Potentially Habitable ExoplanetsCourse AnnouncementsAssignmentsRemoving planetesimals causes LHBModern Models of SS EvolutionEvolution of Planetary OrbitsThe Nice (“Neese”) ModelObservational ConstraintsDr. Lindsay’s Custom materialTerrestrial PlanetsThat last stages of planet makingDifferentiationThe Heat Needed to DifferentiateRadioactivityIsotopesRadioactivityRadioactivityRadioactivityRadioactivityRadioactivityRadioactive DatingRadioactive DatingDifferentiationDifferentiationDifferentiationOutgassingOutgassingBack to DifferentiationTerrestrial PlanetsTerrestrial PlanetsTerrestrial PlanetsTerrestrial PlanetsTerrestrial PlanetsTerrestrial PlanetsGas Giant PlanetsPotentially Habitable ExoplanetsCourse Announcements•Quiz 3 Today–Note about Attendance bonusAssignmentsReading Assignments•Chapter 7: Sections 7.1 – 7.3[Read by Monday, 17 Oct.]Parallel Lectures•No new episodesMastering Astronomy•Chapter 7 Homework[Will be assigned Monday]Removing planetesimals causes LHBAs the small bodies get flung around the early Solar System… [Property 9 explained]•Planetary Migration of the forming gas giant planets moves through the leftover protoplanets and planetesimals slinging them all about and out of the early solar system•This creates an era where these small bodies frequently impact the early planets, i.e., The Late Heavy BombardmentSurfaces of the Moon and Mercury show evidence for heavy bombardment by asteroids via their impact cratersModern Models of SS Evolution DeMeo and Carry (2014)Red: Rocky Blue: Water, Ices, Organics1. Initial Disk determined by Condensation Hyp./Nebular Hyp.- Rocky inner -> Icy Outer2. Biggest planetesimals past ice-line get big enough to experience gas drag (and other forces) and move inward3. Inward migration drags icy materials inward and scatters some rocky material outward4. Current Idea: Gas giant planets then migrate outward scattering more materials- Causes Late Heavy Bombardment(1)(2)(3)(4)Evolution of Planetary Orbits•The foremost, and growing in acceptance, framework for how the gas giant planet motions interacted with the remaining protoplanets and planetesimals changed all their orbits to give the current structure of the solar system is called:•The Grand Tack plus Nice Model–They are numerical simulations that give the current structure of the Solar System and make interesting predictions. Now just to test them with observations!–At best can demonstrate that the structure of our Solar System can happen. They cannot say that is exactly how it happened.The nitty-gritty, cutting edge ideasThe Nice (“Neese”) ModelIt’s a city in France referenceNice Model VideoGrand TackNice ModelNice ModelThe Nice Model is a computer simulation to understand how the movement of the planets affected the small leftoversAlso… be careful google-ing this one (add the word planet or planetary).Observational ConstraintsMuch of my research provides observational evidence to test the validity of these predictions•The Grand Tack + Nice Model are very controversial amongst researchers trying to understand the origins and evolution of the Solar System.–However, they do provide testable predictions:1) Amount of asteroids and KBOs2) Amount of mixing of evolved rocky and primitive icy bodies3) Entire removal of initial population of Jupiter Trojans, and replacement with KBO objects•My Jupiter Trojans Project aims to provide observational constraints on whether the Trojans formed with Jupiter, were captured from the Kuiper Belt, or a mixture of both.–A direct observational test to the predictions of these numerical models–My Comet Project and Condensation Theory givea a basis for what compositional indicators to expect if the Trojans are from the Kuiper Belt or formed with JupiterDR. LINDSAY’S CUSTOM MATERIALComparative planetology and general planetsTerrestrial PlanetsThe generalities of Earth-like worldsBasic Concepts behind comparative planetology•Being formed from the same materials, the expectation is that overall, the terrestrial planets are more alike than different.–Terrestrial planets should be largely the same all across the galaxy and universe.•How do we go from a big, uniform, ball of rock and metal to our current planets? What processes are involved?•Physics/Chemistry/Geology(/Biology) the same, but each is quite unique. How is this so and how does that relate to what a terrestrial planet is?•What does this tell us about solar system formation and what we should expect in other planetary systems?That last stages of planet makingFrom our accreted protoplanet to what we recognize as a terrestrial planet•The accretion process builds us a terrestrial planet made of rock and metal, but it is not yet structured like a planet…–All the materials (rock and metal) are mixed up relatively evenly (homogeneously) throughout the protoplanet–BUT.. Earth, the other terrestrial planets, and many asteroids in the solar system are layered into a core, mantle, and crust.•To get to a layered planet, the denser materials need to sink to the center and the lighter material needs to float to the top.–This process of separation according to density is called planetary differentiationDifferentiation•All the terrestrial planets are differentiated, which implies it is a natural consequence of the formation process•To separate according to density, the planet needs to entirely or mostly molten!•To melt a planet, however, we are going to need a lot of energy (heat), where did that come from?The Heat Needed to DifferentiateMelting a planetSources of Energy/Heat1. Gravitational energy from formation–Not enough to melt planet2. Kinetic energy (energy of moving things) from impacts–Likely only sufficient to melt surface down to depths of a few to ten kilometers3. Radioactive decay of unstable elements –this is the strongest contributor.. Enough heat to melt the planet from inside out4. The gravitational energy and friction of the differentiation process itself–Once started, this accelerates the processRadioactivity•The term radioactivity was coined and the field of nuclear radioactivity waspioneered by Marie Curie, who won the Noble Prize for her work.•Elements, defined by the number of protons in their nucleus, exist in several isotopic forms, where all isotopes of an elements contain the same number of protons, but have a varying number of neutrons.The release of radiation from an unstable nucleusMarie
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