RESUMO
The surface of Pluto is more geologically diverse and dynamic than had been expected, but the role of its tenuous atmosphere in shaping the landscape remains unclear. We describe observations from the New Horizons spacecraft of regularly spaced, linear ridges whose morphology, distribution, and orientation are consistent with being transverse dunes. These are located close to mountainous regions and are orthogonal to nearby wind streaks. We demonstrate that the wavelength of the dunes (~0.4 to 1 kilometer) is best explained by the deposition of sand-sized (~200 to ~300 micrometer) particles of methane ice in moderate winds (<10 meters per second). The undisturbed morphology of the dunes, and relationships with the underlying convective glacial ice, imply that the dunes have formed in the very recent geological past.
RESUMO
A study of the past can help us understand present-day management structures. Strong parallels can be seen between the present-day British National Health Service (NHS) and English feudal society in the early Middle Ages. Both systems are hierarchical, both show limited mobility between layers in the hierarchies and in both there is a strong element of central control coexisting with significant day-to-day delegation of responsibility. Ceremony plays a key role in relationships, such as through the swearing of liege homage in feudal society and through formal assessment and appraisal in the modern NHS. Although the NHS clearly does not show parallels for every element of feudal society, it is possible to draw practical lessons from the comparison, particularly relating to the ownership of problems, team-working and appraisal.
