“Mr. Bittering wanted to move to Mars so he bought tickets for his entire family and then they changed into Martians.”
Sashalee Gilmore"Dark They Were and Golden-Eyes"
“The way I see it if you want the rainbow, you gotta put up with the rain” -Dolly Parton
When you accept change, you can truly be happy.
Once Harry accepted that Mars changed his identity, he was happy.
“The wind blew as if to flake away their identities.”
At this point in the story, Harry had NOT accepted the fact his changing. The fact that he hesitated shows the reader that he was NOT happy.
“Mr. Bittering hesitated, and then raised the mirror to his face. There were little, very dim flecks of gold captured in the blue of his eyes.”
Harry had only accepted Mars when he knew he could leave anytime, but once he saw the rockets lying wrecked he was forced to accept he would never leave.
“As long as the rockets had spun a sliver web across space, he had been able to accept Mars. For he had always told himself: Tomorrow, if I want, I can buy a ticket and go back to Earth. But now the web gone, the rockets lying in jigsaw heaps of molten girder and unsnaked wire.”
The setting because it forces someone to start to adapt to their new environment.