Saved on this device

Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Technology

Autonomous Navigation and Hazard Avoidance for Planetary Landers

Quick fact

NASA's Perseverance rover, which landed on Mars in 2021, used an autonomous navigation system that could identify hazardous rocks and craters on its own. It navigated the final descent with no human input, making real-time decisions in less than a second to avoid a crash.

Why this is interesting

When you land a spacecraft on another planet, there is no human at the joystick—and the radio delay from Earth is minutes. How does a lander hit a tiny safe spot on an unexplored moon or Mars, all by itself?