Just as humans continue to ruin the earth's surface and oceans with ecologically dangerous garbage, we are now doing the same thing to the space far above our polluted cities — filling it with aeronautically dangerous debris. This process began half a century ago, on 4 October 1957, when the Soviet Union launched their Sputnik I satellite, which in turn launched the space race between the United States and the Soviet Union. The Soviets' first satellite may exist no more — having burned up while reentering the earth's atmosphere — but it was only the first step in mankind's efforts to explore the heavens. Ever since that first well-known human excursion into outer space, we have followed it with innumerable commercial and military satellites, test rockets, remote exploration vehicles destined for other planets, and even manned missions to Earth's moon.
Those space-bound objects, to varying extents, have resulted in untold benefits to mankind, and a much richer understanding of the cosmos above our heads, as well as the earth below our feet. In that latter category is the knowledge gained from reconnaissance satellites constantly monitoring environmentally critical phenomena, such as the ghastly burning of the Amazonian rain forests. But each launch has also contributed to the growing collection of junk cluttering low Earth orbit (LEO). These items include satellites whose batteries have run out of power, rocket stages discarded mid-flight when they expended the last of their fuel, and even chunks of insulation that separated from NASA's Space Shuttles. In fact, there are well over 13,000 such objects being tracked by the U.S. Space Surveillance Network.
All of these objects are kept in orbit around the earth as a result of the planet's gravitational attraction, thereby preventing them from hurtling off into space — perhaps to become the junk of some other unfortunate planet. Each one of these objects, unless physically destroyed or pushed out of Earth's gravitational hold, will eventually orbit closer and closer to the planet's atmosphere, usually vaporizing upon reentry. Yet this should prove cold comfort for anyone hoping that this junk will be cleaned up without any effort on our part. Like space, time is relative, and "eventually" may turn out to be longer than mankind's survival. Admittedly, some of the objects in LEO are close enough that we may see their destruction within our lifetimes. (This category may include the International Space Station!) But many of these objects are hundreds of miles away from Earth's surface, and would remain orbiting for millions of years.
Another problem is the tremendous amounts of kinetic energy possessed by most of these orbiting objects, since they are generally composed of metal, and are hurtling around the planet at great speeds. Consider, for instance, a satellite that is geostationary, i.e., orbiting above the same point on the earth's surface (intentionally, one would hope). Using the space around the earth as a frame of reference, the satellite will return to roughly the same location 24 hours later, after the earth has rotated once. Because the satellite's full orbit has a greater diameter than does the earth's surface below it, it must travel at a faster speed to remain geostationary. The equatorial circumference of the earth is approximately 40,075 kilometers (24,902 miles), and thus any satellite in a fixed position above the equator would be traveling faster than 1669 kilometers per hour (1037 MPH). Exploding rocket stages generate countless metal shards that can be too small to track, but are often traveling faster than 35,000 KPH (22,000 MPH).
Imagine two such objects colliding. The satellite would be demolished, and generate many new fragments, blasted in all directions — straight towards other satellites, nonfunctional or soon to be made so. NASA scientists have been imagining this nightmare scenario for years, and predict that such a catastrophic chain reaction of collisions is inevitable, even if all space exploring countries were to cease launching any more spacecraft. In essence, each destroyed object would create more projectiles, spreading outwards to claim even more victims — like falling dominoes striking many more, and spreading the carnage until none survived. The odds of this happening will grow dramatically if even a single country acts irresponsibly, as China did, in January 2007, when they tested an anti-satellite weapon that targeted and destroyed an old weather satellite, shattering it into at least a thousand fragments, which within only weeks spread outward for almost 2000 miles in space.
Even if this cataclysmic scenario somehow miraculously fails to unfold, and the space debris simply grows in number with each new spacecraft launch, then it is projected that such launches will eventually be too dangerous to undertake, as there will be far too many fragments to get any spacecraft through such a minefield undamaged. This is known as the Kessler Syndrome, named after a former NASA official.
Some of this space junk is already endangering pilots and passengers who had absolutely no intention of exploring "the final frontier". In March 2007, fragments of a Russian satellite reentered the earth's atmosphere intact, and were seen by the pilot of a commercial jet, a Lan Chile Airbus A340, flying over the Pacific Ocean, near Auckland, New Zealand. Russian authorities had warned pilots of the impending reentry, but miscalculated by approximately 12 hours, which demonstrates how difficult it can be to track even some of the larger pieces of space debris.
Although this problem may not seem immediately applicable to the ecosystem down here on the planet's surface, it may portend a dire warning as to what humans would do to other planets, if and when we attempt to terraform them, i.e., transform them to resemble Earth. Will humans move from one planet to another, trashing them as we go? Will we become cosmic hooligans, leaving every place worse than we found it? Instead of "Homo sapiens", we may instead change our name to "Homo polluters". But would we so readily admit that we have such a flaw? Possibly, but then we might continue making the same mistake, as we seem to do in every other area.
Anyone who would prefer that those pristine planets remain unscathed by the "human touch", may take heart in an unintended consequence of the human junkyard orbiting above our heads. If humans are unable to remove the LEO debris — for technological or financial reasons — then it will form an increasingly impenetrable barrier to future space exploration. This is particularly true if and when the first massive chain reaction of collisions occurs, because that will significantly increase the number of projectiles, and will increase their distribution throughout the LEO.
Regardless of one's opinion on the viability and wisdom of terraforming other planets in particular, or further space exploration in general, most of us would undoubtedly agree that humans should not only stop the pollution of the space surrounding our planet, but we should begin developing methods of clearing the space clutter, before the chain reaction of collisions wipes out a network of satellites that so many countries, businesses, and individuals rely upon for communication and reconnaissance. City lights have already obliterated the visibility of the stars at night. Let's not make things worse by turning the space surrounding the earth into a veritable "Jetsons' Junkyard".