Snow holodeck is now cold, but air pressure

Fixes #18579.

code/modules/holodeck/turfs.dm

@@ -79,8 +79,7 @@
 
 /turf/open/floor/holofloor/carpet/New()
 	..()
-	spawn(1)
-		update_icon()
+	addtimer(src, "update_icon", 1)
 
 /turf/open/floor/holofloor/carpet/update_icon()
 	if(!..())
@@ -96,9 +95,9 @@
 	slowdown = 2
 
 /turf/open/floor/holofloor/snow/cold
-	temperature = 180
+	initial_gas_mix = "o2=22;n2=82;TEMP=180"
 
 /turf/open/floor/holofloor/asteroid
 	name = "asteroid sand"
 	icon = 'icons/turf/floors.dmi'
-	icon_state = "asteroid"
+	icon_state = "asteroid"