Lunar rocks as meteoroid detectors

About 5000 microcraters on seven lunar rocks recovered during the Apollo 12 mission have been systematically studied using a stereomicroscope. Based on comparisons with laboratory cratering experiments, at least 95 percent of all millimeter sized craters observed were formed by impacts in which the impact velocity exceeded 10 km/s. The dynamics of particle motion near the moon and the distribution of microcraters on the rocks require an extralunar origin for these impacting particles. The microcrater population on at least one side of all rocks studied was in equilibrium for millimeter sized craters; i.e., statistically, craters a few millimeters in diameter and smaller were being removed by the superposition of new craters at the same rate new craters were being formed. The population of craters on such a surface is directly related to the total population of particles impacting that surface. Crater size distribution data together with an experimentally determined relationship between the crater size and the physical parameters of the impacting particle, yield the mass distribution of interplanetary dust at 1 AU

Where are innovation indicators, and their applications, going?

This paper reviews the current state of indicators of the activity of innovation and how they are presented for use in the policy process leading to a discussion of the development of new indicators, some outside of the business sector, which raises questions about the definition of innovation. This is followed by a review of plans for the evolution of innovation indicators and their use over the next few years. These plans, national and international, are diverse and this leads to a discussion of international organizations and forums which could facilitate progress towards new indicators and a better understanding of innovation systems

In-situ sputtering from the micromanipulator to enable cryogenic preparation of specimens for atom probe tomography by focused-ion beam

Workflows have been developed in the past decade to enable atom probe tomography analysis at cryogenic temperatures. The inability to control the local deposition of the metallic precursor from the gas-injection system (GIS) at cryogenic temperatures makes the preparation of site-specific specimens by using lift-out extremely challenging in the focused-ion beam. Schreiber et al. exploited redeposition to weld the lifted-out sample to a support. Here, we build on their approach to attach the region-of-interest and additionally strengthen the interface with locally sputtered metal from the micromanipulator. Following standard focused-ion beam annular milling, we demonstrate atom probe analysis of Si in both laser pulsing and voltage mode, with comparable analytical performance as a presharpened microtip coupon. Our welding approach is versatile, as various metals could be used for sputtering, and allows similar flexibility as the GIS in principle

The micrometeoroid complex and evolution of the lunar regolith

The interaction of the micrometeoroid complex with the lunar surface is evidenced by numerous glass-lined microcraters on virtually every lunar surface exposed to space. Such craters range in size from less than .1 micron to approximately 2 sq cm diameter. Using small scale laboratory cratering experiments for calibration, the observed crater-sized frequency distributions may be converted into micrometeoroid mass distributions. These lunar mass distributions are in essential agreement with satellite data. Some physical properties of micrometeoroids may be deduced by comparing lunar crater geometries with those obtained in laboratory experiments. The proponderance of circular outlines of lunar microcraters necessitates equidimensional, if not spherical, micrometeoroids