New Delhi: NASA’s Hubble Space Telescope has discovered that Jupiter’s icy moon, Europa, contains persistent water vapor. Surprisingly, however, this evidence was only found in the hemisphere.
Europa has an icy surface, through which the vast ocean flows. The sea can provide favorable conditions to support life. This observation is especially important because astronomers now better understand the atmospheres of icy moons.
Also, future missions could be sent to the Jovian system, which is half a billion miles from the sun, to explore whether environments far from the sun are suitable for supporting life.
The results of the study were recently published in the journal Geophysical Research Letters.
Previous view of water vapor over Europe
Hubble captured this image of a plume exploding through the ice in Europe in 2013. These observations of water vapor are similar to those of geysers on Earth, according to NASA. However, the feathers were recorded as extending more than 60 miles. The pressure exerted by a plume of water vapor in the atmosphere of Europe is one millionth of the surface pressure of Earth’s atmosphere.
How is the new discovery different?
Hubble observations from 1999 to 2015 showed water vapor over Europe, but new findings reveal that water vapor is spread over a wider area than before. This indicates the fact that water vapor has been constant in Europe for a long time. The part of Europa that is always in the opposite direction of its motion throughout its orbit is the back hemisphere of the Moon, and it is in this hemisphere that water vapor is visible. Scientists do not yet understand the reason for the asymmetry between the anterior and posterior hemispheres.
Recently, Lorenz Roth of the Royal Institute of Technology, Space and Plasma Physics in Sweden used a technique that led to the discovery of water vapor on Ganymede, another moon of Jupiter. When this technique was used to analyze Hubble’s archive of images and spectra, new discoveries occurred in the atmosphere of Europe.
Roth said there is a growing understanding of the icy moon’s atmosphere due to observations of water vapor on Ganymede and in later parts of Europe, according to a statement from NASA. However, he added, the abundance of water that settles on Europa is even more interesting because Europa’s surface temperature is lower than the surface temperature of the Ganymede River. Lower surface temperatures tend to cause condensation of water vapor.
Temperatures in Europe exceed -260 degrees Fahrenheit. Europa’s surface is 60 degrees Fahrenheit colder than Ganymede because the former reflects more sunlight than the latter. Another reason for the surprising new observation is that water ice changes directly from a solid to a vapor without turning into a liquid phase, even though the temperature is lower. This phenomenon is known as sublimation, and has been observed in Europe as well as Ganymede.
How is the study conducted?
Roth selected European ultraviolet observations from the Hubble archive dataset for 1999, 2012, 2014, and 2015, when the moon was in different orbital positions. The Hubble Space Telescope (STIS) imaging spectrometer was used to make these observations. Oxygen is a component of water, and using SITS ultraviolet observations, Roth determined the abundance of oxygen in the European atmosphere. Deduction of the presence of water vapor by interpreting the strength of the emission at different wavelengths.
Why is discovery important?
This discovery is important because it will help future investigations to conduct more extensive research on Europa. NASA’s Europa Clipper mission and the European Space Agency’s Jupiter Icy Moons Explorer mission are some examples of such sensors. Astronomers can also get clues about Jupiter-like planets around other stars in the Milky Way with a proper understanding of the formation and evolution of Jupiter and its moons.
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