"is supposedly the heat shield", yes, this must be pictures from opportunity. She's going back to examine the landing area. Have to say it looks like a dried up old lake. And that piece of "wood" actually looks like something that washed up on the "shores" a long time ago. I hope they are going over to it to check it out with the instruments.
Forgot to mention, you folks see the odd linear track leading to the piece of "wood"? Starts out abouve it at a 45 degree angle, then makes a sharp turn right towards it.