In those days Izzy had been like a kite: all surface area, no mass. In technical terms, it had had a low ballistic coefficient: a way of saying that it was strongly affected by what little atmosphere there was. Once Amalthea had been attached, it was like a kite with a big rock strapped to it. It had a high ballistic coefficient. The rock’s momentum bulled through the evanescent atmosphere and led to much slower orbital decay. But by the same token, when it came time to reboost Izzy’s orbit, a longer burn and a larger amount of propellant were needed in order to accelerate all of that iron and nickel.