APOD: Lunar Farside (2014 Apr 05)

[APOD Robot]

Lunar Farside

Explanation: Tidally locked in synchronous rotation, the Moon always presents its familiar nearside to denizens of planet Earth. From lunar orbit, the Moon's farside can become familiar, though. In fact this sharp picture, a mosaic from the Lunar Reconnaissance Orbiter's wide angle camera, is centered on the lunar farside. Part of a global mosaic of over 15,000 images acquired between November 2009 and February 2011, the highest resolution version shows features at a scale of 100 meters per pixel. Surprisingly, the rough and battered surface of the farside looks very different from the nearside covered with smooth dark lunar maria. The likely explanation is that the farside crust is thicker, making it harder for molten material from the interior to flow to the surface and form the smooth maria.

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[Carol Cullar]

All the craters on the left side of the image appear to sink in; all the craters on the right "plump" outward! Why is that? Does it have to do with the hemispheres having been photographed at different times? This apparent difference makes the splice down the middle of the image very apparent! Is this just my brain? Is everyone seeing the same thing I am? Is there a scientific explanation?

[Boomer12k]

Carol,
Yes, it appears the shadows of the right craters is on the right, and the left craters is on the left, as if they were taken at different times...and this is probably so, as it is a mosaic....

But what a wonder....

:---[===] *

[geckzilla]

Whose moon is this again? Doesn't look like any moon I know.

[Leon M. Green]

Along with the farside crust being thicker, would it not be that there is more cratering because of taking the meteors that might have hit earth? And I find it curious that in the new "Cosmos" program, Neil DeGrasse Tyson very calmly took the position that the moon was formed concurrently with the Earth, and not the result of a very large impact on the Earth that then remained captured in orbit.

[mister T]

Is it possible that the marked difference in the maria/crater ratio from the near to far side is caused by the constant pull of the Earth's gravity on the denser molten core? Thus shifting it closer to the near side surface resulting in more volcanic activity.

[hoohaw]

Sea of Moscow I see. What is the other smaller sea?

[neufer]

---

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is gradually lowering its orbital altitude over the moon. LADEE will continue to make important science observations before its planned impact into the lunar surface later this month.

When will it impact the lunar surface? NASA wants to hear your best guess!

LADEE mission managers expect the spacecraft will impact the moon’s surface on or before April 21. On April 11, ground controllers at NASA's Ames Research Center in Moffett Field, Calif., will command LADEE to perform its final orbital maintenance maneuver prior to a total lunar eclipse on April 15, when Earth’s shadow passes over the moon. This eclipse, which will last approximately four hours, exposes the spacecraft to conditions just on the edge of what it was designed to survive.

This final maneuver will ensure that LADEE's trajectory will impact the far side of the moon, which is not in view of Earth and away from any previous lunar mission landings. There are no plans to target a particular impact location on the lunar surface, and the exact date and time depends on several factors.

"The moon's gravity field is so lumpy, and the terrain is so highly variable with crater ridges and valleys that frequent maneuvers are required or the LADEE spacecraft will impact the moon’s surface," said Butler Hine, LADEE project manager at Ames. "Even if we perform all maneuvers perfectly, there's still a chance LADEE could impact the moon sometime before April 21, which is when we expect LADEE's orbit to naturally decay after using all the fuel onboard."

Anyone is eligible to enter the "Take the Plunge: LADEE Impact Challenge." Winners will be announced after impact and will be e-mailed a commemorative, personalized certificate from the LADEE program. The submissions deadline is 3 p.m. PDT Friday, April 11.

For more information about the challenge and to enter, visit: http://socialforms.nasa.gov/ladee

[Chris Peterson]

Along with the farside crust being thicker, would it not be that there is more cratering because of taking the meteors that might have hit earth?

No, that effect is small. Even at the time of the bombardment, when the Moon and Earth were closer, meteoroid shadowing by the Earth wasn't significant (the Earth only blocked a small part of the sky), and in addition, the Earth acted as a gravitational lens, so it pulled in some bodies that wouldn't have otherwise impacted.

And I find it curious that in the new "Cosmos" program, Neil DeGrasse Tyson very calmly took the position that the moon was formed concurrently with the Earth, and not the result of a very large impact on the Earth that then remained captured in orbit.

I'm not sure if he did or not. That bit caught my ear, as well. I watched the segment a couple of times, and it's just badly written. What he says and what the graphics show aren't quite the same. The explanation for the Moon is quite ambiguous. So I don't know if Tyson holds some non-standard belief about how the Moon formed, or if he just explained it badly.

[Psnarf]

Ha! I knew it! Why, there it is in plain sight!

Sew! who is making book on the crash? What are the odds posted in that Las Vegas Casino that takes all bets?

[Maria! Maria! I just met a flow named Maria! *ouch* I promise, no more show tunes; let go of my arm.]
(Apologies to the cast of "Westside Story")
https://upload.wikimedia.org/wikipedia/ ... de_001.jpg

[BMAONE23]

In this case wouldn't that be "Far Side Story"

[neufer]

Along with the farside crust being thicker, would it not be that there is more cratering because of taking the meteors that might have hit earth?

No, that effect is small. Even at the time of the bombardment, when the Moon and Earth were closer, meteoroid shadowing by the Earth wasn't significant (the Earth only blocked a small part of the sky), and in addition, the Earth acted as a gravitational lens, so it pulled in some bodies that wouldn't have otherwise impacted.

Even without any gravitational lensing effect (which is angularly convergent
but radially divergent making it probably only a 2^nd order effect):

• with a diameter of just 2º in the lunar sky the Earth
  physically blocks only 0.0076% [=0.5 x {1- cos(1º)}] of incoming meteors.

And I find it curious that in the new "Cosmos" program, Neil DeGrasse Tyson very calmly took the position that the moon was formed concurrently with the Earth, and not the result of a very large impact on the Earth that then remained captured in orbit.

I'm not sure if he did or not. That bit caught my ear, as well. I watched the segment a couple of times, and it's just badly written. What he says and what the graphics show aren't quite the same. The explanation for the Moon is quite ambiguous. So I don't know if Tyson holds some non-standard belief about how the Moon formed, or if he just explained it badly.

Tyson was obviously trying to emphasize the planetesimal accretion hypothesis of Viktor Safronov(; see below).

A dramatic representation of the presumed special collisional formation
of the Earth-Moon "binary planet" would have been a distraction from the main point.

<<A widely accepted theory of planet formation, the planetesimal hypothesis of Viktor Safronov (11 October 1917 [my mom's birthday! -ACN] - 18 September 1999), states that planets form out of cosmic dust grains that collide and stick to form larger and larger bodies. When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity, enormously aiding further growth into moon-sized protoplanets. This is how planetesimals are often defined. Bodies that are smaller than planetesimals must rely on Brownian motion or turbulent motions in the gas to cause the collisions that can lead to sticking. Alternatively, planetesimals can form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid-plane of a protoplanetary disk. Many planetesimals eventually break apart during violent collisions, as may have happened to 4 Vesta and 90 Antiope, but a few of the largest planetesimals can survive such encounters and continue to grow into protoplanets and later planets.

It is generally believed that about 3.8 billion years ago, after a period known as the Late Heavy Bombardment, most of the planetesimals within the Solar System had either been ejected from the Solar System entirely, into distant eccentric orbits such as the Oort cloud, or had collided with larger objects due to the regular gravitational nudges from the giant planets (particularly Jupiter and Neptune). A few planetesimals may have been captured as moons, such as Phobos and Deimos (the moons of Mars), and many of the small high-inclination moons of the giant planets.>>

[Jim Leff]

So I don't know if Tyson holds some non-standard belief about how the Moon formed, or if he just explained it badly

It's important to note that Tyson has no writing or producing credit in the series. The executive producer/show-runner/writer is Sagan's widow, Ann Druyan. Tyson is purely a presenter-for-hire. (So why'd he take the job? Hey, how could he not?)

I'm not a fan of this remake. I think it would have been far better if they'd let Tyson run it. But Cosmos is a brand, and brands have owners.

[Chris Peterson]

It's important to note that Tyson has no writing or producing credit in the series. The executive producer/show-runner/writer is Sagan's widow, Ann Druyan. Tyson is purely a presenter-for-hire. (So why'd he take the job? Hey, how could he not?)

Nevertheless, I'm sure that Tyson participated in the writing, and would not say anything he personally considered scientifically incorrect.

[geckzilla]

I'm under the impression that the credits section of any big name production is incredibly political and can be downright petty. If you aren't a member of one of the actors' unions, prepare to get shafted in the credits in some way no matter who you are or what your contribution to the project was.

[Jim Leff]

I'm under the impression that the credits section of any big name production is incredibly political and can be downright petty. If you aren't a member of one of the actors' unions, prepare to get shafted in the credits in some way no matter who you are or what your contribution to the project was.

True, but without going into a lengthy explanation of writing credit in show biz, it's absolutely clear that he's a non-writing host-for-hire here. This is not a situation of someone writing uncredited due to politics. This is someone whose role has been clearly painted via negotiation.

Chris, he absolutely would have input if he felt something was way off, but not final veto, and he'd need to very carefully choose his battles. The fact that this particular point (lunar origins) was left puzzlingly muddy reflects some crappy grudging compromise having been worked out which he felt he could live with. There's a lot of that sort of thing with tv even when you're in control. And Tyson couldn't possibly be more clearly positioned outside of control on this series. So it would be an error to view the Cosmos remake as Tyson's take on anything.

[Chris Peterson]

Chris, he absolutely would have input if he felt something was way off, but not final veto, and he'd need to very carefully choose his battles. The fact that this particular point (lunar origins) was left puzzlingly muddy reflects some crappy grudging compromise having been worked out which he felt he could live with. There's a lot of that sort of thing with tv even when you're in control. And Tyson couldn't possibly be more clearly positioned outside of control on this series. So it would be an error to view the Cosmos remake as Tyson's take on anything.

Not being privy to his contract, I wouldn't venture to guess what his actual degree of control might be. But he is a professional scientist with a reputation to protect. I'd be very surprised if he didn't have veto power over any scientific content.

[Jim Leff]

Not being privy to his contract, you oughtn't question the way the show is credited: a production of Sagan's widow with Tyson acting purely as host.

And unless this particular scene struck you as scientifically repugnant (and thus meriting exertion of veto), then I don't see why his having or not having veto power is relevant.

The original was Sagan's creation, and his ideas. This is not Tyson's show, so it's not putting forth his ideas. Judge him on his books and his own statements.

[geckzilla]

Jim, you have a very black and white way of looking at this matter.

[yellowbag]

where are the alien bases? the structures and the ufos? all us ufologists know that this side of the moon has that, and that is why man has not been allowed to go back there.

[alter-ego]

For those interested.

[neufer]

where are the alien bases?

For those interested

Putin has reclaimed all the farside alien bases with Russian names.

[Anthony Barreiro]

Sea of Moscow I see. What is the other smaller sea?

The small dark spot to the lower left of Moscoviense is the flooded crater Tsiolkovkiy. Mare Ingenii, the only other named mare on the farside, is slightly south/below Tsiolokovskiy and toward the center of the image. Ingenii doesn't look much like a mare in this image. Ingenii is on the western/left-hand edge of the large, irregular, complex South Pole - Aitken Basin.

Wood and Collins' 21st Century Atlas of the Moon is an excellent reference. This labeled topographic map gives a good idea of the depth of the South Pole - Aitken Basin.

(Please note that I have no writing credit for this post. I was hired to narrate this post because of my good looks and dramatic delivery style.)