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3 Priority Questions in Planetary Science for the Next Decade
Pages 69-86

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From page 69... ... As outlined in the sections that follow, in situ analyses and ultimately sample return will be required to achieve major breakthroughs in addressing many of these questions. PRIORITY QUESTIONS Building New Worlds A little over 4.5 billion years ago, a small clump of gas and dust within a giant molecular cloud began to collapse, perhaps triggered by the shockwave from a nearby supernova. Read the entire page →
From page 70... ... Host stars, such as the Sun, have their own life cycle much as planets do, and the changes during that cycle play a profound role in modifying the attendant planets. A variety of critical questions arise about how planetary systems function: • How do the giant planets serve as laboratories to understand Earth, the solar system, and extrasolar planetary systems? Read the entire page →
From page 71... ... TABLE 3.1 The Key Questions and Planetary Destinations to Address Them Crosscutting Themes Priority Questions Key Bodies to Study Building new worlds 1. What were the initial stages, conditions and Comets, Asteroids, Trojans, Kuiper belt objects processes of solar system formation and the nature of (see Chapter 4) Read the entire page →
From page 72... ... Planetary scientists witness similar processes ongoing in exoplanetary systems. Thus, the planetary embryos of the giant planets grew rapidly in the first few million years until they became massive enough to capture directly the most abundant elements in the solar nebula, hydrogen and helium. Read the entire page →
From page 73... ... Suggested explanations for their concentration include condensation of noble gases on extremely cold nebular solids, capture of clathrate hydrates, evaporation of the protoplanetary disk before Jupiter formed, and outgassing of noble gases from the deep interior enriching them in the atmosphere. 16 Each of these hypotheses leads to testable predictions for noble gas abundances in the other giant planets -- definitive answers will require in situ probe measurements -- critical data that researchers lack for Saturn, Uranus, and Neptune. Read the entire page →
From page 74... ... The distribution of bodies in the Kuiper belt may provide key evidence about the orbital migration of the giant planets.25 Measuring the time of formation of individual components that constitute comets will constrain the evolution of objects beyond the orbit of Neptune. Refractory inclusions in the Stardust sample from comet Wild 2 suggest that inner solar system material was mixed out into the Kuiper belt zone.26 Determining the euterium/ d hydrogen and other crucial isotopic ratios in multiple comets from samples of their nuclei could help to address major questions about the roles comets played in delivering water and other volatiles to the inner solar system and in particular to early Earth. Read the entire page →
From page 75... ... Organic compounds are ubiquitous in the Milky Way and other galaxies and include nitriles, aldehydes, alcohols, acids, ethers, ketones, amines, and amides, as well as long-chain hydrocarbons.34,35 The origin of organic molecules in meteorites is complex; some compounds formed as coatings on presolar dust grains in molecular clouds, and others were altered in the warmed interiors of planetesimals when ices in these bodies melted.36 Their chemistries span a range of molecules including amino acids; these molecules provide a partial picture of the prebiotic components that led to life. But scientists lack critical information on organic components in comets and Kuiper belt objects and on how the compositions of organic molecules may vary among these bodies. Read the entire page →
From page 76... ... Mars Global Surveyor discovered a dynamodriven magnetic field that could have held off the solar wind and protected the loss of the early thick atmosphere and its abundant water. But the dynamo was not sustainable and the field collapsed after a few hundred million years, close to the end of the late heavy bombardment, perhaps allowing much of the atmosphere to be eroded away. Read the entire page →
From page 77... ... Characterizing Venus's early environment, whether it was habitable with liquid water present, is a scientific high priority; this will require measurement of the molecular and isotopic composition of the lower atmosphere and the elemental and mineralogic composition of the surface. 46 Beyond Earth, Are There Contemporary Habitats Elsewhere in the Solar System with Necessary Conditions, Organic Matter, Water, Energy, and Nutrients to Sustain Life, and Do Organisms Live There Now? Read the entire page →
From page 78... ... Detailed examination of the nature and interaction of the rich array of solid and liquid organic compounds in Titan's surface environment is a high priority that would reveal new insights into organic chemical evolution on a global scale and, conceivably, detect ongoing biological processes. WORKINGS OF SOLAR SYSTEMS: REVEALING PLANETARY PROCESSES THROUGH TIME How Do the Giant Planets Serve as Laboratories to Understand Earth, the Solar System, and Extrasolar Planetary Systems? Read the entire page →
From page 79... ... 61 Evidently abundant, these objects are similar in size and composition to Neptune and Uranus -- the giant planets about which we know the least. For Jupiter, the Galileo probe provided critical data on isotopes, noble gases, deep winds, and thermal profiles -- data lacking now for Saturn, Uranus, and Neptune. Read the entire page →
From page 80... ... Although impact hazards to Earth are real, they are probably actually reduced by the gravitational influence of the giant planets, especially Jupiter. Astronomical surveys tally the number of asteroids larger than a kilometer at about a million. Read the entire page →
From page 81... ... The giant planets also provide the only examples of processes common to Earth in which strong internal magnetic fields interact with the solar wind. This includes the fluorescing spectacle of Earth's northern lights and similar auroral displays seen near the magnetic poles of Jupiter and Saturn. Read the entire page →
From page 82... ... Galileo showed Ganymede, the only satellite in the outer solar system known to have an internal magnetic field and a magnetosphere. Galileo's probe into the jovian atmosphere revealed that the noble gas abundances were very unlike the Sun's -- processes like helium rain falling into Jupiter's core have been invoked as possible explanations, and more recent observations have shown a dynamic, ever-changing atmosphere, riddled by impacts.78 Saturn's excessive thermal energy might also signal helium rain; direct measurement of its noble gas abundance and isotopic chemistry is required to get an answer. Read the entire page →
From page 83... ... 2005. Origin of the orbital architecture of the giant planets of . Read the entire page →
From page 84... ... 2005. Origin of the orbital architecture of the giant planets of . Read the entire page →
From page 85... ... 2009. Liquid water on Enceladus from observations of ammonia and 40Ar in the plume. Read the entire page →
From page 86... ... 2010. Sequestration of noble gases in giant planet interiors. Read the entire page →

From page 69...

... As outlined in the sections that follow, in situ analyses and ultimately sample return will be required to achieve major breakthroughs in addressing many of these questions. PRIORITY QUESTIONS Building New Worlds A little over 4.5 billion years ago, a small clump of gas and dust within a giant molecular cloud began to collapse, perhaps triggered by the shockwave from a nearby supernova.

3 Priority Questions in Planetary Science for the Next Decade Pages 69-86

3 Priority Questions in Planetary Science for the Next Decade
Pages 69-86