From Wiki[1] the aphelion and perihelion for Mars are 1.381 and 1.666 so I think assuming that Mars orbit is circular is just wrong. The eccentricity is 9%. The inclination of Mar's orbit is also 1.8 degrees which makes a difference as well.

Wiki also lists a closest approach to Earth of 0.372 AU and a furthest distance of 2.675. The graphs on that link do not come close to those figures. They are off by 25%.

Basically I do not understand why someone would take an orbital problem, simplify all the interesting bits out of it and then put it up on a blog. Maybe he was more interested in the maths than the physics.

(1) - https://en.wikipedia.org/wiki/Orbit_of_Mars#Table_of_orbital...