Moon made of small moons?

This video from the USA says about itself:

A 2015 remastered edit of Dr Harrison Schmitt’s lecture, ‘Apollo and the Geology of the Moon’, first delivered 19 December 1973.

Dr Harrison Schmitt was part of the three man crew of Apollo 17 which launched on 7 December 1972, returning to Earth on 19 December. Apollo 17 was the final of NASA’s manned lunar landing missions and therefore Schmitt remains the first and only geologist ever to walk on the Moon.

The following year, Dr Schmitt delivered a lecture on his experiences before a packed audience in the newly refurbished lecture theatre at the Geological Society. Indeed such was the demand for tickets that the lecture was relayed to the British Academy where extra seating had to be provided for another 130 attendees.

This video is a remastered edit of Dr Schmitt’s lecture, created in 2015 by the Geological Society Library. To find out more visit here.

Copyright 1973 & 2015 Geological Society of London
Stills copyright NASA

From Science News:

Many tiny moons came together to form moon, simulations suggest

One giant impact may not be responsible for Earth’s satellite

By Thomas Sumner

11:00am, January 9, 2017

The moon is made of moons, new simulations suggest. Instead of a single colossal collision forming Earth’s cosmic companion, researchers propose that a series of medium to large impacts created mini moons that eventually coalesced to form one giant moon.

This mini-moon amalgamation explains why the moon has an Earthlike chemical makeup, the researchers propose January 9 in Nature Geoscience.

“I think this is a real contender in with the other moon-forming scenarios,” says Robin Canup, a planetary scientist at the Southwest Research Institute in Boulder, Colo., who was not involved in the new work. “This out-of-the-box idea isn’t any less probable — and it might be more probable — than the other existing scenarios.”

A collision between Earth and a Mars-sized object called Theia around 4.5 billion years ago is the current leading candidate for how the moon formed. This impact would have been a glancing blow rather than a dead-on collision, with most of the resulting building materials for the moon coming from Theia. But the moon and Earth are compositional dead ringers for one another, casting doubts on a mostly extraterrestrial origin of lunar material and thus the single impact explanation.

Planetary scientist Raluca Rufu of the Weizmann Institute of Science in Rehovot, Israel, and colleagues dusted off a decades-old, largely disregarded hypothesis that the moon instead formed from multiple impacts. In this scenario, the early Earth was hit by a series of objects a hundredth to a tenth of Earth’s mass. Each impact could have created a disk of debris around Earth that assembled into a moonlet, the researchers’ simulations show. Over tens of millions of years, about 20 moonlets could have ultimately combined to form the moon.

Multiple impacts help explain why Earth and the moon are chemically similar. For example, each impact may have hit Earth at a different angle, excavating more earthly material into space than a singular impact would.

The single impact hypothesis has about a 1 to 2 percent chance of yielding the right lunar mix based on the makeup of potential impactors in the solar system. In the researchers’ simulations, the multiple impact scenario is correct tens of percent of the time. Further investigation of the interiors and composition of the Earth and moon, the researchers say, should reveal whether this explanation is correct.

Competing ideas abound for how Earth got its moon. Earth’s satellite may have formed from one giant impact or from about 20 small ones. By
Thomas Sumner, 6:00am, April 4, 2017: here.

The moon is still old. More precise dating of Apollo 14 moon rocks pegs age at 4.51 billion years. By Christopher Crockett, 2:00pm, January 11, 2017: here.