SMART‐1 end of life shallow regolith impact simulations

The SMART‐1 end‐of‐life impact with the lunar surface was simulated with impacts in a two stage light‐gas gun onto inclined basalt targets with a shallow surface layer of sand. This simulated the probable impact site, where a loose regolith will have overlaid a well consolidated basaltic layer of rock. The impact angles used were at 5° and 10° from the horizontal. The impact speed was ~2 km s^?1 and the projectiles were 2.03 mm diameter aluminum spheres. The sand depth was between approximately 0.8 and 1.8 times the projectile diameter, implying a loose lunar surface regolith of similar dimensions to the SMART‐1 spacecraft. A crater in the basement rock itself was only observed in the impact at 10° incidence, and where the depth of loose surface material was less than the projectile diameter, in which case the basement rock also contained a small pit‐like crater. In all cases, the projectile ricocheted away from the impact site at a shallow angle. This implies that at the SMART‐1 impact site the crater will have a complicated structure, with exposed basement rock and some excavated rock displaced nearby, and the main spacecraft body itself will not be present at the main crater.     

Can the faint submillimetre galaxies be explained in the Λ cold dark matter model?

We present predictions for the abundance of submillimetre galaxies (SMGs) and Lyman-break galaxies (LBGs) in the Λ cold dark matter cosmology. A key feature of our model is the self-consistent calculation of the absorption and emission of radiation by dust. The new model successfully matches the LBG luminosity function, as well as reproducing the properties of the local galaxy population in the optical and infrared. The model can also explain the observed galaxy number counts at 850 μm, but only if we assume a top-heavy initial mass function for the stars formed in bursts. The predicted redshift distribution of SMGs depends relatively little on their flux over the range 1–10 mJy, with a median value of   z ≈ 2.0  at a flux of 5 mJy, in good agreement with the recent measurement by Chapman et al. The counts of SMGs are predicted to be dominated by ongoing starbursts. However, in the model these bursts are responsible for making only a few per cent of the stellar mass locked up in massive ellipticals at the present day.     

High-alumina basalts of Taupo Volcanic Zone,New Zealand

High-alumina basalt occurs at eight localities in the Taupo Volcanic Zone associated with the Okataina, Maroa and Taupo calderas. At Tarawera the basalt is associated with a series of craters aligned NNE, and at K Trig. a series of scoria cones of similar alignment. On a broader scale the eruptive centres lie on three lines probably corresponding to major faults within the graben.Petrographically the rocks are plagioclase-olivine-augite basalts with varying percentages of each mafic phenocryst. Most are fine-medium grained, but the Ongaroto basalt is coarser-grained, and has a higher modal percentage of olivine. Chemically all are high-alumina basalts. The Ongaroto basalts has lower Al₂O₃ and higher MgO, Ni and Cr, and this, together with petrographic evidence, suggests that the rock is a cumulate.All the basalts are likely to be derived from the mantle, with intrusion into the crust controlled largely by faulting.