Europa’s orbit is an ellipse and the satellite’s shape is affected by Jupiter’s gravity, deforming as it passes closer to Jupiter.
This change in shape creates friction within Europa, generating enormous amounts of heat in a mechanism known as tidal heating, which melts some of the ice and forms a vast internal ocean beneath the moon’s thick ice shell.
Europa’s internal ocean is salty and is estimated to have an average depth of about 100 kilometers, with a total volume of water twice that of all of Earth’s oceans, even though this moon is considerably smaller than our planet. .
In addition, internal oceans are believed to exist on the moons of Jupiter, Ganymede and Callisto, and on the moons of Saturn, Titan and Enceladus.
Liquid water is essential for life as we know it, which is why ocean worlds are at the forefront of the search for extraterrestrial life.
Under the sea (of ice)
The autonomous underwater exploration robots envisioned by SWIM are extremely small. Their wedge-shaped bodies measure about 12 centimeters long. A device called a “cryobot” will transport the robots beneath the thick ice sheets of these moons, using nuclear energy to melt the ice. The idea is to put about four dozen robots in the cryobot and have them penetrate the thick layer of ice for several years.
Sending such a large number of exploration robots has advantages. One is that they can explore a wider area. Another is that they are intended to operate in teams, so that multiple robots can explore the same area in overlapping directions, reducing errors in observation data.
Each robot will be equipped with sensors to measure the temperature, pressure, acidity, electrical conductivity and chemical composition of the waters it explores. All of these sensors will be mounted on a chip just a few square millimeters in size.
“People might ask: why is NASA developing an underwater robot for space exploration?” says Ethan Schaller, project leader at NASA JPL, explaining the motivation behind SWIM. “Because there are places in the solar system where we want to go in search of life, and we believe that life requires liquid water.”
This story originally appeared on CABLING Japan and has been translated from Japanese.