Marsis planning tool algorithms and criteria to select operative modes

Definition and design of the scientific algorithms for the planning and commanding activities of the Marsis radar missio

SHARAD radar sounding of the Vastitas Borealis Formation in Amazonis Planitia

Amazonis Planitia has undergone alternating episodes of sedimentary and volcanic infilling, forming an interleaved sequence with an upper surface that is very smooth at the kilometer scale. Earlier work interprets the near-surface materials as either young, rough lava flows or ice-rich sediment layers, overlying a basement comprising the Vastitas Borealis Formation and earlier Hesperian plains. Sounding radar profiles across Amazonis Planitia from the Shallow Radar (SHARAD) instrument on the Mars Reconnaissance Orbiter reveal a subsurface dielectric interface that increases in depth toward the north along most orbital tracks. The maximum depth of detection is 100–170 m, depending upon the real dielectric permittivity of the materials, but the interface may persist at greater depth to the north if the reflected energy is attenuated below the SHARAD noise floor. The dielectric horizon likely marks the boundary between sedimentary material of the Vastitas Borealis Formation and underlying Hesperian volcanic plains. The SHARAD-detected interface follows the surface topography across at least one of the large wrinkle ridges in north central Amazonis Planitia. This conformality suggests that Vastitas Borealis sediments, at least in this region, were emplaced prior to compressional tectonic deformation. The change in radar echo strength with time delay is consistent with a loss tangent of 0.005–0.012 for the column of material between the surface and the reflector. These values are consistent with dry, moderate-density sediments or the lower end of the range of values measured for basalts. While a component of distributed ice in a higher-loss matrix cannot be ruled out, we do not find evidence for a dielectric horizon within the Vastitas Borealis Formation that might suggest an abrupt change from an upper dry layer to an ice-rich lower deposit

Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars

Lobate features abutting massifs and escarpments in the middle latitudes of Mars have been recognized in images for decades, but their true nature has been controversial, with hypotheses of origin such as ice-lubricated debris flows or glaciers covered by a layer of surface debris. These models imply an ice content ranging from minor and interstitial to massive and relatively pure. Soundings of these deposits in the eastern Hellas region by the Shallow Radar on the Mars Reconnaissance Orbiter reveal radar properties entirely consistent with massive water ice, supporting the debris-covered glacier hypothesis. The results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes. Such features may collectively represent the most extensive nonpolar ice yet recognized on Mars

Shallow radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars

The SHARAD (shallow radar) sounding radar on the Mars Reconnaissance Orbiter detects subsurface reflections in the eastern and western parts of the Medusae Fossae Formation (MFF). The radar waves penetrate up to 580 m of the MFF and detect clear subsurface interfaces in two locations: west MFF between 150 and 155◦ E and east MFF between 209 and 213◦ E. Analysis of SHARAD radargrams suggests that the real part of the permittivity is ∼3.0, which falls within the range of permittivity values inferred from MARSIS data for thicker parts of the MFF. The SHARAD data cannot uniquely determine the composition of the MFF material, but the low permittivity implies that the upper few hundred meters of the MFF material has a high porosity. One possibility is that the MFF is comprised of low-density welded or interlocked pyroclastic deposits that are capable of sustaining the steep-sided yardangs and ridges seen in imagery. The SHARAD surface echo power across the MFF is low relative to typical martian plains, and completely disappears in parts of the east MFF that correspond to the radar-dark Stealth region. These areas are extremely rough at centimeter to meter scales, and the lack of echo power is most likely due to a combination of surface roughness and a low near-surface permittivity that reduces the echo strength from any locally flat regions. There is also no radar evidence for internal layering in any of the SHARAD data for the MFF, despite the fact that tens-of-meters scale layering is apparent in infrared and visible wavelength images of nearby areas. These interfaces may not be detected in SHARAD data if their permittivity contrasts are low, or if the layers are discontinuous. The lack of closely spaced internal radar reflectors suggests that the MFF is not an equatorial analog to the current martian polar deposits, which show clear evidence of multiple internal layers in SHARAD dat

Dielectric Mapping of Bulk Polar Ices on Mars With SHARAD Radar Data

Abstract P41B-1372The SHAllow RADar (SHARAD) is a subsurface sounding instrument aboard the NASA's Mars Reconnaissance Orbiter (MRO) spacecraft. The main SHARAD scientific objectives are to map the underground distribution of water over the planet as well as to seek buried geological structures in order to understand the formation of the superficial Martian landscape. SHARAD is working at a 20 MHz central frequency with a 10 MHz bandwidth. Its penetration depth (i.e. the attenuation of the signal) depends of the dielectric properties of the sounded material; typically more than 1 km in water ice with ~7 m of vertical resolution. The Martian polar layered deposits (NPLD) are the largest reservoir of water on the surface. The physical properties of the polar ices is one the main unresolved questions in Martian polar science. In particular, accurate estimation of the dielectric properties is important since it is interrelated to the impurities contamination of the ice and consequently to its rheology; whereas the spatial distribution of the impurities is linked to the interaction of the NPLD with the Martian climate. Moreover, it is also a significant contribution for comparative planetology with terrestrial caps since the Martian ice has the same structure than on Earth (Ice Ih), but accumulated under an extreme planetary environment (mean surface temperature and pressure of 155 K and 0.008 bar respectively). We will present a study over the Gemina Lingula region where the bedrock of the NPLD is imaged by SHARAD. From this, it has been possible to map the dielectric properties of the bulk ice. A data set of 140,000 SHARAD pulses was used. The maps of the dielectric constant and the loss tangent of the ice will be presented. Both properties have a Gaussian distribution giving accurate results. The pick values are consistent with an extremely pure ice. The loss tangent map highlights the spatial distribution of the impurities. A drop of the dielectric constant along Chasma Boreale could be explained by a brutal 250-meter uplift of the base of the NPLD corresponding to an extent of the basal unit below Gemina Lingula

3D Modeling of South Polar Layered Deposits on Mars with SHARAD radar data

abstract EPSC2007-A-0054

North polar deposits of Mars: Extreme purity of the water ice

International audienceThe polar layered deposits are the largest reservoir of water on the surface of Mars. The physical properties of the ice and their spatial distribution are largely unknown. 140,000 data points from the sounding radar SHARAD on the Mars Reconnaissance Orbiter were analyzed over the Gemina Lingula region, one-fourth of the north polar layered deposits area. Maps of the dielectric properties of the bulk ice were drawn up. There is no basal melting signature. A drop of the dielectric constant in north-west of Gemina Lingula could be explained by an abrupt 250-meter uplift of the base. The bulk ice of the studied region has an average dielectric constant of 3.10 (σ = 0.12) and a loss tangent <0.0026 (σ = 0.0005). Analytic interpretations shown the volume of ice is pure at ≥95%. The impurities have a radial distribution, with higher concentrations at margins

North polar deposits of Mars: Extreme purity of the water ice

The polar layered deposits are the largest reservoir of water on the surface of Mars. The physical properties of the ice and their spatial distribution are largely unknown. 140,000 data points from the sounding radar SHARAD on the Mars Reconnaissance Orbiter were analyzed over the Gemina Lingula region, one-fourth of the north polar layered deposits area. Maps of the dielectric properties of the bulk ice were drawn up. There is no basal melting signature. A drop of the dielectric constant in north-west of Gemina Lingula could be explained by an abrupt 250-meter uplift of the base. The bulk ice of the studied region has an average dielectric constant of 3.10 (s = 0.12) and a loss tangent <0.0026 (s = 0.0005). Analytic interpretations shown the volume of ice is pure at 95%. The impurities have a radial distribution, with higher concentrations at margins

Polar layered deposits of Mars as seen by MRO/SHARAD

EGU2007-A-0797