The Europa Clipper Mission (Updated)
by Sam Atkins
The Europa Clipper mission has launched! If you haven’t heard of this, don’t worry! Read here to learn what it is and why you should be excited. For updates on the mission’s progress, check the very bottom of the article.
NOTE: Hover mouse or tap images for captions.
Image credit: NASA/JPL-Caltech
The orbits of Jupiter's four Galilean moons. Image credit: NASA's Eyes on the Solar System
Orbiting around the solar system’s largest planet, Jupiter, are nearly a hundred moons. Most of those moons are very tiny, irregularly shaped and largely inconsequential to us, as far as we know. However, there are four moons in particular that are of great interest, and these are the four largest moons of Jupiter that were first discovered by Galileo back at the early 17th century. These moons are, from closest to furthest: Io, Europa, Ganymede and Callisto. Named after their discoverer, they are known together as the Galilean moons. Each of these worlds are incredibly fascinating in and of themselves, even as fascinating as any planet.
Image of Europa taken by NASA's Galileo spacecraft in the late 1990s. Image credit: NASA/JPL-Caltech
The smallest of these moons is Europa (slightly smaller than our own Moon) but has potentially the largest implications for space exploration. It orbits around Jupiter at an average distance of about 670,000 km (almost twice the distance between our Earth and Moon) but makes a single revolution in just 3.5 Earth days (almost eight times faster than our Moon)!
Several space probes have visited the Jupiter system throughout the last half a century to get close up images of both the planet and its natural satellites. Europa was among them, and we’ve learned much about it since then.
Europa is a frozen world completely covered in ice. It has the smoothest surface in the known solar system, largely lacking the plethora of mountains and impact craters we see across many other terrestrial objects. The ice is highly reflective and gives the moon one of the highest albedos of any moon in the solar system. We have found many very peculiar dark streaks called “lineae,” which can be seen crisscrossing along the entire width of the moon. Europa’s close proximity to Jupiter no doubt exposes it to incredible tidal forces that constantly stretch and flex the moon. This probably accounts for why the moon is so geologically active like Jupiter’s even closer volcanic moon, Io. Perhaps these dark streaks are stress fractures as the icy crust is expanded and contracted by Jupiter’s gravity.
However, the fact that these striking features appear across the whole surface, despite the moon being tidally locked (and thus showing the same face to Jupiter at all times) does beg the question: Why?
Europa almost certainly has a subsurface ocean. Below the hard-as-granite icy crust is miles and miles of liquid salt water. It makes sense. The constant stretching and geological activity from Jupiter’s tidal forces would no doubt heat some portion of the ice below the crust and melt it to a liquid state. As the moon swells and contracts, that water would press up against the crust and cause those stress fractures across the ice above it. Though we don’t have up-close direct images of these plumes like we do with Saturn’s icy moon, Enceladus, we do have direct evidence of them.
The low-res image of the water plumes of Europa, taken by the Hubble Space Telescope, superimposed on a more detailed image of Europa. As you can imagine, the Hubble isn't able to get as good a picture of such a small object that is over 5 times further away than the Sun. Hopefully Europa Clipper can finally get a good close-up image for us. Image credit: NASA/ESA/L. Roth/SWRI/University of Cologne
Europa has powerful geysers that spray out huge plumes of water hundreds of kilometers into space. Photographs from the Hubble Space Telescope, and the currently orbiting Juno space probe as well as reanalysis of old photos taken by the now-destroyed Galileo spacecraft probe have all revealed these plumes. That water is believed to come directly from the subsurface ocean below the crust, the depths of which could potentially reach 60-150 kilometers below the icy crust. There may be more water under Europa’s surface than all the water in all the Earth’s oceans combined.
There is also strong evidence that this subsurface ocean is saltwater. One way to detect this is through spectroscopy which can analyze the chemical signatures of the light reflected off the surface of the water droplets. The Galileo space probe also detected disruptions in Jupiter’s magnetic field in the space around Europa. It’s possible that an ocean of saltwater in Europa which would be electrically conductive could be creating its own special mini-magnetic field that is interacting with Jupiter’s.
The most exciting part about all of this is that this subsurface saltwater ocean could contain life or the potential for life. Saltwater is believed to be essential for life, at least the life that we know of, because it plays such a significant role in all the systems that make life here on Earth possible. It provides a habitat for countless marine and plant-life in Earth’s oceans. In fact, there’s a lot of organisms that can only live in saltwater, such as sharks, sea turtles, corals, shrimp, and even seabirds that rely on saltwater for feeding. Saltwater helps regulate Earth’s climate by absorbing much of the Sun’s energy and distributes it around the oceans via currents. These temperature differences greatly affect wind and weather patterns. Saltwater absorbs carbon dioxide which moderates the amount of greenhouse gases in the atmosphere.m and produce a lot of the oxygen that we breathe. It contains many important minerals that support various biological processes.
This is not to say that it’s guaranteed that wherever we find saltwater, we’ll find life… but we might. Just imagine it… to not only find life in the universe, but to find it in our own backyard, having developed completely independent of us. The implications of that are so profound. We would not only confirm that we aren’t alone, but that in all likelihood life is incredibly common in the universe.
First things first, we don’t have enough scientific data to determine the truth.
Enter: the Europa Clipper mission.
Artist's concept of Europa Clipper passing over Europa. Image credit: NASA/JPL-Caltech
The Europa Clipper mission which is set to launch on October 10th, 2024. The goal of this space probe is to study Europa’s icy shell and subsurface ocean. It will detail the moon’s surface geology, how thick the icy shell is, confirm the existence of a subsurface ocean, determine its composition and ultimately analyze the potential for Europa to be habitable for life.
So, once the spacecraft launches what can we expect?
As many astronomers and astronauts know, even at the scale of our own solar system, spca is pretty huge. Any journey beyond our own planet will likely take years, not only because of the great distances involved but the careful consideration of how the gravity of all the solar system’s massive bodies will carry an given spacecraft across the cosmic oceans.
Watch the five-and-a-half-year journey of the Europa Clipper spacecraft from Earth to Jupiter.
Video credit: NASA's Eyes on the Solar System
Music Credit: Dreaming by Helios
Europa Clipper will launch on October 10th, 2024, from the LC-39A launch pad of the Kennedy Space Center in Florida. Fun fact: this is the exact same launchpad from which the Apollo 11 mission began its historic journey. The spacecraft will take off aboard a Falcon Heavy rocket and begin a 5.5-year journey to Jupiter. Regardless, Europa Clipper will still reach the king of the planets a full 15 months before the JUICE spacecraft does, despite the latter having already left Earth back in April 2023.
The journey to Jupiter is not a simple straight line. Everything in the solar system is constantly moving, everything has gravity constantly tugging on your trajectory and fuel reserves are limited. Therefore, we must allow gravity to do much of the heavy lifting for us.
The first part of the Europa Clipper’s journey will be to travel to Mars to perform a gravity assist maneuver in March 2025. A gravity assist involves the spacecraft pass very close to Mars and allow the planet’s gravity to give the spacecraft a big boost in speed.
From here, Europa Clipper will swing all the way around the Sun in an elliptical orbit (to maintain its speed) and will eventually catch back up to Earth in January 2026 where it will use our own planet as another gravitational speed boost. From here, the spacecraft will finally be set on a path to Jupiter. Remember that as all this time passes, the planets are constantly orbiting the Sun. Where a planet is now is not where it will be a year from now (unless you’re Earth). This means that Europa Clipper will be heading to not where Jupiter is but where it is going to be. This will be the longest part of the journey.
By April 2030, four years and three months after its gravity assist with Earth, Europa Clipper will reach Jupiter, first being ahead of it and allowing the gas giants powerful gravity to slow the spacecraft down and ease toward it. The spacecraft will then enter into an elliptical orbit around Jupiter, using a couple of gravity assists from Ganymede, Jupiter’s largest moon, as help. The science mission objectives will begin immediately. Over the following four years, Europa Clipper is planned to make almost fifty flybys of Jupiter’s icy moon. These flybys will bring the spacecraft incredibly close to the moon, as close as 25 km (16 mi) above the surface, allowing it to take thousands of incredibly hi-resolution images of Europa’s entire surface.
The main body of the Europa Clipper is about 5.27 meters tall (over twice the height of an average human. The body is flanked by two long solar panels which together span 25 meters across from the end of one to opposite end of the other. Image credit: NASA
Placement of the Europa Clipper's various science instruments. Image credit: NASA
The Europa Clipper will be equipped with nine high-tech science instruments that will provide scientists with a wealth of valuable data to analyze for years to come. These instruments include:
A wide angle and narrow angle camera that will extend from the visible light range of the electromagnetic spectrum and slightly into the infrared and ultraviolet wavelengths. These will provide highly detailed images of the planet moon’s surface. Two infrared cameras will be able to distinguish between the various surface temperatures and show us where warm subsurface water may be close or even expelled up onto the surface. It will also be able to map the surface texture and roughness.
Spectroscopic instruments. Light reflected off different elements of matter produced different signatures in that light. By analyzing the signatures using spectroscopic instruments which break up the light into its separate wavelengths, we can actually tell just by looking at an object what it is made out of. Europa Clipper is equipped with an ultraviolet spectrograph will study the atmosphere around Europa and detect water plumes. The infrared spectrometer will study the composition of ices and salts to get a better sense of the moon’s geological history.
Europa Clippers magnometer, a long 8.5 meter boom protruding from the spacecraft will be fitted with sensor that will analyze magnetic fields during Europa flybys. This will actually allow us to confirm the existence of a subsurface ocean, measure its depth and salt content. As said before, the spinning of Jupiter‘s magnetic field is believed to interact with the electrically conducive saltwater below and allowing it to generate its own magnetic field. The magnetometer will also determine how thick Europa’s icy outer shell is (currently guessed to be about 10-15 km thick). This wall help us find out how much the ocean is shielded from Jupiter’s radiation amongst other things.
Jupiter’s magnetic field carries plasma from various local sources (such as from the volcanic moon Io and Jupiter’s own ionosphere). This plasma causes distortions in the magnetic field produced at Europa. Europa Clipper is equipped with Faraday Cups, sensors which will study the density of the plasma which will allow us to distinguish between Europa’s own magnetic field and the distortions that it creates in Jupiter’s magnetic field.
Europa’s orbit around Jupiter is not perfectly circular (as pretty much no natural orbits are). As it gets closer and further from Jupiter, its gravitational field is flexed by the gravity of Jupiter. this will help us better understand why Europa itself flexes and stretches the way it does under Jupiter’s powerful tidal forces and give us more insight into the moon’s internal structure.
Europa Clipper’s radar will use radio waves to penetrate the surface and look directly into the moon’s interior layout using the Doppler effect. This is the same way that we map the surface of oceans here on Earth. Like all light, radio waves have a very fast but finite speed. We also know that light travels at different speeds through certain types of transmittable matter such as water. By sending these radio waves out and timing how long it takes for them to return to us, we are able to get a three-dimensional map of the interior.
Finally, a dust analyzer is fitted on the spacecraft, which will analyze the faint amount of dust kicked up by meteorites that strike the surface of Europa. it will also measure the composition of that dust as well as the water plume that might be floating around the thin atmosphere as well.
Exploring the wonders of our solar system takes time and when Europa Clipper launches on October 10th, 2024, we will still have to wait for it to travel and wait even longer for it to gather data. This is a wait that is worth it. So many important questions will potentially be answered with the science mission.
How does Jupiter’s gravity affect the structure of worlds so small but so close. What implication does this have on robotic and/or human exploration in the future? What kind of worlds can be produced under these stresses? What kind of environments can life exist in? Does our solar system contain places like this outside of Earth?
This is another big step forward in understand our place in the universe.
As the mission proceeds in the coming years, I will be sure to return to this article and provide any updates that might interest you.
UPDATE: Following a short delay due to Hurricane Milton battering the Florida coast, Europa Clipper launched into space on October 14, 2024. It is currently leaving Earth behind, travelling towards Mars at about 40,200 km per hour. It will reach the red planet on March 1, 2025 where it will perform a gravity assist maneuver to gain a speed boost.