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TOPIC: Mercury
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Title: The perihelion of Mercury advance and the light bending calculated in (enhanced) Newton's theory
Authors: M.A. Abramowicz, G.F.R. Ellis J. Horak, M. Wielgus

We show that results of a simple dynamical gedanken experiment interpreted according to standard Newton's gravitational theory, may reveal that three-dimensional space is curved. The experiment may be used to reconstruct the curved geometry of space, i.e. its non-Euclidean metric. The perihelion of Mercury advance and the light bending calculated from the Poisson equation and the equation of motion in the curved geometry have the correct (observed) values. Independently, we also show that Newtonian gravity theory may be enhanced to incorporate the curvature of three dimensional space by adding an extra equation which links the Ricci scalar with the density of matter. Like in Einstein's general relativity, matter is the source of curvature. In the spherically symmetric (vacuum) case, the metric of space 3gik that follows from this extra equation agrees, to the expected accuracy, with the metric measured by the Newtonian gedanken experiment mentioned above.

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Title: The influence of time, shape and tides on the obliquity of Mercury 
Authors: Benoit Noyelles, Christoph Lhotka 

Earth-based radar observations of the rotational dynamics of Mercury (Margot et al. 2012) combined with the determination of its gravity field by MESSENGER (Smith et al. 2012) give clues on the internal structure of Mercury, in particular its polar moment of inertia C, deduced from the obliquity (2.04 ± 0.08) arcmin. 
The dynamics of the obliquity of Mercury is a very-long term motion (a few hundreds of kyrs), based on the regressional motion of Mercury's orbital ascending node. This paper, following the study of Noyelles & D'Hoedt (2012), aims at first giving initial conditions at any time and for any values of the internal structure parameters for numerical simulations, and at using them to estimate the influence of usually neglected parameters on the obliquity, like J3, the Love number k2 and the secular variations of the orbital elements. We use for that averaged representations of the orbital and rotational motions of Mercury, suitable for long-term studies. 
We find that J3 should alter the obliquity by 250 milli-arcsec, the tides by 100 milli-arcsec, and the secular variations of the orbital elements by 10 milli-arcsec over 20 years. The resulting value of C could be at the most changed from 0.346mRČ to 0.345mRČ. 

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Mercury poles give up hints of water ice

A Nasa spacecraft has found further tantalising evidence for the existence of water ice at Mercury's poles.
Though surface temperatures can soar above 400C, some craters at Mercury's poles are permanently in shadow, turning them into so-called cold traps.
Previous work has revealed patches near Mercury's poles that strongly reflect radar - a characteristic of ice.
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Blobrana


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Crater Chao Meng-Fu
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ChaoMeng-Fub.jpg
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Credit NASA/JPL

The crater Chao Meng-Fu near Mercury's south pole was imaged by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) aboard the MESSENGER spacecraft on the 6th November, 2011.
The crater has a diameter of 129 km and is located at Latitude: -88.86°, Longitude: 27.78° E,

Source NASA



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Blobrana


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Title: Explanation for Observed Evidence of Geologically Recent Volatile-Related Activity on Mercury's Surface
Authors: J. Marvin Herndon

High resolution images of Mercury's surface, from the MESSENGER spacecraft, reveal many bright deposits associated with irregular, shallow, rimless depressions whose origins were attributed to volatile-related activity, but absent information on the nature and origin of that volatile matter. Here I describe planetary formation, unlike the cited models, and show that primordial condensation from an atmosphere of solar composition at pressures of one atmosphere or above will lead to iron condensing as a liquid and dissolving copious amounts of hydrogen, which is subsequently released as Mercury's core solidifies and escapes from the surface, yielding the observed pit-like features with associated highly-reflecting matter. The exiting hydrogen chemically reduces some iron compound, probably iron sulphide, to the metal, which accounts for the bright deposits.

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Epic volcanic activity flooded Mercury's north polar region

Planetary scientists at Brown University and participating institutions have discovered vast, smooth plains around Mercury's north pole that were created by volcanic activity more than 3.5 billion years ago. The lava flows were epic: They filled craters more than a mile deep and cover 6 percent of Mercury's surface, an area that would cover nearly 60 percent of the continental United States, the scientists write in the journal Science.
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MESSENGER Teleconference

image 1.1

Moon-Mercury image comparison. (Left) The near side of the Moon, showing the dark volcanic areas (maria) composed of lava flows and the bright, heavily cratered highland crust. (Right) Mariner 10 view of Mercury showing that, unlike the Moon, there is no brightness contrast between the cratered terrain and the smooth plains. The Moon is about one-quarter of the diameter of Earth; Mercury is about one-third of the diameter of Earth.

Credit: Lick Observatory (left); NASA/Jet Propulsion Laboratory/U.S. Geological Survey (right)

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Close-ups reveal a weirder Mercury

The first major release of results from NASA's MESSENGER spacecraft, which settled into orbit around Mercury last March, is forcing researchers to reconsider some of their most fundamental ideas about the nature and history of the Solar System's innermost planet.
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NASA Spacecraft Confirms Theories, Sees Surprises at Mercury
 
NASA scientists are making new discoveries about the planet Mercury. Data from MESSENGER, the first spacecraft to orbit Mercury, is giving scientists important clues to the origin of the planet and its geological history and helping them better understand its dynamic interior and exterior processes.
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, or MESSENGER, has been orbiting Mercury since March 18. To date the spacecraft has provided tens of thousands of images showing detailed planetary features. The planet's surface previously had been seen only at comparatively low resolution but is now in sharper focus.
The spacecraft also has collected extensive measurements of the chemical composition of Mercury's surface and topography and gathered global observations of the planet's magnetic field. Data now confirm that bursts of energetic particles in Mercury's magnetosphere are a continuing product of the interaction of Mercury's magnetic field with the solar wind.
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Mercury's Surface in Exaggerated Colour

mer1.jpg
Credit: NASA/JHU APL/CIW

The robotic MESSENGER spacecraft recently completed over 100 orbits of Mercury. Messenger's cameras have recorded detailed pictures utilising eight different colours across visible and near infrared light, exploring the surface composition and looking for clues to the history and evolution of the solar system's innermost planet.

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