Mars is much farther away from the Sun than Earth is. While Earth is an average of 93 million miles from the Sun, Mars orbits the star at an average distance of 142 million miles. So while it takes Earth 365 days to complete one rotation around the Sun, it takes Mars almost twice as long, 686 days, to complete one revolution around.

 

At its farthest mars is 235,000,000 away. Traveling at 20 miles per second, it would take about 4.5 months to get to mars.

At its closest Mars is only 35,000,000 miles from Earth. Traveling at 20 miles per second, it would take a little less than 3 weeks to get to mars.