Planet V is a hypothetical fifth terrestrial planet posited by NASA scientists John Chambers and Jack J. Lissauer to have once existed between Mars and The Asteroid Belt. In their hypothesis the Late Heavy Bombardment of the Hadean era began after perturbations from the other terrestrial planets caused Planet V's orbit to cross into the asteroid belt. Chambers and Lissauer presented the results of initial tests of this hypothesis during the 33rd Lunar and Planetary Science Conference, held from March 11 through 15, 2002.
The Hypothesis
According to the hypothesis, there were five terrestrial planets that formed during the planetary formation era. These being Mercury, Venus, Earth, Mars, and finally Planet V. Planet V supposedly began on a low-eccentric orbit between Mars and the Asteroid belt, and it was around 1.8 to 1.9 AU's away from the Sun. While this orbit was long lived, the orbit was unstable at a time scale of 600 million years. Eventually, perturbations from the inner planets drove Planet V onto a high eccentric orbit that crossed into the inner asteroid belt. This caused many asteroids to scatter into Mars-crossing and resonant orbits by their close encounters with Planet V. Many of these said asteroids eventually drove into Earth-crossing orbits, temporally enhancing the lunar impact rate. This process continued until Planet V was ultimately lost, most likely by colliding with the Sun after entering the V6 secular resonance.
