https://www.cnbc.com/2018/06/01/elon-musk-responds-to-boeings-claim-it-will-beat-spacex-to-mars.html > SpaceX billionaire Elon Musk clapped back to Boeing CEO Dennis Muilenburg's claim that Boeing will be the first space company to get to Mars. > "Do it," Musk tweeted Thursday in response to a story about the assertion.