Origins, Worlds, and Life A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (2022) / Chapter Skim
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4 Question 1: Evolution of the Protoplanetary Disk
4 Question 1: Evolution of the Protoplanetary Disk
Pages 102-129
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From page 102... ...
The evolution of the protoplanetary disk had four sequential, but partially contemporaneous phases: (1) the initial molecular cloud collapse and disk formation; (2)
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From page 103... ...
Astronomical observations of hundreds of protoplanetary disks indicate they have a large range in mass with a median of about 1 percent of the Sun's mass and have rich substructures, including holes, gaps, and rings (Andrews et al.
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From page 104... ...
These data demonstrate that the molecular cloud core was not fully homogenized or digested of its inherited interstellar components (Nittler and Ciesla 2016) , and that laboratory measurements of minute isotopically anomalous materials can be used to investigate the molecular cloud collapse, inherited proto-solar components, and disk evolution.
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From page 105... ...
2014) and chemical thermodynamics indicate that the most abundant species in the starting material of the solar system and, presumably, of the molecular cloud core were hydrogen (H2)
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From page 107... ...
. Spatially resolved astronomical observations of isotopologues of C- and Obearing species in protoplanetary disks and the interstellar medium can address the role of self-of shielding.
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From page 108... ...
, laboratory analyses of returned samples of comets and terrestrially-collected interplanetary dust and meteorite samples, and ground- and space-based telescopic observations of the composition (gas, ice, dust) of comets, Kuiper belt objects, and protoplanetary disks.
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From page 109... ...
. Transient heating during impacts between planetesimals has also been recently studied PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-8
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From page 110... ...
It is unclear how much of the diversity in the organic matter observed across chondrites and cometary dust samples is due to differences in hydrothermal parent body processing and how much reflects differences in the materials accreted to different parent bodies. Moreover, the range of formation locations, temperatures and mechanisms spans accretion as icy mantles on anhydrous minerals in the outer nebula, accretion to metal grains and chondrules in the inner nebula, and as direct nebular condensates (Alexander et al.
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From page 111... ...
Such substructures may have formed as the result of these disk transport mechanisms or alternatively by the accretion of giant planets, and whether planets or substructures came first is unclear. In either case, the formation of substructures themselves would have then influenced subsequent disk evolution, possibly serving as a barrier to further transport in their locations or instead filtering the grain sizes of transported materials.
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From page 112... ...
Planetesimals that form earlier end up with more active 26Al, larger bodies are better able to insulate materials warming up in the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-11
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From page 113... ...
● Determine if, how, when and where gaps, rings, or holes developed in the nebular disk through spacecraft isotopic and elemental measurements of gas, dust, ice and organic components in outer and inner solar bodies; return of asteroid and comet surface samples; disk transport modeling; ground- and space-based astronomical measurements of protoplanetary disks; and laboratory petrologic, isotopic and paleomagnetic analyses of returned and terrestrially collected samples. ● Constrain the original compositions and processing histories of dust, gas, ice and organic matter in the solar nebula through return of asteroid and comet surface samples; astronomical observations of young stellar objects and outer solar system volatiles; and modeling of heating and radiation processing; and laboratory petrographic, elemental, and isotopic analyses of returned and terrestrially collected asteroid and comet samples.
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From page 114... ...
. If the formation of all igneous objects within chondrites PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-13
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From page 115... ...
. Alternatively, some studies that consider a distribution of velocities and higher sticking efficiencies PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-14
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From page 117... ...
Returning to the previous examples, the high 15N/14N ratio in Titan's nitrogen supports an alternative source as the most important N-bearing constituent in Titan's building blocks. This isotopic measurement is consistent with the aforementioned warm origin of Titan's building blocks that would have prevented the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-16
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From page 118... ...
● Constrain accretion processes in protoplanetary disks by resolved studies of the volatile composition as well as of the composition, sizes and shapes of grains using ground- and space based telescopic observations of protoplanetary disks. ● Understand the processes of accretion, fragmentation and deformation associated with grain and particle collisions through laboratory grain accretion experiments, observations of collisions in dense giant planet rings, and modeling.
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From page 119... ...
through limited direct and indirect evidence. Astronomical observations of the abundance of dust and gas and of active accretion onto protostars indicate that protoplanetary disks have estimated lifetimes from <1 to ~20 million years with a mean value of 2 million years (Mamajek 2009)
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From page 120... ...
In fact, paleomagnetic measurements of several meteorite groups indicate that the solar nebula dispersed sometime between 1.2 and 3.9 million years after CAI-formation in the region where ordinary chondrites formed and between 2.5 and 4.9 million PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 4-19
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From page 121... ...
There are very few direct constraints on the gas density itself, with most indicating simply whether a solar nebula analogous to that observed for actively accreting protoplanetary disks is present or absent. Finally, there are virtually no constraints on the evolution of the composition of the residual gas.
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From page 122... ...
(Eds.) , From Protoplanetary Disks to Planet Formation.
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From page 127... ...
2018. The retention of dust in protoplanetary disks: Evidence from agglomeratic olivine chondrules from the outer solar system.
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From page 128... ...
2005. Streaming Instabilities in Protoplanetary Disks.
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