Exposure test: does a deeper crater (more removed) carry more mass excess at centre / floor?
highland     [20, 40)    n=3094  centre rho=-0.36 p=6.1e-83  floor rho=-0.20 p=8e-29  centre by depth third {'shallow': -0.15, 'mid': -0.38, 'deep': -0.75}
highland     [40, 80)    n=1179  centre rho=+0.01 p=0.82  floor rho=-0.06 p=0.042  centre by depth third {'shallow': -0.26, 'mid': -0.32, 'deep': -0.15}
highland     [80, 150)   n= 285  centre rho=-0.17 p=0.0038  floor rho=-0.15 p=0.014  centre by depth third {'shallow': -1.03, 'mid': -1.54, 'deep': -2.11}
highland     [150, 400)  n=  59  centre rho=-0.47 p=0.00015  floor rho=-0.31 p=0.017  centre by depth third {'shallow': 4.35, 'mid': -0.17, 'deep': -0.57}
mare_intact  [20, 40)    n=  28  centre rho=-0.21 p=0.31  floor rho=+0.00 p=0.99  centre by depth third {'shallow': 0.02, 'mid': -0.45, 'deep': -0.5}
mare_intact  [40, 80)    n=  24  centre rho=-0.41 p=0.047  floor rho=-0.39 p=0.06  centre by depth third {'shallow': 0.74, 'mid': 0.07, 'deep': -0.32}
mare_partly  [20, 40)    n=  58  centre rho=-0.29 p=0.035  floor rho=-0.23 p=0.078  centre by depth third {'shallow': -0.24, 'mid': -0.1, 'deep': -0.82}
mare_partly  [40, 80)    n=  36  centre rho=-0.18 p=0.31  floor rho=-0.23 p=0.19  centre by depth third {'shallow': 0.69, 'mid': 0.13, 'deep': -0.59}
mare_buried  [20, 40)    n= 107  centre rho=-0.07 p=0.5  floor rho=+0.00 p=0.97  centre by depth third {'shallow': 0.12, 'mid': 0.21, 'deep': 0.08}
mare_buried  [40, 80)    n=  43  centre rho=+0.01 p=0.96  floor rho=-0.01 p=0.96  centre by depth third {'shallow': 0.12, 'mid': 0.8, 'deep': 0.05}
mare_buried  [80, 150)   n=  17  centre rho=+0.27 p=0.29  floor rho=+0.21 p=0.42  centre by depth third {'shallow': -0.43, 'mid': -0.0, 'deep': 0.3}
