A Son of the Rock

From Astronomy Picture of the Day for 6/7/2018, this is a picture of Pluto’s moon Charon (though which is primary and which satellite when one’s diameter is only twice the other’s is pushing it) taken by the New Horizons probe in its journey through Pluto’s system.

The inset shows the first ever indication of Charon’s existence – a grainy bump on an indistinct photograph from 40 years ago.