Rosetta and its comet are getting close to a major milestone - here's what we know about the mission so far

There are more than 4,000 known comets in the solar system, but there's one we understand more than the rest, thanks to the European Space Agency's ongoing Rosetta mission.

Right now, the Rosetta mission has a satellite in orbit around Comet 67P/Churyumov-Gerasimenko as well as a lander on its surface.

And this August the mission will hit a major milestone when the comet passes closest to the sun. This will be the first time a spacecraft and probe have been this close to a comet during its closest approach to the sun.

Here's a recap of the heroic mission, what it has taught us so far, and what we still hope to learn: