请告诉我关于太阳系行星的简要信息，每个行星要列出名称、大小排在第几、离太阳的距离等信息，要求答案必须是json格式输出。
user
```json
{
  "planets": [
    {
      "name": "Mercury",
      "size_rank": 1,
      "distance_from_sun": "57.9 million km"
    },
    {
      "name": "Venus",
      "size_rank": 2,
      "distance_from_sun": "108.2 million km"
    },
    {
      "name": "Earth",
      "size_rank": 3,
      "distance_from_sun": "149.6 million km"
    },
    {
      "name": "Mars",
      "size_rank": 4,
      "distance_from_sun": "227.9 million km"
    },
    {
      "name": "Jupiter",
      "size_rank": 5,
      "distance_from_sun": "778.5 million km"
    },
    {
      "name": "Saturn",
      "size_rank": 6,
      "distance_from_sun": "1.434 billion km"
    },
    {
      "name": "Uranus",
      "size_rank": 7,
      "distance_from_sun": "2.871 billion km"
    },
    {
      "name": "Neptune",
      "size_rank": 8,
      "distance_from_sun": "4.495 billion km"
    }
  ]
}
```
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