This is an interesting question and I can’t wait to see what you figured out, since I’m also quite new to this. After reading it I see that there are plenty of questions of box2d (the physics engine corona uses) and curved surfaces. Here’s some interesting one’s I’ve found…
http://www.box2d.org/forum/viewtopic.php?t=8180 - Circular collisions on curved surfaces
https://gamedev.stackexchange.com/questions/70669/how-do-i-make-a-curved-surface-out-of-rectangular-blocks
just google box2d and curved and you’ll find loads of question - unfortunately in lots of languages but hey box2d is box2d 
Another useful tool I found: https://github.com/jkbmat/Bakalarska-praca an online box2d scene editor to test out physics. Very cool.
My theory is your player object would have to be a circle body and the “land” would be some sort of chain body like sporkfin says. Remember the physics body does not have to look like your actual sprite character - you could use the hidden body’s x and y to place your sprite and make sure your rotation is correct as per the land.