Question about the rules following death when burial is not an option.

I’m writing a sci fi story in which a lot of people died, 10% of humanity when aliens attack earth. Some humans flee the planet but things go wrong and now they are stuck on another planet with a lot of bodies. As I understand it, which isn’t much, in Judaism, the deceased should be buried within 24 hours and cremation is not allowed generally. What would the rules be in a situation with a staggering number of casualties and no ability to bury them in the ground? Does ice count as the ground? Can you bury a large number of people at sea? Do the extraordinary circumstances make cremation acceptable? I’m not jewish and know next to nothing about Judaism. I’m coming at this question from near absolute ignorance but I don’t want to write something disrespectful or that violates something sacred.