Previous & Current Research

Solving the 'Faint Uranus' Paradox of Planetary Heatflow

The solar system's ice giants Uranus and Neptune have presented a longstanding paradox to the study of planetary interior dynamics. These two planets have similar masses, radii, and magnetic fields. However, Uranus emits at least an order of magnitude less heat than Neptune, a discrepancy commonly known as the 'Faint Uranus Problem.'

This difference in heatflow has been attributed to the inhibition of convection in the deep interior of Uranus. However, if convective inhibition affects the interior of Uranus but not Neptune, it is then challenging to account for the qualitatively similar magnetic fields of Uranus and Neptune. Yet, if convective inhibition occurs in Neptune as it is thought to occur in Uranus, another heat source must be invoked to account for Neptune's substantially greater luminosity.

Bailey & Stevenson (in press, PSJ) suggest a mechanism that can self-consistently account for these planets' different heat flows, as well as their similar magnetic fields. We show that existing gravity and rotation data support a picture in which hydrogen-water demixing is taking place today in Neptune but not Uranus. We show that this mechanism (Figure above; see paper for detailed explanation) can release gravitational potential energy, powering the observed heatflow of Neptune. Moreover, we outline tests for this hypothesis that can be used by future missions to the solar system's ice giants.

Understanding How Hot Jupiters Form

Hot Jupiters are exoplanets with roughly the mass of Jupiter, orbiting on very close, several-day orbits around their stars. The way these planets form has been debated for decades. The consensus viewpoint has favored an origin beyond the snow line (similar to Jupiter in our own solar system), followed by long-range inward migration. An alternative hypothesis for the origin of hot Jupiters has been that they tend to form close to their stars.

Bailey & Batygin (2018) showed that the period-mass distribution of hot Jupiters can be accounted for with a simple model in which the planet forms close to the star. In this model, as depicted in the figure above, the planet forms outside the magnetospheric truncation radius carved out by the star, and is fed material for growth by the viscously accreting disk. The resulting model predicts a power-law cutoff for the hot Jupiters that agrees empirically with the observed period-mass cutoff of the hot Jupiter population.

The Search for Planet Nine

Several works have attempted to pinpoint Planet Nine's location in the sky by assuming the eccentric Kuiper Belt Objects found in the outermost solar system reside in low-order mean motion resonances with Planet Nine. Challenging this search method, Bailey et al. (2018) used N-body simulations to show that, for eccentric Planet Nine, high-order mean motion resonances become prevalent. These high-order resonances are less useful for locating Planet Nine than low-order resonances. Therefore, we showed it is not yet possible to effectively locate Planet Nine with mean motion resonances.

The origin of the small but significant six-degree tilt of our sun compared to the plane of the planets is a longstanding problem in solar system formation theory. Bailey et al. (2016) showed that Planet Nine has the effect of tilting the the planets relative to the sun. Given early Planet Nine constraints, this effect was thought to be potentially responsible for the entire tilt of the sun's axis. However, as Planet Nine constraints were refined, the expected precessional effect diminished. Strictly speaking, the sun remains almost inertial and tilts only a minuscule amount; the planets are what is gradually tilted with respect to the sun, like a precessing top. (Geometric diagram below; details can be found in the linked paper)

Characterizing Interactions Between Life and the Carbon Cycle

The Shuram Excursion
The Shuram excursion is the largest globally recorded dip in carbon-13 abundance, relative to carbon-12, in the Earth's rock record. It occurs during a time of explosive eukaryotic diversification and the evolution of new modes of biomineralization. I am currently turning my focus to develop a new class of models for the Shuram Excursion that treats this event as a combination of primary carbon cycle signal and diagenetic processes.

Ediacaran & Cambrian Fossils
The structural polysaccharide chitin, in addition to protein and minerals, is generally known to have been a major structural component of the shells of all animals arising in the Cambrian explosion, such as trilobites. Currently, I am leading work to better understand the half-life of chitin in rocks under taphonomic conditions, and to better classify the structure and relative taxonomic relationships of small shelly organisms leading up to the Cambrian explosion.

Copyright © 2021 Elizabeth Bailey