4th August 2011 - 2 Earth's Two Moons

A new proposition suggests that when the moon formed from the impact of an asteroid with the earth 4.5 billion years ago, that it wasn't just one moon formed, but two.

Why would anyone think that? There is a difference between the near and far sides of the moon. The two sides have different terrains, a different crust thickness and different amounts of so called KREEP (potassium (K), rare earth elements (REE), phosporous (P)) elements.

For details see Nature: Early Earth may have had two moons - Richard Lovett

26th May 2011 Coral and Day Length

Coral lays down a layer of calcium carbonate every day. These layers can be counted, and so a thicker layer of 365 of them represent a year. Without knowing the length of a year, could we tell it's 365 days? Yes. The thickness of the layers varies with the seasonal variation in day length so there is a cyclic pattern to the layers. [2]

What about coral fossils? What do they tell us? Looking at fossils from 400 million years ago, there are about 410 layers per year. [1] What does this mean? Since the time it takes Earth to orbit the Sun is constant, it means that the length of a day was shorter, about 21 hours long [1,2]. Hence the earth is now spinning more slowly than it was 400 million years ago. Extrapolating back to 4.5 billion years ago, when a massive collision caused the formation of the moon [3], each day would only last about 6 hours.[1]

1. http://www.channel4.com/programmes/catastrophe/episode-guide/series-1/episode-1 16:00-19:30 minutes
2. http://www.don-lindsay-archive.org/creation/coral-clocks.txt
3. http://en.wikipedia.org/wiki/Moon#Formation

20th April 2011 Atmosphere on the Moon

The Moon has a surface boundary exosphere which has somewhere between a few hundred thousanda and a few million molecules per cubic centimetre. This would be considered a good vacuum on Earth.

Dust in the Atmosphere

There has also been dust observed in the atmosphere but how can that be when there isn't enough atmosphere for weather?

• The moon is bombarded with meteorite which kick up dust but there is more in in the atmosphere than this would account for.
• On the day side of the moon, ultraviolet rays are strong enough to displace electrons from surface dust leaving it positively charged. These dust particles repel each other going in the direction possible which is up. This leads to dust plumes. This dust eventually returns to the surface under gravity.

Water on the Moon

Ice has been found in shaded craters, and water molecules in the soil raising the question of whether there is a lunar water cycle.

LADEE Mission

In May 2013, the launch of LADEE (Lunar Atmosphere and Dust Environment Explorer) is planned.  It will sample the moon's exosphere and measure its conditions.

Why care about the Moon's Atmosphere?

In order to understand our own atmosphere, we need to look at other atmospheres. Looking at Venus's atmosphere gave an understanding of the greenhouse effect. Earth is so closely tied to the moon than once a month Earth passes through the Moon's  tail, caused by solar winds, and the Moon passes through the Earth's. What effect does this have? There are many unanswered questions about the Moon's atmosphere but hopefully there will be some answers over the next few years.

Sources

Wikipedia:Moon dust NASA: LADEE mission Wikipedia: Atmosphere of the Moon 365 Days of Astronomy: 20th April 2011 The Moon's Mysterious Exosphere Podcast by Brian Day, NASA Lunar Science Institute

12th April 2011 Moon

Unlike the Earth the Moon's axis is only at 1.5 degrees to the Sun. This means that it has no seasons, and that each place receives the same amount and type of sun all year long. This means that some places, namely craters at the poles, are permanently in shadow. If anything lands in those craters, it will never see the sun again, and never receive any heat. What does this mean? If ice lands in a crater at the poles, then it will stay there. So what is in those craters? Maybe one day we will find out. Starts with a Bang