Archive for June 8, 2017

06/08/2017 – Ephemeris – The late heavy bombardment of the inner planets

June 8, 2017 1 comment

Ephemeris for Thursday, June 8th. Today the Sun will be up for 15 hours and 28 minutes, setting at 9:25, and it will rise tomorrow at 5:57. The Moon, 1 day before full, will set at 6:22 tomorrow morning.

The Moon and many bodies of the inner solar system have many craters which bear witness to many meteorite hits. In studying lunar samples brought back by the Apollo astronauts, from Russian lunar sample return missions and meteorites found on Earth that came from the Moon planetary scientists found that many of their ages correspond to a narrow range of dates of 3.8 to 4.1 billion years ago. Radioisotope dating of rocks would date them to the last time they were molten. This lead to the hypothesis that about a half billion years after the planets were formed, the inner solar system bodies were pelted with millions of asteroids in what is known as the late heavy bombardment. The reason is not completely understood, but one hypothesis is that the outer planets migrated destabilizing the asteroid belt causing the solar system to be a shooting gallery.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Lunar seas

Lunar seas and their ages. Credit NASA.

Migration of the outer planets

How the migration of the outer planets caused the Late Heavy Bombardment. Credit James Green, Director Planetary Science, NASA.