Smith wrote:
Please excuse this naive query:

How is it possible to know that we have not just deposited some "earth
DNA" on Titan, via a single (or multiple) viral or bacterial
hitchhiker?
[...]

I realize that clean rooms are used for vehicle and instrument
fabrication, that heat of atmospheric entry, the 7 year transit time
and the radiological environment of interplanetary space all mitigate
against this possibility, but...

One compromised bacterium?
One (or a dozen, or a few hundred) virus/viruses?
How sure do you want to be before you think you "know"?

Lots of Greetings!
Volker