197 research outputs found
The effects of the target material properties and layering on the crater chronology: the case of Raditladi and Rachmaninoff basins on Mercury
In this paper we present a crater age determination of several terrains
associated with the Raditladi and Rachmaninoff basins. These basins were
discovered during the first and third MESSENGER flybys of Mercury,
respectively. One of the most interesting features of both basins is their
relatively fresh appearance. The young age of both basins is confirmed by our
analysis on the basis of age determination via crater chronology. The derived
Rachmaninoff and Raditladi basin model ages are about 3.6 Ga and 1.1 Ga,
respectively. Moreover, we also constrain the age of the smooth plains within
the basins' floors. This analysis shows that Mercury had volcanic activity
until recent time, possibly to about 1 Ga or less. We find that some of the
crater size-frequency distributions investigated suggest the presence of a
layered target. Therefore, within this work we address the importance of
considering terrain parameters, as geo-mechanical properties and layering, into
the process of age determination. We also comment on the likelihood of the
availability of impactors able to form basins with the sizes of Rachmaninoff
and Raditladi in relatively recent times.Comment: Accepted by PSS, to appear on MESSENGER Flybys special issu
Material Units, Structures/Landforms, and Stratigraphy for the Global Geologic Map of Ganymede (1:15M)
In the coming year a global geological map of Ganymede will be completed that represents the most recent understanding of the satellite on the basis of Galileo mission results. This contribution builds on important previous accomplishments in the study of Ganymede utilizing Voyager data and incorporates the many new discoveries that were brought about by examination of Galileo data. Material units have been defined, structural landforms have been identified, and an approximate stratigraphy has been determined utilizing a global mosaic of the surface with a nominal resolution of 1 km/pixel assembled by the USGS. This mosaic incorporates the best available Voyager and Galileo regional coverage and high resolution imagery (100-200 m/pixel) of characteristic features and terrain types obtained by the Galileo spacecraft. This map has given us a more complete understanding of: 1) the major geological processes operating on Ganymede, 2) the characteristics of the geological units making up its surface, 3) the stratigraphic relationships of geological units and structures, and 4) the geological history inferred from these relationships. A summary of these efforts is provided here
The Morphology of Craters on Mercury: Results from MESSENGER Flybys
Topographic data measured from the Mercury Laser Altimeter (MLA) and the Mercury Dual Imaging System (MDIS) aboard the MESSENGER spacecraft were used for investigations of the relationship between depth and diameter for impact craters on Mercury. Results using data from the MESSENGER flybys of the innermost planet indicate that most of the craters measured with MLA are shallower than those previously measured by using Mariner 10 images. MDIS images of these same MLA-measured craters show that they have been modified. The use of shadow measurement techniques, which were found to be accurate relative to the MLA results, indicate that both small bowl-shaped and large complex craters that are fresh possess depth-to-diameter ratios that are in good agreement with those measured from Mariner 10 images. The preliminary data also show that the depths of modified craters are shallower relative to fresh ones, and might provide quantitative estimates of crater in-filling by subsequent volcanic or impact processes. The diameter that defines the transition from simple to complex craters on Mercury based on MESSENGER data is consistent with that reported from Mariner 10 data
New Morphometric Measurements of Peak-Ring Basins on Mercury and the Moon: Results from the Mercury Laser Altimeter and Lunar Orbiter Laser Altimeter
Peak-ring basins (large impact craters exhibiting a single interior ring) are important to understanding the processes controlling the morphological transition from craters to large basins on planetary bodies. New image and topography data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Lunar Reconnaissance Orbiter (LRO) spacecraft have helped to update the catalogs of peak-ring basins on Mercury and the Moon [1,2] and are enabling improved calculations of the morphometric properties of these basins. We use current orbital altimeter measurements from the Mercury Laser Altimeter (MLA) [3] and the Lunar Orbiter Laser Altimeter (LOLA) [4], as well as stereo-derived topography [5], to calculate the floor depths and peak-ring heights of peak-ring basins on Mercury and the Moon. We present trends in these parameters as functions of rim-crest diameter, which are likely to be related to processes controlling the onset of peak rings in these basins
Maximizing the value of Solar System data through Planetary Spatial Data Infrastructures
Planetary spatial data returned by spacecraft, including images and
higher-order products such as mosaics, controlled basemaps, and digital
elevation models (DEMs), are of critical importance to NASA, its commercial
partners and other space agencies. Planetary spatial data are an essential
component of basic scientific research and sustained planetary exploration and
operations. The Planetary Data System (PDS) is performing the essential job of
archiving and serving these data, mostly in raw or calibrated form, with less
support for higher-order, more ready-to-use products. However, many planetary
spatial data remain not readily accessible to and/or usable by the general
science user because particular skills and tools are necessary to process and
interpret them from the raw initial state. There is a critical need for
planetary spatial data to be more accessible and usable to researchers and
stakeholders. A Planetary Spatial Data Infrastructure (PSDI) is a collection of
data, tools, standards, policies, and the people that use and engage with them.
A PSDI comprises an overarching support system for planetary spatial data.
PSDIs (1) establish effective plans for data acquisition; (2) create and make
available higher-order products; and (3) consider long-term planning for
correct data acquisition, processing and serving (including funding). We
recommend that Planetary Spatial Data Infrastructures be created for all bodies
and key regions in the Solar System. NASA, with guidance from the planetary
science community, should follow established data format standards to build
foundational and framework products and use those to build and apply PDSIs to
all bodies. Establishment of PSDIs is critical in the coming decade for several
locations under active or imminent exploration, and for all others for future
planning and current scientific analysis.Comment: 8 pages, 0 figures. White paper submitted to the Planetary Science
and Astrobiology Decadal Survey 2023-203
A Pragmatic Path to Investigating Europa's Habitability
Assessment of Europa's habitability, as an overarching science goal, will progress via a comprehensive investigation of Europa's subsurface ocean, chemical composition, and internal dynamical processes, The National Research Council's Planetary Decadal Survey placed an extremely high priority on Europa science but noted that the budget profile for the Jupiter Europa Orbiter (1EO) mission concept is incompatible with NASA's projected planetary science budget Thus, NASA enlisted a small Europa Science Definition Team (ESDT) to consider more pragmatic Europa mission options, In its preliminary findings (May, 2011), the ESDT embraces a science scope and instrument complement comparable to the science "floor" for JEO, but with a radically different mission implementation. The ESDT is studying a two-element mission architecture, in which two relatively low-cost spacecraft would fulfill the Europa science objectives, An envisioned Europa orbital element would carry only a very small geophysics payload, addressing those investigations that are best carried out from Europa orbit An envisioned separate multiple Europa flyby element (in orbit about Jupiter) would emphasize remote sensing, This mission architecture would provide for a subset of radiation-shielded instruments (all relatively low mass, power, and data rate) to be delivered into Europa orbit by a modest spacecraft, saving on propellant and other spacecraft resources, More resource-intensive remote sensing instruments would achieve their science objectives through a conservative multiple-flyby approach, that is better situated to handle larger masses and higher data volumes, and which aims to limit radiation exposure, Separation of the payload into two spacecraft elements, phased in time, would permit costs to be spread more uniformly over mUltiple years, avoiding an excessively high peak in the funding profile, Implementation of each spacecraft would be greatly simplified compared to previous Europa mission concepts, minimizing new development while achieving the key Europa science objectives. We will report on the status of this evolving concept, and will solicit community feedback, as we pursue an innovative and low-cost ways to explore Europa and investigate its habitability
Long-lived explosive volcanism on Mercury
The duration and timing of volcanic activity on Mercury are key indicators of the thermal evolution of the planet and provide a valuable comparative example for other terrestrial bodies. The majority of effusive volcanism on Mercury appears to have occurred early in the planet's geological history (~4.1–3.55 Ga), but there is also evidence for explosive volcanism. Here we present evidence that explosive volcanism occurred from at least 3.9 Ga until less than a billion years ago and so was substantially more long-lived than large-scale lava plains formation. This indicates that thermal conditions within Mercury have allowed partial melting of silicates through the majority of its geological history and that the overall duration of volcanism on Mercury is similar to that of the Moon despite the different physical structure, geological history, and composition of the two bodies
Reimagining Heliophysics: A bold new vision for the next decade and beyond
The field of Heliophysics has a branding problem. We need an answer to the
question: ``What is Heliophysics\?'', the answer to which should clearly and
succinctly defines our science in a compelling way that simultaneously
introduces a sense of wonder and exploration into our science and our missions.
Unfortunately, recent over-reliance on space weather to define our field, as
opposed to simply using it as a practical and relatable example of applied
Heliophysics science, narrows the scope of what solar and space physics is and
diminishes its fundamental importance. Moving forward, our community needs to
be bold and unabashed in our definition of Heliophysics and its big questions.
We should emphasize the general and fundamental importance and excitement of
our science with a new mindset that generalizes and expands the definition of
Heliophysics to include new ``frontiers'' of increasing interest to the
community. Heliophysics should be unbound from its current confinement to the
Sun-Earth connection and expanded to studies of the fundamental nature of space
plasma physics across the solar system and greater cosmos. Finally, we need to
come together as a community to advance our science by envisioning,
prioritizing, and supporting -- with a unified voice -- a set of bold new
missions that target compelling science questions - even if they do not explore
the traditional Sun- and Earth-centric aspects of Heliophysics science. Such
new, large missions to expand the frontiers and scope of Heliophysics science
large missions can be the key to galvanizing the public and policymakers to
support the overall Heliophysics program
MESSENGER at Mercury: Early Orbital Operations
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, launched in August 2004 under NASA's Discovery Program, was inserted into orbit about the planet Mercury in March 2011. MESSENGER's three flybys of Mercury in 2008-2009 marked the first spacecraft visits to the innermost planet since the Mariner 10 flybys in 1974-1975. The unprecedented orbital operations are yielding new insights into the nature and evolution of Mercury. The scientific questions that frame the MESSENGER mission led to the mission measurement objectives to be achieved by the seven payload instruments and the radio science experiment. Interweaving the full set of required orbital observations in a manner that maximizes the opportunity to satisfy all mission objectives and yet meet stringent spacecraft pointing and thermal constraints was a complex optimization problem that was solved with a software tool that simulates science observations and tracks progress toward meeting each objective. The final orbital observation plan, the outcome of that optimization process, meets all mission objectives. MESSENGER's Mercury Dual Imaging System is acquiring a global monochromatic image mosaic at better than 90% coverage and at least 250 m average resolution, a global color image mosaic at better than 90% coverage and at least 1 km average resolution, and global stereo imaging at better than 80% coverage and at least 250 m average resolution. Higher-resolution images are also being acquired of targeted areas. The elemental remote sensing instruments, including the Gamma-Ray and Neutron Spectrometer and the X-Ray Spectrometer, are being operated nearly continuously and will establish the average surface abundances of most major elements. The Visible and Infrared Spectrograph channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer is acquiring a global map of spectral reflectance from 300 to 1450 nm wavelength at a range of incidence and emission angles. Targeted areas have been selected for spectral coverage into the ultraviolet with the Ultraviolet and Visible Spectrometer (UVVS). MESSENGER's Mercury Laser Altimeter is acquiring topographic profiles when the slant range to Mercury's surface is less than 1800 km, encompassing latitudes from 20 deg. S to the north pole. Topography over the remainder of the southern hemisphere will be derived from stereo imaging, radio occultations, and limb profiles. MESSENGER's radio science experiment is determining Mercury's gravity field from Doppler signals acquired during frequent downlinks. MESSENGER's Magnetometer is measuring the vector magnetic field both within Mercury's magnetosphere and in Mercury's solar wind environment at an instrument sampling rate of up to 20 samples/s. The UVVS is determining the three-dimensional, time-dependent distribution of Mercury's exospheric neutral and ionic species via their emission lines. During each spacecraft orbit, the Energetic Particle Spectrometer measures energetic electrons and ions, and the Fast Imaging Plasma Spectrometer measures the energies and mass per charge of thermal plasma components, both within Mercury's magnetosphere and in Mercury's solar-wind environment. The primary mission observation sequence will continue for one Earth year, until March 2012. An extended mission, currently under discussion with NASA, would add a second year of orbital observations targeting a set of focused follow-on questions that build on observations to date and take advantage of the more active Sun expected during 2012-2013. MESSENGER's total primary mission cost, projected at $446 M in real-year dollars, is comparable to that of Mariner 10 after adjustment for inflation
Geology of the Victoria quadrangle (H02), Mercury
Mercury’s quadrangle H02 ‘Victoria’ is located in the planet’s northern hemisphere and lies between latitudes 22.5° N and 65° N, and between longitudes 270° E and 360° E. This quadrangle covers 6.5% of the planet’s surface with a total area of almost 5 million km2. Our 1:3,000,000-scale geologic map of the quadrangle was produced by photo-interpretation of remotely sensed orbital images captured by the MESSENGER spacecraft. Geologic contacts were drawn between 1:300,000 and 1:600,000 mapping scale and constitute the boundaries of intercrater, intermediate and smooth plains units; in addition, three morpho-stratigraphic classes of craters larger than 20 km were mapped. The geologic map reveals that this area is dominated by Intercrater Plains encompassing some almost-coeval, probably younger, Intermediate Plains patches and interrupted to the north-west, north-east and east by the Calorian Northern Smooth Plains. This map represents the first complete geologic survey of the Victoria quadrangle at this scale, and an improvement of the existing 1:5,000,000 Mariner 10-based map, which covers only 36% of the quadrangle
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