Scott Kelly, the NASA astronaut with a green thumb, is hosting Answer Time on Tumblr right from the ISS. What's "Answer Time," you ask? It's like Reddit's AMA where the host fields questions from readers, so if you missed Kelly's AMA earlier this year, now's your chance. Here's a short background on Kelly, in case you're still thinking of what to ask: he's known as the American who has spent the most time in space and is currently on a year-long mission aboard the ISS.