XPost: sci.physics, alt.propaganda.statistics, talk.politics.guns
XPost: alt.fan.rush-limbaugh, sac.politics

https://www.theregister.com/2025/03/11/greenhouse_gases_reduce_satellite_c apacity_paper/?td=keepreading

Earth's atmosphere is shrinking due to climate change and one of the
possible negative impacts is that space junk will stay in orbit for
longer, bonk into other bits of space junk, and make so much mess that low Earth orbits become less useful.

That miserable set of predictions appeared on Monday in a Nature
Sustainability paper titled "Greenhouse gases reduce the satellite
carrying capacity of low Earth orbit."

Penned by two boffins from MIT, and another from the University of
Birmingham, the paper opens with the observation: "Anthropogenic
contributions of greenhouse gases in Earth's atmosphere have been observed
to cause cooling and contraction in the thermosphere."

The thermosphere extends from about 90 km to 500 km above Earth's surface. While conditions in the thermosphere are hellish, it's not a hard vacuum.
NASA describes it as home to "very low density of molecules" compared to
the exosphere's "extremely low density."

Among the molecules found in the thermosphere is carbon dioxide (CO2),
which conducts heat from lower down in the atmosphere then radiates it
outward.

"Thus, increasing concentrations of CO2 inevitably leads to cooling in the upper atmosphere. A consequence of cooling is a contraction of the global thermosphere, leading to reductions in mass density at constant altitude
over time."

That's unwelcome because the very low density of matter in the
thermosphere is still enough to create drag on craft in low Earth orbit û enough that the International Space Station requires regular boosts to
stay in orbit.

It's also enough drag to gradually slow space junk, causing it to descend
into denser parts of the atmosphere where it vaporizes. A less dense thermosphere, the authors warn, means more space junk orbiting for longer
and the possibility of Kessler syndrome instability û space junk bumping
into space junk and breaking it up into smaller pieces until there's so
much space junk some orbits become too dangerous to host satellites.

Which is bad because we're using low Earth orbit a lot these days for
things like broadband satellites.

The paper warns we may need to revisit such plans soon.

"Modelled CO2 emissions scenarios from years 2000-2100 indicate a
potential 50-66 percent reduction in satellite carrying capacity between
the altitudes of 200 and 1,000 km."

The good news is the paper notes that satellite makers know Kessler
syndrome instability is a possibility, so often build collision avoidance capabilities that let them avoid debris.

The authors hope manufacturers and operators work together on many debris- reduction tactics, and that greenhouse gas emissions are reduced to keep
the thermosphere in fine trim. «


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