holsinger: it does. a couple ways to think about it read in some orbits the density of space debris is high enough to where the rate of close approaches, or potential collisions, is such that continued collisions would actually cause cascading creation of debris and further collisions. that's mously known as the kessler syndrome. in most orbits that is not the problem, though to be clear a , wide variety of spacecraft that are crewed, actively engage in avoance maneuvers. for example, the international space station engages in a wide variety of avoidance maneuvers each and every year. laura private space companies : now are launching satellites bigger than we've seen before, and many countries are looking to space to expand military capabilities. so that means more launches and more debris up there. what needs to be done to ensure that earth's orbit is not continuously cluttered? prof. holsinger: the are a combination of things that we can do. so number one, when we launch spacecraft, it behooves us to e

. >> meaning, they were able to pick up jones, but da holsinger was not. >> by did you decide to put> i didn't have a body. and that was the defining. not a lot of cases where the duke victim has a double life and has been lying to family and friends here because of her double life, the possibility that defense attorney could throw out there that she ran off with some rich clients and is living on a beach in brazil or something. >> as the years passed, paige's story with from the front of the paper to be filed away on microfiche. where was she? >>> coming up, they were about to find out, and it would transform the case. >> now, we need to make a critical decision. >>> when "dateline" continues. because a lot can happen in 48 hours. cetaphil. we do skin. you do you. we've always loved taking care of our home. but last year, grandpa here broke his arm. we realized some home maintenance jobs aren't worth the risk. that's when we called leaffilter to protect our gutters. leaffilter's patented filter technology keeps debris out of your gutters for good. they gave us a free inspection and