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Like people who share news via Twitter, Facebook and Linkedln, cells, too, make use of multiple modes of information exchange. Some send out hormones, which travel far and wide via the bloodstream; others emit neurotransmitters, which carry signals between one neuron and another. But virtually all cells network with their neighbors via extensive collections of channels that directly connect the inside of one cell with the inside of the next.

Planets are a little like dogs: they all belong to the same general group, but they look so different you can’t always tell. That’s especially true of the gas giants in the outer solar system, like Jupiter, and the lapdogs closer in, like Mars. This year, two NASA spacecrafts going to those two planets will help answer the question of how such different kinds of celestial bodies came to be.