Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1901.04611

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

Shigeru Ida·Takeru Yamamura·Satoshi Okuzumi
View original source ↗Read source document ↗Export metadata ↓

Abstract

The Earth's ocean mass is only 2.3 x 10^{-4} of the whole planet mass. Even including water in the interior, it would be at most 10^{-3}-10^{-2}. Ancient Mars may have had a similar or slightly smaller water fraction. It is important to clarify the water delivery mechanism to rocky planets in habitable zones in exoplanetary systems, as well as that to the Earth and Mars. Here, we consider water delivery to planets by icy pebbles after the snowline inwardly passes the planetary orbits and derive the water mass fraction (f_{water}) of the final planet as a function of disk parameters and discuss the parameters that reproduce f_{water} comparable to that inferred for the Earth and ancient Mars. We calculate the growth of icy pebbles and their radial drift with a 1D model, and accretion of icy pebbles onto planets, by simultaneously solving the snowline migration and the disk dissipation, to evaluate f_{water} of the planets. We find that f_{water} is regulated by the total mass (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 t_{snow}/t_{pff} < 10 or > 10 is important. Deriving an analytical formula for f_{water} that reproduces the numerical results, we find that f_{water} of a rocky planet near 1 au is ~ 10^{-4}-10^{-2}, in the disks with initial disk size ~ 30-50 au and the initial disk mass accretion rate ~ (10^{-8}-10^{-7}) M_sun/y. Because these disks may be median or slightly compact/massive disks, the water fraction of rocky planets in habitable zones may be often similar to that of the Earth, if the icy pebble accretion is responsible for the water delivery.

Explore related subjects

astro-ph.EP

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Shigeru Ida, Takeru Yamamura, Satoshi Okuzumi. 2023-03-17. Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks. https://doi.org/10.1051/0004-6361%2F201834556

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

High water D/H ratio of the interstellar object 3I/ATLAS is consistent with a low-metallicity origin

Recent JWST observations have revealed unusually high $^{12}$C/$^{13}$C ratios in carbon-bearing molecules of the interstellar object 3I/ATLAS, consistent with formation in a lower-metallicity environment than the present-day local interstellar medium (ISM). 3I/ATLAS also exhibits an exceptionally high water D/H ratio, exceeding those in Solar System comets and nearby low-mass star-forming regions. Here we investigate whether this high water D/H ratio can be reproduced in a low-metallicity formation scenario, using gas-ice astrochemical models. Assuming that the water observed in 3I/ATLAS was inherited from the parent molecular cloud and core, we perform a grid of astrochemical models covering the cloud to core stages, varying the gas density, ultraviolet radiation field ($χ$), cosmic-ray ionization rate ($ζ$), and metallicity, while solving thermal balance for the gas temperature. We find that lower metallicity enhances H$_3^+$ deuteration and, more importantly, its transfer to water ice. In contrast, water D/H ratio depends non-monotonically on $χ$ and $ζ$, because of competing chemical and thermal effects. In our models, the observed water D/H ratio is most readily reproduced at subsolar metallicities, $\lesssim0.5Z_\odot$, and relatively high cloud densities of $\sim$10$^4$ cm$^{-3}$ without strong constraints on either $χ$ or $ζ$, as long as $ζ<10^{-15}$ s$^{-1}$. The D/H ratio of methane normalized by that of water is not sensitive to the metallicity, being consistent with the similar values observed in 67P/Churyumov-Gerasimenko and 3I/ATLAS. These results suggest that water deuteration may provide a complementary probe of the metallicity and physical condition of the parent molecular cloud and dense core of interstellar objects.

astro-ph.EP↗
arXiv2026

Spectral Evolution of Ceres' Surface and Implications for Space Weathering

The surface of Ceres exposed to the space environment will be gradually altered, but the evolution of its spectral properties remains poorly understood. Here we analyze visible and infrared spectra acquired by the Dawn mission to investigate spectral variations across different surface units. We identify local shifts of a few nm toward shorter wavelengths in the 2.7 $μ$m band center, predominantly associated with freshly exposed slumping and impact materials. Our analysis suggests that compositional variations in Ceres' regolith are unlikely the explanation for the band center shift, and therefore it may represent a spectral evolution within 10$^6$ years. Combining previous studies about the spectral reddening on Ceres, we propose a two-stage spectral evolution on Ceres. The blue-shifted regions are interpreted as the youngest materials. Within 10$^6$ years after exposure, these materials become spectrally bluer, the 2.7 $μ$m band weakens, and its center shifts toward longer wavelengths. Then the evolution is characterized by spectral reddening and strengthening of the 2.7 $μ$m band without the band center shift. Based on the previous laboratory work and observations on other C-complex asteroids, we suggest that the observed spectral variations may be attributed to the chemical and/or physical changes of the regolith, possibly associated with space weathering.

astro-ph.EP↗
arXiv2026

Detecting transiting exoplanets in simulated PLATO data: A comparison of light curve filter and transit search algorithms

Aims: Our goal is to test and compare transit search methodologies, and provide recommendations as to the best practices to be implemented by the upcoming ESA PLATO mission, in order to achieve its goal of detecting Earth-like planets in the habitable zones of Sun-like stars. Methods: We generate simulated two-year PLATO light curves with injected planets with sizes 0.5--2.0 $R_\oplus$, and compare the performance of the CETRA, umbra, and nuance transit search methods. CETRA and umbra require pre-filtered light curves and we test the biweight, Huber spline, Lowess, and YSD-Lowess filters. nuance uses a Gaussian process to model the stellar variability at all proposed transit parameters. Results: nuance achieves the best performance, recovering 61.2% signals using a simple harmonic oscillator Gaussian process kernel, and it performs especially well for both hot and fast-rotating stars. However, when multiple Huber spline filter windows are considered, both CETRA and umbra can match nuance's performance. CETRA matches nuance with four windows, recovering 61.3% of signals. umbra matches nuance with two windows, recovering 61.7% of signals. Recovery rates exceeding nuance are possible by using more windows. The computational cost of running nuance is so high that running CETRA or umbra on multiple windows is preferred. Conclusions: The PLATO pipeline should use the Huber spline with a range of window sizes as its primary light curve filter. CETRA should be updated to use the warped least-squares templates implemented in umbra. The use of nuance should be considered for hot, rapidly rotating stars.

astro-ph.EP↗