Last month, NASA launched the Europa Clipper, which will reach Jupiter’s Europa in 2030. Europa is one of the most interesting and intriguing objects in the solar system for research. I was so impressed by the recent studies and riddles of Europa that I would like to share some of them in this edition ofCore Elements.
Rasoul Sorkhabi
Editor, Core Elements
The Europa Clipper Mission
Photo of the Europa Clipper launch in Florida, JHPHOTODAD/Shutterstock.com
Europa is the fourth largest of Jupiter’s 95 moons, and the sixth largest moon in the solar system after Ganymede, Titan, Callisto, Io, and Earth’s moon. With a diameter of 1,900 miles, Europa is roughly ten percent smaller than our moon.
Context:
Since 1972, when spectroscopic analyses showed that Europa has an icy surface and may hold liquid water beneath, this moon has fascinated scientists.
From 1995–2003, the Galileo space probe orbited Jupiter and provided the bulk of the information we currently have of Europa and its sister moons.
Meet Europa Clipper: The $5 billion Europa Clipper was built by NASA’s Jet Propulsion Laboratory, the largest planetary spacecraft built by the United States.
It was launched from Cape Canaveral, FL. on October 14, using SpaceX’s Falcon Heavy rocket. Watch the full video here.
After journeying 1.8 billion miles, the Europa Clipper will reach its target in April 2030 and will conduct a series of flybys of Europa while in orbit around Jupiter.
Tech on board: The Europa Clipper carries nine scientific instruments: Imaging system cameras, thermal emission imaging, U.V. spectroscopy, a mapping spectrometer, a magnetometer, a plasma instrument for magnetic sounding, radar for ocean-surface sounding, a mass spectrometer, and a surface dust analyzer.
These instruments will collect massive data around Europa’s hidden liquid ocean and possible hydrothermal vents on the ocean floor.
What’s next: This mission may eventually lead to other missions to land on Europa and drill into its icy crust.
Go deeper: Read this article on the mission published in New Scientist.
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Much of the scientific characteristics of Europa are still unknown. The Europa Clipper will provide answers to some of these riddles of Europea’s geology and life, but we have to wait for another six years to see the data. For now, let’s look at what we do and don’t know about Europa.
Active geology:
Europa’s icy surface is the smoothest known body in the solar system. It has only a few craters.
Europa’s surface is crisscrossed by reddish streaks. These indicate recent geological activity.
Despite its icy surface, Europa is more of a rocky moon. The first 20 km of its crust is ice, followed by 80 km of liquid water. The inner part of Europa is rocky, and it may even have a metallic core.
Hidden ocean: Europa is more than 750 million kilometers from the sun with surface temperatures of -184 F (-160 C). However, it is not an entirely frozen celestial body.
In 1999, spacecraft Galileo discovered signs of liquid water beneath Europa’s surface.
The evidence is based on the discovery of a weak secondary magnetic field in Europa, which indicates the flow of highly electrically conductive material in Europa’s interior. The fluid is considered to be liquid water with dissolved salt.
The Hubble Space Telescope also detected plumes of water vapor erupting from Europa’s surface.
Heat source: So,what keeps Europa’s subsurface liquid ocean from freezing?
In AGU Advances, Lemasquerier and colleagues modelled two heat sources for Europa’s interior:
Radiogenic heating from the decay of radioactive minerals in the mantle
Tidal heating as Europa is stretched and compressed by Jupiter’s giant gravity
Microbial life: Many scientists suspect that Europa’s hidden ocean may contain microbial life thriving on hydrothermal vents on Europa’s ocean floor; however, two studies presented at the 55th Lunar and Planetary Science Conference in March argued against this idea.
Paul Byrne and colleagues argued that tidal stresses from Jupiter or compressional stresses from the cooling of Europa’s crust are not strong enough to fracture Europa’s rocky body.
Austin Green and colleagues showed that geothermal energy within Europa is not sufficient to produce volcanic activity.
Atmospheric oxygen: Europa’s thin atmosphere contains oxygen, and a recent study in Nature Astronomy tries to answer where that oxygen may come from and in what concentrations it exists, based on data collected in 2022 from NASA’s Juno spacecraft.
It seems that Europa’s icy surface serves as its lungs to generate oxygen. This is how it works:
High-energy particles emitted from Jupiter’s powerful magnetic field irradiate Europa’s icy surface and split water molecules into oxygen and hydrogen.
Researchers estimate that Europa manages to produce at most 18 kilograms of oxygen per second. This is far less than 1,000 kilograms of oxygen per second estimated previously by computer models.
It is not clear that the oxygen would reach Europa’s liquid ocean that supposedly harbors microbes. If there is life in Europa’s ocean, it would have to manage with little oxygen and no sunlight.
Last week’s quiz was: Why do clay minerals swell when very wet and shrink when very dry?
Because of their chemical composition, layered structure (hence interlayer space), and minute size (smaller than 2 micros), clay minerals absorb water molecules very easily and expand in thickness by as much as 100 percent. The process is reversable, and clay minerals shrink upon drying (that is how mud cracks form). Read more here.
This week’s question is: Why does the far side of the Moon remain invisible to us on Earth, even though the Moon is rotating?
Please send your response by November 21 to editorial@aapg.org (subject line: Core Elements Quiz)
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