The Surprising Ways Mars is Hostile to Life

Sadly I found this rather shallow because there was no connection made between the planetary magnetic fields, the Van Allen belts, atmosphere and radiation.
The main issue with Mars is _lack of a consistent magnetic field_ . There are some areas with the odd magnetic loop, but not others, so there are pockets of thin atmosphere.
Note: Mars has no reason to wobble when Jupiter comes near unless its mass is distributed unevenly, the varying axis tilt could perhaps be due to the strong magnetic field of Jupiter picking up on stray magnetic loops on Mars and pulling it around.
But back to the magnetic field. The _only_ reason any planet has an atmosphere is because its magnetic field prevents it from being blown away. Mars's 95% CO2 is not an accident, the lighter gases simply get blown away by the solar wind, but the heavier ones stay. Similar thing on Venus. 
On the earth the magnetic field protects the atmosphere by diverting solar charged particles into bands or belts around the earth, known as the Van Allen belts. These lethal areas of radiation are therefore full of solar radiation that now doen't strike the surface, unlike on Mars and the moon, killing all life.
So lets have less 'I don't knows' and more physics please !