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RE: The Moon
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Credit: N. Carboni

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L

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Neumayer crater
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While ESA's SMART-1 mission is running on its last orbits around the Moon before its planned lunar impact on 3 September 2006, the spacecraft 'star tracker' – or attitude camera - is taking exciting pictures of the ever approaching surface.

One week before the end of the SMART-1 mission, the SMART-1 Mission Control Team at the European Space Operations Centre (ESOC) in Germany are working together with the Danish Technical University (DTU), manufacturer of the star tracker, to demonstrate that this attitude camera is not only capable of determining the spacecraft attitude by looking at the stars, but can also be used for exciting peeks at the Moon. The DTU star tracker is a light-weight instrument, weighing only 3.2 kilogrammes including the baffles, and operates highly autonomously.
With only a few days to go, the flight control team is taking advantage of the star tracker being blinded by the moonlight to fuel the imagination and take images at close distance.

Neumayer crater
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Credit ESA

This image was taken on 23 August at 10:42 UT, from 165 kilometres above the Moon surface, while SMART-1 was travelling at a speed of 1.93 kilometres per second. The two craters visible on the image are 'satellite' craters to the Neumayer crater. Satellite craters are identified by the name of their parent crater and an additional letter.
On the star tracker image the crater with the sharp rim is called Neumayer M (located at a latitude of 71.6° South, and a longitude of 78.5° East) and the one with the smooth rim is called Neumayer N (at a latitude of 70.4° South, and a longitude of 78.7° East). The image is slightly smeared as the spacecraft is moving at high speed and at low altitude. This image was taken as a test, which means the spacecraft pointing was not optimised for taking images with the star tracker.

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Crater Cuvier
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This high-resolution image, taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA's SMART-1 spacecraft, shows the young crater 'Cuvier C' on the Moon.

CuvierC
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Credit ESA

AMIE obtained this sequence on 18 March 2006 from a distance of 591 kilometres from the surface, with a ground resolution of 53 metres per pixel. The imaged area is centred at a latitude of 50.1º South and a longitude of 11.2º East, with a field of view of 27 km. The North is on the right of the image.

"This image shows the resolving power of the SMART-1 camera to measure the morphology of rims and craters in order to diagnose impact processes, or to establish the statistics of small craters for lunar chronology studies" - Bernard Foing, SMART-1 Project scientist.

Cuvier C, a crater about 10 kilometres across, is visible in the lower right part of the image. Cuvier C is located at the edge of the larger old crater Cuvier, a crater 77 kilometres in diameter. The upper left quadrant of the image contains the smooth floor of Cuvier, only one fourth of which is visible in this image.

Crater Cuvier was named after the creator of the comparative anatomy, Georges Cuvier, a 19th century French naturalist (1769 - 1832).

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Crater Jacobi
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This high-resolution image, taken by the advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, shows part of crater Jacobi in the southern hemisphere of the Moon. The rim of the crater is seen on the upper edge of the image.

Jacobi
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AMIE obtained this sequence on 18 March 2006 from a distance of about 578 kilometres from the surface, with a ground resolution of 52 metres per pixel. The imaged area is centred at a latitude of 56.5º South and a longitude of 10.9º East, with a field of view of 27 km. North is at the right of the image.
The crater Jacobi itself is much larger than this image - about 70 kilometres in diameter - whereas this image only shows an area of about 25 square kilometres. The single prominent crater to the upper right of the image centre is ‘Jacobi W’, with a diameter of only 7 kilometres. It is possible to note the peculiar surface structure in the upper left area of the image, indicating several heavily eroded kilometre-sized craters having roughly the same size.

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Mezentsev, Niepce and Merrill craters
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This image, taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 spacecraft, provides an 'oblique' view of the lunar surface towards the limb, around the Mezentsev, Niepce and Merrill craters, on the far side of the Moon.

http://www.esa.int/images/SIDEVIEW_with_labels_L.jpg
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"This cratered terrain is similar in topography to near-side highlands, while the far-side equator bulge can reach heights of 7 km, and the South Pole Aitken basin has depths down to 8 km" - Bernard Foing, SMART-1 Project scientist.

AMIE obtained this sequence on 16 May 2006. The imaged area is centred at a latitude of 73º North and a longitude of 124º West(or 34 º further than the West limb seen from Earth).

Normally, the SMART-1 spacecraft points the AMIE camera straight down, in the so-called Nadir pointing mode. In this image, AMIE was looking out 'the side window' and pointing towards the horizon, showing all craters in an oblique view. The largest craters shown are Mezentesev, Niepce and Merrill, located on the lunar far side, not visible from the Earth. Mezentsev is an eroded crater 89 kilometres in diameter, while Niepce and Merrill have the same size 57 km.

Mezentsev is named after Yourij Mezentsev, a Soviet engineer (1929 - 1965) who was one of the first people to design rocket launchers. Joseph Niepce was the French inventor of photography (1765 - 1833), while Paul Merrill was an American astronomer (1887 - 1961).

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Fossil Bulge
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Title: LONG-WAVELENGTH LUNAR GEOLOGY AND THE FOSSIL BULGE.
Authors: Garrick-Bethell1 and M. T. Zuber1, 1 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology.

Introduction: Ever since Laplace it has been known that the Moon is not in hydrostatic equilibrium with its present tidal and spin state. Jeffreys considered the problem in 1915, and showed in 1937 that the ratio of the libration parameter á = (C-B)/A to â = (C-A)/B is 0.63, in disagreement with the predicted ratio of 0.25 for a synchronous satellite. Thus the idea that the Moon holds a "fossil bulge" of a past tidal-rotational state was difficult to accept.
There are, however, at least several good reasons why the lunar fossil bulge hypothesis has persisted: the Moon’s orbit evolved relatively close to Earth as it cooled, statistical noise in the lunar gravity spectrum cannot fully explain the high power of the low-order terms, the lunar lithosphere was able to support loads, and timescales of crystallization of the magma ocean are now slower than previously believed. There are also good reasons to suspect the Moon may not bear a fossil bulge, such as insufficient time available to form a lithosphere thick enough to support the implied loads, and the fact that large-scale density heterogeneities cannot be ruled out.

moonbulge3
Reflection of the northern farside gravity potential onto SP-A.

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RE: The Moon
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The far side of the Moon boasts an unusual bulge at the equator, whose origin has baffled scientists for centuries, but according to a new study in today's issue of the U.S. journal Science, a possible explanation could be that early in the Moon's history the orbit may have differed during the crucial stage in which the lunar magma ocean was solidifying.

This age-old mystery of the 'fossil bulge' was first brought to attention by mathematician Pierre-Simon Laplace in 1799 (Ed - Hummm), and since then various explanations have been proposed but have failed to fit the exact dimensions of the Moon.
Today's study showed that the moon's shape can be justified if the Moon was in an oval, or 'eccentric' orbit, 100 million years after its formation. Ian Garrick-Bethell, co-author of the paper and PhD student from the Massachusetts Institute of Technology, USA described the resulting shape of the moon as like half an American football.
For the model to work, Garrick-Bethell had to take into consideration the process of how the fossil 'freeze-in', or solidification, actually works. He framed his research around the question: "how can you freeze-in a single-axis football component in a plastic Moon, when the Moon is continually spinning with respect to the Earth thereby changing the axis that gets the football deformation?"

Along with fellow colleagues, Garrick-Bethell modelled specific orbits that were possible solutions, including one similar to the present state of Mercury. The researchers said that if the Moon was spinning 1.5 times on its own axis for each time it orbited the Earth, instead of only once as it does now, it would have been spinning fast enough to stretch the cooling magma.

"At any point in its orbit, the Moon's rotation stretches it like a flattened basketball, while tides from the Earth stretch it like a football. We thought of different scenarios that could increase the flattening component, and one of the most straightforward ones is to simply assume that the Moon was once spinning faster" - Garrick-Bethell.

"It is well known that (an eccentric) orbit is stable for Mercury (which has a 3:2 resonance), so we explored what values of eccentricity would give the current lunar moments of inertia in a 3:2 resonance, if any" - Garrick-Bethell.

According to Garrick-Bethell, these findings can be used for future work along similar lines as there is still much left to be studied about the evolution of the Earth and Moon system.

"There are always new ways of looking at old problems. Very little is definitively known about the early evolution of the Earth-Moon system" - Garrick-Bethell.

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An eccentric orbit in the Moon's distant past might be responsible for the mysterious bulge around its middle, according to Ian Garrick-Bethell and colleagues from the Massachusetts Institute of Technology.

The excess material around the lunar equator has been known since 1799 when French mathematician Pierre-Simon Laplace first noticed it. The reason, however, has been a mystery until now.
The Moon's peculiar shape can be explained if the satellite moved in an eccentric oval-shaped orbit 100 million years after its violent formation, when the satellite hadn't yet solidified.
It was like a big ball of molasses and all around the equator it got deformed.
Around that time, conditions, such as orbit shape and position, were optimal for it to cool down and become the solid moon that we now know.
Today, the Moon's orbit around the Earth is nearly circular.
To predict the Moon's position and orbit millions of years ago, Garrick-Bethel and colleagues extrapolated backwards from ancient records of the timing of historical solar eclipses and of changes in the distance between the Earth and Moon.

This finding will be detailed in the August 4 issue of the journal Science.

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Lunar swirls are strange markings on the Moon that resemble swirling cream in coffee. They seem to be curly-cues of pale moondust, twisting and turning across the lunar surface for dozens of miles. Each swirl is utterly flat and protected by a magnetic field.

One of the swirls, Reiner Gamma Formation, can be seen through a backyard telescope. It lies near the western shores of Oceanus Procellarum (the Ocean of Storms) and looks at first sight like a strangely disorganized crater. Indeed, that's what most astronomers thought it was until 1966 when NASA's Lunar Orbiter II spacecraft flew overhead and photographed Reiner Gamma from point blank range. Whatever it was in that grainy black and white photo, it was not a crater.
Before long, two more swirls were found on the Moon's farside. They lie directly opposite the nearside impact basins Mare Imbrium (the Sea of Rains) and Mare Orientale (the Eastern Sea). Impacts on one side of the Moon, it seemed, made swirls on the other side. No one could explain how.



The mystery deepened in 1972 when it was discovered that the swirls were magnetised.
The strongest fields were located above Lunar Swirls.

"The swirls have magnetic fields measuring a few hundred nano-Tesla (nT) at ground level (Earth's magnetic field, for comparison, is 30,000 nT). If you walked around a swirl with a magnetic compass, the needle would swing back and forth in a confusing way. You'd quickly get lost because the magnetic fields are so jumbled" - Bob Lin of UC Berkeley.

Lin believes these strange fields are an important clue to the origin of swirls, and he offers this possibility:

"Almost four billion years ago, the Moon had a liquid iron core and a global magnetic field. Suppose an asteroid hit the Moon. The blast would make a cloud of electrically conducting gas ('plasma') that would sweep around the Moon, pushing the global magnetic field in front of it. Eventually, the cloud would converge at a point directly opposite the impact, concentrating the magnetic field at that point" - Bob Lin.

Eons later, the Moon's core cooled and its global magnetic field faded away. Only the strongest, tangled patches remained--the swirls.

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