A&A 423, L5-L8 (2004)
DOI: 10.1051/0004-6361:200400013

Letter

Nonuniform viscosity in the solar nebula and large masses of Jupiter and Saturn

L. Jin

College of Physics, Jilin University, 119 Jie Fang Rd, Changchun, Jilin 130023, PR China
    e-mail: jinl@email.unc.edu

Dept. of Physics and Astronomy, Clemson Univ., Clemson SC 29634, USA

(Received 1 June 2004 / Accepted 24 June 2004 )

Abstract
I report a novel theory that nonuniform viscous frictional force in the solar nebula accounts for the largest mass of Jupiter and Saturn and their largest amount of H and He among the planets, two outstanding facts that are unsolved puzzles in our understanding of origin of the Solar System. It is shown that the nebula model of uniform viscosity does not match the present planet masses. By studying current known viscosity mechanisms, I show that viscosity is more efficient in the inner region inside Mercury and the outer region outside Jupiter-Saturn than the intermediate region. The more efficient viscosity drives faster radial inflow of material during the nebula evolution. Because the inflow in the outer region is faster than the intermediate region, the material tends to accumulate in Jupiter-Saturn region which is between the outer and intermediate region. It is demonstrated that the gas trapping time of Jovian planets is longer than the inflow time in the outer region. Therefore the gas already flows to Jupiter-Saturn region before Uranus and Neptune can capture significant gas. But the inflow in the Jupiter-Saturn region is so slow that they can capture large amount of gas before the gas can flow further inward. Hence they have larger masses with larger H and He content than Uranus and Neptune. I also extend the discussion to the masses of the terrestrial planets, especially low mass of Mercury. The advantages of this theory are discussed.

Key words: solar system: formation -- solar system: general -- planets and satellites: formation -- accretion disks

© ESO 2004