What goes up into space must later come down. Of those objects that make it into orbit, most of them are dragged down, but some objects can keep whizzing around for decades.

The Department of Defense tracks tens of thousands of artificial objects around Earth, but many fragments are too small to track. Any one of these tiny bits moving at hyper-speed could cause impact damage on satellites or space stations, causing anything from dents to explosions. One big target is the International Space Station (ISS). It routinely takes hits from sub-millimeter-sized particles and actively dodges larger bits multiple times each year.

And smaller spacecraft are in danger too. In 2009, a U.S. commercial satellite tore through a Russian military satellite, each bursting into a debris cloud that encircled the planet.

NASA astrophysicist Donald Kessler first analyzed a phenomenon, now called the Kessler Syndrome, nearly 40 years ago. He predicted that pieces of broken satellites and other space objects could create a “debris belt” around Earth. These little pieces of space junk can crash into our space objects, and could someday halt space activity.

The primary focus of this passage is _______________.