Archive for NASA

Evidence for Liquid Water on Mars?

Posted in Astrohype, The Universe and Stuff with tags , , , , , , , , on September 28, 2015 by telescoper

There’s been a lot of excitement this afternoon about possible evidence for water on Mars from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars Reconaissance Orbiter (MRO). Unfortunately, but I suppose inevitably, some of the media coverage has been a bit over the top, presenting the results as if they were proof of liquid water flowing on the Red Planet’s surface; NASA itself has pushed this interpretation. I think the results are indeed very interesting – but not altogether surprising, and by no means proof of the existence of flows of liquid water. And although they may indeed provide evidence confirming that there is water on Mars,  we knew that already (at least in the form of ice and water vapour).

The full results are reported in a paper in Nature Geoscience. The abstract reads:

Determining whether liquid water exists on the Martian surface is central to understanding the hydrologic cycle and potential for extant life on Mars. Recurring slope lineae, narrow streaks of low reflectance compared to the surrounding terrain, appear and grow incrementally in the downslope direction during warm seasons when temperatures reach about 250–300K, a pattern consistent with the transient flow of a volatile species1, 2, 3. Brine flows (or seeps) have been proposed to explain the formation of recurring slope lineae1, 2, 3, yet no direct evidence for either liquid water or hydrated salts has been found4. Here we analyse spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars instrument onboard the Mars Reconnaissance Orbiter from four different locations where recurring slope lineae are present. We find evidence for hydrated salts at all four locations in the seasons when recurring slope lineae are most extensive, which suggests that the source of hydration is recurring slope lineae activity. The hydrated salts most consistent with the spectral absorption features we detect are magnesium perchlorate, magnesium chlorate and sodium perchlorate. Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.

Here’s a picture taken with the High Resolution Imaging Science Experiment (HIRISE) on MRO showing some of the recurring slope lineae (RSL):


You can see a wonderful gallery of other HIRISE images of other such features here.

The dark streaky stains in this and other examples are visually very suggestive of the possibility they were produced by flowing liquid. They also come and go with the Martian seasons, which suggests that they might involve something that melts in the summer and freezes in the winter. Putting these two facts together raises the quite reasonable question of whether, if that is indeed how they’re made, that liquid might be water.

What is new about the latest results that adds to the superb detail revealed by the HIRISE images – is that there is spectroscopic information that yields clues about the chemical composition of the stuff in the RSLs:



The black lines denote spectra that are taken at two different locations; the upper one has been interpreted as indicating the presence of some mixture of hydrated Calcium, Magnesium and Sodium Perchlorates (i.e. salts). I’m not a chemical spectroscopist so I don’t know whether other interpretations are possible, though I can’t say that I’m overwhelmingly convinced by the match between the data from laboratory specimens and that from Mars…

Anyway, if that is indeed what the spectroscopy indicates then the obvious conclusion is that there is water present, for without water there can be no hydrated salts. This water could have been absorbed from the atmospheric vapour or from the ice below the surface. The presence of salts would lowers the melting point of water ice, so this could explain how there could be some form of liquid flow at the sub-zero temperatures prevalent even in a Martian summer. It would not be pure running water, however, but an extremely concentrated salt solution, much saltier than sea water, probably in the form of a rather sticky brine. This brine might flow – or perhaps creep – down the sloping terrain (briefly) in the summer and then freeze. But nothing has actually been observed to flow in such a way. It seems to me – as a non-expert – that the features could be caused not by a flow of liquid, but by the disruption of the Martian surface, caused by melting and freezing, involving  movement of solid material, or perhaps localized seeping. I’m not saying that it’s impossible that a flow of briny liquid is responsible for the features, just that I think it’s far from proven. But there’s no doubt that whatever is going on is fascinatingly complicated!

The last sentence of the abstract quoted above reads:

Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.

I’m not sure about the “strongly support” but “contemporary water activity” is probably fair as it includes the possibilities I discussed above, but it does seem to have led quite a few people to jump to the conclusion that it means “flowing water”, which I don’t think it does. Am I wrong to be so sceptical? Let me know through the comments box!



Pluto and the Pavilion

Posted in Biographical, Football, History with tags , , , , , on July 14, 2015 by telescoper

This is a busy week in many ways and for many reasons, but the main activity revolves around Graduation at the University of Sussex; the ceremony for graduates from my School (Mathematical and Physical Sciences) takes place on Thursday which gives me a couple of days to practice the pronunciation of the names I have to read out!

Anyway, last night there was a very Commemoration Dinner in the Dining Room of Brighton Pavilion:


The decor is a little understated for my tastes, and in any case I was among a group of about 40 guests who were seated elsewhere owing to the popularity of the event. In fact I was in the Red Drawing Room, which as its name suggests is, er, red:


Anyway, the dinner itself was splendid with particularly fine wine to boot. One of the topics of conversation was the forthcoming flypast of Pluto by the NASA New Horizons spacecraft. As the token astrophysicist on my table I tried my best to answer questions about this event. In fact the closest approach to Pluto takes place about 12.50 pm today (BST) but it will take some time for the images to be downloaded and processed; data transmission rates from the outer edge of the Solar System are rather limited! After passing Pluto, the spacecraft will carry on out of the Solar System into interstellar space. One thing I didn’t know until this morning was that the discoverer of Pluto, Clyde Tombaugh, expressed a wish that when he died his ashes should be sent into space. In fact, they are on New Horizons,  being carried past the planet object he found just 85 years ago. I find that very moving, but it’s also so inspiring that such a short time after Pluto was discovered a spacecraft is arriving there to study it. We humans can do great things if we put our minds to them. Science provides us with constant reminders of this inspirational fact. Unfortunately, politics tends to do the opposite…

I hope to provide a few updates with images from New Horizons if I get time. Here to whet your appetite is today’s stunning Astronomy Picture of the Day, showing Pluto and its largest moon, Charon, in the same frame:


Here’s a close-up of Pluto from yesterday:


And if that isn’t enough, click here for a simulation of the detail we expect to see when New Horizons reaches its closest approach to Pluto.

Honoris Causa, Dr Chryssa Kouveliotou

Posted in Education, The Universe and Stuff with tags , , , , , on July 10, 2014 by telescoper

This morning I had the privilege of participating in a graduation ceremony at the University of Sussex. It was great to get to shake the hands of all the successful graduates as they crossed the stage to receive their degrees. I hope I’ll be able to collect a few pictures of the occasion and post them in due course.



I also had the privilege of being able to present an extremely distinguished honorary graduand, Dr Chryssa Kouveliotou. Here the oration I delivered, which I’m posting simply to record her amazing achievements and to underline that she is one of many people who have done the MSc in Astronomy at Sussex University and gone on to do great things…



It is both a pleasure and an honour to present for the award of the degree of Doctor of Science, Dr Chryssa Kouveliotou.

Inspired by watching Neil Armstrong take his first step on the moon, Dr Kouveliotou always wanted to be an astronaut but, with no such opportunities apparently on offer in her native, she instead chose a career in astronomy. However, when she completed college Greece her astronomy professor (who shall remain nameless) advised her that there was no future for her in astrophysics. She has never known whether he really thought it was a poor choice or whether it was because she was a woman. Determined to follow her own path, she disregarded him completely and, even though her open-minded parents’ preference was for her to settle down and stay in her home country, she left to study for her Master’s degree in Astronomy at the University of Sussex; the topic of her dissertation was “The Sodium emission cloud around Io: mapping and correlation with Jupiter’s magnetic field”. She received the MSc in Astronomy in 1977. Although the topic of her subsequent research was rather different, the connection with magnetic fields remained strong.

Dr Kouveliotou then moved to Germany to do postgraduate research on the-then very new topic of gamma-ray bursts. Indeed, she may well have been the very first person to complete a thesis on this, which remains to this day an extremely active and exciting field of research. Gamma-ray bursts are considered to be the most powerful explosions in the universe, second only to the Big Bang itself.

After completing her PhD, Dr Kouveliotou returned to Greece to teach Physics and Astronomy at the University of Athens. All the while she knew that she really wanted to do research so spent her free time pursuing this goal. Every vacation and on her one-year sabbatical she went to the USA to undertake research at the National Aeronautics and Space Administration (NASA). Her work was on solar flares but she moonlighted during evenings, nights and weekends researching her ‘first love’ gamma-ray bursts. Because of the research she undertook outside her “day job”, she found a series of bursts which all came from the same part of the sky and, as a result, became part of the discovery team for a brand new phenomenon called a soft gamma-ray repeater.

By observing gamma rays produced in space, her team discovered an example of a new class of exotic astronomical object called a magnetar, an object which has a magnetic field trillions of times stronger than that of the Earth. A magnetar is now known to be a type of neutron star, a burnt-out relic resulting from the death of an ordinary star in a supernova explosion.

Dr Kouveliotou has always loved to ask big questions, to look at the universe and ask how nature expresses itself. By overcoming obstacles in her path she really has reached the stars. In January 2013 Dr Chryssa Kouveliotou was named the Senior Scientist for High Energy Astrophysics, Science and Research Office at NASA’s Marshall Space Flight Center in Hunstville, Alabama.

She has received many awards for her work, including the Dannie Heineman Prize for Astrophysics and the NASA Exceptional Service Medal in 2012 and the NASA Space Act Award in 2005. She was also named amongst Time Magazine’s 25 Most Influential People in Space in 2012. In 2003 she was honoured with the annual Rossi Prize by the High Energy Astrophysics division of the American Astronomical Society for a significant contribution to high-energy astrophysics. In 2002 she received the Descartes Prize which recognises scientific breakthroughs from European collaborative research in any scientific field. In the awards bestowed upon her she has also been recognised for her effectiveness at creating the sort of large collaboration needed to make effective use of multi-wavelength astronomical observations.

Dr Kouveliotou has published almost 400 papers in refereed scientific journals and has been amongst the top 10 most-cited space science researchers in the academic literature across the world. She has been elected chair of the Division of Astrophysics of the American Physical Society and is a member of the Council of the American Astronomical Society, of which she chairs the High Energy Astrophysics Division.

Vice-Chancellor, I present to you for the degree of Doctor of Science, honoris causa, Dr Chryssa Kouveliotou.



Article of the Day!

Posted in The Universe and Stuff with tags , , , , , , on July 31, 2013 by telescoper

Back in the office today, the heatwave having given way to grey drizzle and cool breezes (at least for the time being). I’ve got stacks of paperwork to catch up on, but fortunately I’ve got time to post a quick congratulatory message to Ian Harrison, who is author of today’s NASA ADS Article of the Day! Ian is a PhD student in the School of Physics & Astronomy at Cardiff University and was supervised by me until I abandoned ship to come here to Sussex earlier this year; he’s got a postdoctoral research position lined up in the Midlands (Manchester) when he finishes his thesis. The other author, Shaun Hotchkiss, is coming to Sussex as a postdoctoral researcher in October.

Anyway, the paper is a nice one, called A consistent approach to falsifying ΛCDM with rare galaxy clusters. Here’s the abstract:

We consider methods with which to answer the question “is any observed galaxy cluster too unusual for ΛCDM?” After emphasising that many previous attempts to answer this question will overestimate the confidence level at which ΛCDM can be ruled out, we outline a consistent approach to these rare clusters, which allows the question to be answered. We define three statistical measures, each of which are sensitive to changes in cluster populations arising from different modifications to the cosmological model. We also use these properties to define the “equivalent mass at redshift zero” for a cluster — the mass of an equally unusual cluster today. This quantity is independent of the observational survey in which the cluster was found, which makes it an ideal proxy for ranking the relative unusualness of clusters detected by different surveys. These methods are then used on a comprehensive sample of observed galaxy clusters and we confirm that all are less than 2σ deviations from the ΛCDM expectation. Whereas we have only applied our method to galaxy clusters, it is applicable to any isolated, collapsed, halo. As motivation for future surveys, we also calculate where in the mass redshift plane the rarest halo is most likely to be found, giving information as to which objects might be the most fruitful in the search for new physics.

In case you’re wondering, the rather Popperian nature of the title is not the reason why I’m not among the authors. I’m just not the sort of supervisor who feels he should always be an author of papers done by his research students even when they had the idea and did all the work themselves. From what I’ve heard talking to others, we’re a dying breed!

Cosmic Swirly Straws Feed Galaxy

Posted in The Universe and Stuff with tags , , , , , on June 5, 2013 by telescoper

I came across this video on youtube and was intrigued because the title seemed like a crossword clue (to which I couldn’t figure out the answer). It turns out that it goes with a piece in the Guardian which describes a computer simulation showing the formation of a galaxy during the first 2bn years of the Universe’s evolution. Those of us interested in cosmic structures on a larger scale than galaxies usually show such simulations in co-moving coordinates (i.e. in a box that expands at the same rate as the Universe), but this one is in physical coordinates showing the actual size of the objects therein; the galaxy is seen first to condense out of the expanding distribution of matter, but then grows by accreting matter in a complicated and rather beautiful way.

This calculation includes gravitational and hydrodynamical effects, allowing it to trace the separate behaviour of dark matter and gas (predominantly hydrogen).  You can see that this particular object forms very early on; the current age of the Universe is estimated to be about 13 – 14 billion years. When we look far into space using very big telescopes we see objects from which light has taken billion of years to reach us. We can therefore actually see galaxies as they were forming and can therefore test observationally whether they form as theory (and simulation) suggest.

Sic Transit Gloria Monday

Posted in The Universe and Stuff with tags , , , on June 11, 2012 by telescoper

I can never resist a terrible pun, so thought this would be an especially  good day to post this video from NASA’s Solar Dynamics Observatory,  showing views of last week’s Transit of Venus taken at several different wavelengths..


Tinker Tailor Soldier…Astronomer?

Posted in Science Politics, The Universe and Stuff with tags , on June 4, 2012 by telescoper


Tinker Tailor Soldier…Astronomer?

Originally posted on The e-Astronomer:

Not often I write two posts in one day, but here is an unexpected piece of news. It seems that the US National Reconnaisance Office have given two free telescopes to NASA. Its all explained at this NY Times article. They are as big as HST but have a wider field of view. They were designed for looking down of course.  Apparently there has been a secret study team and their conclusion is that one of these beasts would be perfect WFIRST, which had seemed to be kicked into the long grass.

They don’t exactly have the rest of the money yet or an actual approval … but the WFIRST fans are talking about shooting for 2020 … a year behind Euclid.

Ooooo what fun. Spot of healthy competition.

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