Note: I apologise if there are some formatting problems with this entry in some browsers, I seem to have a bug somewhere and I won't have time to track it down until tomorrow. Thanks for your patience. John F
Discoveries from the DPS 2015 conference are about to hit the news:
Edit: I have just heard (here) that this morning's Pluto session at DPS 2015 is under a stealth embargo. I wonder why? If anyone knows, drop a comment in the comment box! End Edit
This week is the DPS conference, which is a big event where planetary science teams from all over the world present their discoveries. There are usually a few headlines to come out of a DPS meeting, and always some surprises. The major space news outlets will have reporters on the ground to cover on the talks and discoveries (there's a list of them here), and it's well worth keeping an eye on them as this should be a fascinating week. I can't afford to go to DPS*, so instead I've spent the weekend working my way through all the abstracts of the papers to try and give you a taste of what news might be coming out of the meeting. The title link takes you to the DPS website, if you want to browse the abstracts yourself - some are pretty cagey about their results, but a lot are really fascinating in their own right! I'm sorry the abstract titles don't link to the originals, I'd link to the interesting ones directly but it seems the site won't allow it.
Now, what might we expect from this week?
These two abstracts touch on the possibility of finding surface ponds on Mars today, on the detection of something releasing methane on the planet today near Curiosity rover, and on the discovery of organic molecules in Martian mudstone deposits.
Mars Science Laboratory's rover, Curiosity: Ongoing investigations into the habitability of Mars:
NASA’s Curiosity rover has the objective to determine whether Mars was habitable. The rover’s science team has achieved that and more, including two major firsts in planetary science. First, Gale Crater was determined to once have an aqueous environment and able to support microbial life, evidenced by conglomerates and the detailed analyses of the drill samples . Second, the age dating of rock on another planet – radiogenic and cosmogenic noble gases in a mudstone yielded a K-Ar age of 4.21 ± 0.35 Ga while 3He, 21Ne, and 36Ar yielded surface exposure ages of 78 ± 30 Ma , suggesting the potential to find rocks whose organic content has not yet been destroyed by cosmic rays. Indeed, organic compounds have been found in samples from the Sheepbed mudstone . Reports of plumes of methane in the martian atmosphere have defied explanation to date. Curiosity measured a constant background level of atmospheric methane with a mean value of 0.69 ± 0.25 ppbv, consistent with methane released from the degradation of interplanetary dust and meteorites. However, in four consecutive measurements spanning two months, the rover measured a ten-fold increase (7.2 ± 2.1 ppbv), suggesting that methane was actively added from an unknown source . Periodic measurements will continue, perhaps revealing the possible sources of high methane, whether biological or abiological. Enhancing our concept of Mars’ capability to support life, the Curiosity rover has detected nitrogen-bearing compounds of 110–300 ppm of nitrate in scooped sand, and 70–1,100 ppm of nitrate in drilled mudstone. Discovery of martian nitrogen has important implications for a nitrogen cycle at some point in martian history . More recent exploration has focused on the investigation of a mudstone-sandstone geologic contact, high Si and H abundances, and organics. These and the latest results from Curiosity will be discussed, exploring the transition of Mars from a habitable world to the desert planet it is today.
Liquid Water Lakes on Mars Under Present-Day Conditions:
Sustainability and Effects on the Subsurface:Decades of Mars exploration have produced ample evidence that aqueous environments once existed on the surface. Much evidence supports groundwater emergence as the source of liquid water on Mars [1-4]. However, cases have also been made for rainfall  and snow pack melts .
Whatever the mechanism by which liquid water is emplaced on the surface of Mars, whether from groundwater seeps, atmospheric precipitation, or some combination of sources, this water would have collected in local topographic lows, and at least temporarily, would have created a local surface water system with dynamic thermal and hydrologic properties. Understanding the physical details of such aqueous systems is important for interpreting the past and present surface environments of Mars. It is also important for evaluating potential habitable zones on or near the surface.
In conjunction with analysis of surface and core samples, valuable insight into likely past aqueous sites on Mars can be gained through modeling their formation and evolution. Toward that end, we built a 1D numerical model to follow the evolution of small bodies of liquid water on the surface of Mars. In the model, liquid water at different temperatures is supplied to the surface at different rates while the system is subjected to diurnally and seasonally varying environmental conditions. We recently simulated cases of cold (275 K) and warm (350 K) water collecting in a small depression on the floor of a mid southern latitude impact crater. When inflows create an initial pool 3 m deep and infiltration can be neglected, we find that the interior of the pool can remain liquid over a full Mars year under the present cold and dry climate as an ice cover slowly thickens . Here we present new results for the thermal and hydrologic evolution of surface water and the associated subsurface region for present-day conditions when infiltration of surface water into the subsurface is considered
|Above: The Sheepbed mudstone on Mars, which has become a scientific treasure trove. Courtesy of JPL/NASA.|
There're a lot of papers on Pluto - these are just a few that caught my eye; They touch on the presence of tholin (an important biological precursor), evidence for active geysers and volcanoes today on Pluto, and the effects of it's biggest moon, Charon, on it's surface.
Vigorous Convection Underlies Pluto’s Surface Activity:
Against many expectations, New Horizons’ images of the surface of Pluto and Charon show seemingly young surfaces. On Pluto, images of an equatorial region south of the Tombaugh Regio reveal a mountain range with peaks jutting as high as 3,500 meters. The low concentration of craters for these mountains suggests an age of 100 million years, indicating that Pluto is geologically active. Other evidence for geologic activity includes a fault cross-cutting ridges, smooth lightly cratered plains with flow fronts, and a pair of apparent stratovolcanoes. Charon similarly possesses very few craters and a spectacular system of troughs. Both observations suggest the possible presence of active cryogeysers and cryovolcanoes. The underlying cause of modern tectonic and volcanic activity on any object is likely a vigorous mantle convection regime. We are thus led to consider what determines planetary vigor. While Pluto and Charon seem to be quite active, Ceres and the much larger Callisto seem to lack modern endogenic activity, even though all of these bodies are likely to possess water ice mantles
Pluto: Distribution of ices and coloring agents from New Horizons LEISA observations:
Pluto was observed at high spatial resolution (maximum ~3 km/px) by the New Horizons LEISA imaging spectrometer. LEISA is a component of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Sci. Rev. 140, 129) and affords a spectral resolving power of 240 in the wavelength range 1.25-2.5 µm, and 560 in the range 2.1-2.25 µm. Spatially resolved spectra with LEISA are used to map the distributions of the known ices on Pluto (N2, CH4, CO) and to search for other surface components. The spatial distribution of volatile ices is compared with the distribution of the coloring agent(s) on Pluto's surface. The correlation of ice abundance and the degree of color (ranging from yellow to orange to dark red) is consistent with the presence of tholins, which are refractory organic solids of complex structure and high molecular weight, with colors consistent with those observed on Pluto. Tholins are readily synthesized in the laboratory by energetic processing of mixtures of the ices (N2, CH4, CO) known on Pluto's surface. We present results returned from the spacecraft to date obtained from the analysis of the high spatial resolution dataset obtained near the time of closest approach to the planet. Supported by NASA’s New Horizons project.
The Icy Cold Heart of Pluto:
The locations of large deposits of frozen volatiles on planetary surfaces are largely coincident with areas receiving the minimum annual influx of solar energy; familiar examples include the polar caps of Earth and Mars. For planets tilted by more than 45 degrees, however, the poles actually receive more energy than some other latitudes. Pluto, with its current obliquity of 119 degrees, has minima in its average annual insolation at +/- 27 degrees latitude, with ~1.5% more energy flux going to the equator and ~15% more to the poles. Remarkably, the fraction of annual solar energy incident on different latitudes depends only on the obliquity of the planet and not on any of its orbital parameters.
Over millions of years, Pluto's obliquity varies sinusoidally from 102-126 degrees, significantly affecting the latitudinal profile of solar energy deposition. Roughly 1Myr ago, the poles received 15% more energy that today while the equator received 13% less. The energy flux to latitudes between 25-35 degrees is far more stable, remaining low over the presumably billions of years since Pluto acquired its current spin properties. Like the poles at Earth, these mid latitudes on Pluto should be favored for the long-term deposition of volatile ices. This is, indeed, the location of the bright icy heart of Pluto, Sputnik Planum.
Reflected light and emitted thermal radiation from Charon increases annual insolation to one side of Pluto by of order 0.02%. Although small, the bulk of the energy is delivered at night to Pluto's cold equatorial regions. Furthermore, Charon's thermal infrared radiation is easily absorbed by icy deposits on Pluto, slowing deposition and facilitating sublimation of volatiles. We argue the slight but persistent preference for ices to form and survive in the anti-Charon hemisphere.
|Above: The Tombaugh Regio area of Pluto, where nitrogen glaciers are invading the surrounding valleys. Courtesy of NASA.|
Venus gets a surprising number of interesting abstract, probably because the Japanese Akatsuki probe is about to make another attempt at getting into orbit. These two really leaped out at me: One describes how the chemistry of Venus atmosphere could well be more complex and unexpected that we've thought. The other is sort of a round up of the questions we still haven't got answers for about this weird world.
Chemistry in the Venus clouds: Sulfuric acid reactions and freezing behavior of aqueous liquid droplets
Venus has a thick cloud deck at 40-70 km altitude consisting of liquid droplets and solid particles surrounded by atmospheric gases. The liquid droplets are highly concentrated aqueous solutions of sulfuric acid ranging in concentration from 70-99 wt%. Weight percent drops off with altitude (Imamura and Hashimoto 2001). There will be uptake of atmospheric gases into the droplet solutions and the ratios of gas-phase to liquid-phase species will depend on the Henry’s Law constant for those solutions. Reactions of sulfuric acid with these gases will form products with differing solubilities. For example, uptake of HCl by H2SO4/H2O droplets yields chlorosulfonic acid, ClSO3H (Robinson et al 1998) in solution. This may eventually decompose to thionyl- or sulfuryl chlorides, which have UV absorbances. HF will also uptake, creating fluorosulfonic acid, FSO3H, which has a greater solubility than the chloro- acid. As uptake continues, there will be many dissolved species in the cloudwaters. Baines and Delitsky (2013) showed that uptake will have a maximum at ~62 km and this is very close to the reported altitude for the mystery UV absorber in the Venus atmosphere. In addition, at very strong concentrations in lower altitude clouds, sulfuric acid will form hydrates such as H2SO4.H2O and H2SO4.4H2O which will have very different freezing behavior than sulfuric acid, with much higher freezing temperatures (Carslaw et al, 1997). Using temperature data from Venus Express from Tellmann et al (2009), and changes in H2SO4 concentrations as a function of altitude (James et al 1997), we calculate that freezing out of sulfuric acid hydrates can be significant down to as low as 56 km altitude. As a result, balloons, aircraft or other probes in the Venus atmosphere may be limited to flying below certain altitudes. Any craft flying at altitudes above ~55 km may suffer icing on the wings, propellers, balloons and instruments which could cause possible detrimental effects (thermal changes, reduced buoyancy, effects on control surfaces, plugging of sample inlets, etc.). Therefore, de-icing equipment should be considered when designing aircraft expected to fly at high altitudes in the Venus clouds.
Some questions about the Venus atmosphere from past measurements:
The many missions undertaken in the past half a century to explore Venus with fly-by spacecraft, orbiters, descending probes, landers and floating balloons, have provided us with a wealth of data. These data have been supplemented by many ground based observations at reflected solar wavelengths, short and long wave infrared to radio waves. Inter-comparison of the results from such measurements provide a good general idea of the global atmosphere. However, re-visiting these observations also raises some questions about the atmosphere that have not received much attention lately but deserve to be explored and considered for future measurements.
These questions are about the precise atmospheric composition in the deep atmosphere, the atmospheric state in the lower atmosphere, the static stability of the lower atmosphere, the clouds and hazes, the nature of the ultraviolet absorber and wind speed and direction near the surface from equator to the pole. The answers to these questions are important for a better understanding of Venus, its weather and climate. The measurements required to answer these questions require careful and sustained observations within the atmosphere and from surface based stations. Some of these measurements should and can be made by large missions such as Venera-D (Russia), Venus Climate Mission (Visions and Voyages – Planetary Science Decadal Survey 2013-2022 or the Venus Flagship Design Reference Mission (NASA) which have been studied in recent years, but some have not been addressed in such studies. For example, the fact that the two primary constituents of the Venus atmosphere – Carbon Dioxide and Nitrogen are supercritical has not been considered so far. It is only recently that properties of binary supercritical fluids are being studied theoretically and laboratory validation is needed.
With the end of monitoring of Venus by Venus Express orbiter in November 2014 after nearly a decade of observations and the imminent insertion of JAXA’s Akatsuki spacecraft into orbit around Venus, it is a good moment to consider the unanswered or unexplored questions about Venus.
|Above: The strange UV absorbing clouds of Venus. courtesy fo ESA.|
The ever fascinating Saturn system gets its share of mentions. The first is on the polar jets of Enceladus (which may be more like curtains than jets) and the second mentions evidence pointing to cryo volcanoes on Titan - a really exciting prospect for alien life hunters, given that Titan is already host to masses of pre-biotic chemistry!
Drawing the Curtain on Enceladus' South-Polar Eruptions
For a comprehensive description of Enceladus' south-polar eruptions observed at high resolution, they must be represented as broad curtains rather than discrete jets. Meanders in the fractures from which the curtains of material erupt give rise to optical illusions that look like discrete jets, even along fractures with no local variations in eruptive activity, implying that many features previously identified as "jets" are in fact phantoms. By comparing Cassini images with model curtain eruptions, we are able to obtain maps of eruptive activity that are not biased by the presence of those phantom jets. The average of our activity maps over all times agrees well with thermal maps produced by Cassini CIRS. We can best explain the observed curtains by assuming spreading angles with altitude of up to 14° and zenith angles of up to 8°, for curtains observed in geometries that are sensitive to those quantities.
Titan’s mid-latitude surface regions with Cassini VIMS and RADAR
The Cassini-Huygens mission instruments have revealed Titan to have a complex and dynamic atmosphere and surface. Data from the remote sensing instruments have shown the presence of diverse surface terrains in terms of morphology and composition, suggesting both exogenic and endogenic processes . We define both the surface and atmospheric contributions in the VIMS spectro-imaging data by use of a radiative transfer code in the near-IR range . To complement this dataset, the Cassini RADAR instrument provides additional information on the surface morphology, from which valuable geological interpretations can be obtained . We examine the origin of key Titan terrains, covering the mid-latitude zones extending from 50ºN to 50ºS. The different geological terrains we investigate include: mountains, plains, labyrinths, craters, dune fields, and possible cryovolcanic and/or evaporite features. We have found that the labyrinth terrains and the undifferentiated plains seem to consist of a very similar if not the same material, while the different types of plains show compositional variations . The processes most likely linked to their formation are aeolian, fluvial, sedimentary, lacustrine, in addition to the deposition of atmospheric products though the process of photolysis and sedimentation of organics. We show that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions. The surface albedo variations together with the presence of volcanic-like morphological features suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanism processes (with important implications for the satellite’s astrobiological potential) as also indicated by new interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses . However, an explanation attributed to exogenic processes is also possible . We will report on results from our most recent research on the surface properties of Titan.
|Above: The Plumes of Enceladus, which may actually be more like a ribbon of gushing gas. Courtesy of NASA.|
Astronaut plays bagpipes in space to pay tribute to a colleague.
Astronaut Kjell Lindgren played Amazing Grace on the pipes after recording a message about research scientist Victor Hurst, who died suddenly aged 48. Dr Hurst worked as a research scientist and instructor. The pipes were especially made by a Scottish firm, McCallum Bagpipes. Kenny Macleod from the company told told BBC Scotland Lindgren had got in touch two years ago to say he was going to the space station and wanted to play the pipes while he was there.
Macleod said:"They're made of plastic - they're just easier to keep clean and to make sure they're not contaminated. They're also lighter."
Lindgren paid tribute to Dr Hurst: "He always had a quick smile, a kind word. I don't know if anyone was more enthusiastic and professional about being involved in human space flight."
|Above: Kjell Lindgren plays Amazing Grace in tribute to Dr Hurst.|
Testing touch screens for space craft cockpits
Although it might seem like a bit of a trivial thing, the way an astronaut controls their space craft is very important. Back in the day a spaceship's cockpit was full of switches and dials, but newer designs are moving towards touch screens. While that's great (very Star Trek) in theory, there's still a question mark over how well the astronauts will be able to use them in microgravity. Microgravity can have a detrimental effect on the human body—muscles atrophy, bones weaken, and the immune system doesn’t function properly. Is co-ordination affected as well? The Fine Motor Skills experiment aims to find out. it's simple enough: Crew members just need to complete four kinds of task on an i-pad, at regular intervals. But it's implications could be huge:
“Many tasks performed inside a modern spacecraft will involve fine motor skills such as typing or interacting with a computer touchscreen,” says Kritina Holden, Principal Investigator for the Fine Motor Skills experiment. “In the future, astronauts will use portable computers for many tasks, including maintenance, training, medical treatment, science, time lining, and scheduling....Our real concern is making sure that future crewmembers can use their computer-based devices with accuracy onboard and on a planetary surface after a long voyage, for example to Mars.”
Above: A NASA science cast video on the Fine Motor Skills Experiment.