Long-Ago Giant Impact May Have Created Moon's Mysterious Grooves

A baby planet at least as large as New Jersey that smashed into the moon billions of years ago might have created the mysterious grooves that score the lunar surface, a new study suggests. This finding could shed light on a violent era of impacts that once bombarded Earth and the rest of the inner solar system, researchers said. Mare Imbrium is surrounded by grooves and gashes large enough to be seen from Earth even with small telescopes.