SpaceX updated Falcon 9's booster and tweaked its "legs," which are supposed to be able to support its weight when it lands. One of its previous attempts failed, because its legs didn't lock properly and gave out. According to VP for flight reliability, Hans Koenigsmann, that's pretty much all they changed: "There's minor changes on the nuts-and-bolts level, but that is basically all the changes that we did." Since its next step is to prove that the rocket that landed can be reused, SpaceX announced at a press con that it's launching the same Falcon 9 in May or June if tests ensure that it's still in perfect working condition.

Landing from the chase plane pic.twitter.com/2Q5qCaPq9P — SpaceX (@SpaceX) April 8, 2016 Onboard view of landing in high winds pic.twitter.com/FedRzjYYyQ — SpaceX (@SpaceX) April 9, 2016 The 1st stage of the Falcon 9 just landed on our Of Course I Still Love You droneship. Dragon in good orbit pic.twitter.com/SYyUCDZE3k — SpaceX (@SpaceX) April 8, 2016 Congrats SpaceX on landing a rocket at sea. It's because of innovators like you & NASA that America continues to lead in space exploration. — President Obama (@POTUS) April 8, 2016