2024-03-19 12:45:01
Jupiter’s satelliteseuropa” is one of the celestial bodies that is thought to have a vast ocean inside. It is thought that the ocean is supplied with oxygen produced by the decomposition of surface ice, so if there is life that breathes oxygen, it may be a valuable source of oxygen. However, there is insufficient data to estimate the amount of oxygen produced on Europa, and the estimated minimum and maximum values vary by a factor of 1,000.
A research team led by JR Szalay of Princeton University estimated the amount of oxygen generated on the surface of Europa based on observation data from NASA’s Juno spacecraft. the result,Oxygen generation rate is 6 to 18 kg per secondIt was estimated that. This results in a relatively small amount, which may be insufficient for oxygen-breathing life forms.
[▲Figure: Oxygen is thought to be generated by the decomposition of ice on Europa’s surface and supplied to the ocean. This study further narrowed down the estimated amount of oxygen generated (Credit: NASA, JPL-Caltech, SWRI & PU)]
■Is oxygen supplied to Europa’s ocean?
Jupiter’s satelliteseuropa” is a celestial object that has been attracting attention for many years, although it is a smaller satellite than the Earth’s moon. Although the entire surface is covered with ice, it is thought that there is an ocean composed of abundant liquid water inside. It is thought to be much larger than the Earth’s oceans.
If there is an ocean, there is a possibility that it has its own life. If Europa does have its own life, it may resemble microorganisms that live in an environment similar to Earth’s deep ocean floor. Such life works by metabolizing the high-temperature hydrothermal water that rises from the ocean floor and the inorganic substances contained therein. They are adapted to the deep sea, an environment where light cannot reach them and cannot rely on photosynthesis, so they do not need the oxygen produced during the photosynthesis process.
However, this assumption does not mean that there is no life on Europa that requires oxygen. Europa has only a thin atmosphere on its surface, and charged particles (electrified particles) present in space collide with the ice at high speeds. Then, the water molecules that make up the ice break down, releasing hydrogen and oxygen molecules and atoms. If oxygen molecules were to be generated inside the ice, rather than on the outermost surface of the ice that is in contact with space, it would be difficult for them to escape into space, so they would eventually be taken into the inner ocean.
If this process generates a large amount of oxygen molecules, it may be possible to sustain life that breathes oxygen without relying on photosynthesis. However, it is difficult to estimate the amount of oxygen generated on Europa, and previous studies have ranged from 0.3 to 300 kg per second, with estimates varying by a factor of 1,000.
■The amount of oxygen supplied to the ocean is estimated to be small.
Szalay and his team are working on NASA’s Jupiter probeJuneauWe estimated the amount of oxygen produced on Europa based on observation data from “. Juno’s instruments are equipped to observe charged particles, and when Europa approaches, it can detect charged particles escaping from Europa, which are substances created by the decomposition of ice. This was data that previous Jupiter probes had not been able to obtain.
Szalay and his colleagues confirmed that Juno’s observation data contained electrically charged hydrogen and oxygen atoms, and estimated the amount of oxygen molecules generated from this. From the amount of hydrogen released, Szalay et al.The amount of oxygen generated on the surface of Europa is 6 to 18 kg per second.(12±6kg/s). This is a relatively small value. Moreover, this is the amount generated on the surface, not the amount that is supplied to the ocean. Although the rate of supply to the ocean is unknown, the maximum amount generated is 18 kg per second, which indirectly indicates that the supply is quite small.
It was also discovered that a different process than previously expected occurs in the detachment of molecules from the surface of Europa. Until now, it was thought that the main desorption of hydrogen molecules was thermal desorption, which occurs in areas where the surface temperature is locally high. However, the average speed of hydrogen molecules measured this time indicates that the main process is desorption without heat. The details remain unclear in this research
. A deeper understanding of the processes occurring on Europa’s surface will be essential for considering the amount of oxygen molecules supplied to the ocean.
*Sputtering, where charged particles collide with molecules and eject them directly, and Joule heat, where the heat generated by a small electric current flowing through ice activates the movement of molecules, are estimated to occur.
Based on this study, even if Europa does have its own life, there may be very little or no oxygen-breathing life on Europa. Additionally, there are multiple celestial bodies other than Europa that are predicted to have oceans beneath their ice, which may affect estimates of the ocean environment.
- Source JR Szalay, et al.
- “Oxygen production from dissociation of Europa’s water-ice surface”. (Nature Astronomy) DC Eagle, et al.
“NASA’s Juno Mission Measures Oxygen Production at Europa”. (NASA Jet Propulsion Laboratory)
Written by Riri Aya
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