SH54A-01 INVITED 16:00h
Magnetic Mapping of the Moon and Mars Using Electron Reflection Magnetometry
One of the major surprises of the Apollo 15 & 16 lunar missions was the discovery of hundreds of patches of strong remnant magnetization of the lunar crust, ranging from tens to hundreds of km scale size. Most of these regions were mapped through the serendipitously discovered electron reflection (ER) method for remote sensing of surface magnetic fields. Since then electron reflectometers have been flown on the Mars Global Surveyor and Lunar Prospector missions. We present here high sensitivity full global maps of the surface magnetic fields of both planetary bodies. Remarkably strong surface magnetic fields have been detected, especially for Mars. These detailed maps show complex structure, but the origin and history of the magnetization on both bodies still remains a mystery. Impact processes, however, are clearly important in erasing magnetism on both bodies, and may also be involved in producing magnetization on the Moon. Recently, the ER method has been used to probe of the structure of the upper Martian atmosphere. For both the Moon and Mars there is evidence for closed magnetospheres/cylinders at least some of the time, and the interaction of the solar wind with these structures can be complex. Evidence for magnetic reconnection and for non-fluid effects have been found.
SH54A-02 INVITED 16:15h
Exploring the Moon and Mars solar wind interaction using energetic neutral atoms
The Moon and Mars are non-magnetized bodies. Therefore the solar wind can interact directly with the surface of the Moon and the upper parts of Mars' atmosphere. This is in contrast to the situation at magnetized planets, where the planet is protected by a magnetosphere. The solar wind interaction can be remotely studied by energetic neutral atom (ENA) imaging. Here we consider the energy regime 10 eV-10 keV, and review the different sources of ENAs at the Moon and at Mars. At the Moon, ENAs are produced by sputtering resulting from the precipitating solar wind. These sputtered neutrals can be imaged by an orbiting ENA detector. These images can produce information on space weathering, magnetic anomalies, and surface composition. At Mars, hydrogen ENAs are produced by charge exchange between solar wind protons and neutrals in Mars' exosphere. Imaging of these ENAs provide global information on the distributions of ions and neutrals. It is however not straight forward to extract this information from an ENA image, since we only know the ENA flux integrated along lines of sight. Inverse modeling is needed to extract parameters from observed ENA images. Another production mechanism for ENAs is that when solar wind protons and hydrogen ENAs precipitate onto the upper parts of Mars' atmosphere, they produce an outflux of ENAs by sputtering and backscattering, respectively. Also, a source of oxygen ENAs is from photoionized oxygen that is accelerated, and then charge exchange with neutrals. Another possible source of ENAs at Mars is from solar wind charge exchange with the Phobos gas torus. For Mars we also review the effects on the different ENA populations of using hybrid or MHD models for computer simulations of the ENA production. Observations of the above mentioned ENA populations at Mars can, with the help of modeling, provide, e.g., estimates of oxygen escape and carbon dioxide sputtered by oxygen ions.
SH54A-03 INVITED 16:30h
Radiation and the Exploration of the Moon and Mars: Current Knowledge, Challenges, and Required Measurements
The NASA Exploration Initiative calls for a long term human presence on the Moon and eventually Mars, and radiation is among one of many environmental factors that may affect both system and human safety in this endeavor. The importance of radiation in spacecraft operations was recently underscored by a host of anomalies and failures occurring throughout the solar system during the Halloween storms in 2003. A combination of measurements, modeling, and predictive capabilities should provide a framework to mitigate this threat for a variety of future space and planetary missions. Here we consider the energetic, highly penetrating ionizing radiation found in Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) in the context of the exploration of the Moon and Mars. The high-Z and energy GCR spectra have been fairly well characterized, while the occurrence of SEPs is still an active area of current research. SEP composition is primarily protons and usually limited to $<$ GeV energies, yet their intensity and variability make these events an important consideration when compared to the relatively low-flux but constant GCR background. SEP events may be especially relevant for operations on the lunar surface, while only exceptionally intense and energetic SEPs may impact the surface of Mars due to the presence of an atmosphere. For both GCR and SEP radiation fields, a major uncertainty for exposure on the surface or in transit is the interaction of these particles with the atmosphere, shielding materials and subsurface regolith, since secondaries can represent a large contribution to the absorbed dose in a given location. We will discuss the current state of knowledge regarding the radiation environment on the Moon and Mars, some specific examples of system failures, and the need for experimental validation of radiation transport models through strategically chosen measurements on future human precursor missions.
SH54A-04 INVITED 16:45h
Dusty Plasma Effects on the surfaces of the Moon and Mars
After a long break following the Apollo missions, the Moon is likely to become again the target of in situ investigations, serving as our gateway to land people on Mars. Although a layer of fine dust had been predicted for the moon, dust "storms" were not anticipated because of the absence of an atmosphere. The Lunar Ejecta and Meteorite (LEAM) experiment detectors deployed by Apollo 17 showed, unexpectedly, that most impacts were due to lunar dust levitated and transported electrostatically. There are significant technical challenges related to the mitigation of dust hazards for humans and instruments. For example, dust clinging to space suits became a nuisance for the astronauts returning to their habitats on the Moon. The surface of Mars represent a very different environment, where charging is likely to occur due to wind-entrained dust collisions, in addition to possible UV charging. These effects are likely to results in electrostatic discharges and possibly interfere with surface instrumentation and human activities. In this talk we will review our current theoretical models for dusty plasma effects on the Moon and Mars, and also summarize ongoing laboratory efforts to verify these models. These experiments address dust charging, electrostatic levitation and transport on the Moon, and also the possible electrification and discharges that might occur on Mars. We will conclude with a summary of the outstanding issues to be addressed by in situ measurements and the possible instrumentation for these investigations.
SH54A-05 17:00h
Mars Aeronomy Science Themes and the NASA Exploration Initiative
NASA convened a workshop on 18-19 August to reexamine Mars upper-atmosphere science questions in light of the new Exploration Initiative, with more than 80 scientists participating. The upper atmosphere is an important part of the martian climate system. Determining the nature and history of the martian climate, the chemical weathering and alteration of the surface, and the planet's habitability requires understanding the roles of the solar wind and solar radiation inputs; the physics, chemistry, and dynamics of the upper atmosphere; and the escape of volatiles to space. The upper atmosphere also plays important roles in programmatic aspects of the Mars exploration program, including communications, energetic particle and radiation environments that can affect humans, the lifetimes of orbiting spacecraft, operational aspects of orbital missions, and aerobraking operations. Important aspects of the upper-atmosphere can be observed from the unique perspective of the planned Mars Telecommunications Orbiter, especially with observations potentially made over an entire solar cycle. Although some limited observations are being made of the upper atmosphere at present, even combined with possible results from MTO they will not provide the detailed information necessary for either science or programmatic issues. The necessary observations can be obtained from a dedicated spacecraft mission with appropriate orbit, lifetime, and instrumentation. The necessary observations are thought to be possible within the confines of a Scout-class mission, although detailed analysis of this opportunity has not been done.
SH54A-06 17:15h
Lunar surface and atmosphere analysis through in situ pickup ions
The United States is about to embark on another great space adventure; humans and robots in synergy, to explore the Moon, Mars, and beyond. The exploration of the lunar atmosphere is therefore possible, and timely. The Moon has an atmosphere, a collisionless exosphere in which material released from the surface is gravitationally bound. It is very tenuous and very fragile, very much affected and expected to be very much affected by the anticipated lunar exploration program. It is the purpose to this talk to outline the breakthrough science that can be done from a platform in a near-lunar orbit, detecting pickup ions from surface and atmospheric sources. We will discuss expected sources and sinks of these species. We will also focus on transient events from lunar quakes and from meteoritic impacts. Finally, we discuss a possible implementation of an instrument that could do these breakthrough measurements.
SH54A-07 17:30h
The Lyman-Alpha Mapping Project (LAMP)
LAMP is a UV spectrograph investigation recently proposed for the LRO mission. Its three main objectives are to (i) identify and localize exposed water frost in permanently shadowed regions (PSRs), (ii) characterize landforms and albedos in PSRs, and (iii) demonstrate the feasibility of using natural starlight and sky-glow illumination for future lunar surface mission applications. A supplemental objective is to assay the lunar atmosphere and its variability. The LAMP spectrograph will accomplish these objectives by measuring the signal reflected from the nightside lunar surface and PSRs using the interplanetary HI Ly$\alpha$ sky-glow and FUV starlight as light sources. Both these light sources provide fairly uniform, but faint, illumination (e.g., the reflected Lya signal is expected to be ~$\sim10$~R). Thanks to LAMP's sensitivity, however, by the end of the nominal 1-year mission the SNR for a Ly$\alpha$ albedo map will be $>100$/km$^2$ in the polar regions, allowing the characterization of subtle compositional and structural features. LAMP is based on the flight-proven ALICE series of spectrographs that are flying on Rosetta and built for New Horizons.
SH54A-08 17:45h
Latest Results from the DCIXS X-ray spectrometer on the SMART-1 ESA mission to the Moon
The ESA SMART-1 mission to the Moon was successfully launched on 27 Sept 2003. A major payload element is D-CIXS, a Compact X-ray Spectrometer which will provide high quality spectroscopic mapping of the Lunar surface. At the same time it demonstrates a radically novel approach to building a type of instrument essential for the Mercury cornerstone mission. It will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, using new technology which does not require cold running, with its associated overheads to the spacecraft. It consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy, and a solar monitor to provide the calibration of the illumination necessary to produce global map of absolute Lunar elemental abundances. X-ray measurements can also provide insight into the solar wind interaction with the Moon. SMART-1 is due to enter Lunar orbit on 17 Nov 2004. It has already been turned on and is functioning well, and is providing useful calibration data, as well as unique remote sensing of terrestrial fluorescence. It also shows very little degredation as a result of high exposures during its 18 month long flight.
http://sspg1.bnsc.rl.ac.uk/Share/d-cixs.htm