Energetic Requirements for Dynamos in the Metallic Cores of Super‐Earth and Super‐Venus Exoplanets

Blaske, Claire; O’Rourke, J. G.

doi:10.1029/2020je006739

Cited by 8 publications

(5 citation statements)

References 81 publications

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“…Boujibar et al 2020;Bonati et al 2021;van Summeren et al 2013). Simple scaling laws predict that the actual cooling rate of the core would increase with planetary mass faster than the critical value required to drive convection (Blaske and O'Rourke 2021). Super-Venus (and super-Earth) planets are also likely to have basal magma oceans (Soubiran and Militzer 2018) made of liquid silicates that are electrically conductive enough to sustain a dynamo (e.g.…”

Section: Venus' Magnetic Fieldmentioning

confidence: 99%

Synergies Between Venus & Exoplanetary Observations

et al. 2023

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Here we examine how our knowledge of present day Venus can inform terrestrial exoplanetary science and how exoplanetary science can inform our study of Venus. In a superficial way the contrasts in knowledge appear stark. We have been looking at Venus for millennia and studying it via telescopic observations for centuries. Spacecraft observations began with Mariner 2 in 1962 when we confirmed that Venus was a hothouse planet, rather than the tropical paradise science fiction pictured. As long as our level of exploration and understanding of Venus remains far below that of Mars, major questions will endure. On the other hand, exoplanetary science has grown leaps and bounds since the discovery of Pegasus 51b in 1995, not too long after the golden years of Venus spacecraft missions came to an end with the Magellan Mission in 1994. Multi-million to billion dollar/euro exoplanet focused spacecraft missions such as JWST, and its successors will be flown in the coming decades. At the same time, excitement about Venus exploration is blooming again with a number of confirmed and proposed missions in the coming decades from India, Russia, Japan, the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). Here we review what is known and what we may discover tomorrow in complementary studies of Venus and its exoplanetary cousins.

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Section: Venus' Magnetic Fieldmentioning

confidence: 99%

Synergies Between Venus & Exoplanetary Observations

et al. 2023

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“…For completeness, we list here the polynomial equations used to calculate the different terms. Analogous equations that were developed to model Earth's core can be found in Labrosse (2015), albeit with slightly different notation and additional complexities added to the analytic formulation, and in the Supporting Information for Blaske & O'Rourke (2021).…”

Section: Appendix a Radial Structure Of The Lunar Corementioning

confidence: 99%

“…The energy budget by itself does not reveal whether a dynamo might exist in the lunar core. We must compute the dissipation budgets, again following Labrosse (2015) and studies such as Blaske & O'Rourke (2021). First, we expand Equation (3) in the main text as The effective temperature associated with dissipation from secular cooling is almost identical to T D but slightly hotter: Finally, we can calculate the dissipation sink associated with the thermal conductivity of the core fluid, which is an energy-based definition that is basically equivalent to the usual formula, Q AD ∼ 4πR C 2 k C (dT a /dr), derived from Fourier's law.…”

Section: Appendix a Radial Structure Of The Lunar Corementioning

confidence: 99%

A Long-lived Lunar Magnetic Field Powered by Convection in the Core and a Basal Magma Ocean

2023

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An internally generated magnetic field once existed on the Moon. This field reached high intensities (∼10–100 μT, perhaps intermittently) from ∼4.3 to 3.6 Gyr ago and then weakened to ≲5 μT before dissipating by ∼1.9–0.8 Gyr ago. While the Moon’s metallic core could have generated a magnetic field via a dynamo powered by vigorous convection, models of a core dynamo often fail to explain the observed characteristics of the lunar magnetic field. In particular, the core alone may not contain sufficient thermal, chemical, or radiogenic energy to sustain the high-intensity fields for >100 Myr. A recent study by Scheinberg et al. suggested that a dynamo hosted in electrically conductive, molten silicates in a basal magma ocean (BMO) may have produced a strong early field. However, that study did not fully explore the BMO’s coupled evolution with the core. Here we show that a coupled BMO–core dynamo driven primarily by inner core growth can explain the timing and staged decline of the lunar magnetic field. We compute the thermochemical evolution of the lunar core with a 1D parameterized model tied to extant simulations of mantle evolution and BMO solidification. Our models are most sensitive to four parameters: the abundances of sulfur and potassium in the core, the core’s thermal conductivity, and the present-day heat flow across the core–mantle boundary. Our models best match the Moon’s magnetic history if the bulk core contains ∼6.5–8.5 wt% sulfur, in agreement with seismic structure models.

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“…For example, the lunar surface is frequently impacted by objects large enough to produce light emissions visible from Earth (e.g., Avdellidou and Vaubaillon, 2019;Ortiz et al, 2006;Ortiz et al, 2015). Moreover, bright flashes seen in the atmosphere of Venus have been attributed to meteoroids (Blaske et al, 2023). On Mars, a freshly formed impact craters have been found (Daubar et al, 2023;Posiolova et al, 2022), and possible seismic and acoustic wave signatures from meteoroid entries were detected by NASA's InSight lander (Garcia et al, 2022).…”

Section: Introductionmentioning

confidence: 99%