Lunar and Planetary Institute

The Mars Orbiter Laser Altimeter (MOLA), an instrument on the Mars Global Surveyor spacecraft, has measured the topography, surface roughness, and 1.064‐μm reflectivity of Mars and the heights of volatile and dust clouds. This paper discusses the function of the MOLA instrument and the acquisition, processing, and correction of observations to produce global data sets. The altimeter measurements have been converted to both gridded and spherical harmonic models for the topography and shape of Mars that have vertical and radial accuracies of ∼1 m with respect to the planet's center of mass. The current global topographic grid has a resolution of 1/64° in latitude × 1/32° in longitude (1×2 km 2 at the equator). Reconstruction of the locations of incident laser pulses on the Martian surface appears to be at the 100‐m spatial accuracy level and results in 2 orders of magnitude improvement in the global geodetic grid of Mars. Global maps of optical pulse width indicative of 100‐m‐scale surface roughness and 1.064‐μm reflectivity with an accuracy of 5% have also been obtained.

The Cretaceous-Paleogene boundary approximately 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.

High-resolution gravity data obtained from the dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft show that the bulk density of the Moon's highlands crust is 2550 kilograms per cubic meter, substantially lower than generally assumed. When combined with remote sensing and sample data, this density implies an average crustal porosity of 12% to depths of at least a few kilometers. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low-bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 kilometers, the bulk refractory element composition of the Moon is not required to be enriched with respect to that of Earth.

The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.

The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions-the interaction of cloud systems-display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanismn on Io, complex tectonism on Ganymnede and possibly Europa, and flattened remnants of enormous impact features on Callisto.

The IFA and collaborators are embarking on a project to develop a 4-telescope synoptic survey instrument. While somewhat smaller than the 6.5m class telescope envisaged by the decadal review in their proposal for a LSST, this facility will nonetheless be able to accomplish many of the LSST science goals. In this paper we will describe the motivation for a 'distributed aperture' approach for the LSST, the current concept for Pan-STARRS -- a pilot project for the LSST proper -- and its performance goals and science reach. We will also discuss how the facility may be expanded.

Sedimentary rocks at Yellowknife Bay (Gale crater) on Mars include mudstone sampled by the Curiosity rover. The samples, John Klein and Cumberland, contain detrital basaltic minerals, calcium sulfates, iron oxide or hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The John Klein smectite has basal spacing of ~10 angstroms, indicating little interlayer hydration. The Cumberland smectite has basal spacing at both ~13.2 and ~10 angstroms. The larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating H2O retention. Basaltic minerals in the mudstone are similar to those in nearby eolian deposits. However, the mudstone has far less Fe-forsterite, possibly lost with formation of smectite plus magnetite. Late Noachian/Early Hesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time.

Tourmaline, a mineral often overlooked in petrological studies, is shown to be a useful petrogenetic indicator mineral.-J.A.Z.

ou non, manant des tablissements d'enseignement et de recherche franais ou trangers, des laboratoires publics ou privs.

During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole.

Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered.

We have developed 1-D photochemical and thermochemical kinetics and diffusion models for the transiting exoplanets HD 189733b and HD 209458b to study the effects of disequilibrium chemistry on the atmospheric composition of "hot Jupiters." Here we investigate the coupled chemistry of neutral carbon, hydrogen, oxygen, and nitrogen species, and we compare the model results with existing transit and eclipse observations. We find that the vertical profiles of molecular constituents are significantly affected by transport-induced quenching and photochemistry, particularly on cooler HD 189733b; however, the warmer stratospheric temperatures on HD 209458b can help maintain thermochemical equilibrium and reduce the effects of disequilibrium chemistry. For both planets, the methane and ammonia mole fractions are found to be enhanced over their equilibrium values at pressures of a few bar to less than a mbar due to transport-induced quenching, but CH4 and NH3 are photochemically removed at higher altitudes. Atomic species, unsaturated hydrocarbons (particularly C2H2), some nitriles (particularly HCN), and radicals like OH, CH3, and NH2 are enhanced overequilibrium predictions because of quenching and photochemistry. In contrast, CO, H2O, N2, and CO2 more closely follow their equilibrium profiles, except at pressures < 1 microbar, where CO, H2O, and N2 are photochemically destroyed and CO2 is produced before its eventual high-altitude destruction. The enhanced abundances of HCN, CH4, and NH3 in particular are expected to affect the spectral signatures and thermal profiles HD 189733b and other, relatively cool, close-in transiting exoplanets. We examine the sensitivity of our results to the assumed temperature structure and eddy diffusion coefficientss and discuss further observational consequences of these models.

Research Article| January 01, 1972 Major and Trace Element Abundances in Volcanic Rocks of Orogenic Areas P JAKEŠ; P JAKEŠ The Lunar Science Institute, 3303 Nasa Road 1, Houston, Texas 77058 AUTHOR'S PRESENT ADDRESS: GEOLOGICAL INSTITUTE, CZECHOSLOVAK ACADEMY OF SCIENCES, SUCHDOL 2, PRAHA 6, CZECHOSLOVAKIA (JAKEŠ) Search for other works by this author on: GSW Google Scholar A. J. R WHITE A. J. R WHITE Department of Geology, The Australian National University, Canberra, A. C. T., Australia Search for other works by this author on: GSW Google Scholar Author and Article Information P JAKEŠ AUTHOR'S PRESENT ADDRESS: GEOLOGICAL INSTITUTE, CZECHOSLOVAK ACADEMY OF SCIENCES, SUCHDOL 2, PRAHA 6, CZECHOSLOVAKIA (JAKEŠ) The Lunar Science Institute, 3303 Nasa Road 1, Houston, Texas 77058 A. J. R WHITE Department of Geology, The Australian National University, Canberra, A. C. T., Australia Publisher: Geological Society of America Received: 02 Apr 1971 Revision Received: 26 Jul 1971 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1972, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1972) 83 (1): 29–40. https://doi.org/10.1130/0016-7606(1972)83[29:MATEAI]2.0.CO;2 Article history Received: 02 Apr 1971 Revision Received: 26 Jul 1971 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation P JAKEŠ, A. J. R WHITE; Major and Trace Element Abundances in Volcanic Rocks of Orogenic Areas. GSA Bulletin 1972;; 83 (1): 29–40. doi: https://doi.org/10.1130/0016-7606(1972)83[29:MATEAI]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Major and trace element abundances in volcanic rocks of island arcs vary regularly in both the lateral and in the stratigraphic sequence. The earliest manifestations of island arc evolution are tholeiitic rocks occurring on the oceanic side of recent island arcs. These tholeiites are characterized by chemical features such as low K2O content and relatively high iron enrichment, that is, high FeO/MgO in medium SiO2 (59 percent) rocks. The tholeiites are followed stratigraphically or laterally by calc-alkaline rocks and finally by shoshonites or alkaline rocks, showing progressive increase in K2O content, increase in K2O/Na2O ratio, and decreasing iron enrichment. Trace elements of the potassium type are the most sensitive indicators of compositional variation showing differences between tholeiites and shoshonites by two orders of magnitude. Trace elements and major elements suggest a continuous gradational sequence from tholeiites through calc-alkaline rocks to shoshonites. Rare-earth elements show two diverse abundance patterns: (1) a primitive chondritic-like pattern is characteristic for island arc tholeiitic association; and (2) a fractionated light rare-earth elements enriched pattern is typical for calc-alkaline and shoshonitic and alkaline associations. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.

This article reviews our current understanding of terrestrial planet formation. The focus is on computer simulations of the dynamical aspects of the accretion process. Throughout the review, we combine the results of these theoretical models with geochemical, cosmochemical, and chronological constraints to outline a comprehensive scenario of the early evolution of our solar system. Given that the giant planets formed first in the protoplanetary disk, we stress the sensitive dependence of the terrestrial planet accretion process on the orbital architecture of the giant planets and on their evolution. This suggests a great diversity among the terrestrial planet populations in extrasolar systems. Issues such as the cause for the different masses and accretion timescales between Mars and Earth and the origin of water (and other volatiles) on our planet are discussed in depth.

Research Article| December 01, 1989 Altiplano-Puna volcanic complex of the central Andes S. L. de Silva S. L. de Silva 1Lunar & Planetary Institute, 3303 NASA Road 1, Houston, Texas 77058 Search for other works by this author on: GSW Google Scholar Geology (1989) 17 (12): 1102–1106. https://doi.org/10.1130/0091-7613(1989)017<1102:APVCOT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation S. L. de Silva; Altiplano-Puna volcanic complex of the central Andes. Geology 1989;; 17 (12): 1102–1106. doi: https://doi.org/10.1130/0091-7613(1989)017<1102:APVCOT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Since the late Miocene an ignimbrite flare-up has resulted in a major volcano-tectonic province, the Altiplano-Puna volcanic complex, in the lat 21° to 24°S part of the Central Volcanic Zone of the Andes. The dominant elements of the complex, which defines an area of about 50000 km2 between the Atacama basin and the Altiplano, are several large nested caldera complexes which are the source structures for the major regionally distributed ignimbrite sheets that characterize the complex. The chemical and physical characteristics of these ignimbrites are best reconciled with an origin by large-scale crustal melting. The timing of the ignimbrite flare-up coincides well with thickening of the Central Volcanic Zone crust just prior to the late Miocene, and the coincidence of the Altiplano-Puna volcanic complex with the thickest part of this crust (∼70 km) points to a cause and effect relation. Crustal melting in response to crustal thickening and the heat input from subduction-related magmas is suggested to have resulted in large-scale sificic magmatism. Diapiric uprise of these magmas into a zone of tectonically weakened crust due to strike-slip tectonics associated with the Atacama basin resulted in major ignimbrite eruptions and the formation of the calderas of the Altiplano-Puna volcanic complex. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Abstract Forty-five years after the Apollo and Luna missions returned lunar samples, China's Chang’E-5 (CE-5) mission collected new samples from the mid-latitude region in the northeastern Oceanus Procellarum of the Moon. Our study shows that 95% of CE-5 lunar soil sizes are found to be within the range of 1.40–9.35 μm, while 95% of the soils by mass are within the size range of 4.84–432.27 μm. The bulk density, true density and specific surface area of CE-5 soils are 1.2387 g/cm3, 3.1952 g/cm3 and 0.56 m2/g, respectively. Fragments from the CE-5 regolith are classified into igneous clasts (mostly basalt), agglutinate and glass. A few breccias were also found. The minerals and compositions of CE-5 soils are consistent with mare basalts and can be classified as low-Ti/low-Al/low-K type with lower rare-earth-element contents than materials rich in potassium, rare earth element and phosphorus. CE-5 soils have high FeO and low Mg index, which could represent a new class of basalt.

NASA’s InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018. It aims to determine the interior structure, composition and thermal state of Mars, as well as constrain present-day seismicity and impact cratering rates. Such information is key to understanding the differentiation and subsequent thermal evolution of Mars, and thus the forces that shape the planet’s surface geology and volatile processes. Here we report an overview of the first ten months of geophysical observations by InSight. As of 30 September 2019, 174 seismic events have been recorded by the lander’s seismometer, including over 20 events of moment magnitude Mw = 3–4. The detections thus far are consistent with tectonic origins, with no impact-induced seismicity yet observed, and indicate a seismically active planet. An assessment of these detections suggests that the frequency of global seismic events below approximately Mw = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding Mw = 4 have been observed. The lander’s other instruments—two cameras, atmospheric pressure, temperature and wind sensors, a magnetometer and a radiometer—have yielded much more than the intended supporting data for seismometer noise characterization: magnetic field measurements indicate a local magnetic field that is ten-times stronger than orbital estimates and meteorological measurements reveal a more dynamic atmosphere than expected, hosting baroclinic and gravity waves and convective vortices. With the mission due to last for an entire Martian year or longer, these results will be built on by further measurements by the InSight lander. Geophysical and meteorological measurements by NASA’s InSight lander on Mars reveal a planet that is seismically active and provide information about the interior, surface and atmospheric workings of Mars.

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

It has been proposed that Jupiter's satellite Europa currently possesses a global subsurface ocean of liquid water. Galileo gravity data verify that the satellite is differentiated into an outer H 2 O layer about 100 km thick but cannot determine the current physical state of this layer (liquid or solid). Here we summarize the geological evidence regarding an extant subsurface ocean, concentrating on Galileo imaging data. We describe and assess nine pertinent lines of geological evidence: impact morphologies, lenticulae, cryovolcanic features, pull‐apart bands, chaos, ridges, surface frosts, topography, and global tectonics. An internal ocean would be a simple and comprehensive explanation for a broad range of observations; however, we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm, soft ice with only localized or partial melting. Two different models of impact flux imply very different surface ages for Europa; the model favored here indicates an average age of ∼50 Myr. Searches for evidence of current geological activity on Europa, such as plumes or surface changes, have yielded negative results to date. The current existence of a global subsurface ocean, while attractive in explaining the observations, remains inconclusive. Future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within Europa today.