h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Back in 2004 the astronomy magazine Sky and Telescope published the Lunar 100. It’s a list of one hundred features on the Moon which was compiled by Prof Charles Wood, ex NASA lunar scientist, to illustrate some of the geological features and history of our own satellite.

The one hundred items are listed in order of easiest to most difficult. The idea being to identify these features in the same way that a Messier object hunter might do with the Messier list of 110 items.

In some respects the Lunar 100 list is easier, as all the features are located within a half degree of each other on the Moon’s surface. In other respects it’s a lot harder as some of the features can only be seen when the phase of the Moon is correct and the shadow line of the terminator is in the right place. And of course they can only be seen if the Moon’s ‘up’.

Part of the fascination of the Moon lies in its topography and geology. It’s the most accessible planetary body that can be seen from Earth, and to a large extent you are looking at what the Earth would be like if it wasn’t for an atmosphere. So it’s worth having a closer look.

So, I’ve dug out my copy of Rukls and just spent a pleasant evening brushing up on the beautiful drawings therein. The Moon‘s coming up to ‘full‘ in a couple of days when it will be the best time to record No 1 on the list.

http://www.skyandtelescope.com/observing/objects/moon/3308811.html

8 March 2012
Binoculars out tonight for the almost full moon.

L100 No1: The Moon
The Earth's Satellite. A full moon on the 8 March in all its glory. Its topography displays all the turmoil and scars of the great bombardment in the early history of the Solar System.

L100 No3: Mare/Highland dichotomy
Best seen at full moon when even casual observation shows dark and light patches. The dark patches are the lunar mare, or seas. With a pair of binoculars they become more prominent and many of the dark areas can be seen to be vaguely circular. In almost all cases they were caused by cataclysmic impacts in the early life of the Moon. Later eruptions of lava flowed into the basins created by those impacts. When cooled the lava reflects less light and therefore appears darker.

The lower half of the moons face, and particularly the four-o-clock to seven-o-clock area, appear much lighter. This area is the oldest surface seen from Earth and dates back to the original differentiation of the planetary body when molten 4.5 billion years ago. This surface contains a high proportion of Anorthosite, one of the lighter elements which rose to the surface and solidified. Despite its apparent brightness, the overall reflectivity is approximately that of Tarmac as used on our roads.

26 March 2012
Binoculars out again this evening.

L100 Earthlight: Twice reflected light.
The Moon is again accompanied by Venus and Jupiter. It's about 3 - 4 days old and is presenting a cresent. Also clearly prominant is the ashen light of twice reflected sunlight. Within that if carefully observed is the darker portion of the 'seas' within the ashen light, in particular Procellarum and the Imbrium Basin