Ocean worlds around our giant planets are there to be discovered. Europa Clipper is being built
to do just that. Let's find out what it can do. Hi, I'm Jim Green, Chief Scientist at NASA and
this is Gravity Assist. On this season of Gravity Assist, we're looking for life beyond Earth.
I'm here with Dr. Bob Pappalardo and he is a Senior Scientist at JPL in the planetary
science division. He's also the project scientist for the NASA Europa Clipper mission
that's going to Jupiter's moon Europa, a beautiful ocean world. Welcome, Bob, to Gravity Assist.
Thank you, Jim. It's so good to see you and I'm so excited to be here.
Well, how did Jupiter get so many moons and why are they so different?
Well, Jupiter has something like 79 moons. Most of them are little shards from collisions or Jupiter
captures objects that are passing by, but it's these four big ones- the Galilean moons that
are the ones that are much more like worlds. Ganymede is larger than the planet Mercury.
And those four were created along with Jupiter from the same cloud of gas and dust. And the
inner one, Io lost most of its water - does not have an icy surface. The outer two, Ganymede and
Callisto have lots of rock and lots of ice, and Europa is kind of in between with a bunch
of rock and then a skin of h2o, some of which is solid ice at the surface, where it's so cold
and some of which is liquid water -we think down below the surface, which makes Europa
so fascinating that there's a liquid water ocean in there today. It's pretty close to the surface-
13 miles or so and probably it's in contact with rock below so nutrients can seep into that ocean
and potentially serve as a fuel for life. Well, you know, in our ocean, at these
hydrothermal vents, we see life all over the place and it doesn't require light from the sun.
Is that a similar process that may be going on in Europa or do we need sunlight to have life?
We're not talking about fish and whales. That'll be exciting- giant squid or something. But
instead, probably just just single-cell organisms down there. Beneath Europa's icy shell, light
is not going to penetrate, so it's not life that's dependent on photosynthesis that we're
talking about. Instead, life that's dependent on chemical reactions similar to some life on Earth.
Well, over the last several years another set of fantastic research has been done concerning
the possibility of seeing geysers coming out from cracks. When we look at Europa,
we see these crack structures everywhere and yet maybe some of them are active.
So what do you think about the possibility of life gets scooped up and ends up in these plumes?
Yeah, there's tantalizing evidence of these plumes from the Hubble space telescope
and other observations that that says maybe every once in a while Europa lets
out a big burp of activity. When we're there with Europa Clipper we might be able to fly through
such plumes if they're there. We need to confirm them. There might be a range of sizes. We don't
know- are they consistently active or sporadic? What sets them off and can we fly through them
to directly sample the interior of Europa? So Bob, when is it going to be launched?
When will Europa Clipper be on its way? We're scheduled to launch sometime in the
mid-2020s and then depending on the launch vehicle we take, it'll take a few years or up to maybe six
years to get out to Jupiter and we might go on a direct path or we might need a gravity assist.
Listen to the full episode at: nasa.gov/gravityassist