Europa is the fourth-largest moon of Jupiter.
Jupiter’s fourth largest of its 79 moons, Europa, is more like a planet than a moon.
About 1,900 miles/3,100 kilometers in diameter, it’s smaller than our own Moon, but larger than dwarf planet Pluto. It’s got a thin oxygen-rich atmosphere. Europa has a layered inner structure including a liquid iron core, and a magnetic field. It looks like a “veiny eyeball” thanks to fractures in its icy surface.
It’s also got water.
Scientists have long known that Europa has a global ocean of water beneath an 11 mile/18 kilometer thick crust of ice.
Could it host simple forms of alien life? It’s a high-priority target of investigation for space agencies.
So here’s the thing—if scientists could sample Europa’s water they could potentially discover extraterrestrial life for the first time. Wait. Landing a probe on Europa and drilling through the ice? No, that’s not going to happen anytime soon.
Which is why it’s so exciting that yet another group of scientists think a 20-year-old NASA space probe may have already witnessed Europa spew a plume of water from that ocean into space.
The only other body in the solar system thought to do that is Enceladus at Saturn.
Could a couple of space probes—both due to launch in a few years in any case—fly through Europa’s water plumes and detect signs of extraterrestrial life?
This image released by the Jet Propulsion Laboratory 16 December shows a cutaway view of the ... [+]
A new paper published this week in Geophysical Research Letters argues that NASA’s space probe Galileo—which orbited Jupiter between 1995 to 2003, and discovered hints of a subsurface ocean on Europa—may have also collected evidence that the moon occasionally releases some of this water into space.
By using computer simulations and new calculations, a group of researchers at the European Space Agency (ESA) and the Max Planck Institute for Solar System Research (MPS) reproduced data gathered by Galileo’s onboard Energetic Particles Detector (EPD) by modeling the movements of high-energy protons around Europa during the flyby.
Their results—which include changes to high-energy protons in Jupiter’s magnetic field near the moon—can be explained by the presence of plumes of water.
Previously, researchers had assumed the moon itself to have obstructed the detector’s view.
On the left is a view of Europa taken from 2.9 million kilometers (1.8 million miles) away on March ... [+]
The plumes are less spouts of water and more like “cryovolcanic eruptions”—ice volcanoes—that spew liquid instead of molten rock. Neptune’s moon Triton and Pluto’s moon Charon are known to display similar behavior.
The Galileo spacecraft itself was sacrificed in 2003 to protect Europa’s ocean; NASA did not want risk the spacecraft crashing into Europa and contaminating it just in case it does host simple life.
This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off ... [+]
Mounting evidence
Conclusive proof that also Europa spews water into space is still missing, but the study is another piece of evidence.
In 2012 the Hubble Space Telescope detected hydrogen and oxygen in Europa’s atmosphere, and in 2016 it imaged what may be water vapor plumes erupting off the surface (above image).
What is the Jupiter Icy Moons Explorer (JUICE) mission?
Set to launch in 2020, the European Space Agency’s JUpiter ICy moons Explorer (JUICE) will spend three and a half years examining Europa and two of Jupiter’s other large moons, Ganymede and Callisto. Its cameras and ice-penetrating radar will be used to study the composition of Europa’s icy crust, detecting whether there are reservoirs of water between layers of ice.
What is the Europa Clipper mission?
Scheduled to launch in 2023, NASA’s Europa Clipper mission will perform about 45 flybys, in each pass photographing the moon's icy surface in high resolution.
Both probes could now have a flight plan that has them fly through the plumes of water vapor erupting from Europa’s ice crust, thereby sampling its subsurface ocean.
That would be way, way easier—and much quicker—that having to design and send a mission that could land on Europa’s surface and drill through the ice.
Wishing you clear skies and wide eyes.
