Dan Musk's precise denominational affiliation is not overtly identified during his brief appearance. In the letter he writes to his "sweetheart" (presumably his wife) just before he dies, Musk states that his last thoughts "will be a prayer for you, for humanity." Based on this, and his blonde Caucasian appearance, Musk seems to be a believing Christian. However, other religious affiliations, although statistically unlikely, can not be ruled out based on the available textual and visual information.
It would not be surprising if author Frank Miller thought of Musk as a Catholic, given the fact that virtually all other characters in Batman: The Dark Knight Returns for whom religious affiliation can be identified are Catholics.
LOLA (TV ANCHORWOMAN): Hold it . . . We've just gotten word that it's not a conventional nuclear warhead -- we switch you now to Dan Musk, aboard the News Two Shuttle. What's the word, Dan?From: Batman: The Dark Knight Returns #4 (1986), DC Comics: New York City; reprinted in Batman: The Dark Knight Returns hardcover edition, DC Comics: New York City (2002), page 166; written and pencilled by Frank Miller, inked by Klaus Janson, colored by Lynn Varley:
DAN MUSK: Still collating, Lola -- but it's a big one -- heavy megatonnage -- with unusual computer activity -- we can't be certain of its capabilities . . . At the very least, Corto will be leveled -- the fires might spread to mainland South America -- should it generate a sufficient magnetic pulse, there might--
LOLA (TV ANCHORWOMAN): [Cuts Dan Musk off to move onto her next segment.] Thanks for the data, Dan, but we'll all know soon enough what it can do. Right now, we've got author Harlan Ellison in the studio . . .
HARLAN ELLISON (science fiction author): . . . be eating our own babies for breakfast.From: Batman: The Dark Knight Returns #4 (1986), DC Comics: New York City; reprinted in Batman: The Dark Knight Returns hardcover edition, DC Comics: New York City (2002), page 168; written and pencilled by Frank Miller, inked by Klaus Janson, colored by Lynn Varley:
LOLA (TV ANCHORWOMAN): Thank you, Mr. Ellison . . . Yes, Dan? . . .
DAN MUSK: Lola -- if it generates a puulse of sufficient intensity, it could--
LOLA (TV ANCHORWOMAN): Dan-- We've finished our technical segment . . .
DAN MUSK: --it could disrupt the magnetic fields causing--
LOLA (TV ANCHORWOMAN): Coming up-- Viewer opinions . . .
DAN MUSK: Lola-- This is incredible-- Trajectory change-- twenty degrees due East -- the warhead has changed course--
[Superman managed to turn the Soviet-launched warhead in its trajectory so that it is now heading toward an uninhabited desert.]
LOLA (TV ANCHORWOMAN): You heard it here first -- The warhead has somehow been diverted -- It will explode harmlessly in -- What's the name of that desert? . . .
DAN MUSK: It might not be harmless, Lola -- If that pulse is strong enough, it could disrupt all electrical--
[A SKRKK sound is heard aboard Dan Musk's shuttle, as the warhead detonates and causes a devastating electromagnetic pulse.]
DAN MUSK (writing a letter): Sweetheart, The last of the readings gave a hint of what would happen. When the computer failed, I knew for sure.
There's no point in explaining it to the crew. We're all dead anyway -- as dead as this shuttle.
You'll never get this letter. It'll burn up with me when our orbit deteriorates. Still, my last thoughts will be a prayer for you, for humanity . . . and for planet Earth.
Nothing could stop the Russians from emptying their silos at us now. We'd have no defense, no way to retaliate. The one hope we have is that the decision to murder billions has to be made by a human being.