Hawken School, Gates Mills, OH
Imagine if there was a world smaller than our moon, but holds more water than all of earth’s oceans. A world whose oceans are thought to be over 100 miles deep at some points, more than 14 times the depth of the Marianas Trench. What if that world is in our solar system, easily within reach of a space probe. It’s not fiction, it’s Europa. In 2016, the Hubble Space Telescope detected evidence of a plume of water originating from Europa. Similar evidence was detected in 2014 by Hubble and in 1997 by the Galileo spacecraft. Analysis of the data revealed that all three anomalies were detected at the same location on the Jovian moon. The location of the suspected plumes was also significantly warmer than the surrounding region. Galileo has also found that the magnetic field of Jupiter was disrupted around Europa meaning that Europa is generating a magnetic field. This suggests that there is an electrically conductive fluid like a salty ocean underneath the ice.
It has been hypothesized that there are hydrothermal vents at the bottom of the ocean powered by tidal heating which keeps the ocean liquid. If true, then life could originate on Europa like it did on the earth billions of years ago. Nick Lane, a researcher at the University College London proposes that the porous, Sulphur rich rocks of hydrothermal vents could have been able to synthesize amino acids and nucleotides from carbon dioxide and hydrogen. The pores created a gradient separating the acidic ocean from the alkaline fluid of the vents, effectivity acting as an abiotic cellular membrane for protocells. Lane explains that “it’s a bit like a battery”. H+ and OH- ions flowed through the pores and powered the reaction of carbon dioxide, hydrogen, Sulphur, and other chemicals present in the ocean into amino acids and nucleotides which are the building blocks of proteins and DNA.
However, there are limits to life beneath the surface of Europa if it exists. There will be no photosynthesis because sunlight cannot penetrate miles of ice. Without photosynthesis, any life form must find an alternate source of oxygen, or live as simple anaerobic prokaryotes. This means that larger organisms are unlikely to exist there.
Despite having a significant amount of evidence for a vast liquid ocean beneath the surface of Europa, little is known about the Jovian moon. For example, the cracks in the ice, thought to be a result of geological activity due to the ocean, contain a mysterious red substance. We also know nothing about the ocean’s composition other than that it’s salty. The Galileo satellite doesn’t have high enough resolution or crucial equipment like ice penetrating radar to properly observe Europa. A new orbiter or rover with the proper equipment would be able to test for organic compounds in the plumes and surface of the hotspot, detect chemical evidence of hydrothermal vents, and see through the ice for more evidence of an ocean. This would be critical to our understanding of Europa.