With the 50th anniversary this week of the first Moon landing, solar system exploration is in the news again. For example, Jupiter has received a lot of attention over the last year or two, due to the incredibly beautiful and detailed images of the gas giant being sent back by the Juno mission. But I’m disappointed that, after travelling so far, Juno will not have the chance to also have a closer look at one of its most fascinating moons, Europa, widely considered by scientists to be one of most favourable places in the solar system to host some sort of life (other than Earth of course). The last time that we were able to get a good look at it was a couple of decades ago, when the Galileo mission explored the Jupiter system from 1996 to 2003.
Intriguing Europa
Europa is only 3100 km in diameter, a little smaller than our Moon (3475 km diameter) and over 600 million km from Earth, but it is bright enough to be visible through my small telescope. Like many of the moons in the outer solar system, its surface is made principally of rock-solid ice. As you can see in the Galileo image above, the surface is criss-crossed by many fractures, indicating lots of changes and tensions in the ice, and there are very few craters, showing that the activity is pretty recent (in geological terms). The reddish colours are believed to be due to minerals that have escaped from the interior to the surface through the cracks. Analysis of these features have enabled scientists to deduce a lot about what lies below the surface, and what makes Europa particularly interesting is evidence suggesting that there is a substantial sub-surface ocean, potentially an ideal habitat for life
Galileo was the last space mission to get close-up images of Europa – here you can see its amazingly detailed image of some of the very varied surface features – that was 16 years ago, but improved technology means that researchers are still able to investigate this intriguing world from afar.
The image below from the Hubble Space Telescope appears to show what appear to be plumes extending 100 km out from the surface at the bottom left of the moon, and the existence of such plumes is supported by magnetic field data from Galileo, inviting comparison with the spectacular plumes of water vapour discovered on Saturn’s moon Enceladus by the Cassini mission.
Also, imaging by the ground-based ALMA telescope in the Atacama Desert shows thermal variations across the surface of Europa, including a currently unexplained cold spot – by matching these variations with visible surface features researchers should be able to gain a better understanding of what is going on there geologically.
But being so distant, the Hubble and ALMA images are low resolution, limiting the amount of detail that can be seen. More close-up research is needed to start to find answers to the many questions about this enigmatic moon. The science community is acutely aware of Europa’s exciting potential, and in the next few years not just one but two new space missions will set off to explore this icy world in even more detail – ESAs JUICE mission, with launch planned for 2022, and NASAs Europa Clipper scheduled to launch in 2023.
Watch this space – solar system exploration looks set to become even more fascinating.
https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth
https://solarsystem.nasa.gov/missions/galileo/overview/
https://www.nasa.gov/europa/overview/index.html
http://sci.esa.int/juice/
https://public.nrao.edu/news/2018-alma-image-europa/
https://www.nasa.gov/press-release/nasa-s-hubble-spots-possible-water-plumes-erupting-on-jupiters-moon-europa
Image credits:
1. NASA/JPL-Caltech/SETI Institute
2. NASA/JPL/DLR
3. NASA, ESA, W. Sparks (STScI), and the USGS Astrogeology Science Center. Comining images from Hubble Space Telescope, Galileo, Voyager 1, Voyager 2