The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a $8.31$ deg$^2$ subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ($\alpha<-1.2$) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to $4\%\lesssim f_{\mathrm{rem}} \lesssim 10\%$; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.

A clean hot-water drill was used to gain access to Subglacial Lake Whillans (SLW) in late January 2013 as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. Over 3 days, we deployed an array of scientific tools through the SLW borehole: a downhole camera, a conductivity–temperature–depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. Our observations confirm the existence of a subglacial water reservoir whose presence was previously inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37–0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of –0.55~C, consistent with depression of the freezing point by 7.019 MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 µm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our main operational recommendation for future subglacial access through water-filled boreholes is to supply enough heat to the top of the borehole to keep it from freezing.

X-ray diffraction (XRD) has been routinely employed in the Earth sciences to characterize the crystallography of rocks and minerals. Routine characterization of samples too small for analysis by classic automated powder diffraction methods becomes challenging without access to single crystal or micro-diffraction equipment. Here, we show that a traditional Gandolfi camera lined with an image-plate (IP) as the detection medium can return a fully quantitative diffraction pattern from a sub-milligram single grain specimen in a simple and straightforward manner. Data pertaining to peak positions (d-spacings) were assessed using SRM640c Si powder, while intensity data were compared to the certified values for intensity standard SRM676a alumina powder. The refined unit-cell dimension of Si powder differed from the certified value of 5.4312 Å by no more than 0.0003 Å with a standard deviation (σ) of 0.0002 Å among the three experiments. For intensity, the σ and disparity from the certified values of three diffraction experiments on SRM676a were both <2%. The results of a comparative study of the crystallographic parameters determined for a naturally occurring garnet and clinopyroxene given through the refinement of their crystal structure by single-crystal XRD method are presented. These show through Rietveld refinement of X-ray data obtained by the Gandolfi–IP method outlined here that both accurate and precise XRD data can be produced in a timely and cost-effective manner using only an IP, Gandolfi camera, and software freely available on the internet.