NASA's Europa Clipper mission blasts off

A NASA spacecraft called Clipper will spend the next 6 years voyaging, hot on the heels of a similar European probe called JUICE which is also bound for Jupiter, to visit our largest planet’s mysterious moon “Europa”. An important goal of the mission is to determine whether this icy satellite, which is nearly the same size as our own moon, is home to alien life. Europa - which was first discovered by Galileo Galilei in the early seventeenth-century using his homemade telescope - has long fascinated space scientists owing to its unusual geology. Close proximity to Jupiter means it gets gravitationally stretched and squeezed, generating sufficient heat - scientists suspect - to form a liquid ocean tens of kilometres deep that sits beneath a thick icy shell. Periodically, plumes of this “seawater” erupt from the surface, and scientists like Lorenz Roth, who’s at the KTH Royal Institute of Technology in Sweden, have built instruments that are aboard Clipper to scan these plumes from orbit to discover what they’re made of. He was at the recent launch at Cape Canaveral in Florida…

Lorenz - It takes like a minute or two, you see it going up, it looks really like an explosion. And then we were 10 kilometres away, so the sound took like half a minute. You get a huge sound wave, you see it going up and a minute later it's, it's gone. And now it's on its way, not directly to Jupiter, first to Mars, and then actually comes back to Earth and then it goes out to Jupiter. And that is mostly to use Mars to accelerate, to get faster. But it's been really, really cool to see it happening and going on a very nice sunny day then in Florida.

Chris - This thing we call Europa. What is that? And where would I find it in the solar system?

Lorenz - So Europa is, as some say, the second moon of Jupiter. It's one of four large moons of our largest planet in the solar system. There have been space probes visiting the planet and, most of all, a space probe called Galileo like the discovery orbiting Jupiter every time taking pictures and probing electric and magnetic fields in the environments. And then all this information together tells us all these things. What is on the surface, what is even below the surface? What's the gravitation that pulls on the spacecraft from this moon? And this together gives you a good picture like we have today.

Chris - Do we know, or can we postulate, how Europa came to be? Because for instance, we know the Earth's moon was probably formed from a collision event between the early Earth and another small planet. Where did Europa come from?

Lorenz - That's a very interesting thing because we have different kinds of planets in our solar system. We have gas planets like Jupiter and Saturn, for example. And then we have terrestrial planets like the Earth or Mars or Venus. So these terrestrial planets like Earth, they usually do not have moons. The moon of the Earth exists because we think there was a collision. The gas planets on the other side, have moons and they kind of have always been there since the beginning of orbiting the planet. The strongest evidence, I guess, is that these moons are orbiting in the same plane as the rotational plane of the planet, which makes most sense if all is formed at the same time. If you have an object that has been captured later, comes in from a random direction, just happened to come too close to Jupiter at some point, and then the heavy Jupiter captures it, then it rather has kind of a random orbit, quite eccentric. So not a circle, but an ellipse.

Chris - And what's been your interest in the Clipper mission? How did you get involved?

Lorenz - So I'm part of the team that built the UV spectrograph. It's a camera that can break light into wavelength, into its colour, so to say. But it's, it's ultraviolet light. So it's not light we can see with our eyes. This camera was built by the Southwest Research Institute, a place in Texas where I worked before. This is the method we use to study moons. In particular, the atmosphere around the moons, which you can probe very, very nicely in UV light.

Chris - Is there much of an atmosphere around Europa then?

Lorenz - It's a very tenuous or dilute atmosphere. There's not much at all of an atmosphere. It's more than 10 orders of magnitude lower pressure on the surface of the moon compared to the surface of the Earth. No one can breathe there. You could basically feel like it's a vacuum. But it's enough of an atmosphere that you can study it and that you can learn about exchanges, what's coming from the surface, what's been lost into space, which is an interesting part of the whole system of the moon.

Chris - If we talk again in X number of months time, what are you hoping to be reporting to us?

Lorenz - It does take six years, so it is a really long time. That's quite different from others. I mean, often you send things to space and if you only go to Mars, it takes a few months or even closer. Now we have to wait for six years until we really can learn something about Europa. And I mostly want to be surprised because I think that that's kind of the thing. We can make some predictions and we have models and we can say, 'oh, we expect this and we expect the atmosphere and we expect this and we think there's liquid water' and stuff like this. But I'm mostly kind of hoping for many surprises. I can't tell you, which obviously <laugh>, but I want to see things that are actually different than we expect today.