We can now add space debris remediation with tungsten micro-dust to the many geo-engineering proposals on the table for cleaning up the mess humanity is making with our only planet. The proposal, penned by G. Ganguli, C. Crabtree, L. Rudakov, and S. Chappie, under the auspices of the Naval Research laboratory, addresses a serious issue. Small space debris, in particular, presents hazards to satellites in orbit and space launches but cannot be tracked for avoidance. The proposal joins a giant space-cleaning pod allegedly under development by the Russians, a space net, a GOLD balloon and water cannons, as solutions to the space debris problem. Space agencies are prepared to hear any and all ideas on resolutions for what is a serious, growing problem.
In theory, a couple tens of tons of 30 um tungsten dust into low earth orbit, on a trajectory opposite that of the targetted space junk, would be enough to slow space debris with dimensions under 10 cm. The slowed debris would decay into a lower orbit, where it would be expected to fall into earth's atmosphere within a couple of decades, as opposed to the hundreds of years over which it will remain in orbit at current altitudes.
According to the authors of the paper, hundreds of tons of dust from tiny meteorites enters the earth's "immediate environment" daily, so a couple tens of tons of tungsten dust oxidizing in our atmosphere is no big deal. No mention is made of the fact that tungsten, which is found in the earth's crust at about 0.006%, is certainly not a major component of the hundreds of tons of dust entering earth's vicinty.
Tungsten compounds have been associated with stillbirths and abnormal musculoskeletal development in a couple of Russian studies reported in the Registry of Toxic Effects of Chemicals Substances. So why use tungsten? Tungsten is about 1.7 times more dense than lead, so it has sufficient mass to slow down the orbits of the space debris.
The paper also does not address the engineering complications of moving tons of a dust which may have flammable or explosive properties at these small particle sizes, but as space launches already require a good bit of engineering expertise that can surely be ironed out.
Bottom line: we would need to see more than one paragraph dismissing environmental concerns due to the influx of existing stardust before giving this program a go-ahead.
More on Space Debris:
Shocking Space Debris Images
Clearing Space Junk from Earth's Orbit By Launching Water At It?
Too Much Space Junk Makes Astronauts Sleep in Escape Pods
Space Debris Collision Narrowly Avoided
Obama's New Space Policy Includes Cleaning Up Space Junk