Experiment LEND of the NASA Lunar Reconnaissance Orbiter for high-resolution mapping of neutron emission of the Moon

The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.

An exceptionally bright flare from SGR 1806–20 and the origins of short-duration γ-ray bursts

Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.

Maps of subsurface hydrogen from the high energy neutron detector, Mars Odyssey

After 55 days of mapping by the High Energy Neutron Detector onboard Mars Odyssey, we found deficits of high-energy neutrons in the southern highlands and northern lowlands of Mars. These deficits indicate that hydrogen is concentrated in the subsurface. Modeling suggests that water ice-rich layers that are tens of centimeters in thickness provide one possible fit to the data.

Incidence and outcome of hospital-treated head injury in Rhode Island

Hospital discharge summary data were used to identify and study all 2,870 Rhode Island residents hospitalized in-state with head injuries during 1979 and 1980. The overall hospitalized incidence rate was 152 per 100,000 of population per year with age and sex variations similar to those found in other studies. This is consistent with the observation that fatal injury rates in Rhode Island are only 75 per cent of the United States average. Hospitalized incidence rates of head injury for the census tracts in the lowest decile of median income were twice those for census tracts in the highest decile. Smaller increases were also observed with increasing population density. Length of hospital stay increased with age. Discharge to chronic care facilities plus in-hospital deaths increased 20-fold with increasing age. In each age group, in-hospital deaths and discharge to chronic care facilities were associated with long hospital stays.

The role of motor vehicle crashes in causing certain injuries

Hospital discharge data from Rhode Island were used to assess the role of motor vehicle crashes in causing several types of serious injuries. Motor vehicle crashes were the cause of injury for approximately two-thirds of patients hospitalized with injuries to the chest organs, liver, and spleen, and approximately one-third of those with traumatic pneumothorax or hemothorax, and injuries to the head, kidney, intestine, distal femur, pelvis, and patella.