The Rosetta spacecraft and its comet are about to hit a major milestone

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: 

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Here is a selfie of the Rosetta spacecraft in orbit around Comet 67P, shown in the background. Rosetta was launched in 2004 and spent 10 years in space catching up to the comet. When it arrived, scientists were shocked by the space rock's bizarre double-lobed shape.

Here you can see jets that the comet is ejecting as ice turns to a gas in the vacuum of outer space. Comet 67P is expected to get more active as it approaches the sun with increasingly more jets spewing off the surface.

This is the first picture that the camera on Rosetta took of Comet 67P after starting to orbit it on August 6, 2014. The spacecraft is about 60 miles above the comet's surface in this brilliant shot.

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