APOD: Mare Orientale (2011 Mar 12)

[APOD Robot]

Mare Orientale

Explanation: Shaped like a target ring bull's-eye, the Mare Orientale is one of the most striking large scale lunar features. Located on the Moon's extreme western edge, it is unfortunately difficult to see from an earthbound perspective. Still, this mosaic of the multi-ring impact basin, the youngest of the large lunar basins shows off intriguing details (full resolution mosaic), based on Wide Angle Camera images from the Lunar Reconnaissance Orbiter. Only partially flooded by lava the Mare Orientale is over 3 billion years old, about 600 miles (950 kilometers) across and was formed by the impact of an asteroid sized object. The collision caused ripples in the lunar crust resulting in the concentric circular features. Though it may seem a little ironic to denizens of the space age who recognize the Moon as a dry and airless world, a dark, smooth lunar region is called a mare (plural maria), Latin for sea, because astronomers once thought such regions might actually be seas.

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[orin stepanek]

Smooth surface; might make a good landing site.

[neufer]

Smooth surface; might make a good landing site.

The best landing sites (e.g., the Sea of Tranquility) are also the most boring.

[KennyB]

What happens to all the debris from an impact like this. Wouldn't there be some huge dust clouds that would be seen?

[Chris Peterson]

What happens to all the debris from an impact like this. Wouldn't there be some huge dust clouds that would be seen?

Yeah... if anybody was watching three billion years ago! Much younger craters do show evidence of impact ejected debris around them. But most of the craters on the Moon are billions of years old, and any structure in ejected material has long since eroded away (yes- there is erosion on the Moon, it's just a very slow process).

[KenS]

It looks like the asteroid exposed multiple cycles of layering of material deposited on the moon's surface, either by volcanic periods or sequential solidification of different minerals.

[biddie67]

Could an impact on the moon like this have possibly knocked the moon out of its orbit, either into the
Earth or free it completely from its orbit around the Earth?

Could any of that impact affect the oceans on Earth?

[Chris Peterson]

Could an impact on the moon like this have possibly knocked the moon out of its orbit, either into the
Earth or free it completely from its orbit around the Earth?

Not even close.

Could any of that impact effect the oceans on Earth?

An impact like that would definitely have produced debris that reached the Earth as lunar meteorites. I doubt the effect was significant, either on the land or the oceans.

[Phil T, Sweden]

Why is it that from whichever direction one looks there are very few craters which look like a glancing blow ? How come all the impacts look perpendicular to the plane of the Moon's surface ?

[Chris Peterson]

Why is it that from whichever direction one looks there are very few craters which look like a glancing blow ? How come all the impacts look perpendicular to the plane of the Moon's surface ?

Because craters are always round, except for extremely angled impacts- less than 10 or 15 degrees. And there are a small percentage of oblong or chained crater structures to account for the small number of glancing impacts.

[johnniem]

What are the small square black overlays? at first i thought they were metrics in the system for measuring... but too random for that, i think

[salmo italian]

Plural of "mare" is "mari", not "maria".

[owlice]

Plural of "mare" is "mari", not "maria".

In Latin, the plural of mare is maria.

[neufer]

Plural of "mare" is "mari", not "maria".

In Latin, the plural of mare is maria.

Click to play embedded YouTube video.

[bystander]

The plural of maria is "Maria Maria"

Click to play embedded YouTube video.

[JohnD]

Why is it that from whichever direction one looks there are very few craters which look like a glancing blow ? How come all the impacts look perpendicular to the plane of the Moon's surface ?

Phil,
This was discussed in the recent Nearside thread: http://asterisk.apod.com/viewtopic.php?f=9&t=23063

As I suggested there, look for "Messier" a double crater that is the result of an impact by something that nearly skimmed the surface and missed, but didn't. The main crater is just off circular. See: http://www.astronet.ru:8104/db/varstars/msg/1200372

John

[Beyond]

There seems to be a few more oblong craters in that area. Maybe a meteor shower??

[JohnD]

Oblong craters?
Where?

The rectilinear structure in M.Orientale, at about seven o'clock in the APOD image is, I think, a graben, where parallel faults have allowed a block of ground to sink down.

John

[garry]

If the crater was caused by an impact, why then are there 3 concentric rings forming terraces? This not does not fit in with standard impact theory.

[JohnD]

garry,
It very much fits with theory.
See: http://lroc.sese.asu.edu/news/index.php ... tatis.html
And: http://www.lpi.usra.edu/nlsi/training/illustrations/ which includes information specifically about M.Orientalis.

And there is an interesting explanation of "Crater morphology" on this site: http://passc.net/EarthImpactDatabase/In ... pacts.html
It shows the changing shape of impact craters as the size of the impactor increases, and uses Orientale as the top end example.

Briefly, a small crater's walls remain until weathering or further impacts break them down. In an enormous crater the surrounding rocks have insufficient strength to maintain its shape and they slump into the void, moving in a roughly radial direction to form the circumferential ridges.

John

[Beyond]

Oblong craters?
Where?

In the url you posted. I see five surrounding the two big ones, one of which has the 'rays'. http://www.astronet.ru:8104/db/varstars/msg/1200372

[DavidLeodis]

In the information in the image data with the image that is brought up through the "full resolution mosaic" link in the explanation it states "Time (DOY:001) 2010-01-01T00:00:00". I'm confused about that Does it mean the image data was acquired in the first second of January 1st 2010 or is it phrasing used when the actual date/time is not known I've done a search and found that DOY will be Day of Year. Thanks for any help.

[JohnD]

Beyond,
Look around for other pics of the Messier pair. They are near the edge of the Moon as seen from Earth, so you are looking at them, and the 'normal' craters around at a significant angle. Look in the Mare Fecunditatis on this APOD: http://apod.nasa.gov/apod/ap110303.html
So the normal, circular craters look oval. Oval, not oblong!

John

[Beyond]

Beyond,
Look around for other pics of the Messier pair. They are near the edge of the Moon as seen from Earth, so you are looking at them, and the 'normal' craters around at a significant angle. Look in the Mare Fecunditatis on this APOD: http://apod.nasa.gov/apod/ap110303.html
So the normal, circular craters look oval. Oval, not oblong!

John

Ok JohnD, after comparing oblong and oval pictures, i can see that the craters are not quite long or narrow enough to make it to oblong shape, so they are ovals.
My bad! I should have used the 'shorter' word. In school i was only 'average' in English.
Say, does JohnD have anything to do with the Beach Boys song?

[JohnD]

That was the Sloop JohnB.
But your remark makes me think we are same generation!

John