Appears to be a portion of the undersurface of the orbiter. Black tiles have been stripped away from the underlying structure, leaving the white silica core visible. Of particular interest is the corner tile which reminds me of the outboard trailing edge of the right wing. If the left wing leading edge and underside were responsible for the loss of vehicle, then that debris should not be located in Louisiana or Texas. The debris in La or Tx should be the material furthest from the structure that lacked TPS protection.