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The Rosetta Mission – Part 2


Rosetta for me, scientifically, is the whole package

On choosing a comet

With Rosetta, we were going to go to a comet, now we had to select a particular comet, and there are a particular class of comets called periodic comets.  Comet Halley was the first periodic comet that was discovered. Basically, we can reproduce its orbit over years, we know its going to come back over a certain amount of time, so we were looking at that class of comets, in particular shorter period comets because we don’t want something that has an 80 year period going round the sun because if we miss something, everything goes offline in terms of our production of the spacecraft, it’s going to throw us off completely, so we were focusing more on shorter period comets.  Now in 2003 we were due to launch and there was a problem with the rocket with another launch and that delayed us, we were originally going to another comet called Wirtanen and as soon as there was a delay in the launch that meant we had to scrub that particular comet because, although it was something like a five year period around the sun, matching the launch to the trajectory of the comet with a delay meant that it was a no go. So Churyumov–Gerasimenko, the comet that we’ve gone to, was the choice because it was the closest to the Wirtanen in a way, it meant that we didn’t have to change very much on the spacecraft, because if one can imagine that in 2003, when we were about to launch, we changed everything at that point, everything is built near enough so you can’t go back and suddenly change the size of the solar panels, it just takes too much, you know, you can’t modify too much once it’s built, so we were constrained by the capability of the spacecraft and the lander to choose where we should be going, and that’s where 67P Churyumov-Gerasimenko came, because of that.

On the human connection to this mission

There’s something about Rosetta that enabled people to connect with it; I’d describe it as sexy once we started talking about the mission, and what I meant by that was it had all these many facets that people were attracted to it by: it was sexy science, it was exploration, it was technologically challenging, there was drama involved, all of those entities added together, it was something that drew people towards it.  And then when you go through the new change, the new style of ESA’s communication as well, the European Space Agency made a big effort in changing the way they did communication, they basically threw out the old way of doing things which was very dusty and stuff and did something new, the cartoons that were then developed off the back of the mission, which I think are a fantastic vehicle in particular for children of all ages from four up to eighty, it works very well in just portraying what we’re doing with the mission and there is that connection, that personality of the spacecraft and that wonderment of exploration that you’re riding alongside, and that connection with everyone that you can follow what’s going on with the mission.  And, yes, on each of the operational events, in particular the landing, you have that connection with Philae as its going down that its there, its now on the surface of this alien body and I think the same was done for previous missions in some way, so with the Huygens lander but also what was done with Beagle 2 as well, Colin Pillinger did a great job in highlighting the fact that we had this fantastic opportunity scientifically, but also there was a connection there saying, there’s this probe that we’re going to put on an alien planet, we did this, humans did this.

On the mission’s findings

Rosetta for me, scientifically, is the whole package, we have to look at the entire journey that Rosetta has undergone in terms of when it’s been close to the comet; when it came out of hibernation the comet was going towards the sun, in August this year, 2015, we were at perihelion, when the comet was closest to the sun and then it moved away again.  So that is the key for me with the science, that a lot of the really great science will come out of once we’ve got all of that data and can compare and contrast the in and the out paths to see how the comet is actually interacting, how it works.  Up to now though we’ve had some fantastic results in terms of the age of the comet, the structure of the comet, how it got that fantastic shape, that was one of the biggest…I wouldn’t say shocks, it was a surprise to have this wonderful duck-shaped object, by studying the surface and showing that it has a particular layered structure, we were able to show that…if you imagine two onions colliding from the structure we see that it looks like two onions have collided, so immediately you say it’s not a single entity that was eroded, if you think if it was that, if you again compare it to an onion, that it’s got layers, we showed that it’s got layers, if it was a single entity that it had been eroded it would be like an onion with bite marks out of it, but it doesn’t look like that, it looks like two onions that have smacked together, so that’s for me a fundamental result that we’ve had in terms of where this thing came from and that feeds into our understanding of general dynamics in the outer solar system. 

Some of the chemical entities that we’ve found on the object match what we consider to be viable from a comet. The key thing is comets are considered to have - and we have discovered - all of the building blocks of life.  Now this is key to point out, the comet does not have life on it, there is no evidence of that, it has though the building blocks, it has things that are considered or things that are parts of sugar,  which are fundamental blocks to build up DNA, for instance. We have seen proteins on previous comets, and that’s what we’re studying at the moment, looking to hone the signals and get it out of the signals that we have with Rosetta whether we’re seeing those entities as well, so it’s all the stuff that can build up towards life, and that’s key in connecting why we look at comets, they are the leftovers, the debris of the origin the solar system.   So at the beginning of the solar system there was a massive cloud of dust and gas.  At that stage we look at the comets as being leftover from that, they were the ingredients that went in to build the solar system. So if all the ingredients were reasonably equal, what makes Earth so special, what was the dynamic process that we underwent to be where we are today?  Why is water on the Earth?  How did it get delivered? What is so special about Earth? And you do that by looking at raw ingredients, and that’s what you get from the comets.

On setting mission goals

We started the mission with a set of clear goals which were quite high level in terms of, you know, one of them being studying comets to connect with the origin of the solar system, but you look at the comet, one of the other goals was to see how activity works, how cometary activity…what makes the ice on the surface suddenly turn into gas and then lift off and draw dust and other material off the surface of the comet. Now we have our ideas about that, we have observations from previous missions, but being there for a long time meant that we were able to observe this over time and see how that interaction works.  Of course, we had those clear goals, we’ve answered some of them, some of the first measurements we wanted to make were of the different flavours of water that are coming off of the comet, which would give us an indication of where the comet came from and its place in the solar system’s evolution.  But the same as with any time you go and measure something, you have to change your ideas and you discover something that’s not as expected, and as always we have many more questions now that we’re there, and that’s what science is all about and that’s what makes it exciting and interesting that we now are saying, well, what we proposed or what we had considered previously is actually a bit off and now why is that, and then you fork off in another direction because you’ve got a whole new are of science that you have to investigate based on what we’re seeing with Rosetta now. 

- Dr Matt Taylor