Why is Space Mountain always so dirty?

Let me rephrase that, why is Disneyland's Space Mountain always so dirty?

During my many visits to Disneyland in 2007, Space Mountain, more often than not, would be caked in dirt. Judging from my findings on Flickr and other picture posting sites, not much has changed since then. Pundits offer a wide range of explanations from "Anaheim is so polluted that the exterior gets dirty quickly" to "Since they repainted it white they just can't keep it clean" to "You just went on a day it happened to be dirty".

Now look, I'm as pathetic a Disneyland fan as they come. I went practically two or three times a week in 2007. Space Mountain was dirty at least half of the time I was there (to be fair I wasn't exactly keeping a journal). That's just bad show. However, I decided to leave it as something that could not be helped and forgot about it.

Then I went to Tokyo Disneyland. Much to my surprise Space Mountain was clean. It was immaculate in fact. You could eat off of that thing. I must have arrived on a day it was just washed. After all, Disneyland's version is cleaned once in a while.

After I arrived home I decided to investigate further. I did a search on Flickr for pictures of Space Mountain. Photos taken shortly after the attraction's re-opening in 2005 appear to be pretty clean (I've never seen it this clean in person), and it stays that way for most of 2005.

Here's Space Mountain in December of 2005 looking a little worn. It's not a deal breaker but it could clearly use a wash. Unfortunately, they actually let it get worse than this way too often.

Just try finding a picture like these of Space Mountain Tokyo. You might have a hard time. The worst I could find is the first image here. Some have suggested that it rains so often in Tokyo that it's a simple matter to keep that flavor of Space Mountain clean. Then again, when it rains in Anaheim it actually makes Disneyland's Space Mountain look worse as the dirt runs down the sloped architecture. Tokyo should also have pollution that wreaks havoc with the attraction's white paint scheme, just like Southern California.

So what's going on here? Is it physically impossible for Disneyland to keep Space Mountain's exterior clean? Let's say it takes four guys getting paid $20 an hour to clean Space Mountain. The whole process might take, let's say, three hours. That's $240 dollars or nearly three 1-day park hoppers. If you know how they actually wash this thing and how often, please let me know.

Does the Oriental Land Company make sure their version of Space Mountain is cleaned more often? Is there some intrinsically unique factor in Anaheim that makes Disneyland's Space Mountain a horror to wash? Is there no excuse and it's simply bad show? Please, could someone who speaks Japanese talk to the OLC and ask them how they do it?

I don't know. Maybe I'm blowing it all out of proportion. What I really want to know is why Space Mountain was suddenly closed without warning to have entire thing rebuilt from the ground up a few years back. Usually when you want to update a classic attraction you don't just build it all over again...