Why do space zombies look so much sexier than other zombies?
I'm guessing in this case, silicone sealant?
because airless space preserves the bodies better?
Hang on, let me put on my nerd glasses real quick...
Well, actually. The airlessness is often taken to mean that "Space" is right around 0 Kelvin, when there's no Ambient temperature in space. Heat is ultimately a measure of molecular motion, no molecules, no motion. Also, the anerobic environment wouldn't be a great place for the microbes that typically break down exposed flesh to live in.
On the other hand, if you happen to be near a Star, then the environment also lacks the atmosphere, magnetosphere, and ionosphere which protects us on the surface from being blasted by radiation which would basically burn you to a crisp, instantly. On the surface of the moon, the "Daytime" (With the caveat that the day is actually half a Month) can reach 250+ degrees Fahrenheit, instantly. That's right about the temp you set your oven, or crock pot to slow cook a pot roast.
That's just the Photons. So, while you're right in assuming that it would be Sterile, that's only really because you're talking about the conditions in a Vacuum Autoclave. However, this is Radiant, and directional. So, assuming they're not rotating, I would expect one side to be zombie pale, and the other to be blackened by the sun:
Like this.