Found this one yesterday:-
http://www.smashwords.com/books/view/117635
In The Tide: a science fiction short story by Linda Nagata
"The rings of Saturn have been poisoned with a cloud of nanomachines designed to infect and destroy smart technology, including spacecraft control centers. Aron is a molecular designer with an unspoken passion for Indigo, a modified human adapted for life in space. Together they descend into Saturn’s poisoned rings in a desperate attempt to salvage an abandoned spacecraft. "