JOHN YANG: Earlier this week, the latest entry in the new race for space commerce lifted off from the Kennedy Space Center.

If all goes well, it would be the first ever private spacecraft to land on the moon.

According to data from the United Nations Office for Outer Space Affairs, 2023 was a record year for launching satellites, probes, landers and other objects into space.

But scientists worry that those plumes of exhaust that trail rockets arcing into the skies could be scattering harmful pollutants into the pristine upper layers of the Earth's atmosphere.

Freelance science journalist Shannon Hall recently wrote about this new era of space pollution in the New York Times.

Shannon what's in this rocket exhaust and why are some scientists concerned about it?

SHANNON HALL, Freelance Science Journalist: That is a great question right now.

Rocket exhaust has black carbon in it, and scientists are very concerned that black carbon, which is black, will absorbs the sun's radiation and heat the atmosphere.

Specifically, they're worried that it's going to heat the stratosphere.

We care about the stratosphere tremendously because it is home to the ozone layer, which protects us from the sun's harmful radiation.

So if we're increasing the number of rocket launches, we could actually increase the risk of skin cancer, cataracts, and immune disorders here on ground because we have harmed the ozone layer.

JOHN YANG: Were there concerns about.

I think you said this in this article.

At one point, there were concerns about a hole being over the Kennedy Space Center.

But what happened?

What did they find about that?

SHANNON HALL: We did worry about that at the beginning of the space shuttle era.

We actually found that there weren't enough rocket launches at the time to really create a cataclysmic issue.

The ozone hole disappeared relatively quickly.

The same might not be true going forward as we just launch more and more rockets into orbit.

JOHN YANG: And also for more and more sites.

Is that a concern as well?

SHANNON HALL: It is a concern, yes.

We are just going to be seeing a tremendous increase in the number of rocket launches from multiple sites across the globe, as various government agencies and private agencies as well join in this new space race.

JOHN YANG: Now, this concern about the black soot heating up the stratosphere, is this something that research has shown, or is this, I don't want to say speculation, but sort of a theory theorizing this could happen?

SHANNON HILL: That's a great question because the research is really just now catching up to the speed of the space race.

But there have been a number of studies in recent years.

One study showed that rocket emission is 500 times better at heating the stratosphere than aviation, for example.

Another study published in 2022 found that if we increase the number of rocket launches by just a factor of 10, we could warm the stratosphere by as much as two degrees Celsius in various places, and that would degrade the ozone layer over much of North America, all of Europe, and a good chunk of Asia as well.

So we are starting to see evidence that this could drastically harm the stratosphere.

JOHN YANG: Does anyone regulate the exhaust coming out of these rockets, either in the United States or anywhere in the world?

SHANNON HALL: No.

I spoke with a number of sources who actually compared this to the Wild West.

There are no regulations with respect to atmospheric pollution from rocket exhaust right now.

JOHN YANG: What are the potential solutions, people looking at?

Is there such a thing as green rocket fuel?

SHANNON HALL: That's a great question.

There really is no such thing as green rocket fuel, because even if were to change from hydrocarbon fuel, which is what we're using now, to say something that emitted.

Water is actually a greenhouse gas at these upper layers of the atmosphere.

So no matter what, we are likely going to cause harm on the environment.

But we can certainly tweak how much harm is caused.

That is the ultimate hope.

JOHN YANG: And tweak it.

How?

How would they do that?

SHANNON HALL: So scientists are hopeful that they can do the research to know how many rocket launches will be too many, know what types of fuel to use, know what types of materials to use, so that we don't cause quite as much harm on the environment.

But again, this is really just an open question right now.

Scientists are at the beginning stages of their research to try to understand where we are and what the future might look like.

JOHN YANG: Now, there's also an issue about old satellites sort of falling out of orbit and disintegrating as they come into the Earth's atmosphere.

What's the issue there?

What's the concern there?

SHANNON HALL: Yeah.

So the issue is that what goes up must come down.

Right.

These satellites are actually designed to fall back to the Earth after five to 15 years.

We do that so that we don't leave them in orbit.

That creates a space junk problem, a different story.

And we don't want them to impact the Earth.

Right.

We don't want to cause a hazard to life here on Earth.

So they're designed to fall back to the Earth and disintegrate in the atmosphere.

And scientists don't know what impact that's going to have on the atmosphere yet, but if they're disintegrating, they're going to leave a stream of pollutants in their wake.

And one study, a NASA study last year actually took a jet up into the stratosphere and sampled the most common particles in the stratosphere.

And they found that within 10 percent of those particles were pollutants from these disintegrating satellites.

Now, 10 percent might not sound like a lot, but given that we're at the very beginning of this new satellite race, that was actually pretty alarming.

JOHAN YANG: Freelance science journalist Shannon Hall.

Thank you very much.

SHANNON HALL: Thank you.