Despite what the title suggests, this serial is actually set on Earth, not Mars. Indeed the focus is even tighter since it mostly plays out in and around a stately home, where the Doctor works to prevent the god Sutekh following his servants to Earth and leading to its total destruction. As a narrative it manages to be reasonably straightforward and do what most of these serials do, but yet at the same time have plenty in there if you are willing to go with it.
The limited location means that the serial does build a good sense of tension, with the lumbering mummies providing the standard slow moving monster to be an immediate and creepy threat, but yet at the same time the bigger picture plays out. The threat to the world is contained by choice here, so the serial doesn't feel like it is doing world destruction on the cheap simply by playing it out in this one place (more or less). The bigger themes and villains work well, whether it is the changing of timelines, the idea of the Doctor perhaps struggling against a much stronger force (rather than doing a comedy bit and defeating him with ease, as has been the modern way at times). There was certainly enough to keep me interested, while the standard horror/chase stuff worked too.
The cast are solid. Baker of course is very good; playing a sense of nervousness and obligation well as part of his usual turn. Sladen continues to be well-used as a companion, and she does well as a result. The supporting cast is generally pretty good; with some nice twists and turns in their playing, and generally good presence from the villains (Woolf, Archard). The production budget is not particularly stretched, and the mummies are not the most imposing design even if they are a solid device in a lumbering way; but generally it looks good enough and uses the places well. Generally speaking, a good serial which does the standards well enough, but offers a bit more to engage with if you want it.