The National Academies Press

Currently Skimming:

Pages 246-277

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 246... ... 246 ORIGINS, WORLDS, AND LIFE in the thick clouds produce significant albedo variations (hence amount of solar energy absorbed) on decennial timescales, potentially modifying superrotation (Pérez-Hoyos et al. Read the entire page →
From page 247... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 247 but it remains unclear if surface formation/release, transport, and sequestration/trapping of volatiles are universal processes across all exosphere-only rocky bodies. Strategic Research for Q6.3 • Determine how atmospheric waves drive atmospheric dynamics and energetics, especially phenomena such as supperrotation and lower-upper atmosphere coupling by observing wave amplitudes, periods, phases, and spatiotemporal distributions in thermal and direct wind measurements over multiple annual cycles on Venus, Mars, and Titan. Read the entire page →
From page 248... ... 248 ORIGINS, WORLDS, AND LIFE FIGURE 9-4 (a) Dynamic clouds on Venus as seen in composite Akatsuki UVI camera images. Read the entire page →
From page 249... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 249 Observations of surface changes caused by aeolian processes often constitute our only information on near-surface wind patterns and environmental conditions. The composition of volatile species in planetary atmospheres drives the formation, evolution, and stability of ices across planetary surfaces. Read the entire page →
From page 250... ... 250 ORIGINS, WORLDS, AND LIFE Q6.4c What Can Aeolian Features and Their Temporal Variation Tell Us About Near-Surface Winds and Other Atmospheric Variables? What Are the Mechanisms That Connect Wind-Driven Surface Modifications to Environmental Conditions? Read the entire page →
From page 251... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 251 Q6.4f What Do the Present-Day Methane Cycle on Titan and Past Water Cycle(s) on Mars Tell Us About How Hydrologic Cycles Operate and Exchange Material Between Surface and Atmospheric Reservoirs? Read the entire page →
From page 252... ... 252 ORIGINS, WORLDS, AND LIFE FIGURE 9-5 Atmospheric escape processes. Those on the left act on unmagnetized planets; those on the right act on magnetized planets. Read the entire page →
From page 253... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 253 FIGURE 9-6 Multiple processes contribute to the formation and evolution of surface-boundary exospheres. Source terms include both endogenic processes such as natural radioactivity in the crust and outgassing/plumes from localized regions, and exogenic processes such as photon, micrometeoroid, and charged particle bombardment. Read the entire page →
From page 254... ... 254 ORIGINS, WORLDS, AND LIFE Q6.5a How Does the Presence or Absence of Intrinsic or Parent Body Magnetic Fields Influence the Escape of Gases from Solid Planets and Satellites? The hypothesis that a global magnetic field shields the atmosphere from solar wind-driven loss processes seems intuitively obvious, as the solar wind plasma and its electromagnetic fields cannot then interact directly with the upper atmosphere. Read the entire page →
From page 255... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 255 mass loading in the extended exosphere that transfers momentum from the upstream solar wind, remains poorly quantified and may vary significantly with, for example, object size and solar inputs. For bodies with intrinsic magnetic fields, such as Earth (Toledo-Redondo et al. Read the entire page →
From page 256... ... 256 ORIGINS, WORLDS, AND LIFE • Reveal the factors that control the structure, composition, and dynamics of surface boundary exospheres (e.g., Mercury, Moon, Ceres, and Europa) by simultaneously measuring energetic inputs and escaping species for at least one orbit and preferably for a substantial portion of the solar cycle. Read the entire page →
From page 257... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 257 FIGURE 9-7 Temperature profiles on three terrestrial planets and one moon, all of which have relatively dense atmospheres. Condensation clouds are present on Earth and Mars, photochemical haze is present on Venus, and Titan has both. Read the entire page →
From page 258... ... 258 ORIGINS, WORLDS, AND LIFE detection limits of either the rover or the orbiter (Webster et al. Read the entire page →
From page 259... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 259 atomic hydrogen and other light species is critically dependent. Ion-neutral chemistry is another key process in the interaction of the neutral atmosphere and exosphere with the ionosphere. Read the entire page →
From page 260... ... 260 ORIGINS, WORLDS, AND LIFE • Constrain the photochemical paths that take methane to more complex hydrocarbons in methane rich atmospheres (primarily Titan, but also including Triton, Pluto, and other KBOs) by measuring the composition of hazes and aerosols in the atmosphere and on the surface. Read the entire page →
From page 261... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 261 Gronoff, G., P Arras, S Read the entire page →
From page 262... ... 262 ORIGINS, WORLDS, AND LIFE Kivelson, M.G., and F Bagenal. Read the entire page →
From page 263... ... QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION 263 Siegler, M.A., R.S. Miller, J.T. Read the entire page →
From page 264... ... Q7 PLATE: One of the poles of Jupiter, as imaged by the JunoCam instrument onboard the Juno spacecraft in 2019. SOURCE: Courtesy of NASA/JPL-Caltech/SwRI/MSSS/G. Read the entire page →
From page 265... ... 10 Question 7: Giant Planet Structure and Evolution What processes influence the structure, evolution, and dynamics of giant planet interiors, atmospheres, and magnetospheres? The giant planets comprise 99.5 percent of the mass of the solar system, apart from the Sun, and 96 percent of the solar system's total angular momentum.1 They are the most massive remnants of accretion from the Sun's nebular disk and to have played a substantial role in shaping the overall architecture of the solar system. Read the entire page →
From page 266... ... 266 ORIGINS, WORLDS, AND LIFE FIGURE 10-1 Interiors of Jupiter, Saturn, Uranus, and Neptune (not to scale) Read the entire page →
From page 267... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 267 chemical interactions, determination of their enrichment compared to that of the major gases is an essential clue to understanding giant planet evolution (Guillot and Gautier 2015) Read the entire page →
From page 268... ... 268 ORIGINS, WORLDS, AND LIFE FIGURE 10-2 Atmospheric composition varies in the vertical direction owing to thermochemistry in the deep troposphere, cloud chemistry in the upper troposphere, and photochemistry in the stratosphere. Stratospheric water comes from external (ring rain and cometary) Read the entire page →
From page 269... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 269 may separate from hydrogen (Bailey and Stevenson 2021) , which would affect the structure, chemistry, and evolution of these planets. Read the entire page →
From page 270... ... 270 ORIGINS, WORLDS, AND LIFE FIGURE 10-3 Visualizations of the interior structure (top panels) and magnetic fields (bottom panels) Read the entire page →
From page 271... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 271 Q7.2a How Does Composition Change with Depth in Giant Planet Interiors? Recent measurements of Jupiter's and Saturn's gravitational fields, as well as observations of waves in Saturn's rings, have revealed that both planets have dilute cores. Read the entire page →
From page 272... ... 272 ORIGINS, WORLDS, AND LIFE Given the spatial complexity of the ice giant dynamos, measurements of Uranus's and Neptune's magnetic fields would likely be a powerful tool to constrain their internal dynamics (Soderlund and Stanley 2020) Read the entire page →
From page 273... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 273 Strategic Research for Q7.2 • Determine the interior structure and composition of Uranus and Neptune using gravity and magnetic field mapping. • Search for the locations and extent of discrete layers in the deep interior in all four giant planets, using planet/ring seismology (i.e., the ability to detect planetary seismic waves from perturbations in the motion of ring particles) Read the entire page →
From page 274... ... 274 ORIGINS, WORLDS, AND LIFE FIGURE 10-4 Cloud bands, zonal winds, and deep rotation on the outer planets. The wind profiles are shown at the same scale for each planet and show zonal jets reaching 200–400 m/s; Jupiter and Saturn exhibit prograde equatorial jets, while Uranus and Neptune's are retrograde. Read the entire page →
From page 275... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 275 Q7.3c How and Why Do Discrete Meteorological Features (e.g., Storms and Vortices) Evolve? Read the entire page →
From page 276... ... 276 ORIGINS, WORLDS, AND LIFE to centuries-long intervals between convective outbursts, a potential explanation for apparent differences in the intrinsic luminosities of Uranus and Neptune (Smith and Gierasch 1995; Li and Ingersoll 2015) Read the entire page →
From page 277... ... QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION 277 FIGURE 10-5 Comparison of size and geometry of the giant planet magnetospheres. For scale, the purple box at Jupiter spans ~1 million km, and the Uranus box spans ~650,000 km. Read the entire page →

From page 246...

... 246 ORIGINS, WORLDS, AND LIFE in the thick clouds produce significant albedo variations (hence amount of solar energy absorbed) on decennial timescales, potentially modifying superrotation (Pérez-Hoyos et al.