The robotic spacecraft that made these journeys and transmitted the pictures are triumphs of scientific ingenuity.

Over the next century the solar system will instead largely be mapped out by flotillas of tiny robotic spacecraft, he predicted.

Scientists are increasingly concerned that the costs of ever-more complex robotic spacecraft will be unaffordable by constrained science budgets.

A source of oxygen and hydrogen would be useful, he said, even for robotic spacecraft.

Space probes are a form of robotic spacecraft.