当墓碑可能依赖“ liveness_info”时，为什么它包含“ marked_deleted”时间戳？

Question

我正在阅读http://www.beyondthelines.net/databases/cassandra-tombstones/，其中

INSERT INTO locations (
  address,
  status,
  properties
) VALUES (
  'D3-DJ-21-B-02',
  'damaged',
  null
);

收益

[
  {
    "partition" : {
      "key" : [ "D3-DJ-21-B-02" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 18,
        "liveness_info" : { "tstamp" : "2017-01-28T11:58:59.160898Z" },
        "cells" : [
          { "name" : "status", "value" : "damaged" },
          { "name" : "properties", "deletion_info" : { "marked_deleted" : "2017-01-28T11:58:59.160897Z", "local_delete_time" : "2017-01-28T11:58:59Z" } }
        ]
      }
    ]
  }
]

为什么墓碑可以包含marked_deleted时包含liveness_info时间戳？