He'd meant what he said when he told Carol he didn't like the idea of any of them going down there alone, even knowing what she was capable of. This wasn't a place they were familiar with. They had no way of knowing what to expect. He wasn't about to let anyone face that level of uncertainty unprotected.
He was admittedly also just really curious about seeing the planet. Even with the overarching mystery of what had taken place.
Steve heard Tony's comment just as he got to the shuttle and he laughed as he stepped through the door. "If that's your expectation of how the day will go maybe I'll leave you to it?" He gestured back over his shoulder with his free hand, like he could just as easily turn around and go back.