Add which letter to "Mars" to get a word for a fen?

Adding blood, cornstarch or arrowroot, or reducing the liquid, are all ways to do what? Which 1969 musical, starring Lee Marvin and Clint Eastwood, takes its title from painting a covered wagon? Add "Red" to which state's name and you get a breed of chicken? Add which letter to "earth" to get a word meaning scarcity? Add which letter to "sale" to get a type of rock? In the "Addams Family" theme song, the family is creepy and what? A site in Topeka, Kansas, added to the National Park System in 1992 honors which 1954 Supreme Court case? The Quino checkerspot and Laguna Mountains skipper, added to the endangered species list in 1997, are what?