Planum Boreum Research Articles

Investigating the Linkage Between Spiral Trough Morphology and Cloud Coverage on the Martian North Polar Layered Deposits

AbstractThe martian North Polar layered deposits (NPLD) are composed of alternating water‐ice and dust‐rich layers resulting from atmospheric deposition and are key to understanding Mars climate cycles. Within these deposits are spiral troughs whose migration affects deposition signals. To understand the relationship between NPLD stratigraphy and Martian climate, we must identify modern‐day drivers of NPLD ice migration. Prevailing theory posits migration driven by upstream‐migrating bed undulations bounded by hydraulic jumps, caused by katabatic winds flowing over trough walls with asymmetric cross‐sectional relief. This is supported by trough‐parallel clouds, whose formation has been attributed to hydraulic jumps. We present a cloud atlas across the Martian north pole using ∼13,800 THEMIS images spanning ∼18 Earth years. We find trough‐parallel clouds in ∼400 images, with regions nearer to the pole having higher cloud frequency. We compare spiral trough geometry to our cloud atlas and find regions with trough‐parallel clouds often correlate with metrics associated with modern‐day sublimation‐deposition cycles (i.e., relief and asymmetry), but not always. In some regions, troughs with morphologies conducive to cloud formation have no clouds. Overall, trough geometry varies greatly across the deposits, both within and between troughs, suggesting localized differences in deposition relative to migration, varying katabatic wind intensities, differing past climatic states influencing the troughs, varying trough initiation properties, or the possibility of additional mechanisms for trough initiation and migration (e.g., in situ trough erosion). Understanding what controls trough shape variability across the NPLD and how these controls change through time and space is key when interpreting Martian paleoclimate.

SHARAD-based detection and estimation of water-ice content in Korolev crater at the north pole of Mars

SHARAD-based detection and estimation of water-ice content in Korolev crater at the north pole of Mars

Producing 3D radargrams from orbital radar sounding data at Mars: History, results, methods, lessons and plans

The Shallow Radar (SHARAD) instrument aboard Mars Reconnaissance Orbiter (MRO) has been conducting sounding operations of Mars' near surface for more than 16 years. Results of the SHARAD investigation have been well documented in the literature, with relatively high coverage density in the polar regions leading to some of the earliest scientific discoveries there. Data collection and ensuing surprises of SHARAD's primary and first extended science phases were the impetus for choosing the north polar region for producing a first 3D radar image. This early attempt was successful, producing the first 3D radar image of Mars' north polar layered deposits in Planum Boreum, and shortly thereafter a companion 3D radar image of the south polar layered deposits in Planum Australe. Subsequent work refined the 3D methodology used to produce these images, leading to a significantly higher quality 3D image of the former as well as the first 3D radar image of the debris-covered glaciers in the east-central portion of Deuteronilus Mensae (DM) in the mid-latitudes. Prior experience in terrestrial seismic data processing and analysis methods forms the basis of the 3D methodology used with Martian radar data, and has been indispensable in ongoing efforts to improve this methodology to further clarify the 3D images of the targets. The purposes of this article are to review 1) the SHARAD 3D work history and results, 2) the methodology developed and challenges encountered thus far in producing the SHARAD 3D images, 3) the broader impact on the processing and analysis of SHARAD data, and 4) current efforts and plans for producing follow-on SHARAD 3D images. Similarities and differences between orbital radar and seismic sounding and data processing are sprinkled throughout the article as reminders that the outcomes in this case are very much the product of cross-disciplinary knowledge and experience.

Range resolution enhancement of SHAllow RADar (SHARAD) data via bandwidth extrapolation technique: Enabling new features detection and improving geophysical investigation

The SHAllow RADar (SHARAD) is a subsurface sounding radar provided by the Italian Space Agency (ASI) as a facility instrument for NASA's Mars Reconnaissance Orbiter (MRO) mission, the second longest-lived mission to orbit Mars after Mars Odyssey. Developed by an Italian-US Team, SHARAD was designed to investigate to depth of up to one kilometer in the Martian subsurface and to map dielectric discontinuities associated with compositional and/or structural changes. The radar mapping began in November 2006 and, after 16 years of operations, SHARAD has mapped most of the planet's surface (∼55%), contributing a data volume for the entire MRO mission that exceeds that of all the past Mars missions combined.Designed to complement the lower-frequency, relatively narrower bandwidth capability of the MARSIS sounding radar, SHARAD emits an 85μs, frequency-modulated (10 MHz) chirp at a central frequency of 20 MHz to increase the signal-to-noise ratio (SNR) and achieve a finer resolution compared to MARSIS. On the ground, echoes recorded by the radar are range compressed using conventional pulse compression techniques yielding a nominal range resolution of 15 m (vacuum, 5–8 m in typical Martian materials). Additionally, synthetic aperture processing is performed in along-track to increase the resolution up to 300–500 m.Throughout the entire mission duration, SHARAD provided a diverse and extensive range of imaging data. It was able to observe the internal structures of Planum Boreum and Planum Australe, two icy deposits that contain the North and South Polar Layered Deposits (NPLD-SPLD), thought to contain valuable information about the planet's past climate. The radar unveiled the massive deposits of buried CO2 ice below the southern residual ice cap (SRIC), which confirmed the influence of the planet obliquity and insolation in the accumulation of dry ice. Furthermore, it revealed the intricate lava flows structures in the Tharsis Volcanic region, suggesting that the planet experienced deposition by multiple volcanic episodes.However, radar resolution often poses a limitation for subsurface investigations in many regions. Only recently, processing techniques have focused on enhancing SHARAD radargrams vertical resolution by implementing the Bandwidth Extrapolation (BWE) technique. This approach has demonstrated an improvement of the vertical resolution while preserving the time-of-arrival (TOA) and amplitude of the detected echoes. The resulting super-resolved data products exhibit better separation between radar returns, thus improving the overall understanding of the investigated terrains. The obtained results demonstrate the value of implementing the BWE techniques in the data processing pipeline whenever radar sounders are involved.

New Views of the Internal Structure of Planum Boreum from Enhanced 3D Imaging of Mars Reconnaissance Orbiter Shallow Radar Data

We present first results from a new 3D radargram produced from 3399 Mars Reconnaissance Orbiter (MRO) Shallow Radar observations of the north polar region of Mars. While incorporating an additional 5 yr of observations relative to the prior 3D radargram, we employed surface-clutter simulations to improve the coregistration of the input data and thereby enhance the effective vertical resolution of features. Combining those improvements with the geometric corrections and an increase in signal-to-noise ratio afforded by the 3D imaging process, this data product provides new details about the interior of Planum Boreum, the Martian north polar cap. We assess the overall characteristics and compare portions of the new 3D radargram to results from prior studies that used either the prior 3D radargram or sets of 2D radargrams from individual MRO orbits. We find that the new 3D radargram has recovered essentially all of the vertical resolution inherent to the input data, and the increased coverage density has substantially reduced artifacts while enabling much greater detail in the imaging of subsurface layering and structures. These improvements extend throughout the 3D radargram, from the basal units to the shallowest subsurface layering in Planum Boreum, and out into the surrounding plains. Subsurface features such as a buried chasma, other layering structures and unconformities, and trough-bounding surfaces that offset shallow layering are now visible in unprecedented detail. A thorough analysis of this new 3D radargram and its implications for the geologic and climate history of Planum Boreum will extend over many years.

The north polar basal unit of Mars: An Amazonian record of surface processes and climate events

The basal unit is a sedimentary deposit of water ice and lithic fines lying within the Planum Boreum of Mars. It can be divided into two subunits, rupēs and cavi, based on their stratigraphy and age. The basal unit lies between Late Hesperian and very recent (<4 Ma) units, and thus likely represents a record of polar geologic processes and climate events spanning large portions of the Amazonian Period. Despite the numerous recent studies, several key questions remain unanswered regarding its stratigraphic nature, age, and potential as a historical record of surface processes and climate. In this study, we combine the ability of the Shallow Radar (SHARAD) to reveal the large-scale stratigraphy and morphology of the basal unit within Planum Boreum with geologic mapping of visible exposures based on high-resolution imagery. This integrated study reveals that the basal unit has significantly larger extent but smaller volume than previously thought, and demonstrates that radar profiles acquired by SHARAD can provide the necessary stratigraphic correlation to comprehensively study isolated outcrops with high-resolution imagery that would otherwise lack important context. SHARAD also reveals portions of the contact between the rupēs and cavi unit in the innermost region of Planum Boreum which will allow us to better constrain the relative volume of the two units, and thus their water ice and lithic sediment content. New age constraints on the rupēs and cavi unit reveal a history of lithic fines and water ice accumulation and erosion spanning most of the Amazonian Period. Detailed mapping of the basal unit surface morphology underneath the North Polar Layered Deposits provides further insight on the erosional history of the rupēs and cavi units and suggest a more complex resurfacing history than previously thought, likely characterized by an intimate interplay with polar ice growth and retreat. SHARAD also reveals erosional forms in the cavi unit that provide new supporting observations of its hypothesized water ice and sand-sheet structure, confirming that it likely preserved former polar cap ice in its interior.

Calibration of Mars Reconnaissance Orbiter Shallow Radar (SHARAD) data for subsurface probing and surface reflectivity studies

The Shallow Radar (SHARAD) instrument on the Mars Reconnaissance Orbiter (MRO) has been operating since 2006, revealing the detailed layered structure of the polar caps, mid-latitude glacial deposits, and a range of volcanic features. Here we address the major sources of change in the effective gain and signal-to-noise ratio of data collected by SHARAD: (1) the altitude and background noise level, (2) the configuration of the solar arrays (SA) and high-gain antenna (HGA), (3) ionospheric attenuation, and (4) the roll angle of MRO. Background noise fluctuations have a range of ~5 dB, and electromagnetic interference may significantly affect comparisons among limited bands of the full spectrum. We use the dense spatial coverage of sounder data to define a model for gain as a function of SA and HGA orientations, and demonstrate its predictive capability over a 4-dB range with radargrams collected under different configurations. Ionospheric attenuation as a function of the phase distortion correction used in radargram processing is refined through a larger dataset than available in earlier studies. Gain improvements due to MRO rolls up to 28o are also a function of the SA-HGA configuration, such that the maximum span of combined SHARAD gain contributions is about 7 dB. After calibration, Planum Boreum in the north polar layered deposits is ~3 dB less reflective than Planum Australe, and multi-band analysis suggests destructive interference occurs in the more densely layered shallow structure of the northern cap. The new calibration model allows targeting of future observations during optimum conditions over features of interest.

Expedition to Mars North Pole and Creation: There Is a Scientific Research Base

A project of the expedition to the north pole of Mars, which is carried out in two stages, has been developed. In the first stage, a space refueller and a mobile solar battery are delivered to the icy surface of the north pole of Mars. The delivery is carried out with the help of electric rocket ER-7, driven by the electric rocket engine “MARS”, and the source of electricity is a solar battery from gallium arsenide. In the second stage, the space train is formed from two interconnected ER-7 rockets and an orbital takeoff-landing capsule TLC-2, in which three astronauts land on the surface and carry out a complex of physical, biological and geological researches on Mars surface. The space refueller has been developed, which melts the water ice on the surface of Mars and with the help of an electrolyser and a liquefier produces fuel and oxidizer for the operation of the chemical rocket engine of the takeoff-landing capsule. To move astronauts from the north pole to the equator, a spacecraft— marsoplane, which consists of the electric rocket ER-7 and the takeoff-landing capsule TLC-1 is developed. The duration of the expedition is 110 days at a cost of 2 billion dollars.

Compositional Constraints on the North Polar Cap of Mars from Gravity and Topography

AbstractThe polar ice caps are the largest reservoir of water ice on Mars. The north polar ice cap is composed of the ice‐rich north polar layered deposit (NPLD) and a lower‐lying, silicate‐rich basal unit (BU). Together, these units represent a record of Martian climate history throughout the Amazonian period. Here we place a bulk compositional constraint on the BU by modeling its gravity signature in both spatial and spectral domains using two independent approaches. We find the density of the BU to be kg/m3, suggesting that it may contain 55 + 25% water ice. We estimate that the BU contains ~1.5‐m global equivalent layer of water making it one of the largest reservoir of water‐ice on Mars. Our compositional constraint suggests that the north pole of Mars was not only a cold trap for ices but also an aeolian trap for silicates during the Amazonian period.

Buried Ice and Sand Caps at the North Pole of Mars: Revealing a Record of Climate Change in the Cavi Unit With SHARAD

AbstractThe cavi unit at the north pole of Mars is a deposit of aeolian sand and water ice underlying the Late Amazonian north polar layered deposits. Its strata of Middle to Late Amazonian age record wind patterns and past climate. The Mars Reconnaissance Orbiter Shallow Radar (SHARAD) reveals extensive internal and basal layering within the cavi unit, allowing us to determine its general structure and relative permittivity. Assuming a basalt composition for the sand (ε′ = 8.8), results indicate that cavi contains an average ice fraction between 62% in Olympia Planum and 88% in its northern reaches beneath the north polar layered deposits and thus represents one of the largest water reservoirs on the planet. Internal reflectors indicate vertical variability in composition, likely in the form of alternating ice and sand layers. The ice layers may be remnants of former polar caps and thus represent a unique record of climate cycles predating the north polar layered deposits.

MARSIS Radar Data Interpretation to Characterize the Deeper Layers in the North Polar Cap on Mars

We performed a study using radar data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board ESA’s Mars Express spacecraft [23]. MARSIS collects data by transmitting a low-frequency radar pulse, between 1.3 and 5.5 MHz with a 1 MHz bandwidth, which is capable of penetrating below the surface and is reflected by any dielectric discontinuity present in the sub-surface, reaching a depth of analysis of 3.7 km in icy deposits [25]. We analyzed radargrams crossing Planum Boreum, the 1000 km diameter north polar plateau located in the center of Borealis Basin, to study the deeper layered deposits identified in the north polar cap’s stratigraphy (mapped by, e.g., [34]). The main objective of our study was to obtain a stratigraphic geological profile to identify the deep trend of the Cavi unit, one of the main geological units which characterize Planum Boreum. This unit, deposited on a surface of unconformity, indicates the period of compositional variation of the placement materials at the bottom of the north polar plateau, in which the lithic percentage decreased exponentially to the advantage of an almost pure ice composition [34]. The Cavi unit represents an important element for the understanding of the north polar cap evolution, the past climate cycles on Mars, and the changes in the orbital parameters of the planet [27]. The geological profile was obtained through the use of a Geographical Information System, which allowed us to correlate the USGS cartography with MOLA topography, and the MARSIS radargrams. The outline trace covers about 1500 km, passing through the Planum Boreum and the surrounding areas. The final obtained stratigraphic profile allowed us to have a global vision of the stratigraphic relationships of the various units, to show the trend of the Cavi unit, to identify some covered structures, and also to formulate a plausible hypothesis about the evolution of the Planum Boreum. Using this method of radargram interpretation, we showed how to improve geological analysis of planetary sub-surfaces.

IMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

iMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

Automatic Enhancement and Detection of Layering in Radar Sounder Data Based on a Local Scale Hidden Markov Model and the Viterbi Algorithm

Radar sounders are unique instruments for subsurface investigation in both terrestrial and space applications. They are widely employed for monitoring changes to the polar ice sheets and for the study of planetary bodies (e.g., Mars). The analysis of the very large amount of data produced by such systems requires the development of automatic techniques for an objective, accurate, and fast extraction of relevant information from radargrams. In this paper, we propose a novel technique for the automatic detection of layer boundaries based on a local scale hidden Markov model (HMM), which models the radar response in the presence of a layer boundary, and the Viterbi algorithm (VA, which performs the inference step). The proposed technique is based on a divide and conquer strategy that executes the VA using the observation data and the HMM to infer the most likely layer boundary location within a small radargram portion. Finally, a detection strategy is defined to chain together the inferred local layer locations. Furthermore, a novel radargram enhancement and denoising technique tailored to support the detection step is presented. The effectiveness of the proposed technique has been confirmed by testing it on different radargrams acquired by shallow radar over the north pole of Mars. The results obtained point out the superiority of the proposed method in retrieving the position of each layer boundary (and thus of the related intensity and geometric properties) with respect to the state-of-the-art techniques.

3-D Imaging of Mars' Polar Ice Caps Using Orbital Radar Data.

Since its arrival in early 2006, various instruments aboard NASA's Mars Reconnaissance Orbiter (MRO) have been collecting a variety of scientific and engineering data from orbit around Mars. Among these is the SHAllow RADar (SHARAD) instrument, supplied by Agenzia Spaziale Italiana (ASI) and designed for subsurface sounding in the 15-25 MHz frequency band. As of this writing, MRO has completed over 46,000 nearly polar orbits of Mars, 30% of which have included active SHARAD data collection. By 2009, a sufficient density of SHARAD coverage had been obtained over the polar regions to support 3-D processing and analysis of the data. Using tools and techniques commonly employed in terrestrial seismic data processing, we have processed subsets of the resulting collection of SHARAD observations covering the north and south polar regions as SHARAD 3-D volumes, imaging the interiors of the north and south polar ice caps known, respectively, as Planum Boreum and Planum Australe. After overcoming a series of challenges revealed during the 3-D processing and analysis, a completed Planum Boreum 3-D volume is currently being used for scientific research. Lessons learned in the northern work fed forward into our 3-D processing and analysis of the Planum Australe 3-D volume, currently under way. We discuss our experiences with these projects and present results and scientific insights stemming from these efforts.

Three‐dimensional structure and origin of a 1.8 km thick ice dome within Korolev Crater, Mars

AbstractKorolev is an 80 km diameter impact crater located at 72.7°N, 164.5°E containing a large domed deposit. Perennial water ice is thought to be currently unstable there; however, using a 3‐D analysis of the dome's internal radar stratigraphy, we estimate that Korolev's central mound contains between 1400 and 3500 km3 of water ice that is up to 1.8 km thick. Furthermore, the stratigraphic structure of this ice dome is strikingly similar to the north polar layered deposits (NPLD) on Planum Boreum, approximately 600 km to the north. Additionally, our stratigraphic analysis suggests that Korolev ice was not previously part of a once larger polar ice sheet but rather it was deposited locally. We conclude that Korolev Crater's ice likely deposited during the same climate regime as Planum Boreum's NPLD, but independently. This implies that the incorporation of circumpolar ice deposits such as Korolev may prove useful in reconstructing a unique Mars polar climate history.

Planum Boreum basal unit topography, Mars: Irregularities and insights from SHARAD

Shallow Radar investigations of Planum Boreum, Mars' “basal unit” (BU) deposit have revealed multiple reentrants, morphologic irregularities, and thickness trends that differ from those of the overlying north polar layered deposits. We present detailed subsurface maps for these features and offer explanation for genesis of the deposit's morphologic asymmetry, expressed in different erosional characteristics between 0°E–180°E and 180°E–360°E. Additionally, this work revealed a depression in the basal unit that may have provided a site for spiral trough initiation. Interpretations of the findings suggest that antecedent BU topography has a marked impact on modern morphology and that aeolian forces have been the dominant driver of polar deposit accumulation since at least the end of rupes unit emplacement. We find no results requiring explanation beyond common Martian surface processes, including aeolian erosion and impact armoring. To add to the detailed morphologic study of the BU, we mapped the variability of the BU radar reflection character. Combining generalized katabatic wind flow with the radar mapping results suggests that rupes unit material sourced the younger cavi. We present clear evidence that, while compositionally distinct from the overlying layered deposits, the BU and its morphology are intimately linked to the morphology of the north polar layered deposits. Combining geologic evidence with paleoclimate modeling, the deposits contain evidence for a long history of aeolian emplacement and modification.

Spiral trough diversity on the north pole of Mars, as seen by Shallow Radar (SHARAD)

AbstractWe combine observations from ground penetrating radar and optical instruments to conduct a comprehensive survey of spiral troughs on the north polar layered deposits of Mars. Our survey reveals that all north polar troughs have common characteristics, but there is strong regional diversity. We divide the north polar layered deposits (NPLD) into eight regions based on observations of morphology and stratigraphy in order to classify the spiral troughs. Morphologic features that separate the regions include central promontories, topographic undulations, bedrock floors, and trough asymmetry among others. We demonstrate here that the troughs formed during two periods. The first generation of troughs formed on the main lobe and in part of Gemina Lingula during accumulation of ~600 m of ice and dust. The second generation of troughs formed stratigraphically higher and immediately after large‐scale erosion in Gemini Scopuli, which we conclude created the slopes necessary for troughs to form. We test scenarios of trough evolution and find that only three concurrent processes are required for their formation: wind transport, insolation‐induced sublimation, and atmospheric deposition. Our observations are inconsistent with other hypothesized processes to produce spiral troughs, including incision after the formation of the NPLD, fracturing due to flowing ice, and sublimation‐driven patterns from insolation.

Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) after nine years of operation: A summary

Mars Express, the first European interplanetary mission, carries the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to search for ice and water in the Martian subsurface. Developed by an Italian–US team, MARSIS transmits low-frequency, wide-band radio pulses penetrating below the surface and reflected by dielectric discontinuities linked to structural or compositional changes. MARSIS is also a topside ionosphere sounder, transmitting a burst of short, narrow-band pulses at different frequencies that are reflected by plasma with varying densities at different altitudes. The radar operates since July 2005, after the successful deployment of its 40m antenna, acquiring data at altitudes lower than 1200km. Subsurface sounding (SS) data are processed on board by stacking together a batch of echoes acquired at the same frequency. On ground, SS data are further processed by correlating the received echo with the transmitted waveform and compensating de-focusing caused by the dispersive ionosphere. Ground processing of active ionospheric sounding (AIS) data consists in the reconstruction of the electron density profile as a function of altitude. MARSIS observed the internal structure of Planum Boreum outlining the Basal Unit, an icy deposit lying beneath the North Polar Layered Deposits thought to have formed in an epoch in which climate was markedly different from the current one. The total volume of ice in polar layered deposits could be estimated, and parts of the Southern residual ice cap were revealed to consist of ≈10m of CO2 ice. Radar properties of the Vastitas Borealis Formation point to the presence of large quantities of ice buried beneath the surface. Observations of the ionosphere revealed the complex interplay between plasma, crustal magnetic field and solar wind, contributing to space weather studies at Mars. The presence of three-dimensional plasma structures in the ionosphere was revealed for the first time. MARSIS could successfully operate at Phobos, becoming the first instrument of its kind to observe an asteroid-like body. The main goal pursued by MARSIS, the search for liquid water beneath the surface, remains elusive. However, because of the many factors affecting detection and of the difficulties in identifying water in radar echoes, a definitive conclusion on its presence cannot yet be drawn.

Orbital radar, imagery, and atmospheric modeling reveal an aeolian origin for Abalos Mensa, Mars

AbstractIcy deposits surrounding Planum Boreum, Mars, contain crucial information for deciphering paleoclimate and past geologic processes at the martian north pole. One such deposit, Abalos Mensa, is an enigmatic wedge of material located near the ~ 1 km high Rupes Tenuis. Its unique location and lobate morphology have fostered formation hypotheses that assume either fluvial or aeolian erosion of a once‐larger ice deposit. The aeolian scenario posed previously requires impact shielding of ancient basal unit material to provide an erosional remnant which seeds later deposition, while the fluvial hypotheses invoke cryovolcanism beneath the younger north polar layered deposits (NPLD) and associated outflow to erode the adjacent chasmata. Here we combine newly available radar sounding data, high‐resolution imagery, digital elevation models, and atmospheric modeling to examine internal structure and infer both the mechanisms for, and timing of, Abalos Mensa formation. From this integrative approach, we conclude that Abalos Mensa formed as a distinct feature via atmospheric deposition following erosion of Rupes Tenuis and grew concurrently with the rest of Planum Boreum as the NPLD accumulated. The required processes are consistent with those observed today: no exotic phenomena (cryovolcanism, fluvial activity, or impact shielding) appear necessary to explain the formation of Abalos Mensa.

Automatic Extraction and Analysis of Ice Layering in Radar Sounder Data

Nowadays, the interest on the development of orbiting radar sounders for the observation of Earth polar areas is increasing. In this context, the analysis of the structure of the ice stratigraphy is of primary importance for the study of the past history and for the prediction of the evPolution of icy environments. However, as proven by planetary missions, orbiting radar sounders provide a huge amount of data. Thus, the development of automatic techniques for the analysis of these data is of fundamental importance for proper data exploitation. In this paper, we propose a novel method for the automatic detection of subsurface linear features from radar sounder data acquired in icy regions showing extended layering. The proposed method allows the estimation of the position of the linear features with subpixel accuracy. Moreover, each detected linear interface is treated as a single object which is completely described by the position of its points, the estimated local width, and the contrast. This allows the direct measurement of geometrical and radiometric parameters (e.g., slope angle and intensity) without the need of further postprocessing steps. This paper also proposes some measurements for deriving from the output of the proposed technique important variables that can characterize quantitatively the properties of the detected linear features (e.g., mean depth and mean intensity) and their distribution (e.g., number and density of layers). The effectiveness of the proposed method is confirmed by the results obtained on several radargrams acquired by the Shallow Radar on the North Pole of Mars.