We have just measured the shape of the crater that the returner landed on, which is part of the scientific data collection. Then the returner will [put on a] 'new warm coat' to prevent the remaining propellant inside from being frozen during the transportation to Zhurihe Airport, where the propellant will be expelled from [the] returner," said Cao Ruiqiang, a space product assurance assistant, in a China Central Television interview (1:29-1:35).

Why should the propellant avoid freezing? Cooler generally means slower chemical reactions, so safer. There may be a language barrier here, but the propellants on the returner (lander) may have been hypergolic. Apollo's hypergolics tolerated temperatures colder than those at Chang'e's landing point.

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    $\begingroup$ Possibly related (I don't know what propellant Chang'e uses): space.stackexchange.com/q/32580/6944 $\endgroup$ Dec 22 '20 at 14:58
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    $\begingroup$ There's not that many practical choices for storable hypergolic propellants, but beyond that, it's water that's unusual in expanding when it freezes, so the "superpacking" issue can be expected to be a general problem with freezing propellants. $\endgroup$ Dec 22 '20 at 15:31

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