CAPE CANAVERAL, FL — Serena Williams will end retirement to play the inaugural Intergalactic Tennis Championship on Mars this September, declaring Earth competition “child’s play.” The 23-time Grand Slam champion announced at Kennedy Space Center in a skirted spacesuit. “I’ve dominated every court on this planet,” she said. “Time to face beings who evolved for this sport.” Her likely opponent: Zyx’thara of Centauri Prime, a four-armed server reportedly clocking light speed. The Galactic Tennis Federation’s 64-player field includes a gelatinous Andromedan whose whole body is a racquet and a Rigelian crystal that splits mid-rally. “We’re honored Ms. Williams will represent Earth,” said director Admiral Kzzt’pk via translator, noting regulation courts carved into pressurized Martian rock. Williams has trained in zero-g, serving harder in reduced gravity. “Add about 40 mph,” she said, after lofting a ball over the Vehicle Assembly Building. She’s refining her trademark grunt with xenolinguists. Prize: 50 million galactic credits, a neutron-star trophy, and an asteroid’s name. “Earth’s oppressive 1G held me back,” Williams said. “On 0.38G I’m basically flying.” Next stop: Europa. “After a sentient gas cloud bends physics, everything else is wall practice.”