Europa's orbit is an ellipse, and the satellite's shape is affected by Jupiter's gravity, distorting it as it passes close to Jupiter.
This change in shape creates friction inside Europa, generating enormous amounts of heat in a mechanism called tidal heating, which melts some of the ice and creates a vast internal ocean beneath the moon's thick ice shell. .
Europa's interior ocean is salty and estimated to be about 100 kilometers deep on average, with a total volume of water twice that of all Earth's oceans combined, despite this moon being much smaller than our planet.
Additionally, internal oceans are thought to exist on Jupiter's moons Ganymede and Callisto and Saturn's moons Titan and Enceladus.
Liquid water is essential to 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 are about 12 centimeters long. A device called a “cryobot” will carry robots beneath the thick ice shells of these moons, using nuclear energy to melt the ice. The idea is to pack about four dozen robots into cryobots and lower them into thick ice caps over the course of several years.
There are benefits to sending such large numbers of exploration robots. For one thing, they can explore a wider area. The second is that they are envisioned to work in teams, so that multiple robots can explore the same area in overlapping directions, thereby 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 water it explores. All these sensors will be installed on a chip just a few millimeters square.
“People may ask why is NASA developing an underwater robot for space exploration?” Ethan Sklar, project leader at NASA's JPL, explains the inspiration behind SWIM. “Because there are places in the solar system where we want to go to look for life – and we think life requires liquid water.”
This story was originally published on wired Japan And it has been translated from Japanese.