Besides being slow (top speed 0.2kph) and at risk of sandtraps, wheeled rovers like Spirit and Opportunity have other limitations.
除了行驶速度慢（最高时速200米）和有陷入沙中的危险，勇气号与机遇号有其他缺陷。
2
Her hosts held a festive celebration, then showed her the dam, an eight-foot-high sand-and-concrete structure that traps and filters water so that it's available and drinkable year-round.
The existence of vast area of tight sand rock, low permeability of sand rock and plenteous gas supply are all favorable conditions for the formation of deep basin gas traps.