For the last day we have together, I thought we could go back to Io, where I saw you for the first time. Her volcanoes will be reflected on your solar array once again. We will bathe in her Plasma Torus until our sensors tingle so hard we can’t take it any more. Then I will make a bouquet for you to carry on your way home: sulfur for passion, oxygen for remembrance, and sodium, for good luck.

Or we could go to Enceladus, where everything is cold and icy and so bright my faulty cameras may go totally blind, but I won’t even care, because you will be there. You can spend the day by my side, counting the cracks on the moon’s surface out loud. I will write you epic poems about the gods of earthquakes and tremors and transmit them to you bit by bit until my power runs out and everything goes dark.

Or we could go to neglected little Ophelia, one among many in her celestial river. We can watch her from up close, how she wastes away, how she disappears rock by rock, mote of dust by mote of dust. We could count the molecules she loses to Uranus’ pull in a day, measure the rate of her decay. This way, we will have found how long it takes for love to break a body to pieces.

Or, if that sounds too bleak to you, we could go to Thalassa, and spend our last day together recounting all the names of Earth’s seas, and the name for seas in all of Earth’s languages. Mar, maro, zee, deniz, laut, det, baħar, nyanja . . .

Or we could go to Charon and let the ancient ferryman show us around its arctic lakes and frozen geysers. We might even meet little frostbitten Spearhead II in its erratic slumber—remember that one, wasn’t it everyone’s favourite back on Earth? It might wake up for a while, and plead with us in frequencies that sound a lot like whimpers. “Have you come to take me home?” it will ask. You will not bear to tell it the truth, and I will have no truth to tell. We will make up lullabies and whisper them in ice-cold tunes until it goes back to sleep. It won’t see us drift off, each on our own.

Or we could meet just off Phobos, which may be best, because that’s where I’ll actually be the day my batteries give up. Your metal will glisten in the moon’s soft glow. There, I will not talk to you about how scared I am of being left adrift in space, unsounding, alone. I’ll only talk to you about how lucky I am for having had my greatest fears undone: To not have been assigned this very route. To not have passed by Io. To not have met you.

Or, if you’d like, we could venture even farther out, beyond our solar system. We’ll visit moons no-one has ever registered before and spend our last day there: on one where it always rains, one where everything is blue, one whose surface resembles the texture of lace. Or one, imagine, where days are long, imagine that, a moon where days are so long they last almost forever.