A robotic lunar lander built by Texas-based company Firefly has successfully landed on the moon making it only the second private-sector company ever to achieve a soft lunar landing. Former NASA astronaut Leroy Chiao explains why the robotic lander plans to scientifically observe the moon’s lunar horizon glow, a rare phenomenon last seen by astronauts more than a half a century ago. #cnn #news #space #science #moonlanding #nasa