Tiny spacecraft are breaking out of Earth’s orbit

Cheap, small satellites have swarmed into Earth orbit over the past decade, cutting the cost of studying our home planet from space. Now, these spacecraft, some no bigger than a briefcase, are becoming capable enough to venture into deep space—or at least the inner solar system. Two are halfway to Mars, more than a dozen planetary probes are in development, and scientists are coming up with ever more daring ideas for doing cheap, high-risk interplanetary science.