Paul Estrada

Paul Estrada
Astronomy and Astrophysics Research Thrust Chair
Ph.D., Planetary Science, Cornell University
Curriculum Vitae: 
Astrophysics/Planetary Science

If planets are a dime a dozen, moons are less than a penny each. There are at least 139 moons in our solar system, and most of these are the property of the gas giant planets beyond Mars. More than just a nice accompaniment to planets, moons may frequently have habitats in which liquid water could ebb and flow – and possibly be home to life. Planetary scientist Paul Estrada investigates how moons around gas giants are formed, an important question since its answer would give us insight into the nature of moons around the myriad gas giant planets we know orbit other stars.

The birth of moons around gas giant planets is superficially similar to planetary formation; however, as Estrada points out, there are some very important differences. To begin with, the “environment” (pressure, density, temperature) of satellite birth is different from that of the planets. Perhaps most important, satellite systems are more compact, which means things tend to happen much faster than on the planetary scale. Consider that the giant planet Jupiter takes a dozen years to orbit the Sun, a lumbering pace compared to the days required for its moons to orbit once. As a result, once a moon forms, it has much less time to find a way to “survive.” This is because, just like the planets, there is the problem that the leftover gas which eventually dissipates over time (a time much longer than required to form the moons or planets) will slow down a newly forming satellite, causing it to spiral into its host planet. Clearly, this doesn’t always happen, and Estrada’s research elucidates exactly how such a catastrophic fate can be avoided. The incentive to understand satellite formation is strong, as these small worlds might be the most plentiful locations for life in the universe.

Rhea-Rhea Impact (2e6 particles) from SETI on Vimeo.

Rhea_Enceladus_1e6 from SETI on Vimeo.

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Structural and Compositional Evolution of Saturn's Rings

We propose to study the compositional and structural evolution of Saturn's main rings subsequent to meteoroid bombardment, with the ultimate goal of obtaining a better understanding of the rings' origin.

Dynamical Disks: Primary Accretion and Planetary Rings

The main objective of this proposed research is the continued advancement in our understanding of the growth of dust to planetesimals in both nebular and subnebular environments and the structural and compositional evolution of Saturn’s rings.

Global Evolution of Solids in the Circumplanetary Subnebula

In this proposal, we seek to improve our understanding of the coagulation, growth, and evolution of solids in nebulae by specifically attacking a problem that has here-to-fore never been broached: the evolution of solids in the subnebulae of giant planets from which the observed giant planet satellite systems presumably formed.