Here's a curtailment I came up with. Might be too easy for readers of this forum, but I thought I'd give it a shot ...
Although scientists have been searching for evidence of water, they're probably not going to find a ___ on ___.
Any takers?
marsh ... Mars
and to John's: hearth ... heart
And, since Curiosity did not make it to one of the Galilean moons, it positively will not find an _____ on ______.
Emmett
Well that didn't take long.
Galilean moons: Europa, Ganymede, Callisto, Io.
So by the process of elimination, the solution to your curtailment can only be: I ... Io.
Or did I miss something obvious? Don't tell me ... let me keep guessing if I'm wrong.
Ion on Io, maybe?
Sure, that works. But you'll find plenty of ions on Io. Mostly sulfur ions. Do these curtailments have to be factually accurate? Probably not. I'm gonna wait till Emmett weighs back in.
EDIT: No ... wait ... Curiosity never went to Io, so the presence of ions (or not) is a moot point. That solution works Jackie.