APOD: GRAIL Maps the Moons Gravity (2013 Mar 19)

[APOD Robot]

GRAIL Maps the Moons Gravity

Explanation: How did the Moon form? To help find out, NASA launched the twin Gravity Recovery and Interior Laboratory (GRAIL) satellites in 2011 to orbit and map the Moon's surface gravity in unprecedented detail. Pictured above is a resulting GRAIL gravity map, with regions of slightly lighter gravity shown in blue and regions of slightly stronger gravity shown in red. Analysis of GRAIL data indicates that the moon has an unexpectedly shallow crust than runs about 40 kilometers deep, and an overall composition similar to the Earth. Although other surprising structures have been discovered that will continue to be investigated, the results generally bolster the hypothesis that the Moon formed mostly from Earth material following a tremendous collision in the early years of our Solar System, about 4.5 billion years ago. After completing their mission and running low on fuel, the two GRAIL satellites, Ebb and Flow, were crashed into a lunar crater at about 6,000 kilometer per hour.

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[Beyond]

To me,it resembles a pizza going really bad But to a scientist, it may be a pretty sweet study. Hmm... if you add the gravity map of the moon, to how the moon lo looks, would you end up with a study packet of sweet & lo

[bystander]

http://asterisk.apod.com/viewtopic.php?p=188965#p188965

[BobMaller@aol.com]

Am I looking at the Earth side of the moon, the far side of the moon or some combination?

[orin stepanek]

Today's APOD was very interesting with lots of videos! I liked it very much! Good thing the moon isn't too close! Probably wouldn't be to good if it were too far either!

[dougettinger]

What does this GRAIL depiction imply for -

Red spots? Blue spots? Blue spots surrounded by red? Blue spots with red spots in the center? I realize the differences in gravity as described, but does anyone have any advanced ideas about the overall implications? I definitely have my own ideas.

Doug Ettinger
Pittsburgh, PA

[neufer]

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Am I looking at the Earth side of the moon, the far side of the moon or some combination?

Mostly the right hand (trailing) side of the moon.

GRAIL Maps the Moons Gravity

The bright red spot on the upper left is Mare Crisium.

The "Colorado C" near the top is the Humboldtianum basin.

[neufer]

What does this GRAIL depiction imply for -

Red spots? Blue spots? Blue spots surrounded by red? Blue spots with red spots in the center? I realize the differences in gravity as described, but does anyone have any advanced ideas about the overall implications? I definitely have my own ideas.

Isostasy, gravity, and the Moon: an explainer of the first results of the GRAIL mission
By Emily Lakdawalla, Planetary Society

[idoradjr]

It would be interesting to see the gravity map overlaid onto the a topographical map to see if there is a correlation between craters and the gravity differences. Are old craters places of higher gravity and newer craters places of lower gravity, or vice versa, or is there no correlation?

[LocalColor]

Wonderful APOD today and the links to more info are great! Thanks

[Boomer12k]

So...Practical application...if you want to appear LIGHTER....stay in the BLUE LOCATIONS!!!

:---[===] *

[Chris Peterson]

So...Practical application...if you want to appear LIGHTER....stay in the BLUE LOCATIONS!!!

Yes, but you don't need to go to the Moon for that.

[Anthony Barreiro]

Am I looking at the Earth side of the moon, the far side of the moon or some combination?

Mostly the right hand (trailing) side of the moon.

The bright red spot on the upper left is Mare Crisium.

The "Colorado C" near the top is the Humboldtianum basin.

Thanks Neufer, I never would have figured this out on my own. I was trying to match the image with surface maps of the near and far sides. I didn't consider that there might be some near and some far side features -- makes me feel like Dr. Watson once Holmes reveals the obvious but previously unrecognized truth.

[Ernie Wright]

Am I looking at the Earth side of the moon, the far side of the moon or some combination?

Mostly the right hand (trailing) side of the moon.

The bright red spot on the upper left is Mare Crisium.

The "Colorado C" near the top is the Humboldtianum basin.

Thanks Neufer, I never would have figured this out on my own. I was trying to match the image with surface maps of the near and far sides. I didn't consider that there might be some near and some far side features -- makes me feel like Dr. Watson once Holmes reveals the obvious but previously unrecognized truth.

The image is centered on 101.4 degrees E, so almost exactly half near side (left) and half far side.

- Ernie

[Ernie Wright]

It would be interesting to see the gravity map overlaid onto the a topographical map to see if there is a correlation between craters and the gravity differences. Are old craters places of higher gravity and newer craters places of lower gravity, or vice versa, or is there no correlation?

Would a side-by-side comparison help? See the SVS web page for several animations, including one with free-air gravity and topography together. They are correlated, but there are still gravity variations after you subtract the effect of surface elevation. What's left is assumed to be the effect of crust thickness.

- Ernie

[Canadian Grandma]

How reassuring to know that I'm light-headed only because I live in the "Great Lakes" area (blue gravity density)!

[neufer]

So...Practical application...if you want to appear LIGHTER....stay in the BLUE LOCATIONS!!!

Yes, but you don't need to go to the Moon for that.

These ±50 milligal deviations from "the theoretical gravity of an idealized smooth Earth, the so-called earth ellipsoid," are insignificant as compared to the full figured gal size variations from sitting at different points on the Earth's sea level spinning ellipsoid shape.

<<In combination, the equatorial bulge and the effects of the Earth's inertia mean that sea-level gravitational acceleration increases from about 978.0 cm·s⁻² at the Equator to about 983.2 cm·s⁻² at the poles, so an object will weigh about 0.5% more at the poles than at the Equator.>>

Go to the top of Mt. Chimborazo (~0.1% further from the Earth's center/axis)
for a maximal feeling of lightness (i.e., an additional ~0.2% / ~2 gal reduction).

<<Until the beginning of the 19th century, it was thought that Chimborazo was the highest mountain on Earth (measured from sea level), and such reputation led to many attempts on its summit during the 17th and 18th centuries. In 1802, during his expedition to South America, Baron Alexander von Humboldt, accompanied by Aimé Bonpland and the Ecuadorian Carlos Montúfar attempted to reach the summit. From his description of the mountain, it seems that before he and his companions had to return suffering from altitude sickness they reached a point at 5,875 m, higher than previously attained by any European in recorded history. In 1831 Jean Baptiste Boussingault and Colonel Hall reached a new "highest point", computed to be 6,006 m. In 1880 Chimborazo's summit was first climbed by Edward Whymper and the brothers Louis and Jean-Antoine Carrel. As there were many critics who doubted that Whymper had reached the summit, later in the same year he climbed to the summit again choosing a different route (Pogyos) with the Ecuadorians David Beltrán and Francisco Campaña.>>

[revloren]

OK, so how is gravity variable? I thought that gravity was constant to the mass of the entire body. Is this related to the specific densities of the various areas of the moon's crust?

[neufer]

OK, so how is gravity variable? I thought that gravity was constant to the mass of the entire body. Is this related to the specific densities of the various areas of the moon's crust?

Primarily:

• Upwellings of dense basaltic lava produce red mascons.
  
  Small meteor craters with no upwelling produce blue holes.

Isostasy, gravity, and the Moon: an explainer of the first results of the GRAIL mission
By Emily Lakdawalla, Planetary Society

[Chris Peterson]

OK, so how is gravity variable? I thought that gravity was constant to the mass of the entire body. Is this related to the specific densities of the various areas of the moon's crust? :?:

Gravity isn't variable. The gravitational field of the Moon isn't uniform, and that's because the Moon isn't an isotropic or radially symmetric body. Nor is any stony astronomical body.

I live in the middle of a ring of hills, long suspected of being the remnant walls of an old volcanic caldera. However, the local gravity field was mapped, allowing the crustal density variation to be understood, and this demonstrated that this valley is not, in fact, a caldera. As I walk around here, my weight increases or decreases based on the nature of the underlying crust.

[Quigley]

EXTREMELY INTERESTING! I had always wondered if I would instantly "lose weight" if I went to Equador. Thanks for the fascinating APOD.

[neufer]

I had always wondered if I would instantly "lose weight" if I went to Equador.

As my daughter Andrea found out...that sort of depends on how much you care for Guinea pig:

[img3="Dish from Ecuador called "Cuy""]http://upload.wikimedia.org/wikipedia/c ... ish_SG.jpg[/img3]

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<<Guinea pigs (called cuy, cuye, curí) were originally domesticated for their meat in the Andes. Traditionally, the animal was reserved for ceremonial meals by indigenous people in the Andean highlands, but since the 1960s it has become more socially acceptable for consumption by all people. It continues to be a major part of the diet in Peru and Bolivia, particularly in the Andes Mountains highlands; it is also eaten in some areas of Ecuador (mainly in the Sierra) and Colombia. Because guinea pigs require much less room than traditional livestock and reproduce extremely quickly, they are a more profitable source of food and income than many traditional stock animals, such as pigs and cows; moreover, they can be raised in an urban environment. Both rural and urban families raise guinea pigs for supplementary income, and the animals are commonly bought and sold at local markets and large-scale municipal fairs. Guinea pig meat is high in protein and low in fat and cholesterol, and is described as being similar to rabbit and the dark meat of chicken. The animal may be served fried (chactado or frito), broiled (asado), or roasted (al horno), and in urban restaurants may also be served in a casserole or a fricassee. Ecuadorians commonly consume sopa or locro de cuy, a soup dish. Pachamanca or huatia, a process similar to barbecueing, is also popular, and is usually served with corn beer (chicha) in traditional settings.

Peruvians consume an estimated 65 million guinea pigs each year, and the animal is so entrenched in the culture that one famous painting of the Last Supper in the main cathedral in Cusco shows Christ and the twelve disciples dining on guinea pig. The animal remains an important aspect of certain religious events in both rural and urban areas of Peru. A religious celebration known as jaca tsariy ("collecting the cuys") is a major festival in many villages in the Antonio Raimondi province of eastern Peru, and is celebrated in smaller ceremonies in Lima. It is a syncretistic event, combining elements of Catholicism and pre-Columbian religious practices, and revolves around the celebration of local patron saints. The exact form that the jaca tsariy takes differs from town to town; in some localities, a sirvinti (servant) is appointed to go from door to door, collecting donations of guinea pigs, while in others, guinea pigs may be brought to a communal area to be released in a mock bullfight. Meals such as cuy chactado are always served as part of these festivities, and the killing and serving of the animal is framed by some communities as a symbolic satire of local politicians or important figures. In the Tungurahua and Cotopaxi provinces of central Ecuador, guinea pigs are employed in the celebrations surrounding the feast of Corpus Christi as part of the Ensayo, which is a community meal, and the Octava, where castillos (greased poles) are erected with prizes tied to the crossbars, from which several guinea pigs may be hung. The Peruvian town of Churin has an annual festival which involves dressing guinea pigs in elaborate costumes for a competition.>>

[Chris Peterson]

As my daughter Andrea found out...that sort of depends on how much you care for Guinea pig

Cuy is really good, especially barbequed. They have some interesting sauces, as well. I'd compare it to rabbit, and nothing like chicken.

[FLPhotoCatcher]

Using the GRAIL data, a scientist called Wieczorek calculated that the average density of the lunar crust is 2550 kilograms per cubic meter. "This is much, much lower than what has been assumed for lunar crust; in fact, it's lower than the density of granite. We know what the highlands crust is made of, we have samples of it: the density of the minerals that makes up the crust is around 2800-2900 kilograms per cubic meter. For the Moon's density to be so low, Wieczorek says, it must be very porous, fractured and busted up to give it about 12% void space, to a depth of several kilometers below the surface." However, I read somewhere that moonquakes traveled around the moon several times, ringing it like a bell. They said that meant the moons rock (including the crust) had fewer cracks and faults than earth. That would make Wieczorek's conclusion wrong. Maybe it is made of green cheese after all...

[Murphy]

A simple question: If a major object collided with the earth which broke off the moon from the earth, it seems logical that some of the object that hit the earth should still be present. Do we have any physical evidence? Is the composition different from the earth? Or, is it now impossible to differentiate?