re: Railroad Tie on Mars?
LIndy - I've followed the rovers closer than most - I can honestly, hand on heart say, that I have looked at each and every one of the 225,000+ images that Spirit and Opportunity have taken.
It's just a rock - it's a slab of the same rock that can be seen in the walls of Eagle crater, Endurance Crater, Victoria crater and elsewhere - just tilted up because it's been driven over by the rover.
People trying to make something out of it are attention seeking idiots - nothing more.