Abstract Hydrocarbon reservoirs at Titan come in many forms—as gases and condensates in the atmosphere; as surface accumulations of liquid in lakes, slushy soils, and solid sediments; and in the subsurface, perhaps caged within clathrate hydrates and/or as part of a global hydrocarbon aquifer. Because Titan is so far from the Sun and contains multiple atmospheric haze layers, information on its surface features and their composition is extremely difficult to obtain and is acquired via imaging instruments that operate at wavelengths less affected by the haze. Unfortunately, the data are commonly of low resolution, and divergent interpretations abound. However, with the multinational Cassini spacecraft currently orbiting Saturn on its extended Solstice mission, Titan’s surface composition is slowly coming into focus. This review will attempt to synthesize the current state of knowledge of hydrocarbon presence and distribution at Titan, emphasizing those observations that have direct compositional relevance to compounds in the atmosphere and on the surface.

Abstract Rupes Recta, also known as the ‘Straight Wall’, is an individual normal fault located in eastern Mare Nubium on the nearside of the Moon. Age and cross-cutting relationships suggest that the maximum age of Rupes Recta is 3.2 Ga, which may make it the youngest large-scale normal fault on the Moon. Based on detailed structural mapping and throw distribution analysis, fault nucleation is interpreted to have occurred near the fault centre, and the fault has propagated bi-directionally, growing northwards and southwards by segment linkage. Forward mechanical modelling of fault topography gives a best-fitting fault dip of approximately 85°, and suggests that Rupes Recta accommodated approximately 400 m of maximum displacement and extends to a depth of around 42 km. The cumulative driving stresses required to form Rupes Recta are similar in magnitude to those that formed normal faults in Tempe Terra, Mars. The spatial and temporal association with Rima Birt, a sinuous rille to the west of Rupes Recta, suggests a genetic relationship between both structures and implies regional extension at the time of formation.

Abstract Fans, landforms that record the storage and transport of sediment from uplands to depositional basins, are found on Saturn’s moon Titan, a body of significantly different process rates and material compositions from Earth. Images obtained by the Cassini spacecraft’s synthetic aperture radar reveal morphologies, roughness, textural patterns and other properties consistent with fan analogues on Earth also viewed by synthetic aperture radar. The observed fan characteristics on Titan reveal some regions of high relative relief and others with gentle slopes over hundreds of kilometres, exposing topographic variations and influences on fan formation. There is evidence for a range of particle sizes across proximal to distal fan regions, from c. 2 cm or more to fine-grained, which can provide details on sedimentary processes. Some features are best described as alluvial fans, which implies their proximity to high-relief source areas, while others are more likely to be fluvial fans, drawing from larger catchment areas and frequently characterized by more prolonged runoff events. The presence of fans corroborates the vast liquid storage capacity of the atmosphere and the resultant episodic behaviour. Fans join the growing list of landforms on Titan derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between these two planetary bodies.

ABSTRACT This thesis embraces and expands upon a century of research into disparate geological enigmas, offering a unifying catastrophic explanation for events occurring during the enigmatic mid-Pleistocene transition. Billions of tons of “Australasian tektites” were dispatched as distal ejecta from a target mass of continental sediments during a cosmic impact occurring ca. 788 ka. The accepted signatures of a hypervelocity impact encompass an excavated astrobleme and attendant proximal, medial, and distal ejecta distributions. Enigmatically, the distal tektites remain the only accepted evidence of this impact’s reality. A protracted 50 yr search fixated on impact sites in Southeast Asia—the location of the tektites—has failed to identify the requisite additional impact signatures. We postulate the missing astrobleme and proximal/medial ejecta signatures are instead located antipodal to Southeast Asia. A review of the gradualistic theories for the genesis and age of the “Carolina bay” landforms of North America finds those models incapable of addressing all the facts we observe. Research into 57,000 of those oriented basins informs our speculation that they represent cavitation-derived ovoid basins within energetically delivered geophysical mass surge flows emanating from a cosmic impact. Those flows are seen as repaving regions of North America under blankets of hydrated impact regolith. Our precisely measured Carolina bay orientations indicate an impact site within the Laurentide ice sheet. There, we invoke a grazing regime impact into hydrated early Mesozoic to late Paleozoic continental sediments, similar in composition to the expected Australasian tektites’ parent target. We observe that continental ice shielded the target at ca. 788 ka, a scenario understood to produce anomalous astroblemes. The ensuing excavation allowed the Saginaw glacial lobe’s distinctive and unique passage through the Marshall Sandstone cuesta, which encircles and elsewhere protects the central region of the intracratonic Michigan Basin. Subsequent erosion by multiple ice-age transgressions has obfuscated impact evidence, forming Michigan’s “Thumb” as an enduring event signature. Comprehensive suborbital modeling supports the distribution of distal ejecta to the Australasian tektite strewn field from Michigan’s Lower Peninsula. The mid-Pleistocene transition impact hypothesis unifies the Carolina bays with those tektites as products of an impact into the Saginaw Bay area of Lake Huron, USA. The hypothesis will be falsified if cosmogenic nuclide burial dating of Carolina bay subjacent stratigraphic contacts disallows a coeval regolith emplacement ca. 788 ka across North America. We offer observations, interdisciplinary insights, and informed speculations fitting for an embryonic concept involving a planetary-scale extraterrestrial impact.