•The Mariner-10 mapped intercrater plains are re-evaluated with MESSENGER datasets.•A geologic map covering ∼20% of the surface of Mercury was produced.•A majority of the intercrater plains formed ...from volcanic eruptions.•The term “intermediate plains” should not be used to map the surface of Mercury.
Orbital observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft are used to re-evaluate the nature and origin of the oldest mapped plains deposits on Mercury, the intercrater and intermediate plains units defined by Mariner 10 investigators. Despite the large areal extent of these plains, which comprise approximately one-third of the planetary surface area viewed by Mariner 10, their formation mechanism was not well constrained by Mariner 10 imaging. One hypothesis attributed plains formation to ponding of fluidized impact ejecta to create relatively smooth surfaces. Another hypothesis was that these plains are of volcanic origin. To assess the origin of these older plains and the contribution of early volcanism to resurfacing on Mercury, we have used MESSENGER data to analyze the morphology, spectral properties, impact crater statistics, and topography of Mariner 10 type-areas of intercrater and intermediate plains. On the basis of new criteria for the identification of intercrater and intermediate plains derived from these observations, we have remapped 18% of the surface of Mercury. We find that the intercrater plains are a highly textured unit with an abundance of secondary craters, whereas the intermediate plains are composed of both intercrater and smooth plains. We suggest that the term “intermediate plains” not be used to map the surface of Mercury henceforth, but rather this unit should be subdivided into its constituent intercrater and smooth plains units. We argue that a substantial percentage of the intercrater plains are composed of volcanic materials on the basis of (1) examples of areas where ejecta from a small number of superposed craters have transformed smooth plains deposits of volcanic origin into a unit indistinguishable from intercrater plains; (2) the range in ages of intercrater plains deposits as interpreted from crater size–frequency distributions; and (3) the near-global distribution of intercrater plains compared with the uneven distribution of impact basins and their associated ejecta deposits.
The superrotation of the atmospheres of Venus and Titan has puzzled dynamicists for many years and seems to put these planets in a very different dynamical regime from most other planets. In this ...review, we consider how to define superrotation objectively and explore the constraints that determine its occurrence. Atmospheric superrotation also occurs elsewhere in the Solar System and beyond, and we compare Venus and Titan with Earth and other planets for which wind estimates are available. The extreme superrotation on Venus and Titan poses some difficult challenges for numerical models of atmospheric circulation, much more difficult than for more rapidly rotating planets such as Earth or Mars. We consider mechanisms for generating and maintaining a superrotating state, all of which involve a global meridional overturning circulation. The role of nonaxisymmetric eddies is crucial, however, but the detailed mechanisms may differ between Venus, Titan, and other planets.
Observations of Mercury's internal magnetic field from the Magnetometer on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have revealed a dipole moment of ...190 nT RM3 offset about 480 km northward from the planetary equator, where RM is Mercury's radius. We have reanalyzed magnetic field observations acquired by the Mariner 10 spacecraft during its third flyby of Mercury (M10‐III) in 1975 to constrain the secular variation in the internal field over the past 40 years. With the application of techniques developed in the analysis of MESSENGER data, we find that the dipole moment that best fits the M10‐III data is 188 nT RM3 offset 475 km northward from the equator. Our results are consistent with no secular variation, although variations of up to 10%, 16%, and 35%, respectively, are permitted in the zonal coefficients g10, g20, and g30 in a spherical harmonic expansion of the internal field.
Key Points
Mariner 10 flyby magnetic field data are reanalyzed with MESSENGER techniquesNo secular variation in Mercury's dipole moment or dipole offset is evidentResult constrains the low‐degree power spectrum of Mercury's secular variation
Observations of radar speckle patterns tied to the rotation of Mercury establish that the planet occupies a Cassini state with obliquity of 2.11 ± 0.1 arc minutes. The measurements show that the ...planet exhibits librations in longitude that are forced at the 88-day orbital period, as predicted by theory. The large amplitude of the oscillations, 35.8 ± 2 arc seconds, together with the Mariner 10 determination of the gravitational harmonic coefficient C₂₂, indicates that the mantle of Mercury is decoupled from a core that is at least partially molten.
Mapping the distribution and extent of major terrain types on a planet's surface helps to constrain the origin and evolution of its crust. Together, MESSENGER and Mariner 10 observations of Mercury ...now provide a near-global look at the planet, revealing lateral and vertical heterogeneities in the color and thus composition of Mercury's crust. Smooth plains cover approximately 40% of the surface, and evidence for the volcanic origin of large expanses of plains suggests that a substantial portion of the crust originated volcanically. A low-reflectance, relatively blue component affects at least 15% of the surface and is concentrated in crater and basin ejecta. Its spectral characteristics and likely origin at depth are consistent with its apparent excavation from a lower crust or upper mantle enriched in iron- and titanium-bearing oxides.
Experimental studies on DNA transposable elements (TEs) have been limited in scale, leading to a lack of understanding of the factors influencing transposition activity, evolutionary dynamics, and ...application potential as genome engineering tools. We predicted 130 active DNA TEs from 102 metazoan genomes and evaluated their activity in human cells. We identified 40 active (integration-competent) TEs, surpassing the cumulative number (20) of TEs found previously. With this unified comparative data, we found that the Tc1/mariner superfamily exhibits elevated activity, potentially explaining their pervasive horizontal transfers. Further functional characterization of TEs revealed additional divergence in features such as insertion bias. Remarkably, in CAR-T therapy for hematological and solid tumors, Mariner2_AG (MAG), the most active DNA TE identified, largely outperformed two widely used vectors, the lentiviral vector and the TE-based vector SB100X. Overall, this study highlights the varied transposition features and evolutionary dynamics of DNA TEs and increases the TE toolbox diversity.
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•Forty active DNA TEs from mining 102 metazoan genomes increase the TE toolbox diversity•Tc1 elements with high copy numbers and IR-DR structures tend to show high activity•Active TEs show diverged functional features such as insertion profile and cargo capacity•MAG outperforms lentiviral vectors in CAR-T cell therapy
A heterologous survey of 130 DNA transposable elements (TEs) in human cells not only unveils evolutionary and functional features linked to transposition activity but also expands the TE-based genome engineering toolbox by incorporating functionally diverse TEs, particularly the highly potent MAG.
•We examined measurements of Mars thermospheric densities during dust storms.•We used data from Mariner 9, MGS, and MEX.•Dust storms have significant effects on the thermosphere.
The effects of dust ...storms on densities, temperatures, and winds in the lower atmosphere of Mars are substantial. Here we use upper atmospheric observations to investigate how dust storms affect the upper atmosphere of Mars. We use aerobraking accelerometer, ultraviolet stellar occultation, and radio occultation datasets to examine the magnitudes and timescales associated with upper atmospheric density changes during dust storms. We find that: (1) Upper atmospheric conditions can be perturbed by dust storms outside the classical “dust storm season” of Ls=180–360°. (2) The upper atmospheric regions affected by even a small dust event can include nearly all latitudes. (3) Atmospheric temperatures can be affected by dust storms at altitudes as high as 160km. (4) The onset of the upper atmospheric response to a distant dust event can be a few days or less. (5) The characteristic timescale for the decay of the upper atmospheric response to a dust event can be 20–120° of Ls, and it may differ from the corresponding timescale for the lower atmosphere. (6) Average upper atmospheric densities can change by factors of a few during mere regional dust storms and an order of magnitude change is possible for the largest storms: these are general trends and individual density measurements may be greater than suggested by a general trend by a factor of two due to the intrinsic variability of the upper atmosphere. The decay timescale and magnitude of the upper atmospheric response depend on altitude, and larger events have shorter decay timescales. The substantial effects seen in the upper atmosphere illuminate the vertical extent of modified atmospheric circulation patterns and associated adiabatic heating/cooling during extreme dust loading, timescales for the onset and decay of the upper atmospheric response, and highlight potential dangers to spacecraft operations.
The origin of plains on Mercury, whether by volcanic flooding or impact ejecta ponding, has been controversial since the Mariner 10 flybys (1974-75). High-resolution images (down to 150 meters per ...pixel) obtained during the first MESSENGER flyby show evidence for volcanic vents around the Caloris basin inner margin and demonstrate that plains were emplaced sequentially inside and adjacent to numerous large impact craters, to thicknesses in excess of several kilometers. Radial graben and a floor-fractured crater may indicate intrusive activity. These observations, coupled with additional evidence from color images and impact crater size-frequency distributions, support a volcanic origin for several regions of plains and substantiate the important role of volcanism in the geological history of Mercury.
During its first flyby of Mercury, the MESSENGER spacecraft measured the planet's near-equatorial magnetic field. The field strength is consistent to within an estimated uncertainty of 10% with that ...observed near the equator by Mariner 10. Centered dipole solutions yield a southward planetary moment of 230 to 290 nanotesla RM³ (where RM is Mercury's mean radius) tilted between 5° and 12° from the rotation axis. Multipole solutions yield non-dipolar contributions of 22% to 52% of the dipole field magnitude. Magnetopause and tail currents account for part of the high-order field, and plasma pressure effects may explain the remainder, so that a pure centered dipole cannot be ruled out.
This paper discusses the 17th-century Latin translation of Proclus’ Commentary on the First Book of Euclid’s Elements, preserved in Madrid, Biblioteca Nacional de España, MS 9871, produced by the ...Spaniard Vicente Mariner. The author examines the historical context, sources, and motivations behind Mariner’s translation, his intellectual profile, and the potential reasons for translating a mathematical text given his background in literature. Via a comparison of Mariner’s text with the original Greek, this paper delves into Mariner’s translation choices and linguistic nuances to highlight the challenges he faced while translating it. Transcriptions of the collated passage both from Grynaeus’ 1533 editio princeps of Proclus’ text and Mariner’s manuscript are provided in the Appendix. Overall, this paper attempts to shed light on Mariner’s contribution to the Latin reception of Proclus’ work in the early modern period.
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