It was intended as a gift for future human explorers.

This demonstrated the potential of radio communications beyond the Earth for space probes and human explorers.

Colors in the image have been slightly exaggerated but would likely be apparent to a human explorer's eye.

The first living nonhuman intelligent race the human explorers found didn't count.

The problem for human explorers is that such regions are frustratingly out of reach.

The story is told from the points of view of one of the local intelligent life forms and a human explorer.

No human explorer would have marked it for colonization.

The first human explorers to enter Dione had reported a large, empty city made of wood.

Unfortunately for the human explorers who by the luck of the draw got that particular flight plan, it was a one-way trip.

For more than thirty years he had traveled the world, pleading with those in power to send human explorers to Mars.