CREATE TABLE table_16799784_7 (name VARCHAR, diameter__km_ VARCHAR)

what's the name origin of feature of diameter (km) 2,155.0
SELECT name AS origin FROM table_16799784_7 WHERE diameter__km_ = "2,155.0"
SELECT "name" AS "origin" FROM "table_16799784_7" WHERE "2,155.0" = "diameter__km_"