OK! Your theory, Nick, I recall is based on your
well-founded skepticism over the idea that Mars ever had
any benign climate in the past or present.

The gist being that you believe that Mars
was always bitterly cold, and no "fresh water"
would have/could have ever existed as a liquid on its surface
or even beneath.
[Part of the PBS TV program did offer evidence to
support the idea that the Meriani Planum region had a super-briny
acidic sea, resistant to severe-cold, for as
long as it lasted; but that was acidic brine 1,000 times saltier than our
oceans; hardly life supporting]

But!...I'm assuming you have NOW watched an internet playback of
that particular program on PBS TV's science-show, NOVA.

So you would have seen and heard the narrator describe the New Theory that hypothesizes that Mars, 3-4 billion years ago, had a
moon [as large as Vesta? Ceres?] orbiting [for maybe a billion years?]
just outside the Roche Limit on Mars, in a highly inclined orbit
that would have "tidally flexed' the crust and keeping the mantle
molten, allowing for a global magnetic-field to persist for as long as
the moon orbited in its unstable orbit....until it crashed into
the Northern Hemisphere of Mars, blasting away most of the
early Martian atmosphere and water into interplanetary space
[leaving most of the remaining water and air to sputter away from the planet over billions of years];
leaving the magnetic-field on Mars to wilt and fade as well, speeding up the sputtering process for the planet's volatiles.

And the narrator offered the compelling explanation for
the fact that the southern and northern hemispheres on Mars
are distinctly different on Mars as a result of that impact.

It's very compelling, and it does away with the need for your theory.

But...I suspect you will fight this new theory offered by the JPL
planetary scientists.