On Thursday, SpaceX founder Elon Musk threw down the gauntlet on getting humans to Mars. Well, he did it on Twitter, but in 2017, that’s the battleground on which we all must nobly fight.

Here’s what happened: On Thursday morning, CNBC host Jim Cramer asked Boeing CEO Dennis Muilenburg about which company he thinks will get a human to Mars first, his or Musk’s.

“We’re working on that next generation rocket right now with our NASA customers called ‘Space Launch System,’” Muilenburg said. “This is a rocket that’s about 36 stories tall, we’re in the final assembly right now, down near New Orleans. And we’re going to take a first test flight in 2019 and we’re going to do a slingshot mission around the moon.”

Then, Muilenburg came out and said it.

“Eventually we’re going to go to Mars and I firmly believe the first person that sets foot on Mars will get there on a Boeing rocket,” Muilenburg said.

When Fortune re-reported this news and tweeted it out, Musk was quick to respond — and he didn’t hold back.

Screenshot via Twitter

Clearly, SpaceX has had its eyes on Mars for a long time. Musk has even gone so far as saying he wants to “make humans an interplanetary species” by building a permanent settlement on the red planet. In September, he announced SpaceX’s aptly named Big Fucking Rocket (BFR), which the company plans to use a ferry to send humans to Mars. According to Musk, the first crewed missions to the red planet on board the BFR will start in 2024.

This isn’t the first time Muilenburg has challenged SpaceX. At a conference in Chicago last year, Muilenberg said: “I’m convinced that the first person to step foot on Mars will arrive there riding on a Boeing rocket.”

Perhaps the winner of this latest Muilenberg vs. Musk twitter duel was someone else. Bobak Ferdowsi, a systems engineer at NASA’s Jet Propulsion Laboratory (JPL), might have had the last word on the whole situation:

Ferdowsi is of course talking about NASA’s Mars 2020 rover, which will almost certainly beat both Boeing and SpaceX to the red planet. While it won’t be a crewed mission, it’s still a great comeback, and Ferdowsi should be proud.

Who will get a human to Mars first? Only time will tell. For now, we get to live through those leading the charge as they argue on Twitter about it.


Photos via Getty Images / Mark Brake