What prompted Lovell on Apollo 8 to announce "there is a Santa Claus"?

Question

On Apollo 8, following the first trans-Earth injection, when the crew came back into contact with Houston, Lovell said: "Please be informed there is a Santa Claus." (Transcript)

Given that Apollo 8 had already been in contact with ground through Christmas Eve, what prompted Lovell to make this statement at the time that he did?

_{Note: Since motivations cannot be known without the account of the individual, I will take common sense answers speculating on likely reasons that include a statement to the effect that we cannot truly know why he did it. That's assuming we don't have an account from Lovell, of course.}

Answer 1

The first trans-Earth injection from the moon was a high-stakes maneuver; if the Apollo's SPS didn't fire, the crew would have been stuck very far from home. I always took "please be informed there is a Santa Claus" to mean something like "we got what we wanted for Christmas" -- that is, a good burn and a good chance to get home. Basically, a seasonally appropriate way to say "we have good news."

You mention the NORAD Santa tradition, though, and that predates Apollo by a good ways (dating to 1955!), so it might also just be an obscure joke to the effect that Santa prepares for his Christmas Eve run behind the moon where we can't see him.

Lovell himself confirms that it's an allusion to the famous "Yes Virginia" letter in this interview, though he isn't explicit about what he meant when he said it.

Answer 2

From reading the transcript context it seems like Lovell is somewhat jokingly reporting from what they actually saw on their expedition, being the first humans in the vicinity of the Moon. Because they were the first, no one could actually debunk anything, including a claim of finding Santa on the Moon.

Another humorous comment can be found in the Apollo 12 transcript, where ground control order the astronauts to look for the Chinese Moon goddess Chang'e.

Answer 3

Since you comment that this is a semi-serious question intended to allow for some lightheartedness, here goes;

By December 21, 1968 when Apollo 8 was launched and nearly 4 days later as the events described in your questions took place, we only had one and over three years old account of encounter of Santa Claus from outer space. Gemini 6 astronauts Wally Schirra and Thomas Stafford, while orbiting the Earth, saw an object that looked like a satellite going from North to South probably in a polar orbit, on a very low trajectory...:

But this was but one encounter and you know science, it demands repeatability. With the second observation by Lovell good three years later, we finally got a confirmation that Santa Clause and his reindeer exist and that they're on a once per year periodic trajectory with closest approach to Earth just before Christmas each year.

What prompted Lovell on Apollo 8 to announce “there is a Santa Claus”?

Love for the truth!