This week, NASA approved a new mission to the moon, Europa.
Now, if you’re not a space aficionado, you’re probably not super familiar with this moon. It’s one of the largest of Jupiter’s 63 known moons. Europa and three other moons of Jupiter are called “Galilean Moons” because they are so large that Galileo Galilei was able to see them way back in 1610 with one of the world’s first crude telescopes. It’s just a little bit smaller than our own moon.
Why do we care about Europa?
Good question! Moons are boring, right? I mean, look at our moon. It’s a dust bowl sprinkled with craters.
Well, not all moons are like ours. Many are actually very planet-like with atmospheres and weather. A few of these planet-like moons may contain the ingredients necessary to support life. This is precisely why we find Europa so interesting.
Life you say?
The primary reason we want to go to Europa is because we think there might be life there. Crazy, right?
More accurately put, we believe it might have all of the necessary ingredients for life as we know it, of which there are three:
- Ingredient 1: Liquid Water
- Ingredient 2: Energy Source (either from light, or a chemical reaction)
- Ingredient 3: Organic Compounds
1) Liquid Water
Europa is one of only a few places in our solar system (including our planet) that has strong evidence of abundant liquid water. Scientists have evidence that Europa has a relatively thin icy shell (5-20 miles thick) covering a vast liquid water ocean which contains twice as much water as we have here on Earth. That’s a ton of Ingredient 1.
2) Energy source
This one is more complicated. Let’s start from the basics. As you may know, Earth has a radiation belt (the Van Allen radiation belt) that shields us from high energy particles shot out from the sun. They’re great. We love them. Except when we send satellites or spacecraft through them. This is because radiation belts are made out of highly energetic charged particles which can rip through electronics if left unprotected.
Well, Jupiter has the largest radiation belt in the solar system. This means that Europa is constantly bombarded with the same type of high energy protons and electrons. And while this intense radiation can be harmful to satellites, it does something kind of awesome to the surface of Europa. It interacts with Europa’s surface ice and creates something called hydrogen peroxide. Scientists looked at Europa from telescopes here on Earth and confirmed that Europa had a ton of this stuff on the surface.
Hydrogen peroxide is the key to energy! When mixed with liquid water, it decays to oxygen. This chemical reaction produces energy. Some have even considered using hydrogen peroxide as a source of clean energy here on Earth.
But where’s the water? This is where Europa’s thin shell becomes incredibly important. There is evidence that, in some of the thinner parts of the shell, the ocean occasionally wells up from below and washes over the surface. Other places in the solar system that are thought to have subsurface liquid oceans have much thicker shells and their oceans are 100+ miles below the surface. So while Jupiter has other moons with subsurface liquid oceans that are also exposed to intense radiation, their oceans are much deeper, without much hope of water coming up to the surface. No water. No chemical interaction. No energy source.
Determining how much, if any, of Europa’s ocean wells up to the surface will likely be one of the most important outcomes of NASA’s upcoming mission.
Ingredient 2 – likely
3) Organic Compounds
Organic compounds are molecules built from carbon atoms, and all the living organisms on Earth contain carbon. For life as we know it, organic compounds are an essential ingredient.
And interestingly enough, we’ve found organic compounds on a variety of different asteroids. The theory it is not unlikely that Europa could have them, because planetary objects are bombarded by asteroids fairly frequently (just look at all those craters on our own moon!).
Another possibility is that organic compounds could be found in Europa’s interior. Scientists believe that the bottom of Europa’s seafloor may, in fact, be very similar to our own. Its core could be heated up, with hydrothermal vents and geological activity, due to tidal forces caused by the periodic tug from its host planet Jupiter.
This piques scientists’ interests because on Earth, we’ve found diverse organic ecosystems living off these seafloor vents and the chemicals they emit. So....it’s possible the same thing might be happening within Europa.
Ingredient 3 – It’s possible.
So, what's next?
NASA has given the “go ahead” for the Jet Propulsion Laboratory to fully build out a mission to Europa. While landing on the surface would be ideal for collecting scientific evidence, it’s out of the question for now (way too expensive to justify). Instead, JPL will be developing an orbiter mission with a radiation-tolerant spacecraft that will perform 45 flybys at varying altitudes from 16 miles to 1700 miles above the surface.
The spacecraft will have nine different science instruments that will be used to produce high-resolution images of the surface, determine the thickness of the icy shell, measure the strength of Europa’s magnetic field, search for plumes of water, and determine the chemical composition of that water if found.
The launch date is currently TBD, but the target is in the 2020’s. Once launched it will take several years to get there. So like…maybe 2030 timeframe? Gah, so far away. Space missions always take forever. I suppose it’s best to get started sooner than later! Europa life – here we (eventually) come!