What is the largest mass(kg)?
CREATE TABLE "early_u_s_unmanned_lunar_missions_1958_1" (
  "u_s_mission" text,
  "mass_kg" real,
  "launch_vehicle" text,
  "launched" text,
  "mission_goal" text,
  "mission_result" text
);
SELECT MAX("mass_kg") FROM "early_u_s_unmanned_lunar_missions_1958_1";