Continuation of Is the water underneath Europa's ice cap potable?

The referenced question discussed if water from Europa's ice caps is potable or not and from the answers, it was gathered that the water would be too salty to drink and only the most salt tolerant organisms would barely be able to survive the environment.

How can we measure the amount of "saltiness" for extraterrestrial water? Is there any standard scale which scientists have developed to measure the salinity?

  • $\begingroup$ I suspect at least part of the answer is osmolarity, or more specifically tonicity. But of course that's not sufficient on its own to determine potability (or suitability for terrestrial life in general), since the nature of the dissolved ions matters too — some can be a lot more toxic than others. $\endgroup$ Dec 6, 2020 at 10:26
  • $\begingroup$ It is similar to ask if there is any scale for measuring temperature or whatever on/at/in extraterrestrial bodies. $\endgroup$
    – Alchimista
    Dec 9, 2020 at 10:29

1 Answer 1


I am assuming you are asking about measuring the salinity of water remotely, which would exclude landing a probe to directly measure the salinity of water on a celestial body.

The remote measuring of surface salinity of Earth's oceans via satellites is being investigated, the process uses microwaves, with a frequency of 1.4 GHz or wavelength of 21 cm (L-band).

If this was combined with spectroscopy, to identify salt minerals, the plumes of geysers erupting from celestial bodies could be analyzed to determine the salinity of water that was the source of the geysers.

Edit 14 June 2023

Megaplume of water vapor erupting on Enceladus caught by Webb Telescope

Plumes of water vapor erupt from Enceladus via cryovolcanoes that form over cracks in the ice. These plumes can extend hundreds of miles from the surface. When a team of NASA researchers looked closely at the new JWST data ...

Webb’s observations were done using the Integral Field Unit (IFU), which can simultaneously image an object and see the spectra it is giving off, which tells us what substances make up the object. The IFU is part of Webb’s Near-Infrared Spectrograph (NIRSpec) instrument, which can see molecular emissions across a broad range of the infrared spectrum. Infrared emissions coming from the plume revealed not only that it was made up of water vapor, but how far that water vapor extended from the surface, which revealed its immense size.lockquote


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