earth and that their host stars will likely be K dwarfs. This makes Alpha Centauri B, member of the closest stellar system to the Sun that is supposed to host an Earth-mass planet, an ideal target for searches of a superhabitable world.
The advanced rheological models of Andrade (1910) and Sundberg & Cooper (2010) are compared to the traditional Maxwell model to understand how each affects the tidal dissipation of heat within rocky bodies. We find both the Andrade and Sundberg-Cooper rheologies can produce at least 10$times$ the tidal heating compared to a traditional Maxwell model for a warm (1400-1600 K) Io-like satellite. Sundberg-Cooper can cause even larger dissipation around a critical temperature and frequency. These models allow cooler planets to stay tidally active in the face of orbital perturbations-a condition we term tidal resilience. This has implications for the time evolution of tidally active worlds, and the long-term equilibria they fall into. For instance, if Ios interior is better modeled by the Andrade or Sundberg-Cooper rheologies, the number of possible resonance-forming scenarios that still produce a hot, modern Io is expanded, and these scenarios do not require an early formation of the Laplace resonance. The two primary empirical parameters that define the Andrade anelasticity are examined in several phase spaces to provide guidance on how their uncertainties impact tidal outcomes, as laboratory studies continue to constrain their real values. We provide detailed reference tables on the fully general equations required for others to insert the Andrade and Sundberg-Cooper models into standard tidal formulae. Lastly, we show that advanced rheologies greatly impact the heating of short-period exoplanets and exomoons, while the properties of tidal resilience can mean a greater number of tidally active worlds among all extrasolar systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
