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Giant methane storms on Uranus

Most of the times we have looked at Uranus, it has seemed to be a relatively calm place. Well, yes its atmosphere is the coldest place in the solar system. But, when we picture the seventh planet in our solar system invariably the image of a calming blue hazy disc that the spacecraft Voyager 2 took in 1986 comes to mind.

Uranus as seen by NASA’s Voyager 2 NASA/JPL-Caltech

However, all we have previously known about the atmosphere of Uranus has been ’thrown to the wind’ with observations made last year.

In August 2014 a group led by Imke de Pater pointed the Keck telescope at Uranus and were a little bit surprised to see storms raging. It wasn’t as though clouds haven’t been seen before, but the clouds they spotted last year were very much brighter than any seen before. The fact that the storms are bright in the methane spectrum isn’t a surprise – Uranus, and its neighbour Neptune, are pretty much just big balls of methane, water and ammonia (but it does make for a snigger-worthy headline).

Light from Uranus, as captured from my backyard in Sydney. The dips in the spectrum mainly correspond to methane (positions of the methane absorption is shown by the blue lines). Andy Casely

The storms are described in a paper recently published in Icarus, with the pre-print available here. After the first observations, the group put out a call to amateur astronomers to see if they could also observed this unusual activity too. They did, and with this information the group built a case to point the Hubble Space telescope at Uranus, which happened in October. Again, they saw large storms, showing that what they had seen in August hadn’t been a one off event - the weather report on Uranus is looking rather unsettled.

The storms on Uranus, as seen from the Keck telescope. Imke de Pater (UC Berkeley), Larry Sromovosky and Pat Fry (U. Wisconsin), and Heidi Hammel (AURA)

Uranus was the first planet to be discovered in the ‘recent’ era of science. All the planets up to Saturn were observed to be different ‘wandering’ stars by many ancient cultures – so we’ll never know who first spotted them. But Uranus was first observed in 1690 by John Flamsteed. He plotted it six times – but didn’t realise it was different from any other star (he catalogued it to be 64 Tauri). The French astronomer Pierre Lemonnier also observed Uranus, but didn’t distinguish it from the other stars he was watching. It was William Herschel who realised, in 1781 after thinking it was a comet, that he’d seen a planet orbiting further from the sun than Saturn.

Despite knowing where it was for over 300 years, we’ve only in the last decade started to take a detailed view of the Northern hemisphere of Uranus. The observations made by de Pater and her team are the first time this giant region of our solar system has been surveyed by modern telescopes from Earth. This is because of the very strange rotation, which makes Uranus pretty unique.

Our Earth rotates on its axis tilted only slightly from being straight up (if we define up as being perpendicular to a planet’s orbital plane). It is this tilt that drives our seasons.

Uranus has the most extreme tilt of axis in the whole solar system, it is inclined 98° from up. This means Uranus has the most extreme seasons – as each hemisphere of the planet faces the sun as it orbits (a cycle that take 84 years). The upshot is that as the Northern hemisphere has been in winter until recently, and from Earth we have been unable to see it. In 2007 Uranus reached it’s equinox, with the equator pointing at the sun and each of the two hemispheres illuminated.

Uranus' strange orbit explained. M. Showalter/M. Gordon/SETI Institute

The group observed Uranus with the Keck telescope as it past equinox seven years ago. They expected to see storm activity, as parts of the planet that haven’t seen the sun in 20 years started to come to light. They thought it has gone quiet again, which is why 2014’s storms took them by surprise. Added to this is the fact the storms are flaring up in the Northern hemisphere, the part of Uranus that is entering its spring, and thought not to have warmed up from its prolonged winter yet.

Where is the energy to drive these storms coming from? That’s the mystery. Storms on the other gas giants are thought to be fed by energy from their dynamic interiors. Voyager 2 saw that Uranus should have a dynamic interior (it has an active magnetic field like Neptune) but that little of this energy is reaching the atmosphere. This is why Uranus is the coldest planet in our solar system, parts of the atmosphere were observed to be a chilly -224°C.

What this observation of these giant storms really does highlight, is just how little we know about our solar system’s giant icy planets Uranus, and its neighbour Neptune. In the light of the fact that missions like Kepler are finding many other similar planets orbiting distant stars, we really need to sort this out. Hopefully knowing more about our ‘local’ planets will mean that we can understand much more about those further away.

Meanwhile, while we in Australia may have past our summer – think of the Southern hemisphere of Uranus where a 20-year winter is coming….

Going a long way to do a quick data collection

Like many a scientist before me, I have spent this week trying to grow a crystal. I wasn’t fussy, it didn’t have to be a single crystal – a smush of something would have done – just as long as it had a bit of long-range order. But no. Hours spent staring at a screen as the sample I wanted to study failed to sort out its atoms into something I could work with.

Look it is pretty, but it’s not the crystal I was looking for. Author

Sitting, staring at an experimental failure rather does make you think about and question many things. Moving on from the “why did I have this stupid idea in the first place” (which is a bit of a running theme in weeks like this), you try and put your experiments in context.

I’m leaving Japan tomorrow, with a stack of lovely fresh data (and probably some excess baggage fees). Some of my experiments worked, some didn’t - that’s the nature of the beast. No amount of planning and preparation for my three months here would have probably changed that.

Actually three months of experiments (or at least access to equipment) has been a massive luxury for me. Most of my data collections are from central facility instruments, like those offered at the Australian Synchrotron and the Bragg Institute.

Access to these instruments can take a lot of preparation, starting with a peer-reviewed proposal. Then, if you’re fortunate enough to be granted time; months of planning, risk assessments and gathering of equipment go into perhaps 24 hours of precious time on the instrument of your desire.

But what if you’ve put in YEARS of planning, and then had to wait YEARS for a tiny window of results? What if, rather than heading to Japan, you’ve had to journey to Pluto for them? How excited would you be that your tiny window of observation was just coming up?

It’s a good job I’m not on the science team for New Horizons, NASA’s mission to Pluto, as I couldn’t quite image how I’d sleep from now until July when it’s due to make it’s closest approach.

How far away is Pluto? Very. Image taken from NSW, Australia Andy Casely

I feel a bit of affinity with New Horizons, as we’re both about the same amount of time into our research careers (after probably a similar amount time of building/planning for New Horizons and growing/educating for me). When it launched in January 2006 I was few months into my PhD, and at that point I probably felt that I was being propelled at nearly the velocity New Horizons' was.

New Horizons did get to see a bit of the solar system on its journey, in 2007 while winding up it’s speed in a gravity assist orbit, it did a tour of Jupiter. There it took some rather wonderful images of the gas giant planet and it’s rings, and even caught an eruption of the Tvashtar volcano on Io. But since then it’s largely been in hibernation, waiting for 2015 for it’s time to shine.

Picture of Jupiter and its moon Io taken by the New Horizons spacecraft’s flyby in early 2007. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center

(I, on the other hand, have not been asleep since 2007 I should point out!)

When New Horizons reaches its closest approach to Pluto some of its instruments will only have a matter of hours to observe the surface of the icy dwarf. How do you possibly prepare for a window like that?

Well we have some idea, ESA’s Philae lander had a similarly restricted timeline and like New Horizons' years of planning from vast teams of scientists and engineers will have gone into the small observation window. Even once the observations are done, planned down to the seconds, it will be a nervous wait for the results. Not wanting to waste a second of observation, New Horizons will wait until it is past Pluto to send its data bounty back to Earth, a process that will take months after it has flown by.

But, like for me in Japan, the Pluto flyby will only be a step in New Horzions science journey. From there it will continue to fling its way out of the solar system and the hope is that it will encounter a number of other Kuiper belt objects.

We really don’t know much about the whole class of icy dwarf planets, and for me the excitement lies in what new icy geology is there to be explored. I can’t wait to see what materials and in what situations New Horzions turns up on the surface of Pluto and its moon Charon. That’ll be the start of my next (hopefully more successful) experimental adventure.

Why I’m proud to be a crystallographer

This year I have learnt more that it is probably healthy to know about crystal structures. I’ve learnt how you can turn a rabbit green with a protein, read up on French military history and marvelled at how a crystal structure can destroy itself. I’ve even found cement interesting!

When looked at the right way, even cement can be beautiful. This is the crystal structure of tricalcium aluiminate, a vital mineral in cement.

These examples are just the tip of the iceberg, or (to put more appropriately) merely the surface layer of atoms of the science of crystallography and what it has achieved. It’s been a pleasure to discover so much about the field this year.

Why? 2014 was sanctioned by the UN to be the International Year of Crystallography (along with farming and family – or was that family farming?). A definite improvement on last year’s “International year of Quinoa”, but as we loll into December I reckon there’s a few of you out there still scratching your head as to what it’s all about?

Crystallography is the science behind structure, of knowing where your atoms are. There have been some excellent “explainers” already on The Conversation, and a number of videos explaining it.

To date, across the various databases, there’s coming up to 1 million crystal structures that have been determined. That’s nearly a million times a researcher has collected a diffraction pattern (like von Laue did to kick off the whole field in 1911) and interpreted how this could be generated from an arrangement of atoms (like Bragg did in 1912). In an effort to highlight just 365 of them, myself and 40 other researchers, have blogged about one every day. I’d urge you to look over the Crystallography 365 project to see the massive diversity of science that crystallography encompasses.

But why be a crystallographer?

I don’t usually like giving myself a “scientific label” – I have a degree in planetary science, a PhD in physics and my first job was in a chemistry department. I promise you (and my parents) that it did all make some sense at the time. But one thread has run through all of these career twists, and that’s my use of crystallography.

You’ll not find many scientists who call themselves just “crystallographers” and that’s because (as my career to date shows) it’s an inherently interdisciplinary science. Most of us are something else as well, be that geologists, chemists, physicists or biologists. As a scientist starting out, that really appealed to me. I have taken my crystallographic skills, mostly learnt during my PhD in physics, and applied them to problems in fields diverse as forensics, minerals and explosives. I’ve even collected a diffraction pattern of cocoa butter!

My particular crystallographic hero, Kathleen Yardley Lonsdale - who told us that the benzene molecule was flat.

Then there are the role models. In science, as a rule, there are not usually all that many female role models to look up to. But crystallography smashes that out of the park. From Lonsdale to Hodgkin to Megaw to Franklin, women have been front and centre in some of the biggest leaps in crystallography and the community still retains its healthy gender balance.

It’s not just the crystal structure that you can get from these studies, but a very fundamental view of the properties of the material that you are looking at. As a result, crystallography has brought about some of the most famous scientific leaps, 28 Nobels have been awarded through its application. Knowing where the atoms are in materials brings fundamental insights that have revolutionised our world, from the structure of DNA to giant magneto-resistance.

Crystallography is also often at the forefront of “movements” in research. For instance, big data is old news in crystallography, with institutions like the Cambridge Crystallography Database Centre (custodian of a database of over 600,000 crystal structures, mostly of molecular compounds) set up to collate molecular structural information and “mine” that to discover new interactions and even predict how new materials will form.

There’s an argument that much of the success of crystallography has been that it is an inherently “open” science. Most of the software tools that I use day in day out are freeware – developed and maintained by researchers in the field. I’m supremely grateful for their hard work, making tools that are essential to a wide range of scientific projects, with often only citations as reward. Added to this data depositories (such at the Crystallographic Open Database) and standardisation of format have meant that scientists across disciplines can easily communicate their findings to each other.

So every time I collect a diffraction pattern, I enjoy the fact that I’m part of a collective of people (and one robot on Mars) doing the same thing. It’s a fabulous “clan” to belong to, and that’s why I’m proud to be a crystallographer.