Surveyor Spacecraft Research Articles

The solar wind interaction with Mars: Locations and shapes of the bow shock and the magnetic pile‐up boundary from the observations of the MAG/ER Experiment onboard Mars Global Surveyor

The Mars Global Surveyor spacecraft was inserted into an elliptical orbit around Mars on September 12, 1997. It includes the MAG/ER instrument with two magnetometers providing in‐situ sensing of the ambient magnetic field and an electron reflectometer measuring the local distribution function of the electrons in the energy range of 10 eV to 20 keV. This statistical study deals with the identification and the position of the Bow Shock (BS) and of another plasma boundary, the Magnetic Pile‐up Boundary (MPB), proved as permanent by MAG/ER. During the first year of the MGS mission, a total of 290 orbits have been considered to fit the geometric characteristics of these boundaries. The position and shape of these boundaries are compared with previous studies. Good agreement is found with the Phobos 2 observations, suggesting than the mean bow shock and MPB locations are independent of solar cycle phase. The great number of crossings shows that the Bow Shock position and nightside MPB position are highly variable.

Venus‐like interaction of the solar wind with Mars

The magnetometer and electron reflectometer experiment (MAG/ER) on the Mars Global Surveyor (MGS) spacecraft has obtained magnetic field and electron data which indicates that the solar wind interaction with Mars is primarily an ionospheric‐atmospheric interaction similar to that at Venus. However, the global‐scale electric currents and resulting magnetic fields due to the interaction at Mars are locally interrupted or perturbed over distance scales of several hundred kilometers by the effects of paleomagnetic fields due to crustal remanence. In this paper we compare the Mars‐solar wind interaction with the Venus‐solar wind interaction by selecting MGS orbits which do not show significant magnetic perturbations due to crustal magnetic anomalies, and demonstrate that a number of phenomena characteristic of the Venus‐solar wind interaction are also observable at Mars.

Control of the radiative behavior of the Martian polar caps by surface CO2 ice: Evidence from Mars Global Surveyor measurements

The seasonal polar caps of Mars are composed primarily of solid CO2, and their growth and decay play a large part in the planet's atmospheric CO2 cycle. The thermodynamic temperature of the caps is ∼145 K, in equilibrium with the ∼6 mbar atmosphere. The optical properties of CO2 ice require that pure snow with a sufficiently small particle size has a high visible/near‐infrared albedo and a low infrared emissivity in parts of the thermal infrared, particularly in the region between 20 and 50 μm. Dust mixed into or on top of the CO2 ice will lower the visible albedo and bring the thermal infrared emissivity closer to 1. Water ice mixed with the CO2 will have little effect in the visible and near‐infrared to 1.4 μm but can raise the 20–50 μm emissivity if the particle size is >50 μm. Observations of both seasonal polar caps during two of the assessment orbits of the Mars Global Surveyor spacecraft are used to show that there is a strong correlation between visible brightness and low 20–50 μm emissivity. The infrared spectra from the Thermal Emission Spectrometer from regions with low 20–50 μm brightness temperature are consistent with surface deposits of CO2 with millimeter‐sized grains and containing varying small amounts of dust, and they are not consistent with the expected signature of water ice or clouds. Large regions of low emissivity in the spring seasonal caps have not been observed previously. They are correlated with visible bright regions which are known to become brighter as the spring progresses. The visible brightness of the south polar deposits examined is inferred from historical observations, while the brightness of the north polar region is determined from Mars Orbiter Laser Altimeter measurements at 1.06 μm. The model of seasonal CO2 caps with bright, low‐emissivity regions agrees with previous visible observations of bright crater rims, streaks, and other bright areas within the polar caps, some of which may evolve in time from dark, high‐emissivity sheet ice to brighter, fractured, lower‐emissivity ice layers. It is also in agreement with models of the CO2 cycle, which require average polar cap emissivities <0.9.

Martian life “still kicking” in meteorite ALH84001

In 1996, David McKay and his coworkers at NASA's Johnson Space Center claimed that they had evidence of life on Mars and that Martian meteorite ALH84001 was once inhabited, on Mars, by bacteria‐like creatures [McKay et al, 1996].Much of the public and the media accepted their claims, but most scientists were deeply skeptical. Now more than 2 years later, what has become of the Martian microbes? Are they appealing illusions, like Lowell's canals on Mars, or are they real? In the time since the paper by McKay and his colleagues was published, the Pathfinder and Mars Global Surveyor spacecraft have revealed volumes about Mars, and an intense lab study has discovered more secrets of the Martian meteorites, but no agreement has appeared on whether meteorite ALH84001 was ever graced by Martian life.

Signs of Plate Tectonics on an Infant Mars

PLANETOLOGYPivotal to the discovery almost 40 years ago of plate tectonics were rank upon rank of magnetic stripes that march across the sea floor, each marking the orientation of Earth's flip-flopping magnetic field at the moment the crust was born. Now on pages [790][1] and [794][2] of this issue, researchers report magnetic stripes on Mars. The data, gathered by the Mars Global Surveyor spacecraft, suggest that in its early days, Earth's diminutive cousin resurfaced itself the way Earth does today, spreading freshly made crust away from long, narrow volcanic rifts. Yet the shape and pattern of the martian stripes are so different from Earth's that geophysicists are reserving judgment for the moment. [1]: http://www.sciencemag.org/cgi/content/short/284/5415/790 [2]: http://www.sciencemag.org/cgi/content/short/284/5415/794

Magnetic lineations in the ancient crust of mars

The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit, obtained vector magnetic field measurements above the surface of Mars (altitudes >100 kilometers). Crustal magnetization, mainly confined to the most ancient, heavily cratered martian highlands, is frequently organized in east-west-trending linear features, the longest extending over 2000 kilometers. Crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity were found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale. They may be a relic of an era of plate tectonics on Mars.

Evidence for recent volcanism on Mars from crater counts

Impact craters help characterize the age of a planetary surface, because they accumulate with time. They also provide useful constraints on the importance of surface erosion, as such processes will preferentially remove the smaller craters. Earlier studies of martian crater populations revealed that erosion and dust deposition are important processes on Mars. They disagreed, however, on the age of the youngest volcanism. These earlier studies were limited by image resolution to craters larger than a few hundred metres in diameter. Here we report an analysis, using new images obtained by the Mars Global Surveyor spacecraft, of crater populations that extend the size distribution down to about 16 m. Our results indicate a wide range of surface ages, with one region—lava flows within the Arsia Mons caldera—that we estimate to be no older than 40–100 million years. We suggest that volcanism is a continuing process on Mars.

Opacity of the Martian atmosphere from the Mars Orbiter Laser Altimeter (MOLA) observations

In this paper we present an analysis of the Mars Orbiter Laser Altimeter (MOLA) reflectivity measurements from the Mars Global Surveyor (MGS) spacecraft, during period of solar longitudes (Ls) 198° → 212°. Reflectivity can be interpreted as a product of the surface geometrical albedo and the two‐way atmospheric transmission. Relative surface albedos were obtained from the red filter of Viking Color Mars Digital Mosaics (MDIM) to derive opacities at the MOLA wavelength (1.064 µm). Opacity measurements are interpreted in terms of atmospheric aerosol loading in the canyons. We also observed sudden increase of opacity in the northern regions (65°N), which we interpret as condensing ice clouds.

Thermal Infrared Emission Spectroscopy of Salt Minerals Predicted for Mars

Thermal emissivity spectra (2000–400 cm−1) of select carbonate, sulfate, phosphate, and chloride minerals are presented in this study. The suite of samples was chosen to most closely represent the chemistry of the salts predicted for Mars on the basis of the Viking lander data, theoretical and experimental studies, and analyses of the Shergottite–Nakhlite–Chassignite and ALH84001 meteorites. Midinfrared spectra are presented to demonstrate the variation in emissivity between evaporite mineral classes (e.g., carbonates versus sulfates) and within a mineral class (e.g., calcite versus dolomite). Additional emissivity spectra are presented of particle-size fractions for each of the four mineral classes to show the effects of increased energy scattering with decreased particle size. Understanding particle-size effects may be critical for interpreting the emission of Mars where particulate material is common. The unique appearance of the emissivity spectra will aid the identification of the salt minerals on Mars from the midinfrared vibrational data to be acquired by the Thermal Emission Spectrometer aboard the Mars Global Surveyor spacecraft.

Mars global surveyor mission: overview and status.

The Mars Global Surveyor (MGS) spacecraft achieved a 45-hour elliptical orbit at Mars on 11 September 1997 after an 11-month cruise from Earth. The mission is acquiring high-quality global observations of the martian surface and atmosphere and of its magnetic and gravitational fields. These observations will continue for one martian year.

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.

Surveyor Shows the Flat Face of Mars

PLANETARY SCIENCEMars has a great crustal dichotomy: Much of its northern hemisphere is a low-lying plain roughly centered on the north pole, while the rest of that hemisphere and all of the southern hemisphere are ancient highlands. The first results from the altimeter aboard the Mars Global Surveyor spacecraft, reported on page [1686][1], are now indicating that Earth-like tectonic forces and perhaps even an ancient ocean have shaped Mars's northern lowlands. [1]: http://www.sciencemag.org/cgi/content/short/279/5357/1686

Topography of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter.

The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50 degrees is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the channel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in low-lying areas such as Valles Marineris.

Faulty solar panel jeopardizes Mars mapping project

washington A faulty solar panel on the US Mars Global Surveyor spacecraft has led mission managers to suspend normal operations.

Initial data from the Mars Global Surveyor thermal emission spectrometer experiment: Observations of the Earth

The thermal emission spectrometer (TES) on the Mars Global Surveyor spacecraft acquired observations of the Earth from a distance of 4.7 million km for instrument performance characterization on November 24, 1996. The data were calibrated using an internal reference surface and deep space in a manner identical to that which will be used in Mars orbit, and scaled to account for the fact the Earth filled only 9.3% of the field of view. These first, calibrated, in‐flight spectra from the TES confirm the expected instrument performance and radiometric accuracy and precision. The data provide the first known whole‐disk thermal infrared spectral observations of the Earth. These spectra represent how an Earth‐like planet would appear during a search for “extrasolar” planets. Spectral features in the Earth's atmosphere are readily apparent; CO2 (centered at 668 cm−1), ozone (1000–1075 cm−1), and water vapor (200–550 and 1260–1650 cm−1) absorptions are evident. Radiation at the center of the CO2 band arises mainly from the lower stratosphere; near 650 and 700 cm−1 from near the tropopause; and further into the band wings from the troposphere and surface. Thus, in the disk‐averaged sense, the spectrum indicates a warm stratosphere above a tropopause somewhat colder than 215 K, in good agreement with results from similar instruments previously flown in low Earth orbit. The atmospheric window between approximately 800 and 1200 cm−1 is relatively featureless, as expected, given the observing geometry centered over the Pacific Ocean and the partial obscuration by clouds. The derived window brightness temperature, assuming an emissivity of unity, is 270 K, a reasonable average temperature of the ocean surface, the polar regions, and the cloud tops, especially given the uncertainties in the exact scaling to account for the fact that the Earth did not fill the field of view.

Mars Global Surveyor: Ready for launch in November 1996

The Mars Global Surveyor (MGS) spacecraft will be launched toward Mars in November 1996. This mission is the first in the NASA Mars Surveyor Program and has been under development for the past two years. In this report the status of the MGS mission, three months prior to launch, will be described along with three specific topics: aerobraking, the lander to orbiter relay and the common operations project for the Mars Surveyor Program. The Mars Global Surveyor mission is intended to accomplish a portion of the scientific objectives of the Mars Observer Mission which was lost in 1993, three days before entering Mars orbit. To meet the established objectives a low, sun-synchronous, near circular, polar-mapping orbit is required which drives the need for aerobraking before mapping begins. MGS will cany a lander to orbiter relay capability for use with the Russian 1996 lander and small probes to be dropped to the surface of Mars by the 1998 Surveyor Mission. For the Mars Surveyor Program operation of all the landers and orbiters will be conducted under a single cost constrained Mars Surveyor Operation Project.

Mission to Mars to collect a storehouse of scientific data

Just after Election Day, the Mars Global Surveyor spacecraft (Figure 1) will embark on a journey to Mars to examine the surface and the seasonal variations of the atmosphere over an entire Mars year. Mars is an extremely rich mission target because the scientific questions it poses touch on geology, geophysics, geochemistry, atmospheric physics, climatology, biology, and—most of all—comparative planetology.Researchers will use data collected from this mission to compare the planet's formation and evolution with that of Earth, to understand the evolution of climate and water on Mars, and to determine if life has ever existed on Mars. Mars Global Surveyor will acquire a basic global understanding of the planet as it exists today, provide a framework for understanding its past, and help shape a series of small missions to Mars that are being planned for the next 10 years.

Analysis Of Multiple Imagery At Jet Propulsion Laboratory's Image Processing Laboratory

Computer image processing at Caltech's Jet Propulsion Laboratory (JPL) began over a decade ago with digital processing of single images of the lunar surface returned by the Ranger and Surveyor spacecraft. During the past decade, advanced techniques have been developed at JPL for processing large volumes of imagery returned by the more recent planetary spacecraft, including the Mariner 6, 7, and 9 missions to Mars, the Mariner 10 mission to Venus and Mercury, the Viking Orbiter and Lander Mars missions, and the current Voyager mission to Jupiter and Saturn. In addition, the Image Processing Laboratory (I PL) has become involved in processing of earth resources imagery acquired by the Landsat earth orbital satellite and a variety of other sensors flown on aircraft and spacecraft. The trend within the facility has been toward development of technology capable of processing increasingly larger image data bases. A variety of applications in both the planetary and earth observations areas involve merging and/or processing of more than one image and often require correlation of data acquired by a variety of sensors. This paper describes the evolution that has occurred, and the use of multiple imagery is illustrated through a variety of applications.

Surveyor Spacecraft Results Verified

Surveyor Spacecraft Results Verified

Movement of Surveyor 3 spacecraft

An examination of the position of the Surveyor 3 spacecraft as it appeared in the photographs taken by astronauts C. Conrad and A. Bean of the Apollo 12 lunar mission in November 1969 suggested that some changes had occurred in the spacecraft's attitude since the Surveyor operation of April 1967. A detailed study was made by simulating in the laboratory the position of one of the Surveyor spacecraft's footpads and its imprints in the lunar surface. Photographs were taken both from the location of the original Surveyor television camera and from the estimated position of the astronauts. It was found to be impossible to match the footpad and imprint positions and attitude in pictures taken from the two points of view. Consequently, it is tentatively concluded that the Surveyor spacecraft moved a few inches at some time between May 1967 and November 1969. It seems most likely that this movement occurred as a result of a relatively sudden failure of one or two of the shock absorbers on Surveyor's landing gear, since 2 out of the 3 shock absorbers were collapsed at the time of the astronauts' visit.