The BBC reckons it’s just water.
Golf ball?
I bet it’s Jimmy Hoffa.
He and Lord Lucan have been found riding around on Shergar.
I’m just waiting to see how some mass media outlet will totally distort the initial announcement and later on when corrections and adjustments are made after further research, someone will point to that as proof that “the pointy-heads were wrong again”.
My guess, evidence of more water than they ever expected.
Not just water, but apparently there’s already someone there selling time share condos.
crosses fingers I hope they find Usher II.
I hope they find my car keys. I mean, I’ve looked everywhere else for 'em…
Maybe they’ve found all the odd socks!
A big, black, obelisk that was obviously not made by natural processes.
My first thought was “WMD”
A big, pink. flashing neon sign that reads “Live Nude Girls Here” that was obviously not made by natural processes
Osama bin Laden moonied the rover.
I think the two rovers have come together and we are about to have the Ultimate Battle Bots Competition!
I think they’ve found a Starbucks. Oh, no, wait. Those really are everywhere. Nevermind. 
A mailbox near a small white house.
That’s what they’ll find.
Maybe they’ve found the base for Pigs in Spaaaaaaace!
Such a reference deserves acknowledgment. Kudos.
I think they’ll find Santy Claus!
Or maybe a jewel encrusted egg to put in their trophy case…
I strongly suspect it will turn out to be evidence of the existence of water on Mars
