Recap: Global aurora widely distributed around mars due to its complex multipole magnetic field. When coronal mass ejections of plasma arrive at Mars, especially those with a "frozen in" magnetic field oriented a certain direction, the response of the Martian system is losing atmosphere through two losses: 1) "Pickup ions", ionized atmosphere picked up by the solar wind's electric field (this also happens at comets) and 2) simple momentum exchange of solar wind (mostly hydrogen ions, aka protons) with the heavier elements of the martian atmosphere. I recently calculated the Jean's Escape time for H2 vs. CO2 in the Martian environment, and H2 escapes significantly faster, by many orders of magnitude. So the Jean's Escape mechanism is an additional thermal effect that when in combination with the two solar wind related loss mechanisms can definitely explain Mars's thin skies.
All this because Mars lacks a magnetosphere, and we believe that its electromagnetic internal dynamo died at least 3 billion years ago, due to heat loss, as measured in crustal magnetic fields (or actually the lack thereof) near ancient craters. AS I CANNOT REITERATE ENOUGH, the lack of a global magnetic field on Mars is one of the most daunting technological challenges to colonization. We could generate local magnetic fields, but it would require many new novel engineering techniques so as to prevent devices from malfunctioning near the field's (very high field strength) source.
Also, we already knew all of this, and screw you, MAVEN, because you barely beat our contract anyway, and I've moved on to new and better mistresses.