The most fuel-efficient way to reach Mars from Earth is a Hohmann transfer: a half-ellipse tangent to both planetary orbits, requiring the minimum delta-v for an interplanetary crossing. The spacecraft departs from just beyond Earth's orbit and climbs the outbound arc while Mars waits roughly 49 degrees ahead on its slower, outer track. The coast lasts about 241 days before the spacecraft intercepts Mars. Hohmann transfers are used whenever mission planners can afford the longer travel time in exchange for lower propellant mass. The trajectory is a textbook application of the vis-viva equation and Lambert's problem, forming the backbone of every Mars mission architecture from Mariner 4 to future crewed expeditions.