Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks

doi:10.1051/0004-6361/201834556

	Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks
	Ida, Shigeru 1; Yamamura, Takeru 2; Okuzumi, Satoshi 3
	2019-04-03
发表期刊	ASTRONOMY & ASTROPHYSICS
ISSN	1432-0746
卷号	624
摘要	Context. The ocean mass of the Earth is only 2.3 x 10(-4) of the whole planet mass. Even including water in the interior, the water fraction would be at most 10(-3)-10(-2). Ancient Mars may have had a similar or slightly smaller water fraction. What controlled the amount of water in these planets has not been clear, although several models have been proposed. It is important to clarify the control mechanism to discuss water delivery to rocky planets in habitable zones in exoplanetary systems, as well as that to Earth and Mars in our solar system.Aims. We consider water delivery to planets by icy pebbles after the snowline inwardly passes planetary orbits. We derive the water mass fraction (f(water)) of the final planet as a function of disk parameters and discuss the parameters that reproduce a small value of f(water )comparable to that inferred for the Earth and ancient Mars.Methods. We calculated the growth of icy dust grains to pebbles and the pebble radial drift with a 1D model, by simultaneously solving the snowline migration and dissipation of a gas disk. With the obtained pebble mass flux, we calculated accretion of icy pebbles onto planets after the snowline passage to evaluate f(water )of the planets.Results. We find that f(water) terregulatedby the totalmass is (M-res) of icy dust materials preserved in the outer disk regions at the timing (t = t(snow)) of the snowline passage of the planetary orbit. Because M-res decays rapidly after the pebble formation front reaches the disk outer edge (at t = t(pff)), f(water) is sensitive to the ratio t(snow)/t(pff ) which is determined by the disk parameters. We find snow t(snow)/t(pff) < 10 or > 10 is important. By evaluating Mres analytically, we derive an analytical formula of f water that reproduces the numerical results.Conclusions. Using the analytical formula, we find that f(water) of a rocky planet near 1 au is similar to the Earth, i.e., similar to 10(-4)-10(-2), in disks with an initial disk size of 30-50 au and an initial disk mass accretion rate of similar to(10(-)(8)-10(-)(7))M-circle dot yr(-1) for disk depletion timescale of approximately a few M yr. Because these disks may be median or slightly compact/massive disks, our results suggest that the water fraction of rocky planets in habitable zones may often be similar to that of the Earth if icy pebble accretion is responsible for water delivery.
关键词	planets and satellites: formation planets and satellites: terrestrial planets protoplanetary disks
DOI	10.1051/0004-6361/201834556
收录类别	SCI
语种	英语
WOS关键词	Astronomy & Astrophysics
WOS研究方向	Science & Technology
WOS类目	Astronomy & Astrophysics
WOS记录号	WOS:000463134300002
出版者	EDP SCIENCES S A
引用统计	被引频次：31[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
专题	任务一_子任务一循证社会科学证据集成任务一
作者单位	1.Tokyo Inst Technol, Earth Life Sci Inst, Meguro Ku, Tokyo 1528550, Japan 2.Tokyo Inst Technol, Dept Earth & Planetary Sci, Meguro Ku, Tokyo 1528551, Japan 3.Tokyo Inst Technol, Dept Earth & Planetary Sci, Meguro Ku, Tokyo 1528551, Japan
推荐引用方式 GB/T 7714	Ida, Shigeru,Yamamura, Takeru,Okuzumi, Satoshi. Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks[J]. ASTRONOMY & ASTROPHYSICS,2019,624.
APA	Ida, Shigeru,Yamamura, Takeru,&Okuzumi, Satoshi.(2019).Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks.ASTRONOMY & ASTROPHYSICS,624.
MLA	Ida, Shigeru,et al."Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks".ASTRONOMY & ASTROPHYSICS 624(2019).