Martian precession and rotation from Viking lander range data

Yoder, C. F.; Standish, E. M.

doi:10.1029/96je03642

Cited by 117 publications

(87 citation statements)

References 45 publications

(18 reference statements)

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“…2). The statistically significant shift from the previous result is thought to be due to systematic effects in the ranging data that were used exclusively in the previous analysis (1), whereas our seasonal estimates are dominated by the Viking Doppler data. The estimated semiannual term does not agree as well with the model (Fig.…”

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confidence: 42%

“…Determination of the polar moment of inertia yields information on the distribution of mass within the planet, such as whether the planet has a dense core surrounded by a lighter mantle. Analysis of radio tracking measurements from the Viking landers has determined the normalized polar moment of inertia C/MR 2 , where M is the mass of Mars and R is its mean radius, to be 0.355 Ϯ 0.015 (1). However, the uncertainty in this estimate is not small enough to determine with certainty that Mars has a dense core or to distinguish between interior models ranging from an Earth-like composition to iron-enriched compositions characteristic of the meteorites thought to originate from Mars (2).…”

mentioning

confidence: 99%

“…The estimated polar moment of inertia can be used to constrain models of the martian interior (1,18). The polar moment of inertia varies with core size, composition, and temperature profile.…”

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confidence: 99%

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Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

Folkner

Yoder

Yuan

et al. 1997

Science

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282

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Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 Ϯ 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.Little is known about the interior of Mars. From telescopic observations and spacecraft missions, the mass and radius of Mars have been determined and hence its mean density. Because Mars is significantly asymmetric, its polar moment of inertia C cannot be inferred from the gravity field. Determination of the polar moment of inertia yields information on the distribution of mass within the planet, such as whether the planet has a dense core surrounded by a lighter mantle. Analysis of radio tracking measurements from the Viking landers has determined the normalized polar moment of inertia C/MR 2 , where M is the mass of Mars and R is its mean radius, to be 0.355 Ϯ 0.015 (1). However, the uncertainty in this estimate is not small enough to determine with certainty that Mars has a dense core or to distinguish between interior models ranging from an Earth-like composition to iron-enriched compositions characteristic of the meteorites thought to originate from Mars (2).The Mars Pathfinder mission has provided an opportunity to improve our knowledge of Mars' polar moment of inertia and hence our knowledge of Mars' interior. As with the Viking landers, the Pathfinder radio system used for communication with Earth was also used to measure the distance (from the signal travel time) and changes in distance (from the Doppler frequency shift of the signal) between Earth and Mars. These measurements provided information on the changing orbits of Earth and Mars and on the rotation of Mars (3). Of particular interest is the martian rotational information: secular precession and periodic nutation of the spin axis, seasonal and tidal variations in the rotation rate, and Chandler-like wobble of Mars' figure axis relative to the spin axis. These quantities can be used to constrain models of the interior of Mars and estimate the annual mass exchange between the atmosphere and the polar ice caps.The precession is driven by the gravitational torque of the sun acting on Mars' oblate figure and is proportional to (C -(A ϩ B)/2)/C where C Ͼ B Ͼ A are the principal moments of inertia of Mars. The factor C -(A ϩ B)/2 ϭ J 2 MR 2 is already known with high accuracy from detection of Mars' gravity field with the use of Viking orbiter and other tracking data (4). Accurate measurement of the precession is needed to determine the polar moment of inertia. Knowledge of the moment of inertia, combined with measurements of Mars' mass, size, shape, and low-order grav...

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Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

Folkner

Yoder

Yuan

et al. 1997

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“…The parameters of rotation of Mars and their accuracies were found to be close to the corresponding values taken from a paper by Yoder and Standish (1997).…”

Section: The Use Of the Epm Ephemerides In Scientific Researchmentioning

confidence: 56%

Updated IAA RAS planetary ephemerides-EPM2011 and their use in scientific research

Pitjeva

2013

Sol Syst Res

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-The EPM (Ephemerides ofPlanetsThe errors of the current best ranging observations do not exceed several meters, which makes it necessary to compute the ranging correctly up to the 12th significant digit. An appropriate model of the motion of celestial bodies is required to achieve such high precision.The construction of a proper model that would take into account all the significant factors is a serious problem, and the current most feasible way to solve it is to perform numerical integration of the equations of motion of the planets and the Moon on a computer.In the late 1960s several research groups in the United States and Russia developed numerical theories to support space flights. American groups worked at the California Institute of Technology and the Massachusetts Institute of Technology. Russian high-

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“…Pathfinder has provided tests of the validity of remote observations from Earth, orbit, and the surface (2). As predicted, the average elevation of the center of the site was about the same as that of the Viking 1 lander (VL-1) relative to the 6.1-mbar geoid (Table 2), based on delayDoppler radar measurements (17) and tracking results (18); the Doppler tracking and two-way ranging estimate for the elevation of the spacecraft (9) is only 45 m lower than that of the VL-1 and within 100 m of that expected, which is within the uncertainties of the measurements. After landing, surface pressures and winds (5 to 10 m/s) were similar to expectations based on Viking data, although temperatures were about 10 K warmer (6).…”

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confidence: 75%

Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions

Golombek

Cook

Economou

et al. 1997

Science

272

111

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Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than ϳ1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free.Mars Pathfinder (named the Sagan Memorial Station) landed on the surface of Mars on 4 July 1997 (Figs. 1 and 2), deployed a small rover (named Sojourner) (Fig. 3), and collected data from three scientific instruments [named Imager for Mars Pathfinder (IMP), ␣-proton x-ray spectrometer (APXS), and atmospheric structure investigation/meteorology package (ASI/MET)] and technology experiments (1). In the first month of surface operations the mission returned about 1.2 gigabits of data, which include 9669 lander and 384 rover images and about 4 million temperature, pressure, and wind measurements. The rover traversed a total of about 52 m in 114 commanded movements, performed 10 chemical analyses of rocks and soil, carried out soil mechanics and technology experiments, and explored over 100 m 2 of the martian surface.Pathfinder used a rover, carrying a chemical analysis instrument, to characterize the rocks and soils in a landing area over hundreds of square meters on Mars, which provides a calibration point or "ground truth" for orbital remote-sensing observations (1, 2). The combination of spectral imaging of the landing area by the IMP, chemical analyses by the APXS aboard the rover, and close-up imaging of colors, textures, and morphologies with the rover cameras offers the potential for identifying rocks (petrology and mineralogy). Before the Pathfinder mission, knowledge of the kinds of rocks present on Mars was based mostly on the martian meteorites (all mafic igneous rocks) and inferences from Viking data (3, 4). In addition, small valley networks in heavily cratered terrain on Mars have been used to argue that the early martian environment may have been warmer and wetter (with a thicker atmosphere), at which time liquid water may have been stable (5).The Ares Vallis landing site (Fig. 4) was selected because it appeared acceptably safe and offered the prospect of analyzing a variety of rock types expected to be deposited by catastrophic floods, which enable addressing first-order scientific questions such as differentiation of the crust, the development of weathering products, and the nature of the early martian environment and its subsequent evolution (2). In the selection of the Pathfinder landing site...

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Martian precession and rotation from Viking lander range data

Cited by 117 publications

References 45 publications

Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

Updated IAA RAS planetary ephemerides-EPM2011 and their use in scientific research

Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions

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