Posts Tagged ‘Late Heavy Bombardment’

08/04/2022 – Ephemeris – The Late Heavy Bombardment

August 4, 2022 Comments off

This is Bob Moler with Ephemeris for Thursday, August 4th. Today the Sun will be up for 14 hours and 32 minutes, setting at 9:04, and it will rise tomorrow at 6:33. The Moon, 1 day before first quarter, will set at 12:19 tomorrow morning.

The face of the Moon is nearly half uncovered from our point of view, with first quarter occurring at 7:06 tomorrow morning. It shows the string of lunar seas, those gray areas on the moon which lead to the terminator, the Moon’s sunrise line. There are even more and larger seas on the east half of the Moon, as we see it. Most were created about 3.9 billion years ago by asteroid strikes. The same thing happened to the Earth, but plate tectonics destroyed the evidence. Not so on the Moon. The result, many planetary scientists think, was the Late Heavy Bombardment, caused by the changing orbits of mainly Saturn, Uranus and Neptune disrupting the smaller asteroids, and sending them careening through the solar system.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.


Tonights Moon with labels

First quarter Moon with prominent seas labeled. Created using Stellarium, GIMP and LibreOffice.

Nice model infographic

Nice model infographic: Evolution of the solar system. Step 6, with the exchange of Neptune’s and Uranus’ orbits, cause the Late Heavy Bombardment. The Nice model isn’t that nice. It’s named for Nice, France, the city where the model was first developed. The original on the web page was smaller. I enlarged it and sharpened it a bit, so it’s more readable. Credit: Nora Eisner.

The above infographic is from the blog post at by Nora Eisner.

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.