The Rosetta Spacecraft has been in orbit around the comet 67P churyumov-gerasimenko (aka comet C-G) since August of 2014. Since then we have learned a lot about the comet like its odd shape and the composition of the comet. During this trip the mission also sent down the land known as Philae but shortly lost contact with the lander after it reached the comet. Although the lander has lost communication the mission has learned something very important about this comet.
One of the reasons we are so interested in Comets in the first place is because it is a look back to the origins of our solar system and the planet that we live on. We are getting a better picture of how the solar system formed by investigating these objects that have mostly been untouched and changed since the early times of our solar system. One of the things that we wanted to learn about comets is the water that is on the comet. We know that there is frozen water that helps make up comets in our solar system but we want to know if that water is the same as the water on earth. The reason we want to figure this out is because we do not know exactly where earths water came from. One of the theories is that the water came from comet impacts during the early ages of our solar system.
The way that they find out if the water is the same type of water is by a test of the Deuterium/Hydrogen Ratio in the water. This ratio is just looking at two different types of water molecules one of which is the regular H2O that we were all taught in school but Deuterium is the same composition but it just has an extra Neutron on the hydrogen atom which some call a heavier version of water. By looking at the ratio of the mixture of these two versions of water you can think of it as a signature and by comparing the water on the comet and earth we can find out if that water is the where earths water came from.
Unfortunately the water that they found on the comet did not match the water found on earth but the great thing about it is the theory isn’t dead yet. There are many different comets out there from many different locations and maybe one day if we keep looking we may find the source of earths water.
ESA made a short video about this topic below: