Where will you stop? Since July 2022 the date of its first image, the space telescope James Webb (JWST) launched in December 2021, never ceases to provide the most impressive photos from others, thus pushing the limits of our knowledge. It is now appropriate to add an intriguing shot of Enceladus, one of Saturn’s moons, provided by the telescope’s NIRSpec (Near Infrared Spectrum) instrument. What do we see there?
The fountain of water vapor is about 10,000 kilometers high, while the diameter of the Moon is only 500 kilometers! The equivalent on Earth would be a jet over 250,000 km, or two-thirds the distance between Earth and the Moon. It has already been spotted by the probe Cassini In the early 2000s, these remarkable jets were spewing out from a vast ocean of salty liquid water surrounding a rocky core and encased in a thick layer of ice dotted with cracks dubbed “tiger stripes.” This phenomenon betrays an intense geothermal activity whose driving force is still unknown. The ejected water contains ammonia, silica and organic molecules, such as hydrocarbons (methane, propane, formaldehyde…), which makes Enceladus a perfectly acceptable cradle for life.
But monitor JWST Go away. In addition to the size of the aircraft, which exceeds everything one can imagine, it reveals that water is being dumped at a rate of 300 liters per second. Then, due to Enceladus’ relatively fast speed around Saturn (one revolution in 33 hours), this water spreads out in a ring-like jet around the planet and overlaps the outer, wider E-rings. About 30% of this water will remain in this state, while the remaining 70% will be distributed to the rest of the Saturnian system, supplying the other moons and rings.
After this startling discovery, another observation of Enceladus, a longer one, was added to the programme JWST in a few months. He follows…
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