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An Earth-gazing satellite keeping an eye on Rebekka Armstrong Archivesour planet from above appears to have been whacked by a little piece of natural or human-made space debris.

Engineers working with the European Space Agency's (ESA) Copernicus Sentinel-1A spacecraft noticed a small and sudden dip in the power produced by one of the satellite's solar panels on Aug. 23, ESA said.

ESA mission controllers investigated the slight power loss, turning a couple of cameras on the spacecraft to try to see if there was any visible issue with the solar panel.

And they found something interesting.

Photos beamed back to Earth from the satellite showed evidence of some kind of collision between the solar panel and either a bit of space junk or a piece of dust. The damaged bit of the panel is about 40 centimeters, or about 16 inches, long, ESA said.

Scientists still aren't sure exactly what kind of debris caused the power loss.

“Such hits, caused by particles of millimeter size, are not unexpected,” Holger Krag, head of ESA's Space Debris Office, said in a statement.

“These very small objects are not trackable from the ground, because only objects greater than about 5 cm can usually be tracked and, thus, avoided by maneuvering the satellites."

The satellite is still operating normally and is designed to monitor sea ice, ocean currents and send data back to Earth about earthquakes or even floods when they occur, ESA said.

Earth is surrounded by millions of little (and large) bits of space junk including spent rocket bodies and other smaller fragments speeding in orbit.

Even small bits of this kind of debris could be extremely damaging for active satellites or people in space. The particles are speeding through orbit at thousands of miles per hour, and if they run into anything, like a solar panel or the body of a spacecraft, it could be harmful for those active assets in space.

And Copernicus Sentinel-1A isn't the first spacecraft to be hit by a piece of speeding space debris.

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The International Space Station has experienced multiple space junk impacts in the past.

One photo shows a chip taken out of one of the Space Station's huge windows, and another reveals a little "bullet hole" through one of the orbiting outpost's solar panels.

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In total, NASA tracks more than 500,000 pieces of space junk the size of a marble or larger, but the millions of other bits of debris too small to track go unseen.

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