Signs of water plumes on Jupiter’s moon Europa suggest it might harbour life

Jupiter. Image: Getty.

Along with Mars, Jupiter’s moon Europa has long captured the imagination of science fiction writers as a potential place for life in the solar system beyond Earth. In science fact, missions have found hints of a subsurface water ocean below the icy crust of the moon. And where there’s warm, liquid water, and the right chemistry, there could indeed be life.

Finding out whether this is the case is not going to be easy though. One complicated and expensive solution would be landing on the moon and drilling a hole through the ice to sample the water beneath. But now research has thrown up a better option. The exciting results, published in Nature Astronomy, suggest there may be plumes emanating from Europa’s ocean – meaning a spacecraft could simply fly though them to test the water. The findings are important for the upcoming Europa Clipper missions and JUICE missions.

It’s not the first time it’s been suggested that there are geyser-like features on the moon. The Hubble Space Telescope saw transient signs of plumes from Europa’s subsurface ocean in 2012 and 2016. However, the result was controversial – the data was after all captured from far away (Hubble orbits the Earth). The new evidence instead comes from an actual flyby of Europa by the Galileo mission in 1997 – significantly strengthening the evidence that there are plumes on the moon.

We don’t know exactly how thick Europa’s ice shell is or how deep its subsurface ocean is. A 2011 study showed that there are locations where water may be relatively close to the surface in great lakes, near chopped up icy “chaos regions”, which are similar to some Antarctic structures on Earth.

Lessons from Enceladus

The Cassini mission to Saturn discovered huge plumes of water coming from the small moon Enceladus. The first hints were from magnetic field deflections and an abundance of charged particles in a certain region of the moon. We know that the dense gas of newly emerged molecules and atoms in a watery plume becomes charged (ionised) as electrons are knocked off. This makes it electrically conducting, causing changes to surrounding magnetic fields.

Enceladus’s south polar plumes, as seen by Cassini, 30 November 2010. Image: NASA/JPL-Caltech/Space Science Institute.

Next, the plumes were actually spotted in spectacular images, emanating from what looks like tiger stripes near the south pole. There is evidence from gravity measurements that the source is a subsurface ocean.

Cassini flew past Enceladus 22 times, enabling exploration of the plumes ejected directly from the ocean below. As well as simple water, ions and charged grains in the plumes, Cassini found sodium – a sign that the ocean is salty. It also found silicates, which indicate a sandy ocean floor and potentially the existence of hydrothermal vents.

This is important as chemical reactions between sand and water can provide enough energy in the water to feed microbial life (and tends to happen near hydrothermal vents on Earth). Finally, in 2107, Cassini also discovered hydrogen in the plumes, which should be a byproduct of such water-sand reactions. This is as close as you can get to a proof that it is a suitable candidate to host life.

Following these exciting discoveries, the hunt was on for plumes at Europa. Based on the Hubble measurements, estimates in 2012 showed that the amount of water released in the Europa plumes could be a factor 30 times that of Enceladus. The plumes appeared to have a height of some 200km. Like Enceladus, the floor of Europa’s ocean is likely in contact with sand and rock. This is in contrast to some other moons with subsurface oceans – including Ganymede and Callisto – where the ocean floor is ice.

In the new study, magnetometer data from a Galileo flyby less than 400km above Europa’s icy surface was reexamined and compared with a modern computer model of how charged gas on Europa should behave. The results – based on an observed deflection and decrease in the observed magnetic field over a distance of 1,000km – imply that there’s a dense region of charged particles. This is very likely to be the result of a plume, making it the best direct evidence for such an occurence yet.

Upcoming missions

As with Enceladus, the Europa plumes offer the tantalising prospect of directly sampling material from the subsurface ocean. Two future missions will be able to explore this. The European Space Agency’s JUICE mission, which I am involved in developing, is due to launch in 2022 and will arrive in the Jupiter system on 2030. Two close flybys of Europa are planned as part of a sequence, before going into orbit around the moon Ganymede in 2032.

NASA’s Europa Clipper will perform 45 flybys of Europa. Both these missions can explore the plumes in the same way the Cassini orbiter did at Enceladus. Following these, landers or penetrators at Europa have been proposed (but yet to secure funding). In the meantime, sampling the plumes could provide many exciting insights into what’s going on in the ocean. If we are really lucky we may even be able to detect signatures of biological activity. Unfortunately, Cassini was not equipped to look for such signatures at Enceladus.

Image: NASA/JPL-Caltech/SETI Institute.

This means there are now four likely locations for life beyond Earth in our solar systems. First Mars, where conditions were right for life to form 3.8bn years ago. We will explore this further with the ExoMars 2020 rover, which I am also involved in developing. This will be able to drill up to two metres underneath the surface to search for biomarkers, as well as the NASA Mars 2020 rover and the related helicopter recently announced.

But on Europa and Enceladus there could actually be life now, and sampling the plumes will help reveal whether this is the case. At Saturn’s moon Titan, we have also found signs of complex prebiotic chemistry that once gave rise to life on Earth. This means it is a location for future or perhaps current life.

As well as the planned missions to Mars and Europa, it is therefore also important that we also return to the Saturn system to track down where there may be life elsewhere. NASA’s Dragonfly quadcopter proposed for Titan is one possibility.

The ConversationWith so many promising candidates for life in our own solar system, it is exciting to think that it could be just a few years until we discover some form of microbial alien life.

Andrew Coates, Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCL.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Everybody hates the Midlands, and other lessons from YouGov’s latest spurious polling

Dorset, which people like, for some reason. Image: Getty.

Just because you’re paranoid, the old joke runs, doesn’t mean they’re not out to get you. By the same token: just because I’m an egomaniac, doesn’t mean that YouGov isn’t commissioning polls of upwards of 50,000 people aimed at me, personally.

Seriously, that particular pollster has form for this: almost exactly a year ago, it published the results of a poll about London’s tube network that I’m about 98 per cent certain* was inspired by an argument Stephen Bush and I had been having on Twitter, at least partly on the grounds that it was the sort of thing that muggins here would almost certainly write up. 

And, I did write it up – or, to put it another way, I fell for it. So when, 364 days later, the same pollster produces not one but two polls, ranking Britain’s cities and counties respectively, it’s hard to escape the suspicion that CityMetric and YouGuv are now locked in a co-dependent and potentially abusive relationship.

But never mind that now. What do the polls tell us?

Let’s start with the counties

Everybody loves the West Country

YouGov invited 42,000 people to tell it whether or not they liked England’s 47 ceremonial counties for some reason. The top five, which got good reviews from between 86 and 92 per cent of respondents, were, in order: Dorset, Devon, Cornwall, North Yorkshire and Somerset. That’s England’s four most south westerly counties. And North Yorkshire.

So: almost everyone likes the South West, though whether this is because they associate it with summer holidays or cider or what, the data doesn’t say. Perhaps, given the inclusion of North Yorkshire, people just like countryside. That would seem to be supported by the fact that...


Nobody really likes the metropolitan counties

Greater London was stitched together in 1965. Nine years later, more new counties were created to cover the metropolitan areas of Manchester, Liverpool (Merseyside), Birmingham (the West Midlands), Newcastle (Tyne&Wear), Leeds (West Yorkshire and Sheffield (South Yorkshire). Actually, there were also new counties covering Teesside (Cleveland) and Bristol/Bath (Avon), too, but those have since been scrapped, so let’s ignore them.

Not all of those seven counties still exist in any meaningful governmental sense – but they’re still there for ’ceremonial purposes’, whatever that means. And we now know, thanks to this poll, that – to the first approximation – nobody much likes any of them. The only one to make it into the top half of the ranking is West Yorkshire, which comes 12th (75 per cent approval); South Yorkshire (66 per cent) is next, at 27th. Both of those, it may be significant, have the name of a historic county in their name.

The ones without an ancient identity to fall back on are all clustered near the bottom. Tyne & Wear is 30th out of 47 (64 per cent), Greater London 38th (58 per cent), Merseyside 41st (55 per cent), Greater Manchester 42nd (53 per cent)... Not even half of people like the West Midlands (49 per cent, placing it 44th out of 47). Although it seems to suffer also from the fact that...

Everybody hates the Midlands

Honestly, look at that map:

 

Click to expand.

The three bottom rated counties, are all Midlands ones: Leicestershire, Northamptonshire and Bedfordshire – which, hilariously, with just 40 per cent approval, is a full seven points behind its nearest rival, the single biggest drop on the entire table.

What the hell did Bedfordshire ever do to you, England? Honestly, it makes Essex’s 50 per cent approval rate look pretty cheery.

While we’re talking about irrational differences:

There’s trouble brewing in Sussex

West Sussex ranks 21st, with a 71 per cent approval rating. But East Sussex is 29th, at just 65 per cent.

Honestly, what the fuck? Does the existence of Brighton piss people off that much?

Actually, we know it doesn’t because thanks to YouGov we have polling.

No, Brighton does not piss people off that much

Click to expand.

A respectable 18th out of 57, with a 74 per cent approval rating. I guess it could be dragged up by how much everyone loves Hove, but it doesn’t seem that likely.

London is surprisingly popular

Considering how much of the national debate on these things is dedicated to slagging off the capital – and who can blame people, really, given the state of British politics – I’m a bit surprised that London is not only in the top half but the top third. It ranks 22nd, with an approval rating of 73 per cent, higher than any other major city except Edinburgh.

But what people really want is somewhere pretty with a castle or cathedral

Honestly, look at the top 10:

City % who like the city Rank
York 92% 1
Bath 89% 2
Edinburgh 88% 3
Chester 83% 4
Durham 81% 5
Salisbury 80% 6
Truro 80% 7
Canterbury 79% 8
Wells 79% 9
Cambridge 78% 10

These people don’t want cities, they want Christmas cards.

No really, everyone hates the Midlands

Birmingham is the worst-rated big city, coming 47th with an approval rating of just 40 per cent. Leicester, Coventry and Wolverhampton fare even worse.

What did the Midlands ever do to you, Britain?

The least popular city is Bradford, which shows that people are awful

An approval rating of just 23 per cent. Given that Bradford is lovely, and has the best curries in Britain, I’m going to assume that

a) a lot of people haven’t been there, and

b) a lot of people have dodgy views on race relations.

Official city status is stupid

This isn’t something I learned from the polls exactly, but... Ripon? Ely? St David’s? Wells? These aren’t cities, they’re villages with ideas above their station.

By the same token, some places that very obviously should be cities are nowhere to be seen. Reading and Huddersfield are conspicuous by their absence. Middlesbrough and Teesside are nowhere to be seen.

I’ve ranted about this before – honestly, I don’t care if it’s how the queen likes it, it’s stupid. But what really bugs me is that YouGov haven’t even ranked all the official cities. Where’s Chelmsford, the county town of Essex, which attained the dignity of official city status in 2012? Or Perth, which managed at the same time? Or St Asaph, a Welsh village of 3,355 people? Did St Asaph mean nothing to you, YouGov?

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

Want more of this stuff? Follow CityMetric on Twitter or Facebook.

*A YouGov employee I met in a pub later confirmed this, and I make a point of always believing things that people tell me in pubs.