Mars Reconnaissance Orbiter Data Research Articles

Enhancing Mars Gravity Field Solutions with China’s Tianwen-1 Tracking Data

Abstract The Tianwen-1 (TW1) mission, which successfully entered Mars's orbit in 2021, provides a valuable data set for enhancing the understanding of Mars’s gravity field. The highly elliptical near-polar orbit of the TW1 orbiter offers unique sensitivity to long-wavelength gravity signals, complementing the contributions of low-altitude missions like the Mars Reconnaissance Orbiter (MRO). In this study, we used 4 months of TW1 radio tracking data in combination with MRO data to develop a new Mars gravity field model up to degree and order 50. We evaluated the improvement of gravity field determination through power spectrum analysis, gravity anomaly maps, and trajectory precision assessment. The result shows significant improvements in accuracy up to degree and order 30, with an average enhancement of 38% in the zonal harmonic coefficients. There are obvious differences between the two gravity field models in gravity anomaly maps. The range of gravity anomaly errors improves after incorporating TW1 data, with the maximum error decreasing from 53.4 to 46.4 mGal and the average error improving from 8.4 to 7.3 mGal. Additionally, orbit determination experiments confirm that the fused gravity field model enhances trajectory modeling for both MRO and TW1. These findings highlight the scientific value of TW1 tracking data in advancing Mars’s gravity field modeling and provide critical insights for future deep-space missions.

Petrogypsic paleosols on Mars

Unlike the water planet Earth, or furnace planet Venus, Mars is a frigid soil planet, most like the Dry Valleys of Antarctica, which also has paleosols revealing a different past. This study examined rocks in early Amazonian (3000 Ma) sequences of western Candor Chasma, cemented by sulfates and iron oxides. Mars Reconnaissance Orbiter data were used to quantify elevations, and the gypsic bands proved to follow ancient dune surfaces, like petrogypsic horizons of soils. Hesperian-early Amazonian (3700-3000 Ma) gypsic paleosols are widespread on Mars, which also has Noachian (3800-4000 Ma) deeply weathered, kaolinitic paleosols. The Archean (3700-3000 Ma) Earth was similar with both gypsic and deeply weathered profiles. Archean fossil microbes and soils on Earth include acid sulfate and deeply weathered soils, but both life and soil diversified afterward on Earth. There is not yet a fossil record on Mars, but the red planet does have acid sulfate and deeply weathered paleosols of geological ages equivalent to Archean on Earth. Unlike Earth however, there is little evidence of later significant soil formation on Mars.

Study of gravity waves distribution and propagation in the thermosphere of Mars based on MGS, ODY, MRO and MAVEN density measurements

By measuring the regular oscillations of the density of CO2 in the upper atmosphere (between 120 and 190 km), the mass spectrometer MAVEN/NGIMS (Atmosphere and Volatile EvolutioN/Neutral Gas Ion Mass Spectrometer) reveals the local impact of gravity waves. This yields precious information on the activity of gravity waves and the atmospheric conditions in which they propagate and break. The intensity of gravity waves measured by MAVEN in the upper atmosphere has been shown to be dictated by saturation processes in isothermal conditions. As a result, gravity waves activity is correlated to the evolution of the inverse of the background temperature. Previous data gathered at lower altitudes (∼95–∼150 km) during aerobraking by the accelerometers on board MGS (Mars Global Surveyor), ODY (Mars Odyssey) and MRO (Mars Reconnaissance Orbiter) are analyzed in the light of those recent findings with MAVEN. The anti-correlation between GW-induced density perturbations and background temperature is plausibly found in the ODY data acquired in the polar regions, but not in the MGS and MRO data. MRO data in polar regions exhibit a correlation between the density perturbations and the Brunt-Väisälä frequency (or, equivalently, static stability), obtained from Global Climate Modeling compiled in the Mars Climate Database. At lower altitude levels (between 100 and 120 km), although wave saturation might still be dominant, isothermal conditions are no longer verified. In this case, theory predicts that the intensity of gravity waves is no more correlated to background temperature, but to static stability. At other latitudes in the three aerobraking datasets, the GW-induced relative density perturbations are correlated with neither inverse temperature nor static stability; in this particular case, this means that the observed activity of gravity waves is not only controlled by saturation, but also by the effects of gravity-wave sources and wind filtering through critical levels. This result highlights the exceptional nature of MAVEN/NGIMS observations which combine both isothermal and saturated conditions contrary to aerobraking measurements.

Planet-wide sand motion on Mars

Prior to Mars Reconnaissance Orbiter data, images of Mars showed no direct evidence for dune and ripple motion. This was consistent with climate models and lander measurements indicating that winds of sufficient intensity to mobilize sand were rare in the low-density atmosphere. We show that many sand ripples and dunes across Mars exhibit movement of as much as a few meters per year, demonstrating that Martian sand migrates under current conditions in diverse areas of the planet. Most motion is probably driven by wind gusts that are not resolved in global circulation models. A past climate with a thicker atmosphere is only required to move large ripples that contain coarse grains.

Diverse mineralogies in two troughs of Noctis Labyrinthus, Mars

Two troughs in Noctis Labyrinthus display a diversity of mineral assemblages rarely seen spatially collocated on Mars. Minerals identified from Mars Reconnaissance Orbiter data within the troughs include polyhydrated and monohydrated sulfates, an Al clay (e.g., kaolinite or beidellite), Fe/Mg smectites, hydrated silica and/or opal, and a leached clay or jarosite mixture with a doublet absorption between 2.2 and 2.3 μm. Units both pre-date and post-date smaller pits and depressions within the larger troughs, indicating that deposition was coeval with continued extension, collapse, and erosion in the Late Hesperian to Early Amazonian (2–3 Ga). The strata within each trough display a mineralogic diversity consistent with active aqueous processes and/or changing chemical conditions over time, perhaps due to hydrothermal alteration of volcanic ash, influxes of groundwater from nearby Tharsis volcanism, fumarole activity, and melting snow and/or ice. The superposition of younger Fe/Mg smectites over sulfates, Al clays, and hydrated silica and/or opal in both troughs indicates that this region is unique relative to most other locations on Mars, where the opposite progression is observed and the Fe/Mg smectites are Noachian (older than 3.6 Ga) in age. Consequently, these troughs may have been habitable regions on Mars at a time when drier conditions dominated the surface.

Constraints on the origin and evolution of the layered mound in Gale Crater, Mars using Mars Reconnaissance Orbiter data

Gale Crater contains a 5.2 km-high central mound of layered material that is largely sedimentary in origin and has been considered as a potential landing site for both the MER (Mars Exploration Rover) and MSL (Mars Science Laboratory) missions. We have analyzed recent data from Mars Reconnaissance Orbiter to help unravel the complex geologic history evidenced by these layered deposits and other landforms in the crater. Results from imaging data from the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) confirm geomorphic evidence for fluvial activity and may indicate an early lacustrine phase. Analysis of spectral data from the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument shows clay-bearing units interstratified with sulfate-bearing strata in the lower member of the layered mound, again indicative of aqueous activity. The formation age of the layered mound, derived from crater counts and superposition relationships, is ∼3.6–3.8 Ga and straddles the Noachian–Hesperian time-stratigraphic boundary. Thus Gale provides a unique opportunity to investigate global environmental change on Mars during a period of transition from an environment that favored phyllosilicate deposition to a later one that was dominated by sulfate formation.

Geologic setting of serpentine deposits on Mars

Serpentine, recently discovered on Mars using Mars Reconnaissance Orbiter data, is uncommon but found in three geologic settings: (1) in mélange terrains at the Claritas Rise and the Nili Fossae, (2) associated with a few southern highlands impact craters, and (3) associated with a regional olivine‐rich stratigraphic unit near the Isidis basin. Any presently active serpentinization processes would be occurring beneath the surface and mineral products would not be apparent with surface and orbital data; however, finding serpentine in several Noachian terrains indicates active serpentinization processes in Mars' past. Important implications are the past production of magnetite, which may contribute to chemical remnant magnetization of Mars' crust, and production of H2, which is a suitable energy source for chemosynthetic microbial life.

Variability of the south polar cap of Mars in Mars years 28 and 29

We have used Mars Reconnaissance Orbiter data from 2007 and 2009 to compare summer behaviors of the seasonal and residual south polar caps of Mars in those two years. We find that the planet-encircling dust storm that occurred in the first of the two Mars years enhanced the loss of seasonal CO 2 deposits relative to the second year but did not have a large effect on the continuing erosion of the pits and mesas within the residual cap materials. This suggests that the increase of bright frost in some regions of the residual cap observed between Mariner 9 and Viking can be accommodated within observed martian weather variability and does not require unknown processes or climate change.

Phyllosilicates and sulfates at Endeavour Crater, Meridiani Planum, Mars

Phyllosilicates have been identified on the Martian surface from orbit, and are hypothesized to have formed under wet, non‐acidic conditions early in the planet's history. Exposures of these minerals have not yet been examined by a landed mission. Using Mars Reconnaissance Orbiter data, we report the detection of phyllosilicate‐bearing outcrops that may be accessible by the Mars Exploration Rover Opportunity currently exploring Meridiani Planum. The phyllosilicates are associated with layered, polygonally fractured rocks exposed in the rim of the 20 km diameter crater Endeavour. These rocks may have formed via regional or global‐scale processes of aqueous alteration that predated the period of acid sulfate formation recorded in the rocks that Opportunity has studied to date. Detailed characterization by Opportunity could better constrain the conditions under which these phyllosilicates formed. Hydrated sulfates are also detected from orbit in the plains adjacent to Endeavour's rim, providing the first opportunity for ground truth of these detections.

Emplacement of the youngest flood lava on Mars: A short, turbulent story

Recently acquired data from the High Resolution Imaging Science Experiment (HiRISE), Context (CTX) imager, and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard the Mars Reconnaissance Orbiter ( MRO) spacecraft were used to investigate the emplacement of the youngest flood-lava flow on Mars. Careful mapping finds that the Athabasca Valles flood lava is the product of a single eruption, and it covers 250,000 km 2 of western Elysium Planitia with an estimated 5000–7500 km 3 of mafic or ultramafic lava. Calculations utilizing topographic data enhanced with MRO observations to refine the dimensions of the channel system show that this flood lava was emplaced turbulently over a period of only a few to several weeks. This is the first well-documented example of a turbulently emplaced flood lava anywhere in the Solar System. However, MRO data suggest that this same process may have operated in a number of martian channel systems. The magnitude and dynamics of these lava floods are similar to the aqueous floods that are generally believed to have eroded the channels, raising the intriguing possibility that mechanical erosion by lava could have played a role in their incision.

An overview of the Mars Reconnaissance Orbiter (MRO) science mission

The Mars Reconnaissance Orbiter (MRO) is the latest addition to the suite of missions on or orbiting Mars as part of the NASA Mars Exploration Program. Launched on 12 August 2005, the orbiter successfully entered Mars orbit on 10 March 2006 and finished aerobraking on 30 August 2006. Now in its near‐polar, near‐circular, low‐altitude (∼300 km), 3 p.m. orbit, the spacecraft is operating its payload of six scientific instruments throughout a one‐Mars‐year Primary Science Phase (PSP) of global mapping, regional survey, and targeted observations. Eight scientific investigations were chosen for MRO, two of which use either the spacecraft accelerometers or tracking of the spacecraft telecom signal to acquire data needed for analysis. Six instruments, including three imaging systems, a visible‐near infrared spectrometer, a shallow‐probing subsurface radar, and a thermal‐infrared profiler, were selected to complement and extend the capabilities of current working spacecraft at Mars. Whether observing the atmosphere, surface, or subsurface, the MRO instruments are designed to achieve significantly higher resolution while maintaining coverage comparable to the current best observations. The requirements to return higher‐resolution data, to target routinely from a low‐altitude orbit, and to operate a complex suite of instruments were major challenges successfully met in the design and build of the spacecraft, as well as by the mission design. Calibration activities during the seven‐month cruise to Mars and limited payload operations during a three‐day checkout prior to the start of aerobraking demonstrated, where possible, that the spacecraft and payload still had the functions critical to the science mission. Two critical events, the deployment of the SHARAD radar antenna and the opening of the CRISM telescope cover, were successfully accomplished in September 2006. Normal data collection began 7 November 2006 after solar conjunction. As part of its science mission, MRO will also aid identification and characterization of the most promising sites for future landed missions, both in terms of safety and in terms of the scientific potential for future discovery. Ultimately, MRO data will advance our understanding of how Mars has evolved and by which processes that change occurs, all within a framework of identifying the presence, extent, and role of water in shaping the planet's climate over time.

Context Camera Investigation on board the Mars Reconnaissance Orbiter

The Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) is a Facility Instrument (i.e., government‐furnished equipment operated by a science team not responsible for design and fabrication) designed, built, and operated by Malin Space Science Systems and the MRO Mars Color Imager team (MARCI). CTX will (1) provide context images for data acquired by other MRO instruments, (2) observe features of interest to NASA's Mars Exploration Program (e.g., candidate landing sites), and (3) conduct a scientific investigation, led by the MARCI team, of geologic, geomorphic, and meteorological processes on Mars. CTX consists of a digital electronics assembly; a 350 mm f/3.25 Schmidt‐type telescope of catadioptric optical design with a 5.7° field of view, providing a ∼30‐km‐wide swath from ∼290 km altitude; and a 5000‐element CCD with a band pass of 500–700 nm and 7 μm pixels, giving ∼6 m/pixel spatial resolution from MRO's nearly circular, nearly polar mapping orbit. Raw data are transferred to the MRO spacecraft flight computer for processing (e.g., data compression) before transmission to Earth. The ground data system and operations are based on 9 years of Mars Global Surveyor Mars Orbiter Camera on‐orbit experience. CTX has been allocated 12% of the total MRO data return, or about ≥3 terabits for the nominal mission. This data volume would cover ∼9% of Mars at 6 m/pixel, but overlapping images (for stereo, mosaics, and observation of changes and meteorological events) will reduce this area. CTX acquired its first (instrument checkout) images of Mars on 24 March 2006.