update: CNN's November 7, 2023 Japanese scientists want to send a wooden satellite into space links to October 16, 2023 NOAA scientists link exotic metal particles in the upper atmosphere to rockets, satellites

“Two of the most surprising elements we saw in these particles were niobium and hafnium,” said Chemical Sciences Laboratory research chemist Daniel Murphy, who led a team including scientists from CIRES, Purdue and the University of Leeds. “These are both rare elements that are not expected in the stratosphere. It was a mystery as to where these metals are coming from and how they’re ending up there.”


While Murphy and his coauthors estimate that 10% of stratospheric sulfuric acid particles currently contain traces of metals from rockets and satellites, they say that could grow to 50% or more based on the number of satellites being launched into low-earth orbit, and efforts to eliminate space debris at end-of-life by directing it into the atmosphere to burn up.

“There will be a lot of work to understand the implications of these novel metals in the stratosphere,” Murphy said.

As of October 4, the tracking website Orbiting Now lists 8,697 satellites currently in orbit, 7,892 of which are in low Earth orbit and are destined to burn up on reentry.

“At 10%, the current fraction of stratospheric aerosol with metal cores is not large.” said co-author Martin Ross of The Aerospace Corporation. “But over 5,000 satellites have been launched in the past five years. Most of them will come back in the next five, and we need to know how that might further affect stratospheric aerosols.”

Credit: Chelsea Thompson/NOAA

Credit: Chelsea Thompson/NOAA

This in turn links to the published results in October 16, 2023 PNAS: Metals from spacecraft reentry in stratospheric aerosol particles

Weighing 2.9 tons... this heap of old batteries is now the heaviest single piece of garbage to be jettisoned from the International Space Station.

begins Gizmodo's ISS Ditches 2.9-Ton Pallet of Batteries, Creating Its Most Massive Piece of Space Trash

Digital Trends' What was inside the space station pallet jettisoned into space on Thursday says:

On Thursday, March 11, mission controllers in Houston commanded the space station’s Canadarm2 robotic arm to jettison an external pallet containing old nickel-hydrogen batteries into Earth orbit.

The nickel-hydrogen batteries were once used for the ISS’s power system but have since been replaced with newer lithium-ion batteries featuring improved power capacity, smaller size, and lighter mass.

Fortunately, the pallet and the batteries inside it won’t remain as space junk indefinitely (there’s enough of that already orbiting our planet), as the whole lot will burn up when it enters Earth’s atmosphere in several years’ time.

I suppose that it's fortunate for other spacecraft in LEO that they won't stay in orbit for even longer than "several years' time" but without taking any measures to increase drag like attaching some Terminator Tape or equivalent it's still a non-zero risk.

But for those who breathe all that nickel doesn't just go away, it becomes a long term resident of Earth's atmosphere.

Scientific American's Some airborne particles pose more dangers than others; New evidence suggests that breathing nickel and other metals can lead to lung and heart damage, and even death is from 2009, and the science of the effects of PM2.5 and smaller particles on human heath is rapidly evolving.


  1. Considering all of the Nickel Hydrogen that were ever on the ISS that have now all been replaced, what fraction were incinerated in the atmosphere we breathe, and how many total kilograms of nickel does this represent?
  2. Were there any estimates as to what fraction would end up as nickel-containing PM2.5 particles? (the size at which particles tend to remain in our lungs and can sometimes move into the bloodstream and lodge in different organs)


  • 14
    $\begingroup$ Each day, roughly 43.3 (metric) tons of meteoric matter enters the Earth's atmosphere. That material is ~1.72% nickel. So we get ~740 kg of nickel per day from natural sources. (FWIW, there's a fairly wide range of values for the total meteoroid flux on the Net, ranging from 10⁷ to 10⁹ kg/year, but the value I used seems to be the one most frequently used in recent work). $\endgroup$
    – PM 2Ring
    Commented Mar 13, 2021 at 12:13
  • 3
    $\begingroup$ Note that the batteries on ISS were nickel-hydrogen, not nickel-metal-hydride. They contained gaseous hydrogen. $\endgroup$
    – Tristan
    Commented Mar 14, 2021 at 6:04
  • 4
    $\begingroup$ Wait. So let me get this. We're getting Nickelback? No, somebody stop the music :D $\endgroup$
    – user39728
    Commented Mar 15, 2021 at 2:59
  • 4
    $\begingroup$ I actually worked with Nickel in the lab in grad school. The pure metal oxidizes super fast in the atmosphere at high temperatures (e.g., if it's burning like a meteorite). We'll get lots of Nickel oxide, but probably no metallic nickel is my guess. $\endgroup$
    – user39728
    Commented Mar 15, 2021 at 3:02
  • 2
    $\begingroup$ It actually depends on the oxide film that forms. If it were aluminum, the film would block the diffusion of oxygen through the metal, so the oxidation would stop and the rest of the metal would be protected and stay pure. If it were iron, the oxide would form porous scales through which oxygen would diffuse to keep eating away at the iron inside until eventually only iron oxide was left. I think Nickel is more like iron than aluminum, but I don't remember. $\endgroup$
    – user39728
    Commented Mar 15, 2021 at 3:44


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