Basin formation ages and the timing of the migration of the gaseous planets

How old is the oldest surface of the terrestrial bodies? This is one of the key issues of investigating the earliest phase of intense planetary bombardment, because the highest crater frequencies recorded on these planetary surfaces can be used to calculate their age. In the cases of Earth (due to plate tectonics) and Venus (due to recent - probably periodic - resurfacing by continuous global volcanism and/or global crustal overturn), the surface record of the earliest bombardment has been erased, and only isotopic data allow estimates of early-Earth's evolutionary stages. Therefore, we will study here only Mercury, Mars and the Moon, and compare their record of large impact basins, considered to have formed only during the earliest phase of planetary evolution. A correct time-frame for the formation phase of our solar system based on impact flux data would provide a detailed and temporally-calibrated description of the early planetary geological evolution of all terrestrial bodies. It exist different interpretational concepts, based on which the earliest bombardment history can be inferred. One is based on crater counts of lunar surface units of known isotope ages, from which then the flux is extrapolated into the more distant past implying a static orbital evolution model for the planets since their formation. The second concept is suggesting a dynamic orbital evolution of the solar system, such as the 'Nice' model. We will address the questions: What evidence remained of a (late) heavy bombardment on the planetary surfaces? And: Did it happen synchronously?