|Above: The landscape of Gale crater, seen by the Curiosity robot. Courtesy of NASA.|
Five possible new low-budget missions competing for NASA funding
NASA's Discovery class missions are relatively low budget probes that explore interesting but less studied destinations, test new technologies, or some combination of the two. The potential missions are chosen from a pool of proposals via competitive examination, and NASA has whittled its current pool down to five, with the final selection being made next year. The current contenders are:
VERITAS, an orbiter mission to Venus.
DAVINCI would dive into the Venusian atmosphere.
NEOcam, a space telescope that would hunt for asteroids.
'Psyche' would visit an asteroid thought to be a fragment of the core of a log dead protoplanet.
'Lucy' would visit one of the mysterious swarms of Trojan asteroids that follow Jupiter around the Sun.
|Above: Venus. Like hell if all the demons decided to move out and go into law. Reconstructed image courtesy of Don Mitchell.|
New results from the Dawn mission:
The Dawn team have released a topographic map of Occator crater (the one with the mysterious bright spots)......
....and a false colour map of Ceres, showing terrain that is bright in the infra red as red, terrain that is bright in UV as blue, and generally bright terrain as green. These psychedelic fake colours of the dwarf planets surface give clues about its composition.....
Russian Progress spacecraft sets out for the International Space Station, carrying supplies
Above: It's always cool to include a rocket launch. Although I think this one is carrying clean socks for the astronauts.....
Abstracts for the DPS 2015 conference are now available:
The Division for Planetary Science conference is a week long meeting of space boffins and geeks who'll give talks and presentations on space topics from the utterly obscure to the biggest mysteries out there.
You can look at the abstracts yourself here - there're a lot of them- but here're a few (picked out at random) examples to show you how much space is covered:
Liquid Water Lakes on Mars Under Present-Day Conditions: Sustainability and Effects on the Subsurface
Abstract: 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.
 Pieri (1980) Science 210.
 Carr (2006) The Surface of Mars.
 Wray et al. (2011) J. Geophys. Res. 116.
 Michalski et al. (2013) Nature Geosci. 6.
 Craddock and Howard (2002) J. Geophys. Res. 107.
 Clow (1987) Icarus 72.
New results from the analyses of the solid phase of the NASA Ames Titan Haze Simulation (THS) experiment
ABSTRACT: In Titan’s atmosphere, a complex chemistry occurs at low temperature between N2 and CH4 that leads to the production of heavy organic molecules and subsequently solid aerosols. The Titan Haze Simulation (THS) experiment was developed at the NASA Ames COSmIC facility to study Titan’s atmospheric chemistry at low temperature. In the THS, the chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas is cooled to Titan-like temperature (~150K) before inducing the chemistry by plasma, and remains at low temperature in the plasma (~200K). Different N2-CH4-based gas mixtures can be injected in the plasma, with or without the addition of heavier molecules, in order to monitor the evolution of the chemical growth.
Following a recent in situ mass spectrometry study of the gas phase that demonstrated that the THS is a unique tool to probe the first and intermediate steps of Titan’s atmospheric chemistry at low temperature (Sciamma-O’Brien et al., Icarus, 243, 325 (2014)), we have performed a complementary study of the solid phase. The findings are consistent with the chemical growth evolution observed in the gas phase. Grains and aggregates form in the gas phase and can be jet deposited onto various substrates for ex situ analyses. Scanning Electron Microscopy images show that more complex mixtures produce larger aggregates, and that different growth mechanisms seem to occur depending on the gas mixture. They also allow the determination of the size distribution of the THS solid grains. A Direct Analysis in Real Time mass spectrometry analysis coupled with Collision Induced Dissociation has detected the presence of aminoacetonitrile, a precursor of glycine, in the THS aerosols. X-ray Absorption Near Edge Structure (XANES) measurements also show the presence of imine and nitrile functional groups, showing evidence of nitrogen chemistry. Infrared and µIR spectra of samples deposited on KBr and Si substrates show the presence of more aromatic functional groups for more complex gas mixtures, and allowed the determination of the samples’ thickness. These complementary studies show the potential of THS to better understand Titan’s chemistry and the origin of aerosol formation.
Changing Perspectives on Mercury and the Moon:
ABSTRACT: Airless, cratered, and not so different in size, the Moon and Mercury form a natural pair in the inner Solar System. For decades after the 1974 and 1975 Mariner 10 flybys of Mercury, with little compositional information, no concrete evidence for volcanism, and images of less than half of the planet, it was thought that Mercury’s surface may be similar to the lunar highlands: an ancient anorthositic flotation crust subsequently shaped mainly by impact cratering. However, observations from the recently completed MESSENGER mission to Mercury have upended our view of the innermost planet, revealing, for example, a crust that may be rich in graphite and that has been extensively resurfaced by volcanic activity, and geologic activity that may continue today to produce enigmatic “hollows” – a crust very different from that of the Moon. Meanwhile, the Moon has undergone its own revolution, as data from recent spacecraft such as the Lunar Reconnaissance Orbiter reveal sites of silicic volcanism indicative of complex differentiation in the mantle, tectonic activity that may be ongoing, recent volcanic activity that alters the paradigm that volcanism died on the Moon over a billion years ago, and evidence that the early chronology of the inner Solar System may not be as well known as once thought. As our views of these two bodies evolve, a new understanding of their differences informs our knowledge of the variety of processes and styles of planetary evolution, and their similarities point to commonalities among all airless bodies.
Geomorphological Mapping of Sputnik Planum and Surrounding Terrain on Pluto
ABSTRACT: The New Horizons flyby of Pluto in July 2015 has provided the first few close-up images of the Kuiper belt object, which reveal it to have a highly diverse range of terrains, implying a complex geological history. The highest resolution images that have yet been returned are seven lossy 400 m/pixel frames that cover the majority of the prominent Plutonian feature informally named Sputnik Planum (all feature names are currently informal), and its surroundings. This resolution is sufficient to allow detailed geomorphological mapping of this area to commence. Lossless versions of all 15 frames that make up the mosaic will be returned in September 2015, and the map presented at DPS will incorporate the total area covered by these frames.
Sputnik Planum, with an area of ~650,000 km2, is notable for its smooth appearance and apparent total lack of impact craters at 400 m/pixel resolution. The Planum actually displays a wide variety of textures across its expanse, which includes smooth and pitted plains to the south, polygonal terrain at its center (the polygons can reach tens of kilometers in size and are bounded by troughs that sometimes feature central ridges), and, to the north, darker polygonal terrain displaying patterns indicative of glacial flow. Within these plains there exist several well-defined outcrops of a mottled, light/dark unit that reach from several to tens of kilometers across. Separating Sputnik Planum from the dark, cratered equatorial terrain of Cthulhu Regio on its south-western margin is a unit of chaotically arranged mountains (Hillary Montes); similar mountainous units exist on the south and western margins. The northern margin is bounded by rugged, hilly, cratered terrain (Cousteau Rupes) into which ice of Sputnik Planum appears to be intruding in places. Terrain of similar relief exists to the east, but is much brighter than that to the north. The southernmost extent of the mosaic features a unit of rough, undulating terrain (Pandemonium Dorsa) that displays very few impact craters at 400 m/pixel resolution.
This work was supported by the NASA New Horizons project.
Resolving Enceladus thermal emission at the 10s of meters scale along Baghdad Sulcus using Cassini CIRS
Abstract: On 14th April 2012 Cassini executed one of its closest flyby to the South Pole of Enceladus with the primary goal to study the moon’s gravity. During this flyby the Composite InfraRed Spectrometer (CIRS) was orientated such that its three focal planes were dragged across Baghdad sulcus. The instrument was specifically configured to record interferograms with 52 seconds duration. CIRS focal plane 1 (17 to 1000 µm) single circular detector provided a spatial resolution of about 300 meters. CIRS focal plane 3 and 4 (9 to 17 µm and 7 to 9 µm) are 2 1x10 detectors arrays. Both arrays were used in pair mode leading to 5 elements per focal plane and a resolution of about 43 meters across track.
The ground-track speed was so fast during this observation that this was enough time to observe the entire South Polar Region in a single integration. The thermal sources were passed over so rapidly that it is not possible to reconstruct a spectrum from the resulting interferogram, instead features were created in the interferogram whenever the scene temperature changed. The signature of these features was also altered by bit trimming and band-pass filter convolution. To enable interpretation of the interferograms we developed an innovative new approach that included the development of new instrument models, modification of the flight software and multiple in flight validation experiments. Our preliminary results show temperature variability of the tiger stripes at 10s meters scale along track, providing a constraint on the distribution and temperature profile of Enceladus’ endogenic sources.
A similar methodology will be used for the penultimate targeted Enceladus flyby in Oct 28th 2015 and we aim to also present our preliminary analysis of the results from this encounter
TITLE: The primordial nucleus of Comet 67P/Churyumov-Gerasimenko
Abstract: Observations of Comet 67P/Churyumov-Gerasimenko by Rosetta show that the nucleus is bi-lobed, extensively layered, has a low bulk density, a high dust-to-ice mass ratio (implying high porosity), and weak strength except for a thin sintered surface layer. The comet is rich in supervolatiles (CO, CO2, N2), may contain amorphous water ice, and displays little to no signs of aqueous alteration. Lack of phyllosilicates in Stardust samples from Comet 81P/Wild 2 provides further support that comet nuclei did not contain liquid water.
These properties differ from those expected for 50-200 km diameter bodies in the primordial disk. We find that thermal processing due to Al-26, combined with collisional compaction, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles, containing little to no amorphous water ice, and that have experienced extensive aqueous alteration. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. We therefore conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles.
We propose a concurrent comet and TNO formation scenario that is consistent with these observations. We argue that TNOs form due to streaming instabilities at sizes of about 50-400 km and that about 350 of these grow slowly in a low-mass primordial disk to the size of Triton, causing little viscous stirring during growth. We propose a dynamically cold primordial disk, that prevents medium-sized TNOs from breaking into collisional rubble piles, and allows for the survival of primordial rubble-pile comets. We argue that comets form by hierarchical agglomeration out of material that remains after TNO formation. This slow growth is necessary to avoid thermal processing by Al-26, and to allow comet nuclei to incorporate 3 Myr old material from the inner Solar System, found in Stardust samples. Growth in the Solar Nebula creates porous single-lobe nuclei, while continued growth in a mildly viscously stirred primordial disk creates denser outer layers, and allow bi-lobe nucleus formation through mergers.