Humans have launched so much to space that it's actually polluting Earth's atmosphere, a new study found

• Scientists have discovered evidence of various pollutant metals in Earth's stratosphere.
• They traced the metals back to rockets and satellites launched into space.

Earth's atmosphere is changing — potentially for the worse.

A team of researchers has found pollutant metals in Earth's stratosphere — the second layer of our atmosphere — and traced them back to rockets and satellites.

"There are so many rockets going up and coming back and so many satellites falling back through the atmosphere that it's starting to show up in the stratosphere as these aerosol particles," Dan Cziczo, one of the scientists behind a new study detailing the team's findings, said in a statement from Purdue University.

Why it could be a serious problem

Changes to the stratosphere are concerning since it's home to our planet's ozone layer, which protects all life from deadly solar radiation. And humans have already damaged the ozone once before.

So far, it's unclear how these metals are changing the stratosphere's chemistry. The researchers just know that they are.

The team found evidence of aluminum, lithium, copper, and lead, which likely came from rockets and satellites re-entering Earth's atmosphere, the researchers report in their study published Monday in the Proceedings of the National Academy of Sciences.

When anything enters Earth's atmosphere, it's typically in a fiery blaze. In the case of rockets and satellites, all that heat can strip metals off the spacecraft, which end up lingering in the stratosphere.

"What this research shows us is that the impact of human occupation and human spaceflight on the planet may be significant — perhaps more significant than we have yet imagined," Cziczo said in the statement.

An estimated 58,000 more satellites may reach orbit in the next seven years — meaning that as much as 50% of the stratosphere could contain metals from reentry over the next few decades.