| 研究実績の概要 |
The main results that we obtained are as follows.
We find from meteorite age data that the giant planets began their migration at 4480 Ma (Mojzsis et al., 2019; in review).
The cometary bombardment from giant planet migration arrives before 4400 Ma. This delivered some of Earth's water and a lot of water to Mars. From our dynamical simulations we find that Earth's bombardment from leftover planetesimals is also mostly done by this time. Since there was crust formation at 4380 Ma (deduced from dating the oldest terrestrial zircon), 4400 Ma presents the earliest time for life to occur on Earth (Brasser et al., 2019, submitted).
At 4480 Ma Earth was struck by a lunar-sized object that created a temporary H2 atmosphere that was gone by 4200 Ma (Genda et al., 2017). This provides the building blocks for RNA chemistry. Optimal RNA producion occurred around 4350 Ma (Benner et al., 2019, submitted). Thus life probably arose on Earth near 4350 Ma.
We conduct a follow-up study on exoplanets to determine the feasibility of our approach. We have submitted at least three papers and are writing two more. We have also established new collaborations and we will pursue this matter over the years to come.
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