In October, Israel-US startup Stardust Solutions announced it had raised $60 million, the largest-ever fundraising round for tech designed to keep the Earth cool by literally dimming the Sun.

The concept, dubbed solar geoengineering, is deceptively simple: by spraying tiny aerosol particles into our planet’s atmosphere, essentially mimicking the effects of a volcano eruption, we could combat the effects of global warming by subtly shading the surface below.

The idea is also incredibly controversial, with scientists calling it reckless and pointing out that the long-term consequences remain unknown. Then there are glaring questions over governance: who gets to say where the particles are released and by whom? And who’s responsible if something were to go wrong?

Now, as The Atlantic reports, Stardust is gearing up to release two documents seemingly intended to keep the hype train trundling along: its guiding principles and a 14-page framework — neither of which divulge any more information regarding the unique particle it’s been been working on.

As Stardust Solutions CEO and former top Israeli government physicist Yanai Yedvab told Heatmap News last year, the company was developing a “scalable or realistic particle that we know from the start how to produce at scale in the millions of tons” and at a relatively low cost, while also being “as safe as, say, flour.”

The environmental effects of a huge amount of sulfate aerosols in the atmosphere are already well understood, since that’s what occurs when a volcano erupts, triggering acid rain and depleting the Earth’s protective ozone layer.

Stardust aims to find an alternative particle that avoids these harmful consequences. But what this particle actually is remains unclear, as the company doesn’t touch upon the topic in its newly-released documents. Yedvab told The Atlantic that the firm aims to unveil its offering “in the coming months.”

Those gaping questions have environmental researchers uneasy, particularly considering Stardust is a private entity that’s looking to sell its proprietary tech to governments or international bodies.

“None of us knows what they are hoping to put into the stratosphere — for a profit,” Center for Future Generations senior fellow and geoengineering expert Cynthia Scharf told The Atlantic.

Scharf also criticized Stardust’s guiding principles, claiming the documents “repeat blithe paeans to transparency, safety, and informed governance.”

The company does have certain reasons to be cautious in its approach. Previous geoengineering experiments have caused uproar in the scientific community. In 2023, for instance, Mexico banned the practice after a startup released small amounts of sulfur dioxide particles into the stratosphere via weather balloons. Another Harvard University-led geoengineering experiment was shut down before it even started in 2021.

While Yedvab assured The Atlantic that the company is looking to be regulated, it’s still entirely unclear what kind of regulatory body — and where it would be located — would be in charge of such a venture.

“We expect and hope that governments will come together in a few years to allow international decision making on [solar-radiation modification], much as they did with the Montreal Protocol,” he said, referring to the 1987 treaty that ratified the phase out ozone-depleting substances.

He also offered a convenient sense of urgency: that it could be a matter of life and death if we don’t act now.

“We want to make sure our children will live in a world where they don’t suffer the horrors of climate change,” Yedvab told The Atlantic. “While this is not the only tool and we should have the full portfolio, I think it’s a unique tool that enables you to hold both sides at once.”

More on the startup: Startup Raises $60 Million to Artificially Cool the Planet