Particle transport and distribution on the Mars Science Laboratory mission: Effects of triboelectric charging

We report on the nature of fine particle (<150 μm) transport under simulated martian conditions, in order to better understand the Mars Science Laboratory’s (MSL) sample acquisition, processing and handling subsystem (SA/SPaH). We find that triboelectric charging due to particle movement may have to be controlled in order for successful transport of fines that are created within the drill, processed through the Collection and Handling for In situ Martian Rock Analysis (CHIMRA) sample handing system, and delivered to the Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments. These fines will be transferred from the surface material to the portioner, a 3 mm diameter, 8 mm deep distribution center where they will drop ∼2 cm to the instrument inlet funnels. In our experiments, movement of different material including terrestrial analogs and martian soil simulants (Mars Mojave Simulant - MMS) resulted in 1-7 nanocoulombs of charge to build up for several different experimental configurations. When this charging phenomenon occurs, several different results are observed including particle clumping, adherence of material on conductive surfaces, or electrostatic repulsion, which causes like-charged particles to move away from each other. This electrostatic repulsion can sort samples based upon differing size fractions, while adhesion causes particles of different sizes to bind into clods. Identifying these electrostatic effects can help us understand potential bias in the analytical instruments and to define the best operational protocols to collect samples on the surface of Mars.     

The chemical variability at the surface of Mars: Implication for sediment formation and rock weathering

Compositional data analysis was performed on chemical compositions of martian surface materials in order to unravel scenarios of past and present weathering and to evaluate the role of meteoritic accumulation. The observed chemical variability is analyzed by means of principal component analysis. Potential reservoirs that may have contributed primary material to soil formation are assessed. Chemical alteration in the course of in situ weathering is described in terms of alteration vectors that link the compositions of fresh rocks and their weathering crusts. The interplay of localized chemical alteration and global scale re-distribution and mixing of fines material is documented through the identification of different soil forming branches. These branches emanate from distinct compositional domains, which comprise basaltic and basalt-andesitic primary materials, and they converge to a global dust composition, which represents the product of chemical and physical disintegration and subsequent global mixing. Mass balance considerations applied to localized weathering phenomena are in line with findings from experimental acid-sulfate weathering on olivine-bearing basalts and the persistence of secondary silica in evaporitic rocks. In addition the composition and oxidation state of involved volcanic gases is deduced. Our findings corroborate the past activity of volcanic exhalation products in combination with liquid water. We conclude that average martian crust is dominated by basaltic materials at its topmost level and that the amount of meteoritic accumulation may contribute about 6 wt% to the martian fines. From the meteoritic contribution minimum soil formation rates of 60±20 cm/Gyr are derived. Sequestration of atmospheric oxygen during weathering of primary materials may account for the oxygen deficiency of the martian atmosphere. A 4-14-m-thick layer of oxidized martian fines may account for the estimated deficit of 1.7×¹⁰¹⁸ mol O₂ in the martian atmosphere depending on the primary oxidation state of volatile volcanic emanations.     

Impact of two DNA repair pathways, homologous recombination and non-homologous end joining, on bacterial spore inactivation under simulated martian environmental conditions

Spores of Bacillus subtilis were used as a model system to study the impact of the two major DNA double-strand break (DSB) repair mechanisms [homologous recombination (HR) and non-homologous end-joining (NHEJ)] on the survivability of air-dried mono- and multilayers of bacterial spores under a simulated martian environment; i.e., an environment with low temperature (−10 °C), pure CO₂ atmosphere (99.99% CO₂), 200-1100 nm UV-VIS-NIR radiation, and 0.69 kPa pressure. Spores in multilayers exhibited low inactivation rates compared to monolayers, mainly due to shadowing effects of overlying spores. Simulated martian UV irradiation reduced dramatically spore viability, whereas when shielded from martian UV radiation, spores deficient in NHEJ- and HR-mediated DNA repair were significantly more sensitive to simulated martian environmental conditions than were wild-type spores. In addition, NHEJ-deficient spores were consistently more sensitive than HR-deficient spores to simulated Mars environmental conditions, suggesting that DSBs were an important type of DNA damage. The results indicated that both HR and NHEJ provide an efficient set of DNA repair pathways ensuring spore survival after exposure to simulated martian environmental conditions.     

Extended survival of several organisms and amino acids under simulated martian surface conditions

Recent orbital and landed missions have provided substantial evidence for ancient liquid water on the martian surface as well as evidence of more recent sedimentary deposits formed by water and/or ice. These observations raise serious questions regarding an independent origin and evolution of life on Mars. Future missions seek to identify signs of extinct martian biota in the form of biomarkers or morphological characteristics, but the inherent danger of spacecraft-borne terrestrial life makes the possibility of forward contamination a serious threat not only to the life detection experiments, but also to any extant martian ecosystem. A variety of cold and desiccation-tolerant organisms were exposed to 40 days of simulated martian surface conditions while embedded within several centimeters of regolith simulant in order to ascertain the plausibility of such organisms’ survival as a function of environmental parameters and burial depth. Relevant amino acid biomarkers associated with terrestrial life were also analyzed in order to understand the feasibility of detecting chemical evidence for previous biological activity. Results indicate that stresses due to desiccation and oxidation were the primary deterrent to organism survival, and that the effects of UV-associated damage, diurnal temperature variations, and reactive atmospheric species were minimal. Organisms with resistance to desiccation and radiation environments showed increased levels of survival after the experiment compared to organisms characterized as psychrotolerant. Amino acid analysis indicated the presence of an oxidation mechanism that migrated downward through the samples during the course of the experiment and likely represents the formation of various oxidizing species at mineral surfaces as water vapor diffused through the regolith. Current sterilization protocols may specifically select for organisms best adapted to survival at the martian surface, namely species that show tolerance to radical-induced oxidative damage and low water activity environments. Additionally, any hypothetical martian ecosystems may have evolved similar physiological traits that allow sporadic metabolism during periods of increased water activity.     

Sublimation kinetics of CO2 ice on Mars

Dynamic models of the martian polar caps are in abundance, but most rely on the assumption that the rate of sublimation of CO₂ ice can be calculated from heat transfer and lack experimental verification. We experimentally measured the sublimation rate of pure CO₂ ice under simulated martian conditions as a test of this assumption, developed a model based on our experimental results, and compared our model's predictions with observations from several martian missions (MRO, MGS, Viking). We show that sun irradiance is the primary control for the sublimation of CO₂ ice on the martian poles with the amount of radiation penetrating the surface being controlled by variations in the optical depth, ensuring the formation and sublimation of the seasonal cap. Our model confirmed by comparison of MGS-MOC and MRO-HiRISE images, separated by 2-3 martian years, shows that ∼0.4 m are currently being lost from the south perennial cap per martian year. At this rate, the ∼2.4-m-thick south CO₂ perennial cap will disappear in about 6-7 martian years, unless a short-scale climatic cycle alters this rate of retreat.     

Raman spectroscopic detection of key biomarkers of cyanobacteria and lichen symbiosis in extreme Antarctic habitats: Evaluation for Mars Lander missions

With proposals that micro-miniaturised Raman spectrometers could soon be part of a suite of analytical instrumentation on the surface of Mars, it is critically important to examine the spectral information that could be forthcoming from attempts to determine key molecular biosignatures under the hostile conditions of extra-terrestrial planetary exploration. Current approaches include the analysis of genuine martian geological material in the form of the SNC class meteorites, the formulation of simulated martian regoliths and the examination of putative martian terrestrial analogues; the latter provide the basis of this paper in the form of Antarctic extremophile habitats. In particular, specimens of epilithic, chasmolithic and endolithic lichen and cyanobacterial colonies sampled along a progressively worsening transect towards a “limits of life” situation, beyond which survival of organisms becomes impossible, provide what is arguably the best terrestrial proving-ground for prototype Raman spectrometers for martian exploration. Here, we report the results of experiments on these extant Antarctic extremophile colonies using a range of Raman excitation wavelengths and experimental conditions and also include a compilation of molecular spectral biosignatures, which may be considered as a suitable database for recognition of bioorganic modification of geological strata.     

Launch of martian meteorites in oblique impacts

A high-velocity oblique impact into the martian surface accelerates solid target material to escape velocity. A fraction of that material eventually falls as meteorites on Earth. For a long time they were called the SNC meteorites (Shergotty, Nakhla, and Chassigny). We study production of potential martian meteorites numerically within the frame of 3D hydrodynamic modeling. The ratio of the volume of escaping solid ejecta to projectile volume depends on the impact angle, impact velocity and the volatile content in the projectile and in the target. The size distribution of ejected fragments appears to be of crucial importance for the atmosphere-ejecta interaction in the case of a relatively small impact (with final crater size <3 km): 10-cm-sized particles are decelerated efficiently, while 30-50% of larger fragments could escape Mars. The results of numerical modeling are compared with shock metamorphic features in martian meteorites, their burial depth, and preatmospheric mass. Although it is impossible to accelerate ejected fragments to escape velocity without substantial compression (above 10 GPa), the maximum temperature increase in dunite (Chassigny) or ortopyroxenite (ALH84001) may be lower than 200 degree. This result is consistent with the observed chaotic magnetization of ALH84001. The probability of microbes' survival may be rather high even for the extreme conditions during the ejection process.     

Determination of the wind induced detachment threshold for granular material on Mars using wind tunnel simulations

Experimental results are presented of wind induced grain detachment under Mars simulation conditions. A simple force balance equation is applied to quantify the wind shear stress required for removal of glass spheres from a sand bed. The transport of fine grained martian dust is simulated by the detachment of hollow glass spheres which resemble low mass density dust aggregates observed to form during simulations when using Mars analogue material. The results agree well with observations of dust removal and wind speed measurements made by the NASA Viking landers at the martian surface. This work supports the suggestion that dust aggregate fragmentation allows wind induced dust entrainment at substantially lower wind shear than that of solid sand grains and has direct application to the study of global dust transport and martian climatology.     

Ejecta from impacts at 0.2-2.3 m/s in low gravity

Collisions between planetary ring particles and in some protoplanetary disk environments occur at speeds below 10 m/s. The particles involved in these low-velocity collisions have negligible gravity and may be made of or coated with smaller dust grains and aggregates. We undertook microgravity impact experiments to better understand the dissipation of energy and production of ejecta in these collisions. Here we report the results of impact experiments of solid projectiles into beds of granular material at impact velocities from 0.2 to 2.3 m/s performed under near-weightless conditions on the NASA KC-135 Weightless Wonder V. Impactors of various densities and radii of 1 and 2 cm were launched into targets of quartz sand, JSC-1 lunar regolith simulant, and JSC-Mars-1 martian regolith simulant. Most impacts were at normal or near-normal incidence angles, though some impacts were at oblique angles. Oblique impacts led to much higher ejection velocities and ejecta masses than normal impacts. For normal incidence impacts, characteristic ejecta velocities increase with impactor kinetic energy, KE, as approximately KE^0.5. Ejecta masses could not be measured accurately due to the nature of the experiment, but qualitatively also increased with impactor kinetic energy. Some experiments were near the threshold velocity of 0.2 m/s identified in previous microgravity impact experiments as the minimum velocity needed to produce ejecta [Colwell, J.E., 2003. Icarus 164, 188-196], and the experimental scatter is large at these low speeds in the airplane experiment. A more precise exploration of the transition from low-ejecta-mass impacts to high-ejecta-mass impacts requires a longer and smoother period of reduced gravity. Coefficient of restitution measurements are not possible due to the varying acceleration of the airplane throughout the experiment.     

CO2 Snow on Mars and Early Earth: Experimental Constraints

Greenhouse warming due to carbon dioxide atmospheres may be responsible for maintaining the early Earth's surface temperature above freezing and may even have allowed for liquid water on early Mars. However, the high levels of CO₂ required for such warming should have also resulted in the formation of CO₂ clouds. These clouds, depending on their particle size, could lead to either warming or cooling. The particle size in turn is determined by the nucleation and growth conditions. Here we present laboratory studies of the nucleation and growth of carbon dioxide on water ice under martian atmospheric conditions. We find that a critical saturation, S=1.34, is required for nucleation, corresponding to a contact parameter between solid water and solid carbon dioxide of m=0.95. We also find that after nucleation occurs, growth of CO₂ is very rapid, and we report the growth rates at a number of supersaturations. Because growth would be expected to continue until the CO₂ pressure is lowered to its vapor pressure, we expect particles larger than those being currently suggested for the present and past martian atmospheres. Using this information in a microphysical model described in a companion paper, we find that CO₂ clouds are best described as “snow,” having a relatively small number of large particles.     

Processing of cometary grains at the nucleus surface

Cometary material inevitably undergoes chemical changes before and on leaving the nucleus. In seeking to explain comets as the origin of many IDPs (interplanetary dust particles), an understanding of potential surface chemistry is vital. Grains are formed and transformed at the nucleus surface; much of the cometary volatiles may arise from the organic material. In cometary near-surface permafrost, one expects cryogenic chemistry with crystal growth and isotope. This could be the hydrous environment where IDPs form. Seasonal and geographic variations imply a range of environmental conditions and surface evolution. Interplanetary dust impacts and electrostatic forces also have roles in generating cometary dust. The absence of predicted cometary dust ‘envelopes’ is compatible with the wide range of particle structures and compositions. Study of IDPs would distinguish between this model and alternatives that see comets as aggregates of core-mantle grains built in interstellar clouds.     

Stability of hydrous minerals on the martian surface

The presence of water-bearing minerals on Mars has long been discussed, but little or no data exist showing that minerals such as smectites and zeolites may be present on the surface in a hydrated state (i.e., that they could contain H₂O molecules in their interlayer or extra-framework sites, respectively). We have analyzed experimental thermodynamic and X-ray powder diffraction data for smectite and the most common terrestrial zeolite, clinoptilolite, to evaluate the state of hydration of these minerals under martian surface conditions. Thermodynamic data for clinoptilolite show that water molecules in its extra-framework sites are held very strongly, with enthalpies of dehydration for Ca-clinoptilolite up to three times greater than that for liquid water. Using these data, we calculated the Gibbs free energy of hydration of clinoptilolite and smectite as a function of temperature and pressure. The calculations demonstrate that these minerals would indeed be hydrated under the very low-P (H₂O) conditions existing on Mars, a reflection of their high affinities for H₂O. These calculations assuming the partial pressure of H₂O and the temperature range expected on Mars suggest that, if present on the surface, zeolites and Ca-smectites could also play a role in affecting the diurnal variations in martian atmospheric H₂O because their calculated water contents vary considerably over daily martian temperature ranges. The open crystal structure of clinoptilolite and existing hydration and kinetic data suggest that hydration/dehydration are not kinetically limited. Based on these calculations, it is possible that hydrated zeolites and clay minerals may explain some of the recent observations of significant amounts of hydrogen not attributable to water ice at martian mid-latitudes.     

Radiative cooling within illuminated layers of dust on (pre)-planetary surfaces and its effect on dust ejection

Temperature gradients in dust beds embedded in a low pressure gaseous environment induce a lift of particles under certain conditions. This effect can erode planetesimals and enables entrainment of dust into the martian atmosphere. Here, we consider a numerical model to calculate the temperature profile in a dust bed which is subject to illumination. We consider the situation when the illumination is switched on and heats the dust bed’s surface and when it is switched off again after a certain time. The calculations focus on the heat transfer by infrared radiation within the dust layer. We find that radiative transfer within the dust bed modifies the absolute temperatures and temperature gradients significantly. This is important for effects which are sensitive to absolute temperatures, i.e. ice sublimation or melting of solids. For low thermal conductivity dust beds of 0.001 W m⁻¹ K⁻¹ it determines the temperature structure of the dust. For higher thermal conductivities the modifications are moderate with respect to dust eruptions as the order of magnitude of temperature gradients stays the same.     

Stability of mid-latitude snowpacks on Mars

Christensen [2003. Nature 422, 45-48] suggested that runoff from melting snowpacks on martian slopes might be responsible for carving gullies. He also suggested that snowpacks currently exist on Mars, for example on the walls of Dao Valles (approximately 33° S). Such snowpacks were presumably formed during the last obliquity cycle, which occurred about 70,000 years ago. In this paper we investigate a specific scenario under conditions we believe are favorable for snowpack melting. We model the rate at which a snowpack located at 33° S on a poleward-facing slope sublimates and melts on Mars, as well as the temperature profile within the snowpack. Our model includes the energy and mass balance of a snowpack experiencing diurnal variations in insolation. Our results indicate that a dirty snowpack would quickly sublimate and melt under current martian climate conditions. For example a 1 m thick dusty snowpack of moderate density (550 kg/m³) and albedo (0.39) would sublimate in less than two seasons, producing a small amount of meltwater runoff. Similarly, a cleaner snowpack (albedo 0.53) would disappear in less than 9 seasons. These results suggest that the putative snowpack almost certainly could not have survived for 70,000 years. For most of the parameter settings snowpack interior temperatures at this latitude and slope do reach the melting point. Under most conditions melting occurs when the snowpack is less than 10 cm thick. The modeled snowpack will not melt if it is covered by a 1 cm dust lag. In general, these findings raise interesting possibilities regarding gully formation, but perhaps mostly during a past climate regime when snowfall was expected to have occurred. If there currently are exposed snowpacks on martian mid-latitude slopes, then these ice sheets cannot last long. Hence they might be time variable features on Mars and should be searched for.     

The H2O and CO2 adsorption properties of phyllosilicate-poor palagonitic dust and smectites under martian environmental conditions

The recent detection of up to ∼10 wt% water-equivalent H heterogeneously distributed in the upper meter of the equatorial regions of the martian surface and the presence of the 3-μm hydrations feature across the entire planet raises the question whether martian surficial dust can account for this water-equivalent H. We have investigated the H₂O and CO₂ adsorption properties of palagonitic dust (<5 μm size fraction of phyllosilicate-poor palagonitic tephra HWMK919) as a martian dust analog and two smectites under simulated martian equatorial surface conditions. Our results show that the palagonitic dust, which contains hydrated and hydroxylated volcanic glass of basaltic composition, accommodates significantly more H₂O under comparable humidity and temperature conditions than do the smectites nontronite and montmorillonite.     

Water sorption on martian regolith analogs: Thermodynamics and near-infrared reflectance spectroscopy

The near-infrared reflectance spectra of the martian surface present strong absorption features attributed to hydration water present in the regolith. In order to characterize the relationships between this water and atmospheric vapor and decipher the physical state of water molecules in martian regolith analogs, we designed and built an experimental setup to measure near-IR reflectance spectra under martian atmospheric conditions. Six samples were studied that cover part of the diversity of Mars surface mineralogy: a hydrated ferric oxide (ferrihydrite), two igneous samples (volcanic tuff, and dunite sand), and three potential water rich soil materials (Mg-sulfate, smectite powder and a palagonitic soil, the JSC Mars-1 regolith stimulant). Sorption and desorption isotherms were measured at 243 K for water vapor pressure varying from 10⁻⁵ to ∼0.3 mbar (relative humidity: 10⁻⁴ to 75%). These measurements reveal a large diversity of behavior among the sample suite in terms of absolute amount of water adsorbed, shape of the isotherm and hysteresis between the adsorption and desorption branches. Simultaneous in situ spectroscopic observations permit a detailed analysis of the spectral signature of adsorbed water and also point to clear differences between the samples. Ferric (oxy)hydroxides like ferrihydrite or other phases present in palagonitic soils are very strong water adsorbent and may play an important role in the current martian water cycle by allowing large exchange of water between dust-covered regions and atmosphere at diurnal and seasonal scales.     

Laboratory simulations of Mars aqueous geochemistry

We report on laboratory experiments in which we allowed an SNC-derived mineral mix to react with pure water under a simulated Mars atmosphere for 7 months. These experiments were performed at one bar and at three different temperatures in order to simulate the subsurface conditions that most likely exist where liquid water and rock interact on Mars today. The dominant cations dissolved in the solutions we produced, which may be characterized as dilute brines, are Ca²⁺, Mg²⁺, Al³⁺, and Na⁺, while the major anions are dissolved C, F⁻, SO²⁻₄ and Cl⁻. Typical solution pH was in the range of 4.2-6.0. Abundance patterns of elements in our synthetic sulfate-chloride brines are distinctly unlike those of terrestrial ocean water or continental waters, however, they are quite similar to those measured in the martian fines at the Mars Pathfinder and Viking 1 and 2 Landing sites. This suggests that salts present in the martian regolith may have formed over time as a result of the interaction of surface or subsurface liquid water with basalts in the presence of a martian atmosphere similar in composition to that of today. If most of the mobile surface layer was formed during the Noachian when erosion rates were much higher than at present, and if this layer is homogeneous in salt composition, the total amount of salt in the martian fines is approximately the same as in the Earth's oceans. The minimum quantity of circulating water necessary to deposit this amount of salt is approximately equivalent to a global layer 625 m deep.     

Radar absorption due to a corotating interaction region encounter with Mars detected by MARSIS

Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a subsurface and topside ionosphere radar sounder aboard the European Space Agency spacecraft Mars Express, in orbit at Mars since 25 December 2003, and in operation since 17 June 2005. The ionospheric sounding mode of MARSIS is capable of detecting the reflection of the sounding wave from the martian surface. This ability has been used in previous work to show that the surface reflection is absorbed and disappears during periods when high fluxes of energetic particles are incident on the ionosphere of Mars. These absorption events are believed to be the result of increased collisional damping of the sounding wave, caused by increased electron density below the spacecraft, in turn caused by impact ionization from the impinging particles. In this work we identify two absorption events that were isolated during periods when the surface reflection is consistently visible and when Mars is nearly at opposition. The visibility of the surface reflection is viewed in conjunction with particle and photon measurements taken at both Mars and Earth. Both absorption events are found to coincide with Earth passing through solar wind speed and ion flux signatures indicative of a corotating interaction region (CIR). The two events are separated by an interval of approximately 27 days, corresponding to one solar rotation. The first of the two events coincides with abruptly enhanced particle fluxes seen in situ at Mars. Simultaneous with the particle enhancement there are an abrupt decrease in the intensity of electron oscillations, typically seen by the Mars Express particle instrument ASPERA-3 between the magnetic pileup boundary and the martian bow shock, and a sharp drop in the solar wind pressure, seen in the proxy quantity based on MGS magnetometer observations. The decrease in oscillation intensity is therefore the probable effect of a relaxation of the martian bow shock. The second absorption event does not show a particle enhancement and complete ASPERA-3 data during that time are unavailable. Other absorption events are the apparent result of solar X-ray and XUV enhancements. We conclude that surface reflection absorption events are sometimes caused by enhanced ionospheric ionization from high energy particles accelerated by the shocks associated with a CIR. A full statistical analysis of CIRs in relation to observed absorption events in conjunction with a quantitative analysis of the deposition of ionization during space weather events is needed for a complete understanding of this phenomenon. If such analyses can be carried out, radar sensing of the martian ionosphere might be useful as a space weather probe.     

Methane adsorption on a martian soil analog: An abiogenic explanation for methane variability in the martian atmosphere

Recent observations suggest methane in the martian atmosphere is variable on short spatial and temporal scales. However, to explain the variability by loss reactions requires production rates much larger than expected. Here, we report results of laboratory studies of methane adsorption onto JSC-Mars-1, a martian soil simulant, and suggest that this process could explain the observations. Uptake coefficient (γ) values were measured as a function of temperature using a high-vacuum Knudsen cell able to simulate martian temperature and pressure conditions. Values of γ were measured from 115 to 135 K, and the data were extrapolated to higher temperatures with more relevance to Mars. Adsorptive uptake was found to increase at lower temperatures and larger methane partial pressures. Although only sub-monolayer methane surface coverage is likely to exist under martian conditions, a very large mineral surface area is available for adsorption as atmospheric methane can diffuse meters into the regolith. As a result, significant methane may be temporarily lost to the regolith on a seasonal time scale. As this weak adsorption is fully reversible, methane will be re-released into the atmosphere when surface and subsurface temperatures rise and so no net loss of methane occurs. Heterogeneous interaction of methane with martian soil grains is the only process proposed thus far which contains both rapid methane loss and rapid methane production mechanisms and is thus fully consistent with the reported variability of methane on Mars.     

A method to infer past surface mass balance and topography from internal layers in martian polar layered deposits

Internal layers in ice masses can be detected with ice-penetrating radar. In a flowing ice mass, each horizon represents a past surface that has been subsequently buried by accumulation, and strained by ice flow. These layers retain information about relative spatial patterns of accumulation and ablation (mass balance). Internal layers are necessary to accurately infer mass-balance patterns because the ice-surface shape only weakly reflects spatial variations in mass balance. Additional rate-controlling information, such as the layer age, the ice temperature, or the ice-grain sizes and ice-crystal fabric, can be used to infer the absolute rate of mass balance. To infer mass balance from the shapes of internal layers, we solve an inverse problem. The solution to the inverse problem is the best set or sets of unknown boundary conditions or initial conditions that, when used in our calculation of ice-surface elevation and internal-layer shape, generate appropriate predictions of observations that are available. We also show that internal layers can be used to infer martian paleo-surface topography from a past era of ice flow, even though the topography may have been largely altered by subsequent erosion. We have successfully inferred accumulation rates and surface topography from internal layers in Antarctica. Using synthetic data, we demonstrate the ability of this method to solve the corresponding inverse problem to infer accumulation and ablation rates, as well as the surface topography, for martian ice. If past ice flow has affected the shapes of martian internal layers, this method is necessary to infer the spatial pattern and rate of mass balance.