An active NASA spacecraft has survived a near-miss with a defunct Russian satellite in low Earth orbit.
Had the two non-maneuverable satellites collided, it wouldn't have just doomed NASA's satellite — which monitors the effects of the sun on the Earth's atmosphere — but could have also potentially started a catastrophic collision cascade with other objects in orbit. The potential scenario of a cascade of satellite debris in low Earth orbit is called Kessler syndrome, and was popularly depicted in the 2013 film"Gravity."Although a cascade of this kind has yet to happen, scientists are increasingly concerned that the growing number of satellites and space junk is making it more likely. Currently, the Department of Defense tracks the 30,000 largest debris pieces, but there are many more that are too small to be followed, according to NASA.