Fire and ice

Talk about your cold cases. More than a century after the sinking of the Titanic, historical detectives are still trying to dissect the tragedy. “Titanic: The New Evidence” makes the argument that an internal fire had more to do with the ship’s demise than an iceberg. The theory is based on photographs collected by the ship’s chief engineer.

7 p.m. Saturday, Smithsonian Channel

The ringmaster

We will have to wait until April for a second season of “Masters of None,” one of TV’s sweetest, smartest comedies, but this weekend creator/star Aziz Ansari is hosting “Saturday Night Live,” a high-profile gig that will hopefully inspire newcomers to check out the sitcom’s stellar first season. Big Sean is the musical guest.

10:29 p.m. Saturday, KARE, Ch. 11

Patient care

I had high hopes that the first season of “Mercy Street,” which takes place in an American hospital during the Civil War, would propel PBS to produce more stateside-set dramas. But so far the series, starring “How I Met Your Mother” seeker Josh Radnor, hasn’t taken off. Perhaps this second season will do the trick.

7 p.m. Sunday, TPT, Ch. 2

Neal Justin