Elisa V. Quintana^1,2 and Jack J. Lissauer²

¹SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043, USA
²Space Science and Astrobiology Division 245-3, NASA Ames Research Center, Moffett Field, CA 94035, USA

Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M_⊕ to 1 M_J) in Jupiter’s orbit at ~5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.

Reference
Quintana EV and Lissauer JJ (2014) The Effect of Planets Beyond the Ice Line on the Accretion of Volatiles by Habitable-zone Rocky Planets. The Astrophysical Journal 786:33.
[doi:10.1088/0004-637X/786/1/33]

Link to Article