It has the biggest volcanic plumes that we know of with exotic
sulphurous compositions, the highest temperature lavas that
we've detected.
It's as hot as 1800 degrees kelvin, so Io wins lots of awards
for being extreme.
Some of us love Io just for its own sake. But it's also a
laboratory for understanding other planets, especially the terrestrial
planets very early in their history, when they were hotter,
they had more heat.
This was a time when life first formed, when plate tectonics
was getting going. In many ways studying very early
Earth is like studying another planet.
Understanding Io might teach us something fundamental, like to
understand that type of volcanic eruption without having one happen
on Earth today.
That would be unfortunate for all of us living here.
Io that's happening today.
Very high effusion rate volcanism, more active than the most active
volcanoes we usually have on Earth, and it changes our whole
view of how planets work.
For terrestrial planets, like the Earth and Moon, our thinking is
that it's kind of like the lifetime of a human being. When you're
young, you're energetic and active and then you get more quiescent and
more and more quiescent, then you die.
Boring! Well, these outer planet satellites are much more like the
Hindu life cycle, where you can be reborn and go through all sorts of
cycles of activity.
So very different concept of how planets work.
We have no shortage of all of unanswered questions and mysteries
throughout the Solar System and beyond.
Io is a little bit larger than Earth's Moon.
It's one of four large moons of Jupiter.
It's the innermost of the four large moons, and three of these
moons are in a residence.
So every time Ganymede orbits Jupiter once, Europa orbits twice
and Io orbits four times.
This means that the distance to massive Jupiter is varying, and
the whole moon changes its shape, where the surface of the moon rises
and sinks as much as 100 metres, in case of Io every 42 hours.
That changing of shape, it's like bending a piece of metal back and
forth. It heats it up!
So we've proposed the Io Volcano Observer
in the discovery programme.
That's NASA's low-cost category of planetary mission, but this mission
would make 10 close flybys of Io while orbiting Jupiter.
It has a suite of instruments, and the tour is
designed so that we fly by Io at just the right times and places.
In order to measure the tidal gravity signature,
we have to have pairs of identical flybys – one when Io is closest to
Jupiter and one that's otherwise identical but when Io is furthest
from Jupiter. So it sees the same signal, except that this difference
in range to Jupiter, which changes the shape of Io.
That will tell us really what's going on inside Io.
Does it really have a magma ocean? And even if it has a magma ocean,
what type of magma ocean?
That's really, I think, the most fundamental thing that we need to
get a spacecraft that makes close flybys of Io, at a minimum.
Landing on Io and orbiting Io would be even better.
You have to understand, though, Io is deep within the intense
radiation of Jupiter.
So Jupiter has a very powerful magnetosphere.
So it's a very high radiation environment, so it's very tough on
electronics. So, you know, we're not going to explore Io the way we
have Mars with these long-live rovers on the surface, unless we
have a revolution in electronics and how to withstand the
radiation. So fast flybys is the way around that for now.
Get in there close, get a bunch of data and get out of that
radiation as fast as you can.
There are volcanic plumes up to several hundred kilometres high.
Very spectacular!
And some of that material may directly escape Io, but also that
high radiation environment and those energetic particles interact
and strip off material. If we're so close that we're flying through
a lava fountain that would obviously be bad for a spacecraft.
We hope to fly through the upper parts of plumes where it's
mostly gas and very small particles that are not
hazardous. Of course, if you make a math error and impact Io, that
would not be good unless it was intentional to dispose of the
spacecraft at the end of the mission.
And that is how we would plan to end it all after the mission is over.
It would mean a great deal to me to see this
mission go forward.
Now, I'm not going to be the one leading the mission at Io,
you know, it has to be the next generation.
You have to think in terms of multi generations when you're
dealing with the outer Solar System and especially when you have
to spend a decade just to get the mission approved.
So for me, though, that's all fine.
I get it started and then I enjoy life and enjoy watching others
carry on.
And I have no doubt that Io will surprise us.
It's a very surprising place, and it's surprised every
mission that's ever looked at it.
The conventional thinking is that there's no way there's life on
Io. It's too hot.
Well, it's only hot over one percent of the surface.
There are certainly places with better temperatures.
It's also thought that there's no water.
Well, we haven't detected water, but we didn't think there was water
on the Moon either for a long time until we got better
measurements, so we might be surprised about that.
And also, what kind of life are we talking about?
The only thing we know how to talk about is life as we know it,
which is carbon and water based life.
So if it's some other kind of life then who knows, all bets are off,
so it's the surprises that will be the most fun and most significant.