Rosetta’s little lander Philae has made all the headlines. But, Rosetta’s mission for studying Comet 67P/Churyumov-Gerasimenko has only just begun. Yesterday, the European Space Agency announced the first major results from the Rosetta spacecraft. Water vapor measurements from the comet.

Water vapor from the comet is “significantly different” than water found on earth according to the ESA. Why is this important?

There’s two main theories that explain the water on Earth. One of them centers around collisions from comets and asteroids. How much water came from comets versus asteroids and vice versa is still hotly debated to this day. And, Rosetta’s latest findings does little to solve the debate.

Figuring out if water from a comet or asteroid could have created Earth’s water involves looking at the proportion of deuterium (a type of hydrogen that has an extra neutron) and normal hydrogen.

The image below shows how much the deuterium to hydrogen proportion differs between Comet 67P and Earth. It also shows how asteroids contain water extremely similar, if not the same, as the water on Earth. The problem is that asteroids have little water on them compared to comets. It would have taken tons of asteroid impacts to form the Earth’s oceans. But, the water is similar to Earth and asteroids can’t be discounted as the source.

DH ratio

The finding did surprise ESA researchers who thought the deuterium-to-hydrogen proportion would be more similar to fellow Jupiter-family comet – Comet Hartley 2. Instead it’s D/H ratio was more than three times greater than Hartley 2.

“This surprising finding could indicate a diverse origin for the Jupiter-family comets – perhaps they formed over a wider range of distances in the young Solar System than we previously thought,” says Kathrin Altwegg, principal investigator for ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis).

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“Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth’s oceans.”

It is strange scientists haven’t been able to find many comets with similar water to Earth. Then again, we’ve only studied about a dozen. Same goes for asteroids.

What does this mean? More incredible, breathtaking missions to comets and asteroids.

I’m glad they didn’t find concrete answers. The past few months of the Rosetta mission and Philae lander have been awesome to watch. I want to see more of these missions attempted.

Image credits: ESA

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