Mitsubishi eclipse 2003 gs

I'm not a hundred percent positive but you could have trown a piston rod or lost something in that general area. To be sure the take a good look at the block top bottom and sides. Try to see if there are any holes in it that shouldn't be there. Did you start losing power after you heard this? Did you have enough oil in it? I heard a similar sound coming from my Avalon when I was on the freeway. I started losing speed so I put the peddle to the floor and heard another clinking noise followed by a lot of smoke. The smoke filled up the cab and had me scared half to death thinking the car was on fire. I ended up just cutting across five or so lanes to get to the shoulder. Afterwards it wouldn't start at all. Just made a clicking noise. Turns out my small leak turned into a huge leak and I lost my engine oil. This causing a piston to seize up. When I gunned it I snapped the rod and it put a fist sized hole in the bottom of my block.