Wanted to say also— Mars and Murdek (sometimes called Phaeton, the former fifth planet, or Tiamet) was the Asgard of Norse mythology, When the planet was habitable, it was inhabited by Norse godlike supermen.
A servator or servant race, the familiar ‘Grey’ alien, is from there originally and brought knowledge (including the ability to make fire) to humankind. The Grey Alien species still walks among us, and maybe still survives on Mars. and are serpentlike and aquatic even though Mars hasn’t had oceans since prehistoric times. Today, Mars is an ugly ruin strewn with rocks. There are also bear-sized Orklike or troll-like creatures there which remain. I suspect red-haired Bigfoot creatures on the earth may be from there.
In its heyday, Mars had oceans and red clay mountains like the Appalachians. Its Nordic-looking ‘Sons of God’ visited the earth and took ‘Daughters of Men” as wives.
Mercury is not very interesting. Kinda looks like the moon but redder, like Mars.