What does a comet smell like?

Rosetta has managed to sniff the comet 67P and scientists, like Matt Taylor, have reconstructed what it smells like! Graihagh Jackson went along to give it the sniff test...

Matt - So my name's Matt Taylor. I work for the European Space Agency on the Rosetta mission that's gone to a comet and is still there until September. Was that OK?

Graihagh - That's wonderful. Tell me about the Rosetta mission, what did it set out to do?

Matt - Rosetta is a mission to a comet. It set out in 2004, took ten years to get to its target comet and why do we go to comets? We go to comets because we consider them to be representative of the building blocks of the solar system. So, by studying a comet, you get an idea of what the conditions were, what the material that went into building the solar system. In fact, there's material that we found from the comet by Rosetta that actually predates the Sun. So it's really the primordial soup, the ingredients for that soup, and we get a picture of it by looking at this comet.

We sent the spacecraft up in 2004, it chased down the comet over ten years. In 2014, we turned the spacecraft back on because we'd had the time period where we were in hibernation, we caught the comet, we landed on the comet with Philae and, for the last two years, we've been orbiting the comet and measuring various things on the comet. Looking at it's surface structure and how it evolves in time because a comet is really interesting in that when it goes past the Sun it becomes very active. There's a lot of ice inside it that throws of tons of gas and that heats when you get near the Sun, and then starts to drop off and move away from the Sun.

With Rosetta we've sat next to it all this time observing how that stuff evolves, what the surface does, the surface changes. We think about a metre of the surface disappeared in the time that we've been at the comet with Rosetta, and so that's why we're here talking about Rosetta.

It's actually coming to an end. By September this year we're running low on power, data volume as well. Getting the data down from the spacecraft, it takes over half an hour for the signal to come from the spacecraft. It's a time to say goodbye to Rosetta and that's in September.

And we're going to say goodbye by doing something we've always wanted to do, and always try to do, is get as close as possible to the comet. And we will do that, and we have done that by saying to the engineers we want to crash onto the comet and that enables you to get as close as possible. And so that's what we do and September 30th is when we will say goodbye to Rosetta by crashing into the comet.

Graihagh - Sounds like a sad day?

Matt - I think it's going to be a day of mixed emotions. I know, talking to some colleagues who work on the operations solidly, the ones who drive the spacecraft, that's the end of the mission for them. That's really it, that's it, the end of!

But for us that work on the science side, it's actually the beginning. It's when, although we have been doing science already, it's when you only have time to do science. And that's when we'll be doing the big leaps and bounds and the breakthroughs with Rosetta when we have all that time to do the science, and there's decades of work to do on this data.

Graihagh - I've heard something rather intriguing in that you've done something here where I can sniff the comet 67P?

Matt - Yes. There is a number of, how can I put it, aromatic compounds on the comet that we thought would be really nice to engage people with by saying, this is the stuff. You can visually see the tail and everything but you can't see the gas, but you can smell the gas. And we have a mass spectrometer on both Philae and also the orbiter Rosetta. The one on Rosetta has picked up some fantastic stuff; sulphite compounds, rotten eggs, ammonia are stable so you can imagine what this comet smells like but we thought it would be best to provide a 'scratch and sniff' version for people to enjoy and there have been various reactions from 'it's not that bad' to the 'is it a perfume?' to a child was nearly vomiting on the monitor earlier on... so yes. It stinks basically!

Graihagh - Are you going to show me?

Matt - Yes...

Graihagh - I can smell something perfumed.

Matt - It's perfumy isn't it, yes? But, I mean, the thing is somebody's was saying it's got incense. This one's actually not as bad - maybe I'm used to it now! But, as I say, it's got hydrogen sulphide, ammonia, formaldehyde, methanol. We've also detected on the comet things like hydrogen cyanide but then you wouldn't want to put that on there because you'd sniff (04.23) and then pass out and and probably die.

Graihagh - Let give it another sniff...

Matt - Well somebody was saying incense as well.

Graihagh - it does smell a little bit like frankincense. What I'd imagine going into a meditation shop or something.

Matt - Some kind of hippie head shop, as they're known in the US. I still get mothballs so it still smells like 'a Nan' basically. The comet smells like 'a Nan' so I'll go generic.

Graihagh - So, other than getting a whiff of what 67P smells like, what's the best outcome here? I mean surely we're not going to unpick the entire origins of our universe and solar system?

Matt - Well, with Rosetta we are starting to do that. Really what we've got from Rosetta by spending the two years there by landing with Philae. And adding all of this stuff together, we're just starting to scratch on the surface of the capability of the data from this mission to the extent that we think we have identified primordial building blocks in the comet that are, actually, probably, common with other comets, that we can say we know how comets were made now. And that's quite a big result and the implications there lay in with the general solar system evolution

So that's what we have to look forward to. I wouldn't say we've solved everything but we've done a good job and there's a lot still to do and I'm pretty excited by the science that's going to come out in the next couple of years with Rosetta.