Translation:I met my wife on a train to Russia.
See PAG (Waringhien, Kalocsay: plena analiza gramatiko de esperanto), Section 39, where it is stated: Dr. Zamenhof capitalized the name of nations and months, but not seasons and days of week, neither the name of races (e.g. franco, ruso). If I see the sentence with un-capitalized francio (referring to the country of France), I will report that.
To avoid confusion: Capitalizing names of nations and months is no longer applied in current Esperanto. The rule is that only names of individuals (persons and objects) are capitalized, such as Sofia, Adamo, Francio, Rusio. There are many rusoj or francoj, so these words are not capitalized. And there is a mardo in every week and a septembro in every year, so they are not capitalized.
And since Tero and Suno are names of individual celestial bodies they are normally capitalized as well (maybe not by all). When we talk about suns (sunoj) as a synonym of stars it's not an individual name. So we could say “Suno estas la suno de nia planedo” (The Sun is the sun of our planet).