Turns out, for the 25th anniversary celebration, I contacted Marty and asked him if he remembered what that first message was. He said no. I then suggested that we dream up something worthy and memorable, agree on it, and both stick to the story. He said no, the important thing for folks to note and remember was that at the time, unlike the lunar landing a couple of months earlier, no one thought the event worthy of enough note to think up something memorable or even to record what was said.