Hubble data show persistent water vapor on only one side of the moon Europa

Thanks to data from NASA’s Hubble Space Telescope, astronomers were able to detect, for the first time, the presence of persistent water vapor in Europa’s tenuous atmosphere, one of the Jupiter’s moons. With an average temperature of -100 °C on its surface, the cause of uneven distribution of steam in this small frozen world remains a mystery.

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Astronomers have long suspected that Europa has a vast ocean beneath its surface, so the moon is singled out as a potential host to life as we know it. Understanding the atmosphere of this and other Jupiter moons is essential for planning future exploratory missions for the Jupiter system. Now, for the first time, a study conducted by the KTH Royal Institute of Technology presents evidence of water vapor in this moon’s atmosphere.

(Image: Reproduction/Goddard Space Flight Center/NASA/Paul Morris)

Previous observations have indicated the presence of water vapor in Europa, but have been associated with ice eruption plumes, recorded by Hubble in 2012 — structures very similar to Earth’s geysers, capable to throw the material up to 100 km above the surface. However, the new analysis points to similar amounts of vapor over a much larger area, according to space telescope observations ranging from 1024 The 2015.

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Such information suggests a prolonged presence of water vapor only in the posterior hemisphere of Europa. The reason for this shapeless distribution is still a mystery. To reach this discovery, astronomer Lorenz Roth, from the KTH Royal Institute of Technology and lead author of the study, performed a new analysis of images and spectra from the Hubble archives.

(Image: Playback/Goddard Space Flight Center/NASA/Paul Morris)

According to Roth, vapor detection water on both Europa and Ganymede, another moon of Jupiter, increases understanding of the atmosphere on icy moons. It turns out that, in Europe, the discovery is surprising because there the average temperature is much lower compared to Ganymede. The new observations indicate that water ice is sublimating, that is, passing from solid state directly to gas.

The astronomer analyzed a Hubble dataset, selected ultraviolet observations of Europa in 1999, 2012, 2014 and 2015 — with the moon in various positions — from the Hubble Space Telescope Imaging Spectrograph (STIS). Then, Roth was able to determine the abundance of oxygen, one of the constituents of water, in the moon’s atmosphere and, from the intensity of the emission at different wavelengths, she inferred the presence of steam.


Artistic conception of NASA’s Europa Clipper mission, scheduled to be launched in 2022 (Image: Reproduction/ NASA)

The discovery will be critical for missions that will explore the system from Jupiter’s moons, such as NASA’s Europa Clipper and the European Space Agency’s (ESA) Jupiter Icy Moons Explorer (JUICE). The JUICE mission is scheduled to be launched in 2022, arriving at the gas giant around 2031. There, the probe will study Ganymede, Callisto and Europa — the three largest moons in the system.

The discovery was published in the journal Geophysical Research Letters.

Source: NASA, ESA

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