Scientists warming up to Moon dust, Earth’s proposed sun shield, is not cool

Dusting off a controversial approach to fighting climate change, new research proposes firing lunar dust into space.

Updated Feb 21, 2023 | 04:25 PM IST

Artist's illustration of dust on the Moon's surface | Credit: NASA

  • A group of researchers believes Moon dust launched into space could help decelerate global warming.
  • The lunar dust moonshot is the latest in a series of sci-fi-esque, if controversial proposals.
  • Climate scientists argue that it could have catastrophic consequences for the planet.
In a radical addition to last-ditch climate crisis solutions, three astrophysicists have proposed shooting Moon dust into the space between Earth and the Sun as a way to shield solar radiation if all goes to hell, according to a University of Utah-led study published in the peer-reviewed journal PLOS .
Researchers reckon sunlight could be dimmed by 1.8% — which is equivalent to obscuring our local star six days in a year— if we “ballistically eject dust grains [mined] from the Moon ’s surface” towards a point in space called the first Lagrange point (L1).
Between any two orbital bodies — in this case Earth and the Sun — there are five Lagrangian Points where the gravitational forces effectively balance out, allowing objects like satellites to stay in place. The Earth-Sun L1 is a location about 1.5 km sunwards into Earth's orbit, where introducing a lunar debris sunscreen could help reduce temperatures back home.
The idea — admittedly not the most outlandish solar geoengineering enterprise ever conceived by scientists — is to let Moon dust linger in outer space long enough for it to slow global warming down and to replenish the blanket of lunar regolith when it runs out.

Stratospheric aerosol injection (SAI), one of the most researched solar geoengieering approaches, is a theoretical proposal to spray tiny reflective particles into the stratosphere to reflect sunlight back into space and cool the planet | Pexels

Space mirrors, marine cloud brightening and stratospheric aerosol injection (SAI) are some well-studied, sci-fi-esque solutions that have previously captured the fascination of researchers and policymakers — some of whom are eerily warming up to sunlight reflection.

More trouble than it's worth

Experts believe this approach, at best, is a last resort and, at worst, a “high-stakes gamble” — given its unintended and potentially catastrophic consequences already known to us.
In her 2014 book "This Changes Everything: Capitalism vs. the Climate", Canadian activist and firebrand author, Naomi Klein wrote: “The far more troubling problem with this [technological intervention] approach is that rather than challenging the warped values fueling both disaster denialism and disaster capitalism, it actively reinforces those values."
“Nuclear power and geoengineering are not solutions to the ecological crisis; they are a doubling down on exactly the kind of reckless, short-term thinking that got us into this mess. Just as we spewed greenhouse gases into the atmosphere thinking that tomorrow would never come, both of these hugely high-risk technologies would create even more dangerous forms of waste, and neither has a discernible exit strategy."

- Naomi Klein, This Changes Everything: Capitalism vs. the Climate

There is a fundamental problem with sun-blocking: Not only does it breed further political inertia by creating the illusion that Moon dust would buy Earth more time in its fight against climate change , but the solution also falls short of mitigating carbon emissions — its underlying cause and intensifier.
For all its cooling properties, studies have found that this so-called “Solar Radiation Management” fix is of little comfort to our fragile marine ecosystems that would still be under increasing pressure from threats like ocean acidification — the reduction in pH directly linked to coral bleaching — and ocean warming.

The case against solar geoengineering

Last year, a group of 380 scientists signed an open letter asking world leaders to pledge against the moonshot proposal, citing the enormous risk that comes with an underwhelming increase in albedo — the ratio of sunlight reflected by a planet to the incoming solar radiation.
When interviewed about the research, eminent climate scientist at the University of Pennsylvania, Dr. Michael E. Mann told The Hill that while blocking sunlight would most likely achieve cooling, it could “manipulate our planetary environment in deep and fundamental ways.”
“[The proposed] efforts to offset carbon dioxide-caused warming with sunlight reduction would yield a very different climate, perhaps one unlike any seen before in Earth’s history, with massive shifts in atmospheric circulation and rainfall patterns and possible worsening of droughts,” he explained.

- Michael E. Mann

Political Pandora’s box

Mining expeditions on the lunar surface, let alone the proposal of shooting Moon dust off into space, would be an inextricable web of bureaucracy — thanks to contradictory space policies.
The 1967 Outer Space Treaty recognises extraterrestrial resources as global commons, prohibiting the "appropriation" of any region of space.
Two of its depositories, the United States (USA) and Russia, have conveniently held back from signing the 1979 Moon Treat, which forbids the use of lunar material for non-scientific purposes.
Then there's NASA's Artemis Accords , that grant extraction rights to private entities, and are not signed by Russia and China.

No substitute for decarbonisation

The most alarming argument against geo-engineering and —by extension — Moon dust mining, is that it will disincentivise climate change mitigation efforts.
Coupled with non-binding national commitments to limit global warming to 1.5° C by 2100, this plays into the hands of the corporate-political collusion complicit in pushing policies that continue to undermine climate action and reinforce the delusion that technology will save us — except that we'd have long been incinerated if things stay business-as-usual.
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