"There it is," my mother says, and what she means is that the dot we've been nearing for weeks, the one that's been growing into a larger dot with two smaller dots circling it, has now become even larger than that, growing from a dot to a disc, shining back the light from its sun, until you can see the blue of its oceans, the green of its forests, the white of its polar caps, a circle of colour against the black beyond.