Dark or Bright Halo Pit
Rimless depression (pit crater, caldera) surrounded by a low or high albedo annulus, or halo.
Thedepression with dark halo: on the Moon: Alphonsus-type dark halo crater (Head and Wilson 1979); Dark halo craterlet; Dark-haloed crater/pit. With bright halo: bright halo crater; On Mercury: (diffuse) red spots. The deposit: dark mantling material (Wilhelms and McCauley 1971); Localized dark mantle deposit
Dark- or bright-haloed depressions are generally noncircular/irregular depressions with no sharply raised rim. They have smooth, untextured haloes that are darker or brighter or of a different color than their surroundings. The pit craters on the Moon are often aligned with linear rilles, lineaments, occurring along linear fractures. Rays are not observed.
On the Moon, pits have a radius of about 1 km, with deposits extending to 3–5 km from the pit. On Mercury and Io, they (calderas/paterae) are an order of magnitude larger.
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