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Ocean worlds around our giant planets are there\h
to be discovered. Europa Clipper is being built\h\h

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to do just that. Let's find out what it can do.
Hi, I'm Jim Green, Chief Scientist at NASA and\h\h

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this is Gravity Assist. On this season of Gravity\h
Assist, we're looking for life beyond Earth.\h

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I'm here with Dr. Bob Pappalardo and he is\h
a Senior Scientist at JPL in the planetary\h\h

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science division. He's also the project\h
scientist for the NASA Europa Clipper mission\h\h

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that's going to Jupiter's moon Europa, a beautiful\h
ocean world. Welcome, Bob, to Gravity Assist.\h

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Thank you, Jim. It's so good to see\h
you and I'm so excited to be here.\h

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Well, how did Jupiter get so many\h
moons and why are they so different?\h

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Well, Jupiter has something like 79 moons. Most of\h
them are little shards from collisions or Jupiter\h\h

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captures objects that are passing by, but it's\h
these four big ones- the Galilean moons that\h\h

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are the ones that are much more like worlds.\h
Ganymede is larger than the planet Mercury.\h\h

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And those four were created along with Jupiter\h
from the same cloud of gas and dust. And the\h\h

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inner one, Io lost most of its water - does not\h
have an icy surface. The outer two, Ganymede and\h\h

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Callisto have lots of rock and lots of ice,\h
and Europa is kind of in between with a bunch\h\h

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of rock and then a skin of h2o, some of which\h
is solid ice at the surface, where it's so cold\h\h

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and some of which is liquid water -we think\h
down below the surface, which makes Europa\h\h

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so fascinating that there's a liquid water ocean\h
in there today. It's pretty close to the surface-\h\h

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13 miles or so and probably it's in contact with\h
rock below so nutrients can seep into that ocean\h\h

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and potentially serve as a fuel for life.
Well, you know, in our ocean, at these\h\h

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hydrothermal vents, we see life all over the\h
place and it doesn't require light from the sun.\h\h

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Is that a similar process that may be going on\h
in Europa or do we need sunlight to have life?\h

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We're not talking about fish and whales. That'll\h
be exciting- giant squid or something. But\h\h

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instead, probably just just single-cell organisms\h
down there. Beneath Europa's icy shell, light\h\h

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is not going to penetrate, so it's not life\h
that's dependent on photosynthesis that we're\h\h

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talking about. Instead, life that's dependent on\h
chemical reactions similar to some life on Earth.\h

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Well, over the last several years another set\h
of fantastic research has been done concerning\h\h

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the possibility of seeing geysers coming\h
out from cracks. When we look at Europa,\h\h

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we see these crack structures everywhere\h
and yet maybe some of them are active.\h\h

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So what do you think about the possibility of\h
life gets scooped up and ends up in these plumes?\h

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Yeah, there's tantalizing evidence of these\h
plumes from the Hubble space telescope\h\h

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and other observations that that says\h
maybe every once in a while Europa lets\h\h

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out a big burp of activity. When we're there with\h
Europa Clipper we might be able to fly through\h\h

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such plumes if they're there. We need to confirm\h
them. There might be a range of sizes. We don't\h\h

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know- are they consistently active or sporadic?\h
What sets them off and can we fly through them\h\h

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to directly sample the interior of Europa?
So Bob, when is it going to be launched?\h\h

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When will Europa Clipper be on its way?
We're scheduled to launch sometime in the\h\h

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mid-2020s and then depending on the launch vehicle\h
we take, it'll take a few years or up to maybe six\h\h