Eccentric planets move more comets inward—but deliver less intact chemistry

A new simulation followed 64,000 comets injected between the outermost planets of an eight-planet chain around a star one-tenth the Sun's mass. The model also isolated the final handoff to an Earth-mass temperate planet while varying the planets' starting eccentricities from zero to 0.05. At the highest tested eccentricity, the outermost planet intercepted 11 percent fewer comets and 6 percent more reached the inner system, while the innermost world's overall impact probability changed by less than 3 percent.

The chemistry-friendly portion moved the opposite way. Impacts slower than 15 kilometers per second fell from 25 to 18 percent of impacts, and the fraction of all injected comets producing such gentle collisions dropped by 30 percent. Applying an impact-chemistry model yielded a 31 percent reduction in hydrogen-cyanide survival-equivalent delivery. The study models one compact architecture; it does not measure a known inhabited system or show that comets actually seeded life.

Why it matters

Counting material delivered to a planet is not enough to estimate prebiotic value. Orbital dynamics also control impact speed, which can determine whether fragile molecules survive arrival.

What the source establishes

Fresh preprint submitted to MNRAS with public code and data. Transport and impact statistics come from numerical experiments; chemical yield is model-derived and architecture-specific.