The Rosetta Mission Asks: What is a Comet? Scientists attempt to answer these questions and more as the Rosetta Mission's Orbiter arrives and escorts comet 67/p Churyumov Gerasimenko into our inner solar system.


Comets are very noticeable in the evening skies. That made them very special to humanity. For thousands of years people have been fascinated with comets. Sometimes they scared people, and it's just amazing we know so little about them.

The reason it's very it's exciting right now to be talking about comets is there is a mission called Rosetta.

The Rosetta mission is unique. It's gonna rendezvous with a comet for the first time, it's gonna be the first time we escort or ride along side the comet. The cherry on the top of the Rosetta cake is that we deploy a lander onto the surface of the comet itself.

That's what makes Rosetta sexy. To me, the most exciting, the sexiest mission that's out in the solar system today.

People ask, why do you care about comets? There are uncountable numbers of them in our solar system.

Most of them have been kept in cold storage very far from the sun since the beginning.

Comets are like a time capsule to the early phases of the solar system.

There's information that was trapped from 4.6 billion years ago.

Comets jet in from the outer reaches of the solar system.

When the comet comes close to the sun, it heats up, it's subjected to solar wind.

They have these enormous - what we call - tails stretching across the sky. The main part of the comet is the nucleus. It's a small ball of ice and dust and the coma is the atmosphere around it.

And then the tail extends out back from the coma.

Why are we so interested in comets? We wanna know how our solar system formed.

We wanna know if this water that you're drinking every day wasn't brought by billions and billions of comets at some point.

And we wanna know if your own body is made by this material that was originally brought by comets to Earth.

NASA Jet Propulsion Laboratory, California Institute of Technology

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