A top NASA executive hired in April to guide strategy for returning astronauts to the moon by 2024 has resigned, the space agency said on Thursday, the culmination of internal strife and dwindling congressional support for the lunar initiative.

Mark Sirangelo, named six weeks ago as special assistant to NASA Administrator Jim Bridenstine, left the agency as NASA abandoned a reorganization plan due to a chilly reception on Capitol Hill, Bridenstine said in a statement.