Explorers trudged the Atlantic Ocean searching for World War II artifacts, but they stumbled on something else — a 20-foot-long piece of debris from the Space Shuttle Challenger, which was destroyed shortly after takeoff in 1986.

President Joe Biden will meet Chinese leader Xi Jinping face-to-face on Monday, their first in-person encounter since Biden took office and one that will offer a clarifying opportunity for the world's most important bilateral relationship.