NASA’s Juno spacecraft has directly measured charged oxygen and hydrogen molecules from the atmosphere of one in all Jupiter’s largest moons, Europa. In keeping with a brand new study co-authored by SwRI scientists and led by Princeton University, these observations provide key constraints on the potential oxygenation of its subsurface ocean.
“These findings have direct implications on the potential habitability of Europa,” said Juno Principal Investigator Dr. Scott Bolton of SwRI, a co-author of the study. “This study provides the primary direct in-situ measurement of water components existing in Europa’s atmosphere, giving us a narrow range that would support habitability.”
In 2022, Juno accomplished a flyby of Europa, coming as close as 352 kilometers to the moon. The SwRI-developed Jovian Auroral Distributions Experiment (JADE) instrument aboard Juno detected significant amounts of charged molecular oxygen and hydrogen lost from the atmosphere.
“For the primary time, we have been in a position to definitively detect hydrogen and oxygen with in-situ measurements and further confirm that Europa’s atmosphere is made primarily of hydrogen and oxygen molecules,” said SwRI Staff Scientist and co-author Dr. Robert Ebert.
The source of those molecules is regarded as water ice on Europa’s surface. Jupiter’s rampant radiation breaks H2O’s molecular bonds, forsaking oxygen and hydrogen. The heavier oxygen molecules remain more constrained to the surface, or near-surface atmosphere, while the lighter-weight hydrogen predominately escapes into the atmosphere and beyond. Oxygen produced within the ice is either lost from the atmosphere and/or sequestered within the surface. Oxygen retained in Europa’s ice may go its technique to its subsurface ocean as a possible source of metabolic energy.
“Europa’s ice shell absorbs radiation, protecting the ocean underneath. This absorption also produces oxygen throughout the ice, so in a way, the ice shell acts as Europa’s lung, providing a possible oxygen source for the ocean.” said Princeton University Research Scholar Dr. Jamey Szalay, the study’s lead creator. “We put narrow constraints on the entire oxygen production at Europa currently at around 12 kg per second. Before Juno, previous estimates ranged from a number of kg per second to over 1,000 kg per second. The findings unambiguously display oxygen is constantly produced within the surface, just a very good bit lower than we expected.”
“We designed JADE to measure the charged particles that create Jupiter’s auroras,” said SwRI Staff Scientist and co-author Dr. Frederic Allegrini. “Flybys of Europa weren’t a part of the first Juno mission. JADE was designed to work in a high-radiation environment but not necessarily Europa’s environment, which is consistently bombarded with high levels of radiation. Nonetheless, the instrument performed beautifully.”
The brand new measurements contribute to a greater understanding of Europa and its environment, open the door for newer, more precise models. The study’s latest estimation of how much oxygen is produced inside Europa’s surface, as an illustration, could inform future research related to its subsurface ocean and potential habitability. As these observations provide the primary charged particle composition measurements inside Europa’s vicinity, they supply a crucial latest window into the moons’ complex interaction with its environment.
“Europa is an interesting object because scientists are confident a liquid ocean exists in its interior,” Ebert said. “Water is significant for the existence of life and could be present in or on objects with various characteristics. Europa is a very good place to go looking for water inside our solar system.”
