Building and maintaining the constituency for long-term space exploration

The exploration of space is a long-term endeavor that will require strong public support to weather societal and political changes over the period of its implementation. In August 2006, George Mason University's Center for Aerospace Policy Research organized a workshop to address this issue. The sustainability of space exploration was investigated from a variety of perspectives by invited experts from the space sector as well as from the market research and public relations fields. This paper summarizes the results of the workshop. It presents market research data along with recommendations for an active strategic communications effort as well as public engagement to enhance public support for space exploration, especially among the younger age groups which tend to be uninterested in space activities.     

Energetic Particles and Corotating Interaction Regions in the Solar Wind

This paper reviews three important effects on energetic particles of corotating interaction regions (CIRs) in the solar wind that are formed at the leading edges of high-speed solar wind streams originating in coronal holes. A brief overview of CIRs and their important features is followed by a discussion of CIR-associated modulations in the galactic cosmic ray intensity, with an emphasis on observations made by spacecraft particle telescope ‘anti-coincidence’ guards. Such guards combine high counting rates (hundreds of counts/s) and a lower rigidity response than neutron monitors to provide detailed information on the relationship between cosmic ray modulations and CIR structure. The modulation of Jovian electrons by CIRs is then described. Finally, the acceleration of ions to energies of ～20 MeV/n in the vicinity of CIRs is reviewed.     

An icy mineralogy package (IMP) for in-situ studies of Titan’s surface

We describe the scientific case for and preliminary design of an instrument whose primary goal is to determine the chemistry (element abundance) and mineralogy (compound identity and abundance) of Titan’s surface using a combination of energy dispersive X-ray fluorescence spectroscopy (EDXRF) and X-ray diffraction (XRD). XRD is capable of identifying any crystalline substance present on Titan’s surface at relative abundances greater than ∼1 wt%, allowing unambiguous identification of, for example, structure I and II clathrates (even in the presence of ice), and various organic solids, which may include C₂H₂, C₂H₄, C₄H₂, HCN, CH₃CN, HC₃N, and C₄N₂). The XRF component of the instrument will obtain elemental abundances for 16 < Z < 60 with minimum detection limits better than 10 ppm (including detection of atmospheric noble gas isotopes), and may achieve detection limits of 0.01–1% for lighter elements down to Z = 6 (carbon). The instrument is well suited to integration with other analytical tools as part of a light-weight surface chemistry and mineralogy package. Although considerably less sensitive to elemental abundance than GC–MS (10⁻² vs. 10⁻⁸) it is likely to be significantly lighter (<0.5 kg vs. 10 kg).     

The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument

Space Science Reviews - Modern observatories have revealed the ubiquitous presence of magnetohydrodynamic waves in the solar corona. The propagating waves (in contrast to the standing waves) are...     

Overshooting from convective cores: Theory and numerical simulation

Convective overshooting increases the fraction of the star which is effectively mixed, thus altering models of stellar evolution. If the feed back of overshooting on the structure of the star is neglected the estimated extent of overshooting is very small. If the feed back is included in these estimates then the adiabatic core is extended by a distance comparable to a substantial fraction of the radius of the unstable region. An upper limit on convective overshooting is given by the integral constraint (Roxburgh 1978, 1989) with viscous dissipation neglected. If this constraint is applied to small convective cores then the maximum extent of the penetration region is shown to be at most about 0.18 times the radius of the core independent of the details of energy generation and opacity. The ratio of the maximum penetration distance to the scale height at the edge of the “classical boundary” varies very strongly with core size, and modelling overshooting by taking the penetration distance as a multiple of the scale height is likely to give misleading results. Numerical simulations of two-dimensional compressible convection in a fluid where the central regions are naturally convectively unstable, and the surrounding layers are stable, have been undertaken for different values of the Prandtl number. The results indicate that for low Prandtl numbers viscous dissipation is of decreasing importance and the simple integral condition gives a reasonable estimate of the extent of overshooting. Stellar seismology offers the possibility of detecting the location of the core — envelope interface through a periodic variation of the small frequency separation with frequency.     

A new paradigm for international cooperation in space exploration

In announcing a new Vision for the US space program, President George Bush committed the USA to “a long-term human and robotic program to explore the solar system”, via a return to the Moon, leading to exploration of Mars and other destinations. He also stated that other nations would be invited to join the vision. Many other nations have, or are developing, ‘exploration visions’ of their own. The potential for international cooperation therefore exists, both at the vision and program/project levels. This paper, based on Working Group discussions as part of an AIAA space cooperation workshop,¹ presents an approach for maximizing the return on all global investments in space exploration. It proposes an international coordination mechanism through which all these various national activities could be integrated into an inherently global enterprise for space exploration, a ‘virtual program of programs’. Within the context of the coordination, individual activities would utilize the full range of cooperative mechanisms for implementation. A significant benefit of this mode of conducting cooperation is that it would not require the negotiation of complex overarching international agreements as a precondition for initiating international activity.     

A comment on "the far future of exoplanet direct characterization"--the case for interstellar space probes

Following on from ideas presented in a recent paper by Schneider et al. on "The Far Future of Exoplanet Direct Characterization," I argue that they have exaggerated the technical obstacles to performing such "direct characterization" by means of fast (order 0.1c) interstellar space probes. A brief summary of rapid interstellar spaceflight concepts that may be found in the literature is presented. I argue that the presence of interstellar dust grains, while certainly something that will need to be allowed for in interstellar vehicle design, is unlikely to be the kind of showstopper suggested by Schneider et al. Astrobiology as a discipline would be a major beneficiary of developing an interstellar spaceflight capability, albeit in the longer term, and I argue that astrobiologists should keep an open mind to the possibilities.     

On the survivability and detectability of terrestrial meteorites on the moon

Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (相似文献   

Gypsum-permineralized microfossils and their relevance to the search for life on Mars

Abstract Orbital and in situ analyses establish that aerially extensive deposits of evaporitic sulfates, including gypsum, are present on the surface of Mars. Although comparable gypsiferous sediments on Earth have been largely ignored by paleontologists, we here report the finding of diverse fossil microscopic organisms permineralized in bottom-nucleated gypsums of seven deposits: two from the Permian (～260?Ma) of New Mexico, USA; one from the Miocene (～6?Ma) of Italy; and four from Recent lacustrine and saltern deposits of Australia, Mexico, and Peru. In addition to presenting the first report of the widespread occurrence of microscopic fossils in bottom-nucleated primary gypsum, we show the striking morphological similarity of the majority of the benthic filamentous fossils of these units to the microorganisms of a modern sulfuretum biocoenose. Based on such similarity, in morphology as well as habitat, these findings suggest that anaerobic sulfur-metabolizing microbial assemblages have changed relatively little over hundreds of millions of years. Their discovery as fossilized components of the seven gypsiferous units reported suggests that primary bottom-nucleated gypsum represents a promising target in the search for evidence of past life on Mars. Key Words: Confocal laser scanning microscopy-Gypsum fossils-Mars sample return missions-Raman spectroscopy-Sample Analysis at Mars (SAM) instrument-Sulfuretum. Astrobiology 12, 619-633.