Nasa announcement of water plumes spotted on Europa could give humanity its best chance yet to see aliens

The plumes of water are our best chance yet of meeting our neighbours in our solar system – if they are out there

Andrew Griffin
Tuesday 27 September 2016 06:25 BST
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Hubble Telescope spots water plumes erupting from Jupiter's Europa moon

Humanity might just have got its best chance yet to meet aliens – even if the possibility is still tiny.

Nasa’s announcement that it has spotted plumes of water erupting above Jupiter’s moon Europa means that scientists now have a chance to actually study the water that is thought to lie under its crust. And if they’re lucky that might provide them with evidence of life in those big, covered oceans.

It still isn’t confirmed that what the Hubble Space Telescope saw was definitely a plume, or that the plume definitely came from the water under Europa’s shell. It certainly isn’t confirmed that the water underneath Europa’s crust contains any kind of life.

In the run-up to the event, Nasa announced that it would be making a statement about "surprising activity" that had been spotted on Europa. Many people’s minds instantly went to aliens – especially given Europa’s status as perhaps the most likely place for life to be found in our solar system.

But Nasa then debunked the rumours with a tweet that read: “Monday, we’ll announce new findings from Jupiter’s moon Europa. Spoiler alert: NOT aliens.”

While the discovery certainly isn’t on the same scale as finding aliens, it does give them a tantalising glimpse of the way that they might, potentially, one day be able to do so.

Scientists hope to be able to send a craft to explore those plumes, and examine the liquid that they are made up of. When it does, it will be able to look for evidence of life or the conditions that might be able to bring it about.

Astronomers used Hubble's ability to observe ultraviolet light to look for signs of water above the surface of Europa as the moon crossed the face of Jupiter.

Light reflected from the planet was absorbed at specific wavelengths consistent with the presence of water vapour or particles of water ice.

The results indicated plumes erupting 125 miles (200 kilometres) into space on three occasions during 10 observations over 15 months. All were clustered around Europa's south pole apart from one which had an equatorial origin.

In 2012 another team of Hubble scientists spotted a plume signature above Europa - in this case, the hydrogen and oxygen components of water. However, no further evidence of plumes has come to light until now.

While the scientists are cautiously stressing they have found evidence but not proof, no other natural phenomenon is known that can explain the results.

Astronomer Dr William Sparks, from the Space Telescope Science Institute in Baltimore, US, said at a Nasa news briefing: "If plumes exist, this is an exciting find as it potentially gives easier access to the ocean below, and would allow us to search for signs of life in the ocean of Europa without needing to drill through miles of ice.

"However, I do want to stress that the observations are at the limit of what Hubble can do ... We remain cautious, because we're working at difficult wavelengths for Hubble."

Powerful tidal forces caused by Jupiter's gravity are believed to keep Europa's hidden ocean from freezing solid.

Europa is roughly the same size as Earth's moon, about 3,000km (1,864 miles) in diameter. Yet scientists estimate that its hidden ocean contains twice as much water as all the oceans on Earth combined. The ocean is believed to be in contact with silicate rock, providing a chemical environment potentially suitable for simple life.

Experts are still not sure how the water can penetrate through a blanket of ice 10 to 15 miles thick. Some computer simulations suggest that heat within the ocean may be focused at lower latitudes, making the ice thinner there.

Geoff Yoder, acting associate administrator for Nasa's Science Mission Directorate in Washington DC, said: "Europa's ocean is considered to be one of the most promising places that could potentially harbour life in the solar system."

Europa is not the first moon in the solar system to yield evidence of water vapour plumes. In 2005, Nasa's Cassini orbiter detected jets of water vapour and dust spewing from the surface of Saturn's moon, Enceladus.

The agency is planning a space mission to Europa, likely to be launched in the 2020s, that could confirm the presence of plumes and study them at close range.

The Hubble team's findings are due to appear in The Astrophysical Journal on Thursday.

Additional reporting by Press Association

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