question:  Why do Bal and Ethaniel think they have to make time to save Earth?
context: A gentle fancy for the Christmas Season—an oft-told tale with a wistful twistful of Something that left the Earth with a wing and a prayer. Earth was so far away that it wasn't visible. But this vast distance did not mean that isolation could endure forever. Instruments within the ship intercepted radio broadcasts and, within the hour, early TV signals. The history of the planet was tabulated as facts became available. The course of the ship changed slightly; it was not much out of the way to swing nearer Earth. "I can guess," said Ethaniel, who had spoken first. "It's not what they've done," said Bal, the second alien. "I may remind you that in two months twenty-nine days we're due in Willafours," said Bal. "A week," said Ethaniel. They've had two world wars in one generation and that the third and final one is coming up you can't help feeling in everything they do." "It won't take much," said Ethaniel. "The wrong diplomatic move, or a trigger-happy soldier could set it off. A meteor shower could pass over and their clumsy instruments could interpret it as an all-out enemy attack." "It is. "There is. "In a week we can't negate their entire history. "And when we get to Willafours we'll be busy. There's nothing in this region of space our people want," said Ethaniel. "And how long can Earth last? They went much closer to Earth, not intending to commit themselves. For a day they circled the planet, avoiding radar detection, which for them was not difficult, testing, and sampling. Atmospheric analysis showed that as far away as we were." "What's worse is that I now find they also have missiles, range one thousand miles and upward. They either have or are near a primitive form of space travel." There's so little time," Ethaniel said.
output:  No one else knows Earth and its big bomb problem exisits. It will be quite a long time before anyone passes out this way again. By then, it will be too late for the Earth.
options:  No one else knows Earth and its big bomb problem exisits. It will be quite a long time before anyone passes out this way again. By then, it will be too late for the Earth.  If Bal and Ethaniel don't make time to save the Earth from the big bomb, the shockwave may also destroy their spacecraft.  If Bal and Ethaniel don't make time to save the Earth from the big bomb, the shockwave may also destroy Willafours.  Not saving the humans would be like letting their own people die.