This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.

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Composition of the Continental Crust

[1] The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution. Details of the development, flight operations, data processing, and products are provided for users of this revolutionary data set.

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The Shuttle Radar Topography Mission

Investigating soil moisture-climate interactions in a changing climate: A review

3.01 – Composition of the Continental Crust

[1] EGM2008 is a spherical harmonic model of the Earth's gravitational potential, developed by a least squares combination of the ITG-GRACE03S gravitational model and its associated error covariance matrix, with the gravitational information obtained from a global set of area-mean free-air gravity anomalies defined on a 5 arc-minute equiangular grid This grid was formed by merging terrestrial, altimetry-derived, and airborne gravity data Over areas where only lower resolution gravity data were available, their spectral content was supplemented with gravitational information implied by the topography EGM2008 is complete to degree and order 2159, and contains additional coefficients up to degree 2190 and order 2159 Over areas covered with high quality gravity data, the discrepancies between EGM2008 geoid undulations and independent GPS/Leveling values are on the order of ±5 to ±10 cm EGM2008 vertical deflections over USA and Australia are within ±11 to ±13 arc-seconds of independent astrogeodetic values These results indicate that EGM2008 performs comparably with contemporary detailed regional geoid models EGM2008 performs equally well with other GRACE-based gravitational models in orbit computations Over EGM96, EGM2008 represents improvement by a factor of six in resolution, and by factors of three to six in accuracy, depending on gravitational quantity and geographic area EGM2008 represents a milestone and a new paradigm in global gravity field modeling, by demonstrating for the first time ever, that given accurate and detailed gravimetric data, asingle global model may satisfy the requirements of a very wide range of applications

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011JB008916

The development and evaluation of the Earth Gravitational Model 2008 (EGM2008)

We present measurements of the density of the Martian atmosphere between 170- and 180-km altitude above the high northern latitudes over a 6-month period in 1998, when the solar cycle was beginning to rise out of its activity minimum. These measurements were made from the observed orbital decay of the Mars Global Surveyor (MGS) spacecraft during its Science Phasing Orbits (SPO) (April to September 1998) using X band Doppler tracking observations. The densities that we retrieve are comparable to model values given by Culp and Stewart [1984], Stewart [1987], Mars-GRAM 3.7 [Justus et al., 1996], and recent Mars Thermospheric Global Circulation Model (MTGCM) simulations [Bougher et al., 2000]. However, the SPO period can be divided into two time periods (separated at Ls ≈ 355°∼0°) that are characterized by significantly different orbit-to-orbit variability that is not predicted by these earlier models. The first time period corresponds to the time during which the MGS orbit perifocus moved toward the north pole while the local solar time was 1000–1100; during this period, orbit-to-orbit variability is 50–70%, and our average measured density at 175 km is 0.018±0.007 kg km−3 (between 67° and 72°N and Ls = 315° to 320°). The second time period corresponds to the time during which the orbit perifocus moved south from the north pole and the local time was 1700–1730; during this period, orbit-to-orbit variability is 40–20%, and our average measured density at 175 km is 0.024±0.004 kg km−3 (between 62° and 69°N and Ls = 17° to 28°). For both time periods the observed latitudinal gradient of density on a constant altitude surface exhibited a factor of 3–4 decrease between 60° and 90°N. This gradient is comparable to that expected by the polar vortex (high-latitude wind) effect modeled by the MTGCM for solar medium conditions at southern summer solstice [Bougher et al., 2000]. A southern hemisphere dust storm that the MGS Thermal Emission Spectrometer (TES) observed at Ls = 309° is distinguishable in our data set as a 100% rise in density at 180 km above the 70° northern latitudes 7 days later (Ls = 313°).

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JE001418

Density structure of the upper thermosphere of Mars from measurements of air drag on the Mars Global Surveyor spacecraft

The NASA MESSENGER mission explored the innermost planet of the solar system and obtained a rich data set of range measurements for the determination of Mercury’s ephemeris. Here we use these precise data collected over 7 years to estimate parameters related to general relativity and the evolution of the Sun. These results confirm the validity of the strong equivalence principle with a significantly refined uncertainty of the Nordtvedt parameter η = (−6.6 ± 7.2) × 10−5. By assuming a metric theory of gravitation, we retrieved the post-Newtonian parameter β = 1 + (−1.6 ± 1.8) × 10−5 and the Sun’s gravitational oblateness, $${{J}}_{2 \odot }$$J2⊙ = (2.246 ± 0.022) × 10−7. Finally, we obtain an estimate of the time variation of the Sun gravitational parameter, $$\dot{{G} {{M}}_ \odot} {\mathrm{/}}{{G}}{{M}}_ \odot$$GM⊙°∕GM⊙ = (−6.13 ± 1.47) × 10−14, which is consistent with the expected solar mass loss due to the solar wind and interior processes. This measurement allows us to constrain $$\left| {{\dot{ G}}} \right|{\mathrm{/}}{{G}}$$G°∕G to be <4 × 10−14 per year.The NASA MESSENGER mission collected a rich dataset enabling determination of Mercury’s ephemeris. Here, the authors analyse MESSENGER data obtained over an extended period of time to quantify parameters related to General Relativity.

Solar System Expansion and Strong Equivalence Principle as seen by the MESSENGER mission

The International DORIS Service (IDS) was created in 2003 under the umbrella of the International Association of Geodesy (IAG) to foster scientific research related to the French DORIS tracking system and to deliver scientific products, mostly related to the International Earth rotation and Reference systems Service (IERS). We first present some general background related to the DORIS system (current and planned satellites, current tracking network and expected evolution) and to the general IDS organization (from Data Centers, Analysis Centers and Combination Center). Then, we discuss some of the steps recently taken to prepare the IDS submission to ITRF2013 (combined weekly time series based on individual solutions from several Analysis Centers). In particular, recent results obtained from the Analysis Centers and the Combination Center show that improvements can still be made when updating physical models of some DORIS satellites, such as Envisat, Cryosat-2 or Jason-2. The DORIS contribution to ITRF2013 should also benefit from the larger number of ground observations collected by the last generation of DGXX receivers (first instrument being onboard Jason-2 satellite). In particular for polar motion, sub-milliarcsecond accuracy seems now to be achievable. Weekly station positioning internal consistency also seems to be improved with a larger DORIS constellation.

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The International DORIS Service (IDS) - Recent Developments in Preparation for ITRF2013

The development of the GSFC DORIS contribution to ITRF2014

[1] The problem associated with the large data gap on the farside of the Moon is addressed for constructing a high-resolution global gravity model. By localizing the power law constraint and making it effective only within the farside and limb regions, we mitigate the undesired power-limiting effect on the nearside. Compared to the solution estimated from Lunar Prospector and other satellite tracking data with the globally-applied power law, the locally-constrained solution shows significant improvement of the nearside gravity estimates. Around the areas dominated by craters in the southern hemisphere of the nearside, the correlation with topography approaches nearly 0.95 and the admittance converges to 100–110 mGal/km up to spherical harmonic degree 130, while the globally-constrained solutions distort starting at degree 90. The proposed analysis can benefit the science and operation of other existing and future planetary missions and enhance the geophysical interpretation of the gravity field.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2009GL038556

Frank G. Lemoine

Papers

Density structure of the upper thermosphere of Mars from measurements of air drag on the Mars Global Surveyor spacecraft

Solar System Expansion and Strong Equivalence Principle as seen by the MESSENGER mission

The International DORIS Service (IDS) - Recent Developments in Preparation for ITRF2013

The development of the GSFC DORIS contribution to ITRF2014

Improved nearside gravity field of the Moon by localizing the power law constraint