Roots: Heart of the Comet.
Goofs: Nyssa doesn't know what second-class post is? Whatever did she do while she was postmistress in Stockbridge (The Eternal Summer)?
How do Nyssa and the Jovian enter the TARDIS?
Dialogue Triumphs: "I would never be so selfish as to choose between you. Any of you."
"You won. Well done" (For a dying man's last words that's pretty cool)
Double Entendres: "You're going to reveal yourselves to humankind?"
Continuity: Eight slash Q Panenka is a comet with a 13km circumference and a hollowed-out core housing a 316-strong transit colony (the Panenka Haulage Company) and accompanying mini-economy. Its elliptical orbit takes it between Earth and Jupiter,, making it a cheap means of space freight between Earth and its colonies.
Nyssa feels energised after her rejuvenation (see: Links). The Doctor says he felt the same after his third regeneration "I got quite a lot done"
The comet is craggy, has a circumference of 13.2km and does a cycle in a rapid three years, three months. The comet is an Earth protectorate. The interior of the comet is icy, and inside when not working the crew spend their time pursuing the arts. 'Backers', or piggy-backers on the space lanes must be picked up by law, but can't buy anything on the comet as it is only for sale to company staff. They have to stay 'below decks', essentially.
Jovians live in the atmosphere of Jupiter and are beings of dust and vapour held together by a navigational consciousness. They carry things by materialising around them and carrying them as insubstantial cargo, able to open and pass through doorways (but not locked doors or solid walls). They can emit electrical charges like lightning bolts. The Doctor thought all the Jovians were wiped out when colonies were established . their cities are built of conceptual thought - shared theory like a whale song which one can tune into and an architecture made of ideas. Making actual physical objects is not characteristic of them. He doesn't believe them to be warlike. Only a handful of people in the colony know of them - knowledge is embargoed. The Dr thought they died out before the colonies.
The Jupiter Axis is the government of Earth's Jupiter colonies, seeking independence from Earth, which Major Nash describes as "collectivised and regulated." The President of Eurasia is Sam Chung.
Cyanogen is an explosive gas stored in canisters (an oxygen mix?)
Small-wave neural scramblers don't work on Nyssa. Nyssa describes herself as a research biologist. Nyssa has read about life in the solar system but not Jovians. Tegan nearly tells the Doctor about Nyssa's family.
The Doctor describes the discoverer of Eight slash Q Panenka as "an old friend."
Future History: Mexican cuisine is still popular
Location: The comet Eight slash Q Panenka, 2329.
Links: This story more or less follows The Emerald Tiger by one night for the TARDIS inhabitants. Discussing musical instruments the Doctor begins to say "I used to-" - play the recorder (i.e. in his second incarnation), perhaps? Nyssa refer obliquely to his promise to return for the doomed Adric (Earthshock). He says "Brave heart". He and Turlough don atmosphere suits from the TARDIS (The Web Planet) and the Doctor refers to the Hostile Action Displacement System (The Krotons).
The Bottom Line: Imaginative, visual, clever. Robson turns in a script which, while not among his best, is certainly of his usual high standard. Turlough's escape plan is devilishly good (it's a good Turlough story!), and there's a nice amount of attention paid to the world-building elements aboard the comet.