Mars’ ionosphere mystery explained

Red Planet’s two layers of charged particles sometimes merge, analysis suggests

Mars Express illustration

CLEARING THE AIR  Disagreements between Mars-bound spacecraft (such as the Mars Express, illustrated) and the Viking landers might have to do with the time of day they conducted their investigations of the Red Planet’s ionosphere. 

ESA, C. Carreau

Probing a planet’s ionosphere can be all about the timing.