Editing Planet V (section)

==Hypothesis==
In the Planet V hypothesis, five terrestrial planets were produced during the [[planetary formation]] era. The fifth terrestrial planet began on a low-[[orbital eccentricity|eccentricity]] orbit between Mars and the asteroid belt with a [[semi-major axis]] between 1.8 and 1.9 [[astronomical unit|AU]]. While long-lived, this orbit was unstable on a time-scale of 600 Myr. Eventually perturbations from the other [[inner planet]]s drove Planet V onto a high-eccentricity orbit which crossed into the inner asteroid belt. [[Asteroid]]s were scattered onto [[Mars-crosser asteroid|Mars-crossing]] and [[orbital resonance|resonant orbit]]s by close encounters with Planet V. Many of these asteroids then evolved onto [[Earth-crosser asteroid|Earth-crossing]] orbits temporarily enhancing the [[lunar impact]] rate. This process continued until Planet V was lost most likely by impacting the Sun after entering the ν<sub>6</sub> [[secular resonance]].<ref name=Chambers_Lissauer_2002 />