Upper atmospheric regions of Earth are impacted by human-made space debris. Image shows the limb of the Earth at the bottom transitioning into the orange-colored troposphere, the lowest and most dense portion of the Earth’s atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue- colored atmosphere. The silvery-blue noctilucent clouds extend far above the Earth’s troposphere.
There is growing appreciation that outer space has become a trash bin, with the Earth encircled by dead or dying spacecraft, along with menacing bits of orbital clutter - some of which burns up in the planet?s atmosphere.
The big news of late was a smashup of a commercial Iridium satellite with a defunct Russian spacecraft earlier this year. Then there was that 2007 anti-satellite test by China, purposely destroying one of its aging weather satellites. These events produced large debris fields in space ? adding to the swamp of cosmic compost.
But I sense a line of research that needs exploring: The overall impact of human-made orbital debris, solid and liquid propellant discharges, and other space age substance abuse that winds up in a high-speed dive through Earth?s atmosphere.
There?s a convenient toss away line that is in vogue: that such space refuse simply ?burns up? ? a kind of out of sight, out of mind declaration.
What chemistry is involved given the high heating during reentry of space leftovers made of tungsten, beryllium, aluminum and lots of composite materials? The impact of these materials on Earth?s atmosphere - top to bottom ? would seem worthy of investigation.
As for total mass of uncontrolled objects that re-enter each year ? it?s in the range of 70 ? 80 metric tons. And that?s the trackable, big stuff ? never mind smaller bits of orbital jetsam like bubbles of still-radioactive coolant that has been leaked from old nuclear-powered Soviet satellites.
One study team that looked into the impact of de-orbiting space debris on stratospheric ozone issued their findings back in 1994. The work was done by an aerospace industry firm for the Environmental Management Division of the Space and Missile Systems Center. They reported that objects re-entering the atmosphere can affect ozone in several ways, but not on a significant level globally.
Indeed, as an object plows through the Earth?s stratosphere, a shock wave is created that produces nitric oxide, a known cause of ozone depletion. Spacecraft and rocket motors are composed of metal alloys and composite materials that melt away during re-entry. The researchers found that these materials, as they undergo intense heating, also form chemicals that react directly or indirectly to consume ozone.
Overall, the study found that the physical and chemical phenomena associated with deorbiting debris do not have ?a significant impact? on global stratospheric ozone.
Pass the collection plates
Then there?s the work of Michael Zolensky of Astromaterials Research and Exploration Science at NASA?s Johnson Space Center in Houston, Texas.
Some 20 years ago, Zolensky led a team that found a ten-fold increase in the abundance of large solid particles in the stratosphere between 1976 and 1984. Using high-altitude aircraft, the NASA sampling program was directed at snagging particles of dust from comets and asteroids as they filter down through the atmosphere.
However, when the collection plates were later analyzed, exhaust residue from solid rocket motor firings, protective paints that shed from the outer hulls of spacecraft in orbit, and particles of mostly aluminum from re-entering space hardware were identified.
?I don?t think anyone ever followed up on this,? Zolensky told me. More study is needed on the density of particles, types of particles, how long they are suspended in the atmosphere, and whether or not the amount of deorbiting detritus has increased over time.
Time to get smart
Another scientist flagging this issue is Martin Ross of The Aerospace Corporation in El Segundo, California. He points out that this type of research is one where you need to have the science guys talking to the engineering community. ?And that usually doesn?t happen.?
Ross emphasized that orbital debris impacts on Earth?s atmosphere, at the moment, is not something to be too concerned about. However, now is the time to get smart about what is taking place, he said.
But complicating that investigation, Ross noted, is that airplane and balloons only operate at altitudes lower than where the re-entry process takes place. That upper stratosphere-lower mesosphere region has often been tagged as the ?Ignorosphere,? Ross said.
Even at balloon altitude there has been some recent, unexpected, insight. Scientists at the Indian Space Research Organization announced last March that ultraviolet-resistant bacteria had been found in Earth?s upper stratosphere, purportedly not found elsewhere on Earth.
?Everywhere we look on the Earth, we seem to find something that we could call life,? Ross told SPACE.com. ?So I guess it wouldn?t be too surprising that you?d find some layer of a particular microbe, or something, at various levels in the atmosphere.?
Ross, along with Darin Toohey of the University of Colorado, Boulder?s Atmospheric and Oceanic Sciences Department recently reported that rocket launches may need regulation to prevent ozone depletion.
That study ? published in Astropolitics this past March, an international journal of space politics and policy -- includes analysis from Embry-Riddle Aeronautical University in Daytona, Florida and provides a market analysis for estimating future ozone layer depletion based on the expected growth of the space industry and known impacts of rocket launches.
In that assessment, the global market for rocket launches
may require more stringent regulation in order to prevent significant damage to
Earth?s stratospheric via ozone-destroying rocket emissions in the decades to
The new study was designed to bring attention to the issue in hopes of sparking additional research, Ross said. Furthermore, getting a handle on the makeup of human-made components and debris that speeds through the upper atmosphere ? from an accounting point of view -- would be a fairly simple thing to do, he added.
?All we really have right now are a small handful of observations of the emissions of a few rockets as they ascend to space. Even then, we lack critical observations in the plumes of many other types of rockets to be confident in predictions of the impacts of the space launch fleet as a whole,? Toohey told SPACE.com.
?Add in the unknown impacts of vapors formed during reentry, and you can guess that we have some work to do to provide solid evidence needed by the space launch industry to design new vehicles that minimize those impacts,? Toohey added.
Toohey said the good news is that, if the atmospheric sciences and space launch communities can come together to address this issue, ?we have the expertise and tools to solve this before it ever becomes a serious problem.?
Space ? a Superfund clean-up site
While getting a research handle on the Ignorosphere appears called for, the bigger mess to deal with is how best to de-clutter low Earth orbit.
?Cleaning up space is the next space age?that I guarantee. It?s going to take a major new space program, not just one mission, to clean this stuff up,? said Marshall Kaplan at the Space Department of the Applied Physics Laboratory in Laurel, Maryland.
The time for space debris reduction thinking has come, Kaplan emphasized.
?You might think of this as the U.S. Environmental Protection Agency?s largest Superfund cleanup,? Kaplan told SPACE.com. ?This outweighs any Superfund concept that we?ve ever had before in terms of money and size,? he concluded.
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Leonard David has been reporting on the space industry for more than four decades. He is past editor-in-chief of the National Space Society's Ad Astra and Space World magazines and has written for SPACE.com since 1999.