There are more than 100 million bits of rubbish whizzing around Earth in space.
Japan Aerospace Exploration Agency (JAXA) launched a mission to clear some of it up using a 700m, (2,300 foot) piece of wire.
The plan was to slow down the junk, like bits of old satellites' rockets, and push it into the Earth's atmosphere so it would harmlessly burn up.
But it didn't happen, scientists say the trial run failed as the wire was not actually used.
Leading researcher Koichi Inoue told reporters: "We believe the tether did not get released."
"It is certainly disappointing that we ended the mission without completing one of the main objectives."