Hubble Space Telescope images of Ganymede's aurorae colored blue overlaid on a Galileo space probe image of the moon (Image NASA/ESA)

The Hubble Space Telescope has been used to study Ganymede, the largest Jupiter’s moon, and in particular its aurorae. Analyzing their characteristics, it was possible to get the best clues found so far of the existence of a Ganymede underground ocean of liquid salt water. This ocean may contain more water than it exists on the surface of the Earth.

Artistic cutaway of Saturn's moon Enceladus that shows hydrothermal activity (Image NASA/JPL)

An article just published in the journal “Nature” shows a research based on the detections carried out by NASA’s Cassini space probe. Among other information provided by the mission there’s also evidence that on Enceladus, one of Saturn’s moons, there are signs of the presence of hydrothermal vents. This means that there are waters heated by geothermal energy similar to those existing on Earth, where the presence of various microorganisms abounds, particularly those known as extremophiles.

A comparison of the map of Ligeia Mare on Titan before and after the application of despeckling (Image NASA/JPL-Caltech/ASI)

Since July 2014, NASA’s space probe Cassini has been accomplishing its mission exploring Saturn and its moons, including Titan. Its SAR (Synthetic Aperture Radar) instrument allowed to map almost half of the surface of this satellite, allowing to know its geological features like never before. Now these surveys can offer even more details thanks to a new technique that improves their quality.

The images created thanks to the Cassini space probe’s SAR are “grainy”, like photographs of limited quality. Scientists must strive to interpret the smaller geological features or to identify changes in images of the same area taken at different times. The new technique called despeckling by its developers is improving the situation.