What explosion had an altitude of 539 km?
CREATE TABLE table_148578_1 (explosion VARCHAR, altitude__km_ VARCHAR)
SELECT explosion FROM table_148578_1 WHERE altitude__km_ = "539"
### Context: CREATE TABLE table_148578_1 (explosion VARCHAR, altitude__km_ VARCHAR) ### Question: What explosion had an altitude of 539 km? ### Answer: SELECT explosion FROM table_148578_1 WHERE altitude__km_ = "539"