Pith. sign in

REVIEW 3 major objections 4 minor 30 references

SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft

T0 review · 3 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

Pith's one-line read The paper reports that rolling MRO 120 degrees about its flight axis gave SHARAD signal gains of 9, 11, and 14 dB, revealing basal interfaces at roughly 800 m and 1500 m depth.

desk verdict First results from SHARAD's 120° roll mode show real S/N gains and deeper detections, but the clutter rejection argument needs to account for off-nadir returns beyond the standard 45-km cutoff. read the letter →

arxiv 2505.21810 v2 pith:NAHZ6QQ7 submitted 2025-05-27 astro-ph.EP astro-ph.IMphysics.geo-ph

Nathaniel E. Putzig , Gareth A. Morgan , Matthew R. Perry , Bruce A. Campbell , Jennifer L. Whitten , Fabrizio Bernardini , Alessandro DiCarlofelice , Piero Tognolatti
show 1 more author
Pierfrancesco Lombardo
This is my paper
classification astro-ph.EPastro-ph.IMphysics.geo-ph
keywords SHARADMarsReconnaissanceOrbiterradarsoundingverylargerollMedusaeFossaeFormationUltimiScopulisubsurfaceicesignal-to-noiseratio
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper reports the first three "very large roll" (VLR) SHARAD observations, taken after the Mars Reconnaissance Orbiter rolled 120 degrees about its flight axis, and claims they add 9, 11, and 14 dB of signal-to-noise relative to nearly coincident observations at zero roll. The added signal lets the radar see through materials where its pulses previously faded, reaching basal interfaces about 800 m beneath Medusae Fossae materials and about 1500 m beneath the ice at Ultimi Scopuli. If true, this extends an old orbiter's radar capability without new hardware, giving higher-resolution views of deep interfaces that the lower-frequency MARSIS radar sees only coarsely. It also opens a path toward testing whether bright MARSIS reflections at the south pole come from subglacial liquid water or from other causes.

What carries the argument

The load-bearing device is the very-large-roll observing mode: a method-of-moments numerical model of the SHARAD antenna predicted a maximum in round-trip gain at a 120-degree roll with solar-array gimbals at zero angles, and the prediction is tested by comparing along-track signal-to-noise of the VLR tracks against nearly coincident zero-roll tracks. The comparison pipeline uses clutter simulations to locate the nadir-surface delay time, a buffered search for the surface power maximum, and a noise sample taken 10 microseconds above the surface, which together produce the reported 9, 11, and 14 dB gains.

What would settle it

Recompute the VLR clutter simulations with the actual 120-degree-roll antenna pattern and check whether the reflections labeled basal interfaces in VLR1 and VLR2 coincide with predicted surface clutter; a match at either site would falsify the subsurface interpretation, and a VLR pass directly over the peak MARSIS basal echo could confirm or weaken the 1500 m detection.

Watch

Extended reading notes

Core claim

The central discovery is that a 120-degree spacecraft roll, with the solar arrays stowed flat, is a radar-performance lever. The first three SHARAD very-large-roll observations show signal-to-noise increases of 9, 11, and 14 dB over nearly coincident zero-roll tracks, confirming the gain predicted by a new numerical antenna model. In low-loss terrains the extra signal reaches interfaces that SHARAD had not previously seen: the base of Medusae Fossae materials at about 800 m, and the base of the ice at Ultimi Scopuli at about 1500 m, with improved reflections through the ice stack. In the higher-dielectric terrain of Amazonis Planitia, the gain sharpened a known dipping reflector but did not extend it to greater depth or reveal deeper interfaces, which the paper reads as evidence either that overlying material changes are severe enough to absorb the 14 dB gain or that the reflector truly ends there.

Load-bearing premise

The depth and subsurface-source claims rest on assuming that the standard clutter simulations and the published dielectric constants, both built from lower-roll observing, remain valid at a 120-degree roll; if the true surface echo at that attitude is not where the simulations place it, the new deep reflections and their estimated depths could be misread.

Editorial extensions

If this is right

  • If the VLR gain holds, SHARAD can map the base of Medusae Fossae materials at roughly 800 m and search for internal layering that could indicate buried ice.
  • A VLR pass directly over the strongest MARSIS basal reflection in Ultimi Scopuli would give a SHARAD-power measurement of that interface, informing the subglacial liquid water debate.
  • The 14 dB gain in Amazonis Planitia puts a quantitative bound on how much attenuation or scattering would be needed to explain the reflector's end, leaving a true termination of the interface as a live possibility.
  • Monthly midlatitude VLR observations could probe debris-covered glaciers, volcanic stacks, and other MARSIS follow-up targets that were previously beyond SHARAD's penetration depth.
  • North polar basal units, which have blocked SHARAD from seeing the cap base, are a planned target; a detection would constrain their material properties.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Because the paper's clutter checks use simulations built for the nominal roll geometry and a 45 km cross-track cutoff, recomputing clutter with the true 120-degree-roll antenna pattern is a direct next test; some reflections now labeled subsurface could shift into the clutter class.
  • A systematic VLR campaign across terrains with independently known dielectric constants could turn the 9-14 dB gains into a predictive depth-penetration rule for SHARAD, rather than case-by-case detections.
  • The same roll strategy may transfer to other planetary radar sounders with asymmetric antenna placements, provided the host spacecraft can tolerate the attitude, power, and thermal constraints of a near-inverted roll.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 4 minor

Summary. The paper reports the first three very-large-roll (VLR) SHARAD observations, acquired at 120° spacecraft roll with the solar arrays in the all-zero gimbal position, as a test of a prior antenna-model prediction of roughly 10 dB signal-to-noise improvement. For each VLR observation, the authors compare radargrams and along-track S/N curves with nearly coincident observations at 0° or ≈28° roll. They report mean S/N increases of 9 dB (VLR1, Medusae Fossae/Terra Sirenum), 11 dB (VLR2, Ultimi Scopuli), and 14 dB (VLR3, Amazonis Planitia). They interpret VLR1 as enabling a basal detection at ≈800 m depth in Medusae Fossae materials, VLR2 as reaching the base of Planum Australe ice at ≈1500 m, and VLR3 as improving continuity of a shallow dipping reflector without revealing deeper interfaces. The paper also describes operational constraints, future target plans, and an appendix detailing the S/N estimation workflow.

Significance. If the central claims hold, this paper establishes a new and broadly useful observing mode for a 19-year-old Mars orbiter, with the potential to address longstanding questions about deep subsurface structure, including the MARSIS south-polar basal reflection controversy. The paper has several notable strengths: the S/N gains are direct measurements rather than model-derived quantities; three independent observations are reported, including VLR3 as an honest negative result for deeper penetration; and the work is an explicit, independent test of the authors' earlier antenna-model prediction. The manuscript is also clear about the small number of VLR observations and the operational difficulties. The main scientific payoff, however, rests on the claim that newly seen reflectors are subsurface rather than off-nadir surface clutter, and that issue is exactly where the current analysis is weakest.

major comments (3)
  1. [Section 4, VLR1 paragraph and Figures 4f, 5f, 6e] The manuscript states that VLR1 displays clutter signals that "extend beyond the 45-km cross-track cut-off distance normally used in the generation of cluttergrams," yet the subsurface-source interpretation of the new reflections is repeatedly justified by "the lack of a corresponding feature in the cluttergram" (Figures 4c/4f, 5c/5f, 6c/6e). The supplied clutter simulations were generated with nominal antenna patterns and a 45-km cross-track limit, so they do not rule out surface returns from beyond 45 km at a 120° roll angle, where the antenna pattern and sidelobe geometry differ substantially from nadir. Such off-nadir surface returns could arrive at delay times corresponding to apparent depths of 800–1500 m, exactly where the paper claims basal detections. This limitation is load-bearing for the central claim. Please rerun or extend the clutter simulations using the VLR antenna pattern and a larger cross-track integration limit, or otherwise quantify the delay and along-track ranges over which >45-km surface clutter could appear at 120° roll.
  2. [Appendix, S/N equation and Figures 4b, 5b, 6b] The reported 9, 11, and 14 dB improvements are stated as mean differences between along-track S/N curves that are generated from observations over different ground tracks, at different dates, and with different local surface properties; no uncertainties or significance tests are provided. In addition, the S/N workflow aligns the surface using the nadir-surface delay-time index from the same nominal clutter simulations and then searches within a 7-sample gate. If the predicted delay index is biased at 120° roll, the extracted signal power Ps could be drawn from an off-nadir surface or clutter return rather than the true nadir surface echo, biasing the reported gains. Please provide quantitative uncertainties on each S/N difference (e.g., standard error of the mean over the common track segment, or a bootstrap over along-track samples), state explicitly the along-track overlap over which the mean difference is computed, and ideally validate the S/N extraction on a VLR pass over a region with no known subsurface reflectors.
  3. [Section 4, VLR2 paragraph and Figure 5c] The 1500 m basal detection in Ultimi Scopuli rests on a single VLR pass whose ground track does not cross the primary MARSIS feature, and the reflection power is described as quite low. The interpretation that this is the basal interface would be substantially stronger if the same feature were identified at the same two-way delay in a partially overlapping or repeat VLR observation, or if the authors showed that the apparent depth is stable with respect to the assumed dielectric constant range. As written, the manuscript is appropriately cautious about the liquid-water hypothesis, but the claim "extends SHARAD's capabilities by ~500 m to the overall depth of the base of ice at ~1500 m" is stronger than the single-pass, clutter-limited evidence warrants.
minor comments (4)
  1. [Appendix, radiometric workflow] The inline mathematical notation in the appendix is garbled in the provided text (e.g., "The noise is 𝑓𝑠()𝑓𝑛() extracted 10 μs above..." and the later average-noise-power notation); please ensure the equations and variable definitions are typeset cleanly and all symbols (Ps, Pn, overline-Pn) are defined before use.
  2. [Figure 4b caption and Section 4] The caption states "The mean difference between the black and blue lines is 9 dB" but does not specify whether the mean is taken over the entire plotted extent or only the spatially overlapping segment, nor whether it is computed on the smoothed or raw S/N curves; please clarify this in the caption and in the analogous Figure 5b and 6b captions.
  3. [Section 5, VLR3 discussion] The phrasing "came as a surprise" is a useful statement of expectation, but it would be more informative to state the predicted extension depth or S/N margin implied by the 14 dB gain, so that the negative result can be compared directly with the attenuation hypothesis.
  4. [References] The reference list appears complete, but some entries, such as Croci et al. (2007) and Putzig et al. (2024), are missing page numbers or DOIs; please verify consistency with the journal style.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: VLR S/N gains are direct measurements independently testing the team's antenna model, with no fitted parameter renamed as a prediction.

full rationale

The paper's central result—S/N gains of 9, 11, and 14 dB and the deeper basal detections in VLR1 and VLR2—rests on direct comparisons of SHARAD radargrams acquired at 0° and 120° roll along nearly coincident tracks. The dB gains are measured powers extracted from the radargrams, not outputs of a model fitted to those same radargrams. The antenna model of DiCarlofelice et al. (2024), which includes several of the present authors, provided an independent prediction of roughly 10 dB improvement, and the VLR observations serve as a genuine test of that prediction rather than a restatement of it. No equation in the paper defines the predicted gain in terms of the measured gain, and no parameter is fitted to the VLR data and then presented as a prediction. The use of standard PDS clutter simulations to identify the nadir-surface delay-time index and to argue for subsurface sources is external information, not a self-citation; the paper explicitly notes that VLR clutter extends beyond the 45-km cutoff used in those cluttergrams, which is a caveat on clutter rejection but does not make the derivation circular. External corroboration exists for the deeper interfaces (MARSIS basal detections in Ultimi Scopuli and the previously known Amazonis Planitia interface). Thus the derivation chain is self-contained and non-circular.

Assumptions & free parameters 2 free parameters · 4 assumptions · 0 invented entities

The paper introduces no fitted physical parameters and no new physical entities. Its central result is measured, not derived, but it leans on prior antenna modeling, standard clutter simulations, and assumed dielectric constants. The only hand-chosen processing parameters are the surface-delay buffer and the S/N smoothing window.

free parameters (2)
  • Surface-delay search buffer = 3 samples (0.1125 us)
    Hand-chosen search gate of 7 samples around the clutter-simulated nadir delay; affects S/N histograms but is not fitted to a target result.
  • Along-track S/N smoothing window = 201 samples (~93 km)
    Smoothing applied to along-track S/N plots; the reported 9, 11, and 14 dB improvements are differences of these smoothed traces.
assumptions (4)
  • domain assumption Standard PDS clutter simulations (Christoffersen et al. 2021) are valid at 120 degree roll for identifying nadir surface delay and for ruling out clutter.
    The appendix and Figures 4f, 5f, and 6e use these clutter products for surface alignment and subsurface-source validation, yet the text notes VLR clutter extends beyond the 45 km cutoff used in standard cluttergram generation.
  • domain assumption Antenna model of DiCarlofelice et al. (2024) accurately represents the SHARAD pattern at 120 degree roll with solar arrays in the all-zero gimbal position.
    The paper motivates VLR with this model and interprets the observations as confirmation; the model assumptions are cited rather than re-derived here.
  • domain assumption Dielectric constants from prior literature convert two-way delay to depth for Medusae Fossae materials and polar ice.
    The 800 m and 1500 m depth values depend on assumed subsurface permittivity, not on measurements in this paper.
  • domain assumption Near-coincident comparison tracks have comparable surface, ionosphere, and clutter conditions apart from roll angle.
    The mean S/N differences are attributed entirely to roll angle, with no formal uncertainty or repeated same-track comparison.

how reviews work

0 comments
Cite this review

Pith. "Pith review of SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft." pith.science (2026). https://pith.science/paper/NAHZ6QQ7

@misc{pith2026250521810,
  author       = {Pith},
  title        = {Pith review of: SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/NAHZ6QQ7}},
  note         = {Machine review of arXiv:2505.21810}
}
read the original abstract

Throughout its mission, the Mars Reconnaissance Orbiter (MRO) has often rolled about its along-track axis by up to 28{\deg} to partially compensate for the suboptimal location of the Shallow Radar (SHARAD) antenna along an edge of the spacecraft that is opposite the imaging payload deck, thereby enhancing the signal-to-noise ratio (S/N) of echoes returned from the surface. After recent modeling work predicted that a much larger roll would improve the S/N by ~10 dB relative to nadir-pointed observing, MRO began a limited series of 120{\deg} roll maneuvers to test the effects on radar sounding. Three such SHARAD very-large-roll (VLR) observations have been acquired since May 2023, and they show dramatic improvements in signal clarity and depth of penetration, with S/N increasing by 9, 11, and 14 dB over that of nearly coincident observations at 0{\deg} roll angle. In low dielectric terrains, the first and second VLR observations enabled basal detections at depths previously unachievable, reaching depths of 800 m in Medusae Fossae materials and 1500 m through the ice of Ultimi Scopuli, respectively. The second VLR observation also obtained enhanced reflections throughout the ice stack. In the higher dielectric terrain of Amazonis Planitia, the third VLR observation improved continuity of a dipping subsurface interface, but it revealed neither an extension of the interface to greater depths nor any deeper interfaces. The MRO mission intends to obtain more SHARAD VLR observations of polar terrains and of midlatitude glacial and ground ices, sediments, and volcanics.

Discussion (0). Sign in to comment.

Reference graph

Works this paper leans on

30 extracted references · 24 canonical work pages

  1. [4]

    NASA Planetary Data System , https://doi.org/10.17189/NBDH-2K53

    MRO SHARAD Clutter Simulations Data Products, Browse Products, and Documentation. NASA Planetary Data System , https://doi.org/10.17189/NBDH-2K53. Croci, R., Fois, F., Flamini, E., Mecozzi, R. and Seu, R

    work page doi:10.17189/nbdh-2k53

  2. [8]

    Science , 322 , 1235–1238, https://doi.org/10.1126/science.1164246

    Radar Sounding Evidence for Buried Glaciers in the Southern Mid-Latitudes of Mars. Science , 322 , 1235–1238, https://doi.org/10.1126/science.1164246. Khuller, A.R. and Plaut, J.J

    work page doi:10.1126/science.1164246

  3. [9]

    Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093631

    Characteristics of the Basal Interface of the Martian South Polar Layered Deposits. Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093631. ACCEPTED MANUSCRIPT 20 of 22 DOI:10.3847/PSJ/addbe1 Putzig et al. SHARAD VLR Results - For submission to Planetary Science Journal Lalich, D.E., Hayes, A.G. and Poggiali, V

    work page doi:10.1029/2021gl093631

  4. [11]

    Science Advances , 10 , eadj9546, https://doi.org/10.1126/sciadv.adj9546

    Small variations in ice composition and layer thickness explain bright reflections below martian polar cap without liquid water. Science Advances , 10 , eadj9546, https://doi.org/10.1126/sciadv.adj9546. Lauro, S.E., Pettinelli, E., et al

    work page doi:10.1126/sciadv.adj9546

  5. [12]

    Nature Astronomy , 5 , 63–70, https://doi.org/10.1038/s41550-020-1200-6

    Multiple subglacial water bodies below the south pole of Mars unveiled by new MARSIS data. Nature Astronomy , 5 , 63–70, https://doi.org/10.1038/s41550-020-1200-6. Lauro, S.E., Pettinelli, E., et al

    work page doi:10.1038/s41550-020-1200-6

  6. [15]

    Icarus , 373 , 114716, https://doi.org/10.1016/j.icarus.2021.114716

    The north polar basal unit of Mars: An Amazonian record of surface processes and climate events. Icarus , 373 , 114716, https://doi.org/10.1016/j.icarus.2021.114716. Nerozzi, S., Christoffersen, M.S., Holt, J.W. and Hamilton, C.W

    work page arXiv 2021

  7. [16]

    Remote Sensing , 15 , 4967, https://doi.org/10.3390/rs15204967

    Evidence of Widespread Volcanic Activity near Hebrus Valles on Mars Revealed by SHARAD. Remote Sensing , 15 , 4967, https://doi.org/10.3390/rs15204967. Orosei, R., Lauro, S.E., et al

    work page doi:10.3390/rs15204967

  8. [18]

    IEEE Transactions on Geoscience and Remote Sensing , 60 , 7 pp., https://doi.org/10.1109/TGRS.2021.3094762

    Surface Roughness Prevents Radar Penetration of Some Martian Debris-Covered Glaciers. IEEE Transactions on Geoscience and Remote Sensing , 60 , 7 pp., https://doi.org/10.1109/TGRS.2021.3094762. Petersen, E.I., Holt, J.W. and Levy, J.S

    arXiv 2021

Show all 30 references
  1. [19]

    High Ice Purity of Martian Lobate Debris Aprons at the Regional Scale: Evidence from an Orbital Radar Sounding Survey in Deuteronilus and Protonilus Mensae. Geophys. Res. Lett. , 45 , 11,595-11,604, https://doi.org/10.1029/2018GL079759. Phillips, R.J., Davis, B.J., et al

    doi

  2. [20]

    Science , 332 , 838–841, https://doi.org/10.1126/science.1203091

    Massive CO2 ice deposits sequestered in the South Polar layered deposits of Mars. Science , 332 , 838–841, https://doi.org/10.1126/science.1203091. Putzig, N.E., Seu, R., Morgan, G.A., Smith, I.B., Campbell, B.A., Perry, M.R. and Mastrogiuseppe, M

    doi

  3. [21]

    Icarus , 419 , 115715, https://doi.org/10.1016/j.icarus.2023.115715

    Science results from sixteen years of MRO SHARAD operations. Icarus , 419 , 115715, https://doi.org/10.1016/j.icarus.2023.115715. ACCEPTED MANUSCRIPT 21 of 22 DOI:10.3847/PSJ/addbe1 Putzig et al. SHARAD VLR Results - For submission to Planetary Science Journal Schroeder, D.M. ...

    2023

  4. [22]

    Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL095912

    Alternatives to Liquid Water Beneath the South Polar Ice Cap of Mars. Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL095912. Seu, R., Phillips, R.J., et al

    doi

  5. [23]

    SHARAD sounding radar on the Mars Reconnaissance Orbiter. J. Geophys. Res. , 112 , E05S05, https://doi.org/10.1029/2006JE002745. Simon, M.N., Carter, L.M., Campbell, B.A., Phillips, R.J. and Mattei, S

    doi

  6. [25]

    Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093618

    A Solid Interpretation of Bright Radar Reflectors Under the Mars South Polar Ice. Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093618. Sori, M.M. and Bramson, A.M

    doi

  7. [27]

    Journal of Geophysical Research: Planets , 128 , e2023JE007947, https://doi.org/10.1029/2023JE007947

    Revealing Elysium Planitia’s Young Geologic History: Constraints on Lava Emplacement, Areas, and Volumes. Journal of Geophysical Research: Planets , 128 , e2023JE007947, https://doi.org/10.1029/2023JE007947. Watters, T.R., Campbell, B., et al

    doi

  8. [28]

    Whitten, J.L

    Radar Sounding of the Medusae Fossae Formation Mars: Equatorial Ice or Dry, Low-Density Deposits? Science , 318 , 1125–1128, https://doi.org/10.1126/science.1148112. Whitten, J.L. and Campbell, B.A

    doi

  9. [29]

    Lateral continuity of layering in the Mars South Polar Layered Deposits from SHARAD sounding data. J. Geophys. Res. Planets , 123 , 1541–1554, https://doi.org/10.1029/2018JE005578. Zurek, R., Tamppari, L., et al

    doi

  10. [30]

    Icarus , 419 , 116102, https://doi.org/10.1016/j.icarus.2024.116102

    MRO overview: Sixteen years in Mars orbit. Icarus , 419 , 116102, https://doi.org/10.1016/j.icarus.2024.116102. ACCEPTED MANUSCRIPT 22 of 22 DOI:10.3847/PSJ/addbe1

    2024

  11. [2007]

    241–245., https://doi.org/10.1109/AGPR.2007.386560

    Calibration report of the SHARAD instrument. 241–245., https://doi.org/10.1109/AGPR.2007.386560. Croci, R., Seu, R., Flamini, E. and Russo, E

    2007

  12. [2008]

    SHARAD radar sounding of the Vastitas Borealis Formation in Amazonis Planitia. J. Geophys. Res. , 113 , E12010, https://doi.org/10.1029/2008JE003177. Campbell, B.A., Morgan, G.A., Bernardini, F., Putzig, N.E., Nunes, D.C. and Plaut, J.J. 2021a. Calibration of Mars Reconnaissan...

  13. [2009]

    Icarus , 199 , 295–302, https://doi.org/10.1016/j.icarus.2008.10.007

    Shallow Radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars. Icarus , 199 , 295–302, https://doi.org/10.1016/j.icarus.2008.10.007. Christoffersen, M.S., Holt, J.W., Kempf, S.D. and O’Connell, J.D

    2008 doi

  14. [2011]

    Proceedings of the IEEE , 99 , 794–807, https://doi.org/10.1109/JPROC.2010.2104130

    The SHAllow RADar (SHARAD) Onboard the NASA MRO Mission. Proceedings of the IEEE , 99 , 794–807, https://doi.org/10.1109/JPROC.2010.2104130. DiCarlofelice, A., Tognolatti, P., Bernardini, F., Croci, R., Morgan, G.A., Perry, M.R. and Putzig, N.E

    2010

  15. [2014]

    Journal of Geophysical Research: Planets , 119 , 2291–2299, https://doi.org/10.1002/2014JE004666

    Studies of lava flows in the Tharsis region of Mars using SHARAD. Journal of Geophysical Research: Planets , 119 , 2291–2299, https://doi.org/10.1002/2014JE004666. Smith, I.B., Lalich, D.E., Rezza, C., Horgan, B.H.N., Whitten, J.L., Nerozzi, S. and Holt, J.W

    doi

  16. [2015]

    Evidence for the episodic erosion of the Medusae Fossae Formation preserved within the youngest volcanic province on Mars. Geophys. Res. Lett. , 42 , 7336–7342, https://doi.org/10.1002/2015GL065017. Nerozzi, S., Ortiz, M.R. and Holt, J.W

    doi

  17. [2018]

    Science , 361 , 490–493, https://doi.org/10.1126/science.aar7268

    Radar evidence of subglacial liquid water on Mars. Science , 361 , 490–493, https://doi.org/10.1126/science.aar7268. Petersen, E.I. and Holt, J.W

    doi

  18. [2019]

    Geophysical Research Letters , 46 , 1222–1231, https://doi.org/10.1029/2018GL080985

    Water on Mars, With a Grain of Salt: Local Heat Anomalies Are Required for Basal Melting of Ice at the South Pole Today. Geophysical Research Letters , 46 , 1222–1231, https://doi.org/10.1029/2018GL080985. Voigt, J.R.C., Hamilton, C.W., et al

    doi

  19. [2021]

    Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093880

    Strong MARSIS Radar Reflections From the Base of Martian South Polar Cap May Be Due to Conductive Ice or Minerals. Geophysical Research Letters , 48 , https://doi.org/10.1029/2021GL093880. Campbell, B., Carter, L., et al

    doi

  20. [2022]

    Nature Astronomy , 6 , 1142–1146, https://doi.org/10.1038/s41550-022-01775-z

    Explaining Bright Radar Reflections Below The South Pole of Mars Without Liquid Water. Nature Astronomy , 6 , 1142–1146, https://doi.org/10.1038/s41550-022-01775-z. Lalich, D.E., Hayes, A.G. and Poggiali, V

    doi

  21. [2023]

    Nature Astronomy , 7 , 259–261, https://doi.org/10.1038/s41550-022-01871-0

    Reply to: Explaining bright radar reflections below the south pole of Mars without liquid water. Nature Astronomy , 7 , 259–261, https://doi.org/10.1038/s41550-022-01871-0. Morgan, G.A., Campbell, B.A., Carter, L.M. and Plaut, J.J

    doi

  22. [2024]

    Icarus , 419 , 115802, https://doi.org/10.1016/j.icarus.2023.115802

    A new numerical model of the HF antenna of the Mars Reconnaissance Orbiter’s (MRO) Shallow Radar (SHARAD) and first results from a test at a high-angle spacecraft roll. Icarus , 419 , 115802, https://doi.org/10.1016/j.icarus.2023.115802. Holt, J.W., Safaeinili, A., et al

Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.