Starship Asterisk*

bystander wrote:
What Does the Dark Side of the Moon Look Like?

Six orthographic views of the Moon created from the new WAC global mosaic. From upper left to lower right the central longitude is 0°, 60°, 120°, 180°, 240°, 300°. [i](Credit: NASA/Goddard/Arizona State University)[/i]

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Because the moon is tidally locked (meaning the same side always faces Earth), it was not until 1959 that the farside was first imaged by the Soviet Luna 3 spacecraft (hence the Russian names for prominent farside features, such as Mare Moscoviense). And what a surprise -­ unlike the widespread maria on the nearside, basaltic volcanism was restricted to a relatively few, smaller regions on the farside, and the battered highlands crust dominated. A different world from what we saw from Earth.

Of course, the cause of the farside/nearside asymmetry is an interesting scientific question. Past studies have shown that the crust on the farside is thicker, likely making it more difficult for magmas to erupt on the surface, limiting the amount of farside mare basalts. Why is the farside crust thicker? That is still up for debate, and in fact several presentations at this week's Lunar and Planetary Science Conference attempt to answer this question.

The Clementine mission obtained beautiful mosaics with the sun high in the sky (low phase angles), but did not have the opportunity to observe the farside at sun angles favorable for seeing surface topography. This WAC mosaic provides the most complete look at the morphology of the farside to date, and will provide a valuable resource for the scientific community. And it's simply a spectacular sight!

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) is a push-frame camera that captures seven color bands (321, 360, 415, 566, 604, 643, and 689 nm) with a 57-km swath (105-km swath in monochrome mode) from a 50 km orbit. One of the primary objectives of LROC is to provide a global 100 m/pixel monochrome (643 nm) base map with incidence angles between 55°-70° at the equator, lighting that is favorable for morphological interpretations. Each month, the WAC provides nearly complete coverage of the Moon under unique lighting. As an added bonus, the orbit-to-orbit image overlap provides stereo coverage. Reducing all these stereo images into a global topographic map is a big job, and is being led by LROC Team Members from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). Several preliminary WAC topographic products have appeared in LROC featured images over the past year (Orientale basin, Sinus Iridum). For a sneak preview of the WAC global DEM with the WAC global mosaic, view a rotating composite moon (70 MB video from ASU's LROC website). The WAC topographic dataset will be completed and released later this year.

The global mosaic released today is comprised of over 15,000 WAC images acquired between November 2009 and February 2011. The non-polar images were map projected onto the GLD100 shape model (WAC derived 100 m/pixel DTM), while polar images were map projected on the LOLA shape model. In addition, the LOLA derived crossover corrected ephemeris, and an improved camera pointing, provide accurate positioning (better than 100 m) of each WAC image.

As part of the March 2011 PDS release, the LROC team posted the global map in ten regional tiles. Eight of the tiles are equirectangular projections that encompass 60° latitude by 90° longitude. In addition, two polar stereographic projections are available for each pole from ±60° to the pole. These reduced data records (RDR) products will be available for download on March 15, 2011. As the mission progresses, and our knowledge of the lunar photometric function increases, improved and new mosaics will be released! Work your way around the moon with these six orthographic projections constructed from WAC mosaics.

Orthographic View of the Farside of the Moon
Credit: NASA/GSFC/LROC/Arizona State University
http://asunews.asu.edu/files/images/farside.1600.png

Today, the Lunar Reconnaissance Orbiter Camera (LROC), run by the Arizona State University-based team under Professor Mark Robinson, kicks off a special series of featured images scheduled to be released daily over the next week.

The series of images serves as a prelude to next week’s release of NASA's Lunar Reconnaissance Orbiter team’s set of data from the mission's Exploration Phase along with the first measurements from the Science Phase.

"The LROC map products being released over the next week will not only serve the lunar science community for years to come, but also provide a roadmap for human exploration of our nearest neighbor," says Robinson, a professor in the School of Earth and Space Exploration in ASU's College of Liberal Arts and Sciences.

Among today’s highlighted images is the most detailed view yet of the farside of the Moon.

It was not until 1959 that the farside was first imaged by the Soviet Luna 3 spacecraft. And what a surprise – the farside was a different world, geologically. Unlike the widespread maria on the nearside, basaltic volcanism was restricted to a relatively few, smaller regions on the farside, and the battered highlands crust dominated.

Mosaics from the Clementine images did not observe the farside at illumination angles favorable for seeing surface topography. This mosaic constructed of LROC Wide Angle Camera images, provides the most complete look at the morphology of the farside to date, and will serve as a valuable resource for the scientific community.

LROC acquires high-resolution images of the lunar surface from a 50-kilometer orbit of any spot on the surface with resolutions down to 50 centimeters/pixel (19.7 inches/pixel) while LRO orbits at a speed of 5,800 km/hr (3,600 miles/hour). The imaging system consists of two Narrow Angle Cameras (NACs) to provide high-resolution images, and a Wide Angle Camera (WAC) to provide 100-meter resolution images in seven color bands over a 57-km swath.

The global mosaic released today is comprised of over 15,000 WAC images acquired between November 2009 and February 2011.

NoelC wrote:

batjac1 wrote:
Excuse me, but what is that approximately 60 mile long almost straight black line just to the right of the words Mare Nubium?

That would be Rupes Recta or the "Straight Wall".
Not really a cliff but a gentle change in elevation of a thousand feet or so.

http://en.wikipedia.org/wiki/Alpine_skiing wrote:

Ski trail difficulty ratings in North America: Green circle Easiest
The easiest slopes at a mountain. Green Circle trails are generally wide and groomed,
typically with slope (tangent) gradients ranging from 6% to 25%.

http://en.wikipedia.org/wiki/Rupes_Recta wrote:

Rima Birt rille

<<Rupes Recta is a linear fault, or rille, on the Moon, in the southeastern part of the Mare Nubium. The name is Latin for "Straight Fault", although it is more commonly called the Straight Wall. This is the most well-known escarpment on the Moon, and is a popular target for amateur astronomers.
When the sun illuminates the feature at an oblique angle at about day 8 of the Moon's orbit, the Rupes Recta casts a wide shadow that gives it the appearance of a steep cliff. The fault has a length of 110 km, a typical width of 2–3 km, and a height of 240–300 m. Thus although it appears to be a vertical cliff in the lunar surface, in actuality the grade of the slope is relatively shallow.
To the west of this escarpment is the crater Birt, which is about 10.5 miles in diameter. Also to the west is the Rima Birt rille. At the southern end is a group of hills often called the "Stag's-Horn Mountains", although this name is not officially recognized by the IAU.>>

garry wrote:Yes this is curious. Every crater is circular. This means that every so called impact happened at a perpendicular angle. i.e. 90 degrees. You would think that an impact, somewhere would come in at an angle. You cannot say gravity puled the asteroid, meteor, etc, into a vertical flight because the gravity on the moon is not strong enough!

batjac1 wrote:Excuse me, but what is that approximately 60 mile long almost straight black line just to the right of the words Mare Nubium?

batjac1 wrote:Excuse me, but what is that approximately 60 mile long almost straight black line just to the right of the words Mare Nubium? There is nothing similar to it anywhere else in the image, and it does seem to have a starting point in a crater rim, and an end point near a rectangular looking shape. If you crop it, there is a similar but fainter line from the same starting point to another boxy shape in an otherwise flat looking landscape off to the right.

is that black line some sort of photographic alignment mark or what?

I am not into looking for strange stuff on the moon, but I noticed this and it looks rather odd.

dobrosailor wrote:I was curious why the impact craters are so symetrical. Since this is the near side, any craters in the center of the moon would have had to come directly from earth (in my simplistic view) to get a symetrical crater. Seems like there should be more side impact craters on the earth facing side since they would have to be passing by the earth to hit the moon. I guess it must be gravity is strong enough to arrest the side motion or the moon rotated at one time...

Thoughts,

Craig Willford wrote:
The perturbation of the other kinds of libration, though, could be the very largest source for causing some dynamic libration. The MassCons slightly leading or slightly trailing the center of gravity of the Earth-Moon system would effect work on the Moon, would it not?

Do you know if scientists have detected any dynamic libration?

http://www.csr.utexas.edu/mlrs/dda.html wrote:
Lunar Laser Ranging at McDonald Observatory:
P. J. Shelus, R. L. Ricklefs, J. G. Ries, A. L. Whipple, and J. R. Wiant
McDonald Observatory

<<[Lunar laser ranging (LLR)] analysis has also provided measurements of the Earth’s orbit precession, the 18.6 year nutation, the Moon’s tidal acceleration, lunar rotational energy dissipation and the Moon’s free librations, Earth orientation, and the determination of the obliquity and the equinox.

The lunar libration in longitude, with a period of only 2.9 yr, has a 69 yr beat with another term of similar period; a third mode of that libration has a 24 yr period with respect to the node.>>

Johnny wrote:Why no detailed, untouched, pictures of the far side of the moon...?

neufer wrote:

Beyond wrote:
Hey neufer, in your mar 03, 2011 2:53pm moon post, when i click on >Thomas Harriot<, i get this-->Forbidden
You don't have permission to access /images/photos/ozzy_and_harriet_std.jpg on this server.

How come?? Crooked link

It works for me:

Beyond wrote:
Hey neufer, in your mar 03, 2011 2:53pm moon post, when i click on >Thomas Harriot<, i get this-->Forbidden
You don't have permission to access /images/photos/ozzy_and_harriet_std.jpg on this server.

How come?? Crooked link

k1ns wrote:

• The caption says these photos were captured over a two week period. If so, why do all the shadows seem to indicate that the sun is in about the same position, to the right of the moon?

Craig Willford wrote:That the moon is tidally locked with the nearside facing Earth is a given.

That it slightly rocks back and forth, called libration, is also a given, but less well known. As I recall, it rocks so that about an extra 10% of the Moon's surface becomes visible.

This raises two questions for me:
(1) if the Moon is core-less, then it should be largely frictionless (yes, I know that it does have small moon-quakes, so it isn't wholly frictionless) and so if a frictionless object is perturbed, as all bodies in orbit with at least two others are, then what is to stop the libration from changing? Could the rocking back and forth grow until it goes to a full loop, such as those Carnival rides that have egg shaped caged pods on a Ferris Wheel? The only thing that causes a mass concentration (MassCon) to tidally lock is friction to dampen out the rocking. Are the Moon-quakes adequate to the task?

(2) As it would seem the maria are all on the side facing Earth. Which is the chicken and which is the egg? Did the large impacts occur, causing MassCons and triggering the tidal lock? Or was it that the MassCons were already there and being already tidally locked exposed the nearside to greater risk of the gravitationally lens-focused impacts that caused the maria? Was the Moon tidally locked a very long time ago, such as when the Moon was far closer to the Earth? If so, the rate of rotation of the Moon would have to slow, so as to match the slowing of the rate of revolution around the Earth. (That might be a source of some Moon-quakes, yes?)

http://en.wikipedia.org/wiki/Libration wrote:
There are three types of lunar [kinetic] libration:

• * Libration in longitude results from the eccentricity of the Moon's orbit around Earth; the Moon's rotation sometimes leads and sometimes lags its orbital position.
  * Libration in latitude results from a slight inclination between the Moon's axis of rotation and the normal to the plane of its orbit around Earth. Its origin is analogous to how the seasons arise from Earth's revolution about the Sun.
  * Diurnal libration is a small daily oscillation due to the Earth's rotation, which carries an observer first to one side and then to the other side of the straight line joining Earth's and the Moon's centers, allowing the observer to look first around one side of the Moon and then around the other—because the observer is on the surface of the Earth, not at its center.