The distance between Mars and Earth varies depending on their positions in their respective orbits around the Sun. On average, Mars is about 225 million kilometers (140 million miles) away from Earth. However, the actual distance can range from around 55 million kilometers (34 million miles) at their closest approach (known as opposition) to about 400 million kilometers (250 million miles) at their farthest point (known as conjunction).
The duration of a mission to Mars depends on several factors, including the trajectory, propulsion systems, and mission goals. The travel time can be estimated based on the concept of the Hohmann transfer orbit, which is an elliptical transfer orbit used to travel between two different orbits. Using this method, the approximate travel time for a one-way trip from Earth to Mars is around 6 to 9 months, depending on the specific mission plan and the propulsion technology used.
For a round trip, including time spent on Mars, the total duration of a mission can range from 1.5 to 3 years, depending on the length of the stay on the Martian surface. It's important to note that these estimates are based on current propulsion technologies, and future advancements could potentially reduce travel times.