For many years, nations have sent vehicles to the Moon, Mars and other bodies to explore them, take pictures and even collect samples. But there is a worrying trend in robotic space vehicles - they are becoming heavier, leading to warnings of an obesity crisis.
NASA's latest vehicle, called Curiosity on account of its sexuality, weighs one tonne. That is as heavy as a one tonne bus, or two half-tonne weights. In comparison, NASA's Closet rover from 1973 weighed a mere 200 pounds, or the same as 200 one-pound space vehicles.
So what has caused this massive increase in weight? It is tempting to blame society, or our weight-obsessed culture, but surely it is the fault of the vehicles for allowing themselves to become so flabby.
Diet expert Fatty Chubbock says that Curiosity is having an easy time of it, "lazing around in the low gravity of Mars like a slob." He points out that spaceships have had to increase in size to accommodate the larger vehicles. "It's disgraceful. The spaceships should be built for normal sized robots, these overweight ones need to shape up, and go on my exercise regime. No more fried chips for them."