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During the Apollo era of lunar exploration, mysterious albedo patterns, called swirls, captured the imagination of the scientific community. A key aspect of this interest was due to the discovery that the swirls are associated with localized relatively strong remnant magnetic fields. Analysis of returned soil samples revealed that solar wind, galactic cosmic rays, and micrometeorite impacts change the albedo of surface soil grains, a process known as space weathering that reduces regolith reflectance over time. Thus it was natural to invoke local magnetic structures as shields that retard space weathering resulting in relatively less space weathering of the regolith in regions with the strongest localized magnetic fields. However, the origins of the magnetic anomalies and associated swirls remain enigmatic to this day. We designed the Swirl CubeSat to determine the nature of remnant lunar magnetic fields and investigate their role in moderating space weathering of the regolith and assess their suitability for radiation protection of surface assets. Swirl has one focused observational objective: characterize the magnetic field associated with the Reiner Gamma Swirl (RGS) at sub-kilometer spatial sampling, with 0.5 nTesla accuracy and 100 m spatial precision. In the Swirl mission concept, the Swirl spacecraft, a 6U CubeSat, would deploy as a secondary payload from a vehicle on a deep space trajectory. A series of maneuvers would then place the spacecraft in a low orbit that would then be modified to have a periapse of 5–10 km for thirty orbits passing over RGS. Prime Swirl observations were designed during these low-altitude passes and consist of high-resolution vector magnetic field measurements and monochrome navigation imaging.

High-resolution images from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) reveal the landing locations of recent and historic spacecraft and associated impact sites across the lunar surface. Using multiple images of each site acquired between 2009 and 2015, an improved Lunar Reconnaissance Orbiter (LRO) ephemeris, and a temperature-dependent camera orientation model, we derived accurate coordinates (

When the Apollo astronauts collected samples from Tranquility Base in 1969, they provided an unprecedented window into the processes that shaped the Moon. Ever since, the Moon has served as a “keystone” for understanding planetary geological processes throughout the Solar System. Like all samples that have been returned from the Moon, the Apollo 11 samples were collected from the lunar regolith, a layer of jumbled and pulverized rocks that blankets and obscures the Moon's bedrock geology. When geologists reconstruct the history of the Moon, these samples are like scattered puzzle pieces, each representing important information, but removed from the context of their formation and isolated from the bigger picture of how the Moon's crust was formed. The goal of Moon Diver is to return to Mare Tranquillitatis, taking advantage of the discovery of a natural pit cave entrance exposing a deep cross-section through both the lunar regolith as well as tens of meters of bedrock lava layers. Collecting information on the chemistry, mineralogy, and morphology of these intact bedrock layers would allow us to investigate where rocky crusts come from, how they are emplaced, and the process by which they are transformed into the regolith layer that we see from space. In doing so, the mission would combine the deep knowledge gained by Apollo with the unprecedented in situ access to secondary crust granted by the lunar mare pit to understand these fundamental processes on the Moon, and to use this knowledge as a keystone for understanding the same processes across the Solar System. The success of the Moon Diver concept hinges on accessing the subsurface. The existence of the mare pit provides a cross-section through the lunar maria. Access to the record exposed in the wall of this pit is provided by two critical space technologies: pinpoint landing (allowing the delivery of the payload close to the pit) and extreme terrain mobility (allowing the delivery of capable instruments to the cliff wall). Pinpoint landing is a closed-loop guidance and navigation capability that repeatedly matches visual features from a downward-facing camera to a priori acquired terrain maps. This body-relative navigation is then used with closed-loop control to guide the spacecraft toward its landing target, yielding a tight landing ellipse. Once on the surface, an extreme-terrain robotic explorer, called Axel, would egress from the lander and traverse tens of meters to the pit. The lander provides mechanical support, power and communication to the rover through its umbilical tether. Anchored to the lander, the two-wheeled, tail-dragger rover would pay out its tether as it traverses toward the pit. With the aid of its 300-meter tether, the rover can traverse the steep slopes of the pit funnel and rappel its vertical walls. The rover carries a surface preparation tool together with a suite of three instrument types: (a) a trio of high-resolution cameras (Mars 2020's EECAMs) for acquiring context images of the near and far walls with the near-wall pair in a stereoscopic configuration, (b) an alpha-particle-X-ray Spectrometer (MSL's APXS) for elemental composition, and (c) a multi-spectral microscopic imager (MMI) that uses controlled lighting for minerology. The surface-preparation tool removes dust and patina that may be present on the rock wall by grinding a small area. The surface-preparation tool, the MMI and the APXS would be deployed from their instrument bays in one of the wheel wells. The rover would independently point each of its instruments at the same target of interest on the wall with millimeter-level repeatability. Confidence in the technologies of pinpoint landing and extreme-terrain access is based on helicopter testing of terrain-relative navigation and field testing of extreme terrain mobility respectively. The latter was tested using Axel rover prototypes with integrated science instruments at multiple terrestrial analog sites including a basaltic pit in Arizona. Landing shortly after sunrise, the surface mission timeline is just shy of a lunar day (14 Earth days). Upon landing, the rover would egress from the lander, traverse toward the pit, descend along the pit funnel and rappel down its wall. Throughout its traverse, the rover would acquire multiple measurements of both regolith and mare layers. After descending to the bottom of the layers, the rover will reach a significant overhang. This void space may open into a large cave or lava tube, which could someday provide a protected location for a lunar base. For these reasons, lunar pits provide an exciting new target for lunar exploration.

China’s robotic Chang’e-3 spacecraft, carrying the Yutu rover, touched down in Mare Imbrium on the lunar surface on 14 December 2013. The Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) imaged the site both before and after landing. Multi-temporal NAC images taken before and after the landing, phase-ratio images made from NAC images taken after the landing, and Hapke photometric techniques were used to evaluate surface changes caused by the disturbance of regolith at the landing site (blast zone) by the descent engines of the Chang’e-3 spacecraft. The reflectance of the landing site increased by 10 ± 1% (from I / F = 0.040 to 0.044 at 30° phase angle) as a result of the landing, a value similar to reflectance increases estimated for the Apollo, Luna, and Surveyor landing sites. The spatial extent of the disturbed area at the Chang’e-3 landing site, 2530 m 2 , also falls close to what is predicted on the basis of correlations between lander mass, thrust, and blast zone areas for the historic landed missions. A multi-temporal ratio image of the Chang’e-3 landing site reveals a main blast zone (slightly elongate in the N–S direction; ∼75 m across N–S and ∼43 m across in the E–W direction) and an extended diffuse, irregular halo that is less reflective than the main blast zone (extending ∼40–50 m in the N–S direction and ∼10–15 m in the E–W direction beyond the main blast zone). The N–S elongation of the blast zone likely resulted from maneuvering during hazard avoidance just prior to landing. The phase-ratio image reveals that the blast zone is less backscattering than surrounding undisturbed areas. The similarities in magnitude of increased reflectance between the Chang’e-3 landing site and the Surveyor, Apollo, and Luna landing sites suggest that lunar soil reflectance changes caused by interaction with rocket exhaust are not significantly altered over a period of 40–50 years. The reflectance changes are independent of regolith composition, indicating that they are caused by a change in the physical properties of the regolith, likely microscopic to macroscopic smoothing of the surface, and possibly a change in surface maturity by removal of highly mature very fine-grained regolith components.

Numerous spacecraft have impacted the surface of Moon during the last several decades of lunar exploration. These impacts fall into two categories: relatively high-angle impacts formed by spacecraft on direct trajectories from the Earth and low-angle impacts formed by spacecraft in lunar orbit. The craters produced by the Ranger spacecraft and the Apollo S-IVB boosters are discussed here. The Ranger spacecraft had a mass of ~370 kg (816 lb.), impacted at 2600 km s −1 and formed craters ~14–15 m in diameter. The S-IVB boosters had masses of ~14,000 kg (30865 lb.), impacted at ~2600 km s −1 and formed craters ~35 m in diameter. These impacts are relatively unique due to the low bulk-density of the impactor (28 and 700 kg m −3 , respectively the S-IVB and Ranger spacecraft). Craters produced by the impact of the Ranger spacecraft are similar to other lunar mare craters in which the excavation process was impeded by the underlying solid basalt. Craters produced by the S-IVB impacts are non-circular and exhibit an elongate central mound. It appears that the S-IVB crater excavation also interacted with the basalt but in a more complicated manner than for the Ranger craters. Ejecta and rays associated with these craters are asymmetric and indicate that the excavation flow field varied with time and was not symmetric about the trajectory direction.

The Lunar Reconnaissance Orbiter Camera (LROC) consists of two imaging systems that provide multispectral and high resolution imaging of the lunar surface. The Wide Angle Camera (WAC) is a seven color push-frame imager with a 90∘ field of view in monochrome mode and 60∘ field of view in color mode. From the nominal 50 km polar orbit, the WAC acquires images with a nadir ground sampling distance of 75 m for each of the five visible bands and 384 m for the two ultraviolet bands. The Narrow Angle Camera (NAC) consists of two identical cameras capable of acquiring images with a ground sampling distance of 0.5 m from an altitude of 50 km. The LROC team geometrically calibrated each camera before launch at Malin Space Science Systems in San Diego, California and the resulting measurements enabled the generation of a detailed camera model for all three cameras. The cameras were mounted and subsequently launched on the Lunar Reconnaissance Orbiter (LRO) on 18 June 2009. Using a subset of the over 793000 NAC and 207000 WAC images of illuminated terrain collected between 30 June 2009 and 15 December 2013, we improved the interior and exterior orientation parameters for each camera, including the addition of a wavelength dependent radial distortion model for the multispectral WAC. These geometric refinements, along with refined ephemeris, enable seamless projections of NAC image pairs with a geodetic accuracy better than 20 meters and sub-pixel precision and accuracy when orthorectifying WAC images.

Random bombardment by comets, asteroids and associated fragments form and alter the lunar regolith and other rocky surfaces. The accumulation of impact craters over time is of fundamental use in evaluating the relative ages of geologic units. Crater counts and radiometric ages from returned samples provide constraints with which to derive absolute model ages for unsampled units on the Moon and other Solar System objects. However, although studies of existing craters and returned samples offer insight into the process of crater formation and the past cratering rate, questions still remain about the present rate of crater production, the effect of early-stage jetting during impacts and the influence that distal ejecta have on the regolith. Here we use Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) temporal ('before and after') image pairs to quantify the contemporary rate of crater production on the Moon, to reveal previously unknown details of impact-induced jetting, and to identify a secondary impact process that is rapidly churning the regolith. From this temporal dataset, we detected 222 new impact craters and found 33 per cent more craters (with diameters of at least ten metres) than predicted by the standard Neukum production and chronology functions for the Moon. We identified broad reflectance zones associated with the new craters that we interpret as evidence of a surface-bound jetting process. We also observe a secondary cratering process that we estimate churns the top two centimetres of regolith on a timescale of 81,000 years-more than a hundred times faster than previous models estimated from meteoritic impacts (ten million years).

We describe a novel assay capable of accurately determining the length of short tandem repeat (STR) alleles. STR genotyping is achieved utilizing RecA-mediated ligation (RML), which combines the high fidelity of RecA-mediated homology searching with allele-specific ligation. RecA catalyzes the pairing of synthetic oligonucleotides with one strand of a double-stranded DNA target, in this case a PCR amplicon. Ligation occurs only when two adjacent oligonucleotides are base paired to the STR region without any overlap or gap. RecA activity is required to overcome the inherent difficulty of annealing repeated sequences in register. This assay is capable of determining STR genotypes of human samples, is easily adapted to high throughput or automated systems and can have widespread utility in diagnostic and forensic applications.