When is the next mission to Saturn going to be and what would you want to find
out based on this mission that you don't already know?
Don't know when the next mission is going to be
there are some studies being done in the States at the moment and depending
on which scientist you talk to some would like to focus on Titan and Enceledus
I'd like to focus on Saturn but I'm still not quite sure what we
would want to do we need to get the best out of our data you know one of the
things about about datasets is they're a treasure trove of information and
I think we're pushing the data as hard as we can at the moment but there will
be scientists that come and look at it in the future and find new and
interesting things so I'm partial to Saturn at the moment but that's just
because the end of mission has been so spectacular
Well I presume that it's only
every so often that the other planets are aligned who can do this
slingshot out to Saturn
Yes you can you can do really quick slingshots
The Voyager spacecraft, NASA was really fortunate because
all the planets were lined up beautifully so it took it took Voyager
spacecraft rather a short amount of time but you can always, you can
always get out there it's just whether you want to take five years or ten years
Okay, questions, comments please wave wildly because I have
bright lights shining in my eyes
I was wondering, the visible surface
features of Saturn um I think that there is a different rotation at the equator
than at the pole because it's a gas and I would assume that in the metallic
hydrogen interior which is liquid right because that that's how the dynamo
works that would also be rotating differently and that's what's producing
the magnetic fields and all of these things are moving at different speeds so
I guess to what extent can we say that Saturn has one single day when the
period of the equator of the pole the interior and the rock are all different?
Usually when you talk about the rotation rate of a planet
you're talking about the interior rotation rate but yes there are there
are lots of different rotation rates in the atmosphere and Jupiter's the same
you've got different rotation rates in different parts of the atmosphere
Can we infer the rocky rotation which isn't part of the dynamo from
Can we infer the rotation of the rocky bit which is not part of the dynamo from the
liquid part which is?
I think you're pushing it a little
I mean you can use models and
simulations to try and do that but you can never be sure
Hello yes thank you for a wonderful talk that was splendid
Can I ask you a sort of romantic
question about Enceledus? You showed us a slide that said simple organics
and complex organics what does that mean is that is that life or is that amino acids or what?
It's before amino acids so you would need something else to happen to start
the the life process and that's where the length of period of time comes in
having having ingredients is not enough you need you need the process to be
stable enough over time that something can happen.
Thanks for a great talk
you know that other open question as well as the rotation rate was the age of
the rings and can you say something as to what you currently know about being able
to age the rings and knowing whether they're something very recent or
something that's formed over a great deal of time and what physical
principles do you use to determine that
Oh now you're really pushing my knowledge
I think the only thing I remember about well part of the the
F ring part of the ring grating orbit that the science driving that was to try
and get an understanding of the composition of the rings using gravity
to also try and get an understanding of the age and my recollection is they're
younger than people think what that means I don't know but if you
go to the Cassini JPL website sure that there's a there's a write-up
about that it's it's not my field at all so I don't know the details of it I'm afraid
but my understanding is they're younger than ring scientists thought
they were going to be
But not recent
Okay someone in the gallery, is there a
microphone up there
Alright if I shout out?
Could you tell me please what would you say are the possibilities of life on Enceledus?
Do you think that is the mostly likely one, however you would rate that compared to Titan, to Mars?
What are your views on that? What sort of percentages can you think?
I knew I was going to get one of those
It's very difficult to tell
I would be very surprised if there wasn't bacterial life of some kind
somewhere I think the outer moons in the solar system are a good possibility
because we know for example in in some of the deep regions and our Earth's
oceans you can have you can have bacteria forming and conditions where
you really think it's simply not possible. I think for me the real step
change that's happened in the last 50 years or so which has really been
underpinned by the Cassini observations of Enceladus and the desire and the new
missions that are going to Jupiter's moons is the fact that you can have
liquid water at quite big distances from the parent star. People have always
thought that you can only get liquid water on the surfaces of bodies and so
that you know if you're looking at exoplanets you need to look at planets
that are close to the parent star but we've seen with the Jupiter moon
so Ganymede, Europa and Callisto, we think they all have liquid water under the
surface and we seen with Enceladus as well that you've got liquid water you
don't have to be close to the parent star so I think for me that's been the
real change and I didn't answer your question but
that's as far as I'm gonna go
Okay somebody else in the gallery could you shout please
Enceledus is tidally locked. Can you say whether the tiger stripes point towards Saturn or at an angle to it
They're at an angle to the north pole of Enceledus so I think
they're at an angle to Saturn but but that's just based on looking at the
images but yes they sorry you mean the side that's facing Saturn or the side
that's facing away from Saturn is that what you meant?
- Apologies if my question wasn't very good but basically
if you're Saturn and I'm Enceledus and this is the south pole
are the tiger stripes pointing towards you or at a transverse angle to you?
It's at a transverse angle, yep
Over there please, just wait for the microphone
Thank you for a great talk, also I was wondering for the tiger
stripes do you have any idea where they came from like where they asteroids
colliding in or something like that
Don't think so, I think there was
something happening in the in the interior so there was a huge amount of
pressure building and they had and the liquid water and the the water vapor
that was being generated needed to escape, yeah, we think something
similar happens at Europa one of Jupiter's moons but there it's almost
you know when you see images of you Europa it's almost like you know when you
fly over Greenland I don't know if you've ever flown to the States and you
fly over Greenland and you you look out of the plane you see the bits of ice
breaking off from the edge of the ice shelf that's what it looks like on Europa
It's different in Enceladus but but we think we think it was driven
from internal processes
You know how you showed the image of Enceladus the
expected heat map the actual yeah what's it gets all the extra heat from?
That's the million-dollar question
It depends which scientist you talk to everyone has their different ideas with
the easiest solution is that if if a moon orbits around a planet if the orbit
is completely circular then the moon will feel the same gravitational pull
all the way around but if the orbit is not quite circular so in some parts of
the orbit it's closer to the planet than in other parts the gravitational force
is strongest and so that pulls the interior out of
shape and so it keeps it warm it stops it from cooling down and so the easiest
solution is to have the heat source being the orbit around Saturn
That's the easiest way. There are lots of other ways as well but
You mentioned how fantastic it was to work with such an international team, could you tell us
more about the design process how did you coordinate the design of the
spacecraft in the very beginning?
I wasn't involved right in the beginning
I became involved after the instrument was designed and it had just been delivered
but the way it's working on the Jupiter mission where I am involved in the
design and it will be very similar is that you write a proposal to build an
engine well first of all a space agency decides to select a mission to go
somewhere and they then put out a call for instrument ideas and you write a
proposal and you describe the instrument that you would build and the signs that
you would do and you try and get the best team around you so they've got no
choice but to choose you and you then submit the proposal and you go through a
selection process and a selection team will choose the different
instruments and then you get together and you talk
to the space agencies and you say this is what I want to do and they say okay
we've got 12 instruments where are we going to put them we can't get
instruments getting in each other's way
How heavy can they be? How much data
do they need? And that's the processor we're in at the moment for the Jupiter mission
And for me it's really interesting because it's completely
different to planning the science which we will do once the instrument's been built
[INAUDIBLE]
What we did is we knew on Cassini that the 11 meter boom that we
had was perfect because we didn't see changes taking place on the spacecraft I
hope no one from the European Space Agency's here but when we first started
designing the Jupiter instrument we said to the to the space agency that we
really wanted a long boom and they said no you only need a 5 metre boom and so
what we did is we said to them that the size of the field due to the spacecraft
that we can allow they can we can be allowed to see at the end of the boom
was so small that the only way they could do that was give us a 10 point 6
meter boom but don't tell them I said that
Clearly Enceladus is losing a reasonable amount of mass so the whole phenomenon must be transient
Do you have any idea about what sort of magnitude of time it could last for?
No, we're almost certain it was taking place in the early
Oh I should know this - in maybe the mid-1800s because they were observations made from
the earth of something strange when you looked at Saturn and they didn't know
what it wasn't it took a very long time to work out that there was an E ring in
the first place so it's been happening for a long time not not long in that in
the lifetime of the solar system but yeah it can't go on forever but I'm not
going to put an answer to that I'm not going to give you a number from that I
because I don't know it
Okay one last question over there
You mentioned that the initial plan once you arrived at Saturn was to hang around for four years
but clearly you managed a lot longer
so it would seem that somebody put more fuel in this spaceship than was initially required
- You always do -
So to what extend do you build flexibility into the design in the
mission and how politically difficult is it to get an in flight change?
You always put lots of flexibility in, you always over design because it's
not as if if something goes wrong you can't go and tweak something so you need
really robust instruments for example and one of the things that surprises
people is that the type of instruments we fly the they almost look quite old
compared to some of the new gadgets that we have but the reason that you do that
is to be able to fly an instrument on a spacecraft mission you need to show
there at a technology readiness level of nine, so they need to have flown before
so you can't fly a mobile phone to take pictures because it hasn't shown that it
can work before. So you always over design you always have always have redundancy
For us we had two instruments and on each of those instruments you had
extra power supplies and extra bits so that if something went wrong you could
move to another bit but there's always extra fuel but you also learn how to use
that fuel as well you get to know how the instruments on the spacecraft work
But it went on a lot longer than than anyone thought certainly and then the
political question I've forgotten what it was? Oh you've got to persuade the
funding agencies to fund you because you know to be able to operate the
spacecraft and the instruments and do something useful with the data you need
to pay people to do that and so the way that we did it on Cassini is a year
and a half before the nominal end of mission we put a proposal into NASA
to say we wanted more funding and so you need to almost make a new science case every time
Okay so with that I think I will draw things to a conclusion and
just remains for me to thank Michelle for sending is a super postcard from
Saturn so thank you so much