How Would a Huge Asteroid Strike on the Moon Affect Earth?
As its crater-scarred surface shows, the Moon has had a tumultuous past. Space rocks of all shapes and sizes have slammed into our orbiting satellite.
And yet for billions of years, it has remained a fixture in our sky, revolving around the Earth, powering the tides and providing a beacon in the night.
Could this ever change? Could a sufficiently large asteroid – like a celestial billiards ball – ever knock the Moon off its steady course? And how would this affect life on Earth?
As Clark Chapman, a planetary scientist at the Southwest Research Institute, told Popular Science back in 2010, this scenario is highly unlikely, because it would take a moon-sized object to have any hope of dislodging our Moon. And it's more likely that such a collision would shatter our satellite entirely, sending pieces of it cascading down upon Earth – quite a cataclysmic scenario.
Even the largest-known asteroid in our solar system, the 600-mile-wide Ceres, would hardly hinder the Moon if it somehow struck it.
"The moon orbits the Earth at some 0.635 miles per second," science journalist Sandeep Ravindran wrote. "This orbital momentum is so great that it would overwhelm the impact force of a collision and just continue zinging around the planet."
Such a collision would cause some sparks, however. There'd be quite a light show. Terrestrial onlookers would see an intensely bright flash, followed by days and potentially weeks of meteor showers. Some of these falling lunar pieces might be large enough to reach Earth's surface as meteorites, but it's unlikely. Life on Earth probably wouldn't be affected.
The Moon's remarkable constancy despite any impactors is a good thing for us Earthlings. Ravindran asked University of Hawaii astronomer Gareth Wynn-Williams what would happen if the Moon's orbit was tighter to Earth.
If its new orbit halved its current distance from the Earth, ocean tides would get about eight times as big, Wynn-Williams says. “A lot of New Yorkers would get very wet.”
