The Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft collected orbital observations of the innermost planet from March 2011 until this spring. Perturbations to the orbit by the gravitational pull of the Sun, together with the exhaustion of usable propellant on the spacecraft, led to the impact of the spacecraft onto Mercury’s surface and the end of the mission. The evolution of MESSENGER’s orbit, coupled with the resilient performance of the spacecraft in stressing thermal environments, enabled unique measurements during the final phases of the mission. A series of periapsis-raising orbit-correction maneuvers yielded multiple orbits with closest approaches to the planet in the range ~5–35 km above Mercury’s surface prior to impact. The low-altitude observations by MESSENGER’s Magnetometer enabled the identification and characterization of crustal magnetic anomalies and demonstrated that Mercury’s core dynamo operated early in the planet’s history. Low-altitude measurements by MESSENGER’s Neutron Spectrometer over regions in permanent shadow near Mercury’s north pole have permitted mapping of surface hydrogen for comparison with Mercury’s polar deposits imaged by Earth-based radar and MESSENGER’s camera system. High-resolution images (down to ~1 m per pixel resolution) have shown a range of geological features in unprecedented detail, including examples of Mercury’s enigmatic hollows, and have enabled assessments of layering within crater walls, pyroclastic vents, and volcanic plains. Measurements by MESSENGER’s X-Ray Spectrometer have revealed elemental abundance variations on the scale of a few kilometers, in some cases correlated with the color properties of surface materials. Laser altimetry profiles have filled gaps in previous coverage, particularly near the equator, and additional radio tracking observations have improved the resolution of Mercury gravity field models at mid to high northern latitudes. Observations of the exosphere have revealed highly repeatable seasonal variability as well as unexpected structure in the spatial distribution of species.

We have computed digital terrain models (DTMs) from MESSENGER stereo images following previously established procedures that involve image correlation and least-squares block adjustment techniques. We produced 165 individual small-area models (222 m grid spacing), which in total cover approximately 50% of the planet’s northern hemisphere. To correct for offsets and tilts with respect to the Mercury reference frame, we co-registered the DTMs to laser altimeter profiles. However, because the individual laser altimeter profiles were taken at different times, we have carried out a joint inversion in which we solved simultaneously for Mercury rotation parameters as well as the static transformation parameters for each of the 165 DTMs. In particular, we solved for the orientation of Mercury’s rotation axis, rotation rate, and forced libration amplitude as well as the spatial offsets, rotation angles, and scaling factors of the individual DTMs. We find a large libration amplitude, which, in combination with the measured obliquity, confirms that Mercury possesses a liquid outer core. The mean rotation rate during the observation interval is higher than the expected resonant rate, suggesting that Mercury is undergoing long-period libration. The corrected DTMs in the northern hemisphere, tied to all available laser altimeter data, and the new rotation model represent a valuable realization of the reference grid for mapping applications at Mercury.

BepiColombo is a ESA-JAXA joint mission to Mercury with the aim to understand the process of planetary formation and evolution as well as to understand similarities and differences between the magnetospheres of Mercury and Earth.

The baseline mission consists of two spacecraft, i.e. the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO). The BepiColombo is scheduled to be launched in 2016 by an Ariane-5 and arrive at Mercury in January 2022.

JAXA is responsible for the development and operation of MMO, while ESA is responsible for the development and operation of MPO as well as the launch, transport, and the insertion of two spacecraft into their dedicated orbits. The main objectives of MMO are to study Mercury’s magnetic field and plasma environment around Mercury.

MMO is designed as a spin-stabilized spacecraft to be placed in a 400 km x 12,000 km polar orbit. The spacecraft will accommodate instruments mostly dedicated to the study of the magnetic field, waves, and particles near Mercury.

CDR for MMO was finished in 2011. Spacecraft CDR for ESA modules was finished in Nov. 2013. Mission CDR is expected in this summer.

Final AIV of MMO is expected to finish in this March. MMO will be tranported to ESA/ESTEC in early April and join final AIV for MCS (Mercury Cruise System). After MCS final AIV, each modules will be transported to the launch site (CSG) and prepare for launch.

12th BepiColombo science working team (SWT) meeting, which discusses BepiColombo science related matters, will be held on Sep. 2015 at UK. In this paper, we will report the latest information of MMO project status.

The large-scale dynamic behavior of Mercury's highly compressed magnetosphere is primarily powered by magnetic reconnection, which transfers energy and momentum from the solar wind to the magnetosphere. This drives the large-scale circulation of magnetic flux through the system, predominantly via the substorm, or loading-unloading cycle. We will present a statistical analysis of the average amplitude, duration and frequency of Mercury's loading-unloading cycle using magnetic field data acquired by the Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The largest amplitude loading-unloading events cycle through ~50% of Mercury’s open flux content. We will analyse the combination of magnetotail and solar wind parameters leading to these extreme events.

The Mercury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS) is part of the payload of the Mercury Planetary Orbiter spacecraft of the ESA-JAXA BepiColombo mission. MERTIS’s scientific goals are to infer rock-forming minerals, to map surface composition, and to study surface temperature variations on Mercury. To achieve these science goals MERTIS combines a imaging spectrometer covering the wavelength range from 7-14 microns with a radiometer covering the wavelength range from 7-40 microns. MERTIS will map the whole surface of Mercury with a spatial resolution of 500m for the spectrometer channel and 2km for the radiometer channel.

The MERTIS instrument had been proposed long before the NASA MESSENGER mission provided us with new insights into the innermost of the terrestrial planets. The discoveries of the MESSENGER fundamentally changed our view of Mercury. It revealed a surface that has been reshaped by volcanism over large parts of geological history. Volatile elements like sulfur have been detected with unexpectedly high abundances of up to 4%. MESSENGER imagined structures that are most likely formed by pyroclastic eruptions in recent geologic history. Among the most exciting discoveries of MESSENGER are hollows – bright irregularly shaped depressions that show sign of ongoing loss of material.  

Despite all this new results the MERTIS dataset remains unique and is now more important than ever. None of the instruments on the NASA MESSENGER mission covers the same spectral range or provides a measurement of the surface temperature. The MERTIS will complement the results of MESSENGER. MERTIS will for example be able to provide spatially resolved compositional information on the hollows and pyroclastic deposits – both among the most exciting discoveries by the MESSENGER mission for which the NASA mission can not provide compositional information.

Observations of the MESSENGER spacecraft in orbit around Mercury have shown that volcanism is a very important process that has shaped the surface of the planet. [1] have identified 200 pyroclastic deposits candidates based on color ratio and morphology images. [2] used the visible portion of the MASCS spectrometer to do further analysis on the spectral nature of the deposits. The authors have shown that the deposits have specific UV properties probably caused by Oxygen-Metal charges transfer, and a correlation between the slope of the UV-downturn and the age of the surrounding terrains.

In this study, we use the full range of the MASCS spectrometer (300-1400nm) to characterize the spectral properties of the pyroclastic deposits. Moreover, additional observations have been obtained since the last publications, and this allows specific studies of previously non-imaged deposits. This study shows that the visible slope of the deposits is changing as a function of distance from the vent, as seen on the Moon for pyroclastic deposits and their mafic absorption bands [Besse et al, 2013]. This is consistent with a decrease of thickness of the deposits that are mixed with background material. Surprisingly, the UV-downturn parameter proposed by [2] does not change as the distance to the vent increase. Eventually, the near infrared portion does not appear to have absorption bands in the range 900nm-1200nm, consistent with the very low iron abundance of the surface of Mercury. This could also be due to the lower signal to noise ratio of the near infrared portion of the MASCS instrument, and further analysis are needed to confirm these results.

References:

[1] Kerber et al, (2011) Planet & Spa. Sci, 59, 1895-1909, [2] Goudge et al., 2014, JGR, 119, 635-658. [3] Besse et al., 2011, JGR, 116.

The Mercury Transit (#MercuryTransit2016) is a rare phenomenon that will occur on the 9^th of May 2016 11:12-18:42 UT. Most of the world will be party to this observable event whereby the planet Mercury will pass in front of our sun (a solar transit), visually it will appear as a small black dot moving across the face of the sun. It will occur approximately ten years since the last transit with the next one due in 2019.

Occurring just a year after the end of the MESSENGER mission and a mere few months before the launch of BepiColombo it provides an ideal opportunity to engage the public by highlighting the fascinating science aspects of these missions to Mercury. Furthermore, a dual point observation campaign facilitating live web transmission (possibly in 3D) and world-wide media events will enable the public to feel involved and even observe.

The observation of the transit will produce tangible educational benefits by stimulating interest in reproduction of classical transit measurements, Earth-Sun distance calculations, parallax measurements and the production of science results.

This outreach project will involve and include a multitude of organisations, people, communications channels, conventional media papers, presentations, posters and of course the full plethora of social media. All these actors will need to communicate efficiently, to do so a central control point is planned. This paper will provide details of the plan and it will provide a channel for the community to get involved.

At the Planetary Emissivity Laboratory (PEL, Institute of Planetary Research of the German Aerospace Center, Berlin) we routinely measure emissivity spectra of planetary analogues, in the spectral range from 1 to 100 µm. Complementary measurements include reflectance and transmittance, from the visible to the far-infrared.

The MERTIS instrument on the ESA-JAXA BepiColombo mission will collect for the first time thermal infrared (TIR) spectra (7-14 µm) from the hot surface of the innermost planet, which at noon can locally reach a temperature of 450 °C. To prepare for the interpretation of this new dataset, we built a facility to measure the emissivity of very hot surfaces under vacuum (< 0.8 mbar). A Bruker Vertex 80V evacuable spectrometer is connected to an external chamber where the samples are heated under vacuum to temperatures from 50° to above 800° C. The use of an induction heating system to heat-up the stainless steel cups minimizes heat loss to the chamber. As a standard, we measure 4 grain size ranges, from very fines (<25 µm) to larger grain size (125-250 µm), and when possible even larger grain sizes or slabs. A sample carousel mounted on a high-precision rotating motor allows measuring several samples a day without breaking the vacuum. A monitoring webcam and a large number of temperature sensors (on samples, cups or other hardware parts in the chamber) complete the set-up.

Ongoing laboratory work shows that the high surface temperature of Mercury analogues can significantly affect the spectral characteristics of surface materials. This can lead to misinterpretations when compared to room temperature measurements. The effects have to be taken into account when interpreting spacecraft data, but even more so when designing new instrumentation.