Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Which Diameter (km) has a Name of alma-merghen planitia, and a Year named smaller than 1997?

### Inputs:
table_name: table, columns: ['Name', 'Latitude', 'Longitude', 'Diameter (km)', 'Year named']

### Response:
SELECT MAX Diameter (km) FROM table WHERE Name = alma-merghen planitia AND Year named < 1997