Wait a Minute!
Image credit: Barbara David

There has been a long research trail in deciphering what happens when Earth’s atmosphere is intruded by incoming, human-made space debris.

Much of this past research involved modeling and squeaking out potential and early warning sign findings.

Enter new rarefied research.

Unnatural dust

The just-issued results in the Proceedings of the National Academy of Sciences (PNAS), an investigation led by Dan Murphy, a researcher at the National Oceanic and Atmospheric Administration (NOAA), is welcomed and cautionary news.

Image credit: NOAA

This investigative team of experts detected more than 20 elements in ratios that mirror those used in spacecraft alloys. They found that the mass of lithium, aluminum, copper and lead from spacecraft reentry far exceeded those metals found in “natural” cosmic dust.

Their appraisal flagged the fact that nearly 10% of large sulfuric acid particles — the particles that help protect and buffer the ozone layer — contained aluminum and other spacecraft metals.


As part of NASA’s Airborne Science Program, NOAA’s Murphy and his group flew a WB-57 airplane to sample the atmosphere 11.8 miles (19 kilometers) above the ground in Alaska, where circumpolar clouds tend to form.

Purdue University’s Daniel Cziczo, professor and department head of Earth, Atmospheric, and Planetary Sciences, is a member of that research group and subsequent report.

Chemical Science Laboratory’s Mike Lawler installs the PALMS (Particle Analysis by Laser Mass Spectrometry) instrument into the nose of the WB-57. Photo: Chelsea Thompson, NOAA

Atmospheric measurements were also made by Cziczo and his group from an ER-2 aircraft over the continental United States. By flying those instruments only the freshest, most undisturbed air is sampled.

“We are finding this human-made material in what we consider a pristine area of the atmosphere,” said Cziczo in a Purdue statement. “And if something is changing in the stratosphere — this stable region of the atmosphere — that deserves a closer look.”

Meteorite smoke

Over the years, one response to early thinking about human-made clutter “burning up” in the Earth’s atmosphere was flagging the load of meteoritic material already saturating our biosphere.

“Shooting stars streak through the atmosphere,” Cziczo said. “Often, the meteor burns up in the atmosphere and doesn’t even become a meteorite and reach the planet. So the material it was made from stays in the atmosphere in the form of ions. They form very hot gas, which starts to cool and condense as molecules and fall into the stratosphere. The molecules find each other and knit together and form what we call meteorite smoke.”

Falcon 9 booster topped with sixty Starlink satellites.
Credit: SpaceX


Chemical fingerprint

Purdue’s Cziczo adds, however, that scientists recently started noticing that the chemical fingerprint of these meteoritic particles was starting to change.

That prompted researchers to ask: ‘Well, what changed?’ because meteorite composition hasn’t changed. But the number of spacecraft has, Cziczo responds.

According to the published paper: “The space industry has entered an era of rapid growth. With tens of thousands of small satellites planned for low Earth orbit, that increased mass will be divided into many more reentry events. Given that 10% of stratospheric particles now contain enhanced aluminum, with many more reentry events, it is likely that in the next few decades, the percentage of stratospheric sulfuric acid particles that contain aluminum and other metals from satellite reentry will be comparable to the roughly 50% that now contain meteoric metals.”


What next?

As pointed out in the Purdue statement, there’s an estimate floating about that as many as 50,000 more satellites may reach orbit by 2030.

Space debris plunges to Earth, burning its way through the atmosphere.
Image credit: The Aerospace Corporation

The NOAA research team calculates that in the next few decades, up to half of stratospheric sulfuric acid particles would contain metals from reentry.

But what impact that could have on the atmosphere, the ozone layer and life on Earth is yet to be evaluated.

“Changes to the atmosphere can be difficult to study and complex to understand,” Cziczo said. “But what this research shows us is that the impact of human occupation and human spaceflight on the planet may be significant — perhaps more significant than we have yet imagined. Understanding our planet is one of the most urgent research priorities there is.”

This newly published research in PNAS – found at: https://doi.org/10.1073/pnas.2313374120 — was supported by National Oceanic and Atmospheric Administration climate funding and NOAA’s Earth’s Radiation Budget Initiative and NOAA’s Chemical Sciences Laboratory. This work also involved NASA grant money, as well as grant money from the UK Natural Environment Research Council.

Bottom line – more work to be done. What next? And how best to perform those studies?

Bottom line (2) – watch this space.

Taking the fall. Space hardware dives into Earth’s atmosphere with some fragments making their way to the ground.
Image credit: ESA/D.Ducros

Leave a Reply