Onsite radar shows what lies beneath: In more active periods of the Moon's history, volcanic eruptions created lava plains that formed layers of dark basalt. Without subsurface probing, we can only examine the most recent flows. After the soft landing of the Chang'E-3 spacecraft, Xiao et al. made penetrating radar measurements of the lunar crust with the Yutu rover. Several subsurface layers suggest multiple geologic processes at play throughout the crustal history, including multiple lava flows and the weathering-induced creation of dust and rocky debris. Science , this issue p. 1226

Infrared-terahertz (IRT) resonant absorption complies with unique biomolecule fingerprints, including neurotransmitters, proteins, ribonucleic acid, and deoxyribonucleic acid, rendering it a suitable technology to achieve conformational variations and functional adjustments. Recent research has preliminarily confirmed that IRT waves can reversibly and nonthermally regulate gene expression, transmit biological information, transform protein function, and intervene in the interchange of material at the molecular level. Regarding macroscopic effects, IRT waves can enhance cell motility, improve brain ability, and affect mood. This review article attempts to provide comprehensive insight to illustrate the application of IRT waves in biophysics. Some typical experiments and equipment are summarized to demonstrate how to conduct IRT biophysics research. This cutting-edge field involves interesting research topics spanning physics and biology and opens an avenue to the performance of interdisciplinary research.

Metasurface biosensors have become the core label-free and rapid-detection technology in bioanalysis. Lung cancer and brain cancer are the first leading causes of cancer death among adults and adolescents, respectively, where poor early diagnosis results from expensive detection costs and time consumption. To tackle the above problems, here, we introduce a terahertz-domain metasurface biosensor for cancer diagnosis, relying on a perfectly symmetrical periodic surface structure, which significantly exhibits polarization-insensitivity at 2.05 THz and the high-sensitivity of 504 GHz/RIU (RIU = refractive index unit). According to the frequency shifts and transmittance variations, four cell types are successfully distinguished from each other. The minimum number of cells is required for thousands of cells to display the differences of spectra, which is 1/30 of clinical methods. Furthermore, the results were consistent with pathological results (the gold standard in clinic) by Gaussian curve fitting. The proposed biosensor has really achieved the characterization of cells in normal and cancerous state. This detection strategy dramatically reduced the cost of detection by reuse and time consumption was reduced to 1/20 of the pathology testing. In addition, it is flexible to set samples and easy to realize automatic operation due to the great polarization-insensitivity of the proposed biosensor, which can further reduce labor costs in the future. It is envisioned that the proposed biosensor will present immense potential in the fields of cancer detection, distinguishing different cancers, and identifying primary lesion cancer or metastatic cancer.

The thickness estimation of the top surface layer and surface layer, as well as the detection of road defects, are of great importance to the quality conditions of asphalt pavement. Although ground penetrating radar (GPR) methods have been widely used in non-destructive detection of pavements, the thickness estimation of the thin top surface layer is still a difficult problem due to the limitations of GPR resolution and the similar permittivity of asphalt sub-layers. Besides, the detection of some road defects, including inadequate compaction and delamination at interfaces, require further practical study. In this paper, a newly-developed vehicle-mounted GPR detection system is introduced. We used a horizontal high-pass filter and a modified layer localization method to extract the underground layers. Besides, according to lab experiments and simulation analysis, we proposed theoretical methods for detecting the degree of compaction and delamination at the interface, respectively. Moreover, a field test was carried out and the estimated results showed a satisfactory accuracy of the system and methods.

Reverse-time migration (RTM) has shown its advantages over other conventional migration algorithms for ground-penetrating radar (GPR) imaging. RTM is preferred to be implemented in the computationally attractive 2-D domain, whereas a real measurement can only be conducted in a 3-D domain. Thus, we propose an asymptotic 3-D-to-2-D data conversion filter in the frequency domain for preprocessing of the recorded data for 2-D RTM. The accuracy of the data conversion filter is verified by two numerical tests on a homogeneous and a layered model. Then, we evaluate the effectiveness of the data conversion filter on the imaging result of 2-D RTM, which is applied to simulated multioffset GPR data from a buried pipe model. With the filter, subsurface image by the 2-D RTM matches better with the 3-D RTM result especially in the aspect of phase congruency. Therefore, we conclude that this data conversion filter is necessary for 2-D RTM. We also conducted a laboratory experiment on a volcanic ash pit using a multiinput–multioutput GPR system, which is adopted on the Chang-E 5 lunar exploration lander and works in a stationary mode. The 3-D-to-2-D data conversion filter is applied to the measured multioffset GPR data before the 2-D RTM. The imaging results demonstrate that three marble slabs buried at different depths up to 2 m are clearly imaged.

The atomic magnetometer is currently one of the most-sensitive sensors and plays an important role in applications for detecting weak magnetic fields. This review reports the recent progress of total-field atomic magnetometers that are one important ramification of such magnetometers, which can reach the technical level for engineering applications. The alkali-metal magnetometers, helium magnetometers, and coherent population-trapping magnetometers are included in this review. Besides, the technology trend of atomic magnetometers was analyzed for the purpose of providing a certain reference for developing the technologies in such magnetometers and for exploring their applications.