there have only been two previous missions to mercury, one a long time ago, mariner 10, and then more recently nasa s messenger mission. and this one, bepicolombo, is designed to answer a lot of the questions raised by that messenger mission. so we mentioned in the introduction there the spacecraft is shooting past mercury. it is not actually landing on the planet, is it? what are we watching for in the coming hours? well, the main thing that this flyby is supposed to accomplish is to alter the orbit, alter the trajectory of the spacecraft, as it goes around the sun. they would love to be able to enter orbit right now, because that s after all the goal of this mission to orbit mercury for a couple of years and gather lots of science data. but it s very difficult to enter orbit at mercury. it s a very small planet and the gargantuan gravity of the sun is very close by. so they ll have to fly past it a total of five times before finally entering orbit in 2025. so really all they really