The most obvious sign that there is a lot of junk in space is how much of it has been falling out of the sky lately: a defunct NASA satellite last year, a failed Russian space probe this year.
While the odds are tiny that anyone on Earth will be hit, the chances that all this orbiting litter will interfere with working satellites or the International Space Station are getting higher, according to a recent report by the National Research Council.
The non-profit group, which dispenses advice on scientific matters, concluded that the problem of extraterrestrial clutter had reached a point where, if nothing was done, a cascade of collisions would eventually make low-Earth orbit unusable.
"NASA is taking it very seriously," said Mason A Peck, chief technologist for the National Aeronautics and Space Administration.
There is a straightforward solution: dispose of the space junk, especially big pieces, before they collide and break into smaller ones. Researchers are stepping in with a variety of creative solutions, including nets that would round up wayward items and drag them into the Earth's atmosphere, where they would harmlessly burn up, and balloons that would similarly direct the debris into the atmosphere. Also on the table: firing lasers from the ground. Not to blow things up, which would only make more of a mess, but to nudge them into safer orbits or into the atmosphere. Just last week, researchers at a top Swiss university, the Federal Institute of Technology in Lausanne, announced that they were designing CleanSpace One, a sort of vacuum cleaner in the sky - an $11 million one - that will be able to navigate close to a satellite and grab it with a big claw, whereupon both will make a fiery death dive.