And just as some early explorers made the ultimate sacrifice while searching for unknown lands, space pioneers may also pay a steep price for bravely going where no human has gone before.

CNN: Mars on the brain? Red Planet pioneers to face cosmic mind trip

Predicting the location of the termination shock was hard, the researchers say, because the precise conditions in interstellar space are unknown.

BBC: Voyager impression (Nasa)

What that might be is unknown, but experiments in space have shown that cosmic rays can have some positive impacts on biological materials.

BBC: Earth News - Cosmic pattern to UK tree growth

My work is trying to map that in-between space between known and unknown, the constant hovering between two states.

ECONOMIST: Contemporary art

But sitting here beside this girl as unknown to him now as outer space, waiting for whatever she might say to unfreeze him, now he felt like he could see the edge or outline of what a real vision of Hell might be.

NEWYORKER: Good People

Negroponte says an unknown wiki contributor suggested that the caps lock key be eliminated to save space.

FORBES: Can a network build a potentially huge new product?

The films, showing man in space, on the Moon, on Mars, and the "unknown", fascinated the boy Rutan.

BBC: The Moon

The Zumwalt has the power, cooling, space and weight margin designed to meet the full spectrum of future threats, both known and unknown.

CENTERFORSECURITYPOLICY: Countering Beijing's new weapon

This year the students had to program their SPHERES to deploy dust clouds that could remove space junk from orbit, dock with another satellite to harvest its parts, and maneuver through an unknown field full of debris.

MSN: High schoolers control satellites aboard space station