"The planet Mars is one of the brightest objects in the night sky, easily visible with the unaided eye as a bright red star. Every two years or so, Mars and Earth reach their closest point, called “opposition”, when Mars can be as close as 55,000,000 km from Earth. And every two years, space agencies take advantage of this orbital alignment to send spacecraft to the Red Planet."
How long does it take to reach Mars? Cain informs below:
"When you consider the fact that Mars is only 55 million km away, and the spacecraft are travelling in excess of 20,000 km/hour, you would expect the spacecraft to make the journey in about 115 days, but it takes much longer. This is because both Earth and Mars are orbiting around the Sun. You can’t point directly at Mars and start firing your rockets, because by the time you got there, Mars would have already moved. Instead, spacecraft launched from Earth need to be pointed at where Mars is going to be."The Hohmann Transfer Orbit is predominate method used to reach Mars, a nice link to video illustrates path. German scientist Walter Hohmann first described transfer orbit in his 1925 work, "The Attainability of Heavenly Bodies." Hohmann was influenced, in an interesting note, as was the German Rocket Society by science fiction novel, "Two Planets," written in 1897 by Kurd Lasswitz. Cain supplies data Mariner 7 reached Mars in 1971 in 131 days. Huntsville researchers are working to shorten that time to eight weeks as covered in a recent post.