https://www.reuters.com/article/us-space-exploration-spacex/nasa-tells-spacex-to-halt-lunar-lander-work-pending-contract-challenges-idUSKBN2CH2NP >U.S. space agency NASA has told Elon Musk's SpaceX to halt work under a contract it won to develop a lunar spacecraft, pending the outcome of challenges by rival bidders at the U.S. Government Accountability Office, the agency said on Friday.