Catastrophic Events in the Solar System There are records in the surface and interior of the planets and their satellites that indicate the occurrence of VERY LARGE impacts that have drastically altered the character of the solar system. These events are unpredictable and not adequately accounted for in the standard model of planet formation (Solar Nebula Theory).

Catastrophic Events: Earth The formation of the Moon is now accepted to be due to a grazing collision of a Mars-sized planet with the early Earth after the Earth’s core had formed (Step 6 in the standard model). The collision destroyed the impacting planet and the ejecta re-accreted to form the Moon. The moon has three important physical properties that any formation scenario must predict. The formation of the Moon is now accepted to be due to a grazing collision of a Mars-sized planet with the early Earth after the Earth’s core had formed (Step 6 in the standard model). The collision destroyed the impacting planet and the ejecta re-accreted to form the Moon. The moon has three important physical properties that any formation scenario must predict.

First, the density of the Moon is 3.3 gm/cm 3, substantially less than the Earth’s bulk density, but similar to the density of the Earth’s crust and upper mantle.

Second, Moon rocks are depleted in iron. There is much less iron in Moon rocks than in the rocks found on the Earth’s surface.

Third, Moon rocks are devoid of bound water. Even meteorites have up to 5% water bound into the mineral structures. The Moon has no water in its rocks.

Earth after its iron core has formed A Mars- sized planet on a grazing collision course with the Earth. The Hypothesized Collision that Formed the Moon

Whamo! Crust and upper mantle material is ejected into Earth orbit The Hypothesized Collision that Formed the Moon

The iron core of the impacting body does not escape but falls back into the Earth to join the Earth’s core.

The Hypothesized Collision that Formed the Moon The lighter material from the Earth’s crust and mantle has been heated so much during the impact that the bound water has vaporized and escaped.

The Hypothesized Collision that Formed the Moon Earth’s new Moon has formed from the iron poor and dried out crust and upper mantle rocks of the Earth and its impactor.

Interior of the Moon Notice the relatively small iron core

Venus EarthMars Mercury Moon The Moon’s relatively small iron core bulk geology are consistent with a birth by a violent collision

The Moon preserves a record of catastrophic events itself. This multi- ring impact basin on the Moon is called Mare Oriental.

The impact portrayed in this artist’s impression is far smaller than the impact that created our Moon.

The currently accepted scenario for the Moon’s formation would not have been possible with the aggressive exploration of the Moon and other planets.

Ganymede is a natural satellite the size of Mercury. Its surface preserves the evidence of a giant impact that formed this multi-ring basin called Vahalla. Recent impact craters reveal the clean ice that makes up most of this moons mass.

This small natural satellite called Miranda has surprising surface features for an object its size (236 km radius).

Miranda has both ancient cratered terrain indicating great age and an unusual “chevron”- terrain that indicates recent resurfacing.

This Voyager image of Triton hints at the satellites violent past. Notice the two distinct terrains and the lack of impact craters. The capture event created enough energy to completely melt the satellite erasing previous ancient craters and creating a new terrain.

Cantaloupe-terrain Few Craters and Ice Volcanoes-terrain

This type of terrain is unique in the solar system. The lack of craters implies a relatively young age of this surface.