Water vapour plumes may be being emitted from the icy surface of Jupiter’s moon Europa, Nasa scientists have revealed.
The find - made using the Hubble telescope - is significant because it means we could potentially explore Europa’s ocean and more easily look for “organic chemicals or even signs of life” that originated within it, without digging through miles of ice.
“For a long time humans have wondered if there is life beyond Earth,” Paul Hertz, director of the Astrophysics Division at Nasa Headquarters in Washington said during a teleconference call today, 26 September. “We live in a lucky era where we can address questions like that. On Earth, life is found wherever there is energy water or nutrients, and places that might have those elements are of interest to us. Europa might be such a place. Today’s results increase our confidence that water might be on the surface of Europa and available for us to study without digging.”
Jupiter's moon Europa has a diameter of 1,900 miles making it smaller than Earth's Moon. The 4.5 billion-year-old object has a frozen surface that for years scientists have speculated may be hiding an ocean underneath. To find out more, the space organisation's scientists turned the Hubble Telescope towards Europa. Hertz pointed out that since we cannot fly a mission up close to Jupiter and its moon, Hubble is the “next best thing to study it from afar”.
William Sparks, astronomer with the Space Telescope Science Institute in Baltimore and lead author on a study on the find - published in theAstrophysical Journal - explained today how he used “transit imaging” to identify the suspected plumes.
It’s a type of imaging used to hunt for exoplanets by using the light of a host star to highlight the planet’s shadow. With Europa, Jupiter’s surface created a smooth background of ultraviolet light that highlighted events on Europa’s surface - the plumes could be seen as silhouettes.
The plume candidates were spotted on Europa’s southern tip, and near its equator. The team looked back at 2012 images taken of hydrogen being emitted from the moon and found they were imaged in the same locations as the suspected plumes. Further backing up the plume theory, the team took ten images in all of the moon and only three showed evidence of plumes.
“If the features are real they have to be intermittent because the moon is always seen from same angle and we didn’t see it all the time,” explained Sparks. “If plumes exist this is exciting. It means potentially easier access to signs of life from below the icy surface.”
The team’s theory is that water vents exist on the surface through which plumes emerge before raining back down. Britney Schmidt, assistant professor at the School of Earth and Atmospheric Sciences at Georgia Institute of Technology in Atlanta, presented several different theories for how the plumes could have escaped.
Tidal activity, for instance, could be causing stress on the surface and breaking through. “There are a lot of ways we think water may reach the surface,” she said. “It may not come direct from the ocean, but most of the materials spent some time there.”
Sparks stressed that the new find does not prove the existence of plumes; it provides evidence that “they may be present” and points to future avenues of study.
Despite Galileo Galilei discovering the moon in 1610 – in the first discovery of a moon other than Earth's – most of the knowledge we have about the icy mass comes from the Galileo mission to Jupiter, which ran from 1995 to 2003.
The mission, named after the astronomer, photographed Europa in unprecedented detail and revealed its "fractured surface," including "pits" and "domes" created by ice movements. "Like our planet, Europa is thought to have an iron core, a rocky mantle and an ocean of salty water beneath its ice crust," Nasa said.
Using data from the Hubble Telescope, in 2013, Nasa said it had discovered water vapour "venting" from the surface of Europa. "The discovery that water vapour is ejected near the south pole strengthens Europa's position as the top candidate for potential habitability," Nasa's Lorenz Roth said at the time.
Cracks on the moon's surface, known as linea, may be venting vapour into space, the scientists continued. Although, Nasa could not determine how deep the water may be. It was suggested the vapour could be being released from a sub-surface ocean or from the ice being warmed near its surface.
In December 2015 Nasa signed a contract for the creation of a spacecraft called Juice.
The probe – JUpiter ICy moons Explorer – will launch in 2022 and arrive at Jupiter eight years later. For more than three years it will orbit Jupiter and collected data on three of its moons: Ganymede, Europa and Callisto. Towards the end of the mission it will orbit around Ganymede, which is also believed to have a liquid ocean beneath its surface.
This article was originally published by WIRED UK
