LEGO is producing four Advent Calendars during 2019 and images of each set are now available. They take inspiration from City, Friends, Star Wars and Harry Potter so cover four of the most popular current themes.
You can view images of their packaging, showing minimal spoilers, along with links to their contents after the break...
LEGO began exploring space during 1964, when 801-3 Rocket was produced. However, the most prominent Space subtheme is definitely Classic Space. LEGO evidently recognises its enormous popularity, including excellent references to the range in myriad modern sets.
Important contemporary examples, such as 21109 Exo Suit and 70841 Benny's Space Squad, have elicited comments regarding the potential return of Classic Space. That definitely seems to have become increasingly possible but there has also been discussion concerning whether Classic Space should return or instead remain a highlight within LEGO's long history.