P31D-01
Mars Reconnaissance Orbiter: Integrating Results From the Primary Science Phase
The Mars Reconnaissance Orbiter (MRO) recently completed its one-Mars-year Primary Science Phase, observing the Martian atmosphere, surface and subsurface with 7 science investigations using 6 science instruments and tracking of the spacecraft as it orbited Mars. In addition, an eighth investigation made use of the onboard accelerometers during a 5-month period of MRO aerobraking to characterize upper atmospheric structure. Hallmarks-and challenges-of the MRO science mission have been: 1) unprecedented spatial resolution at all wavelengths used when observing from orbit; 2) coordinated imaging of local areas; and 3) the balancing of mapping, regional survey, and targeted observation of selected locales, frequently including repeat observations for stereo or for change detection. This talk will give an overview of the data return, including coverage in various observing modes, and will review how the various data sets have combined to provide new perspectives in our attempts to understand Mars, its present climate and its past evolution. Examples include the combination of surface compositional and morphologic information--on scales comparable to those examined by a terrestrial field geologist-to understand modification of the surface, revelations of the interior structure of the polar ice caps and of ice-rich deposits elsewhere which illuminate climate changes in recent geologic time, and monitoring of modern day variations, particularly as they reveal seasonal and inter-annual redistribution of dust and water, but also as they characterize ongoing mass wasting and cratering of the surface. Together, these all point to a complex history of change on Mars, with alternating episodes of significant water activity early in the planet's history, but with some water activity occurring in later geologic times, including the modern era.
P31D-02
One Martian Year of Atmospheric Observations by the Mars Climate Sounder
The Mars Climate Sounder (MCS) completed its first year of observations of the Martian atmosphere obtaining vertical profiles of temperature, dust, condensates, and water vapor. In this overview we show comparisons of retrievals from MCS with results from the Mars Global Surveyor Thermal Emission Spectrometer and Radio Science investigations. Agreement is generally good to excellent for temperature profiles where measurements overlap; however, MCS retrievals of the vertical distribution of dust depart from the standard model derived from nadir-viewing instruments. Activities in support of entry descent and landing of the Phoenix lander presented an opportunity for the intercomparison of multiple instruments and models. Some results from that work are presented here. The extended vertical coverage and high vertical resolution of MCS observations have been used to study the thermal structure of the lower and middle atmosphere. The meridional circulation at solstice is inferred to be significantly more vigorous, and that the warming due to the descending branch of the Hadley cell is more intense and extends further poleward than had been predicted.
P31D-03
MRO Mars Color Imager (MARCI) Investigation Primary Mission Results
The Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) investigation was designed to recover the wide angle camera science objectives of the Mars Climate Orbiter MARCI which was destroyed upon arrival at Mars in 1999 and extend the daily meteorological coverage of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide angle investigation that was systematically conducted from March 1999 to October 2006. MARCI consists of two wide angle cameras, each with a 180° field of view. The first acquires data in 5 visible wavelength channels (420, 550, 600, 650, 720 nm), the second in 2 UV channels (260, 320 nm). Data have been acquired daily, except during spacecraft upsets, since 24 September 2006. From the MRO 250 to 315 km altitude orbit, inclined 93 degrees, visible wavelength images usually have a pixel scale of about 1 km at nadir and the UV data are at about 8 km per pixel. Data are obtained during every orbit on the day side of the planet from terminator to terminator. These provide a nearly continuous record of meteorological events and changes in surface frost and albedo patterns that span more than 1 martian year and extend the daily global record of such events documented by the MGS MOC. For a few weeks in September and October 2006, both camera systems operated simultaneously, providing views of weather events at about 1400 local time (MOC) and an hour later at about 1500 (MARCI). The continuous meteorological record, now spanning more than 5 Mars years, shows very repeatable weather from year to year with cloud and dust-raising events occurring in the same regions within about 2 weeks of their prior occurrence in previous years. This provides a measure of predictability ideal for assessing future landing sites, orbiter aerobraking plans, and conditions to be encountered by the current landed spacecraft on Mars. However, less predictable are planet-encircling dust events. MOC observed one in 2001, the next was observed by MARCI in 2007. These occurred at different times of year. While popularly known as global dust storms, the nomenclature is misleading, as in each case a storm did not raise dust nor saltate sand on a global basis. Instead, multiple regional storms created a dust haze which obscured much of the martian surface from viewpoints above the lower atmosphere, but in each case the dust opacity was never so high that one could not determine where dust was being raised and where it was not. Within weeks of the end of the 2001 and 2007 global dust events, martian weather returned to its normal, repeatable pattern, with one exception: occasionally thereafter, dust storms were observed in regions where dust-raising had not been seen in the previous years. In these cases, winds capable of raising dust likely occurred at that location every year, but only became visible following a planet-encircling dust event and deposition of dust on a surface that previously did not have sufficient dust to raise. Other MARCI results center on seasonal monitoring of water vapor in the atmosphere, particularly by taking advantage of the anti-correlation between ozone (observable using the UV channels) and water vapor. Owing to their higher spatial resolution than the MOC daily global coverage, details of seasonal polar cap retreat became more apparent, as with these data it is now possible to separate surface frost from ground-hugging fog which forms along the retreating cap edge. MARCI images and meteorological observations are posted weekly on the Internet for public consumption, and the data are archived every 6 months with the NASA Planetary Data System.
P31D-04 INVITED
MRO Context Camera (CTX) Investigation Primary Mission Results
The Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) acquires panchromatic images of Mars at ~6 m/pixel; the majority cover areas 30 km wide by 43 to 313 km long. As of 31 August 2008, 36% of Mars was imaged at 6 m/pixel and 10.8% was covered more than once. Areas imaged multiple times include stereopairs and locations covered repeatedly to monitor dust-raising events, seasonal frost patterns, or landforms and albedo features known or anticipated to change. CTX provides context for data acquired by other MRO science instruments, as well. Using our knowledge of imaging performance as a function of seasonal atmospheric, frost, and insolation conditions from the 4 Mars-year Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) investigation, we undertook several time-dependent campaigns to create 6 m/pixel mosaics of regions such as Hellas Planitia, the south polar residual cap (covered in spring and in summer), and the north polar region. In addition, we obtained 6 m/pixel mosaics of the Valles Marineris, Sinus Meridiani, Marte Valles, Athabasca Valles, portions of the northern plains, fretted terrain and chaotic terrain, large volcanoes, yardang-forming materials in Amazonis and Aeolis, the small volcanoes and platy flows south of Cerberus, and many other regions. We monitored thousands of mid-latitude gullies, and we used our MOC experience to target dust-raising events that repeat every year at the same locations. Retreat of cliffs formed in layers of CO2 ice in the south polar cap was observed for the 5th southern summer since 1999. Dozens of new impact craters and crater clusters were observed; all formed since 1999 and some formed during the MRO Primary Mission. We routinely re-targeted the new impact sites to see how they change and alert other MRO instrument teams so they could observe them. CTX images of the cratered highlands emphasize the view that the upper crust of Mars is layered with interbedded filled and buried valleys, fluvial channels, and impact craters ranging in diameter from meters to hundreds of kilometers. CTX observations reiterate a critical MOC result regarding small, sub-kilometer diameter craters: the substrates most resistant to erosion retain the most small craters (and the boulders produced by the impacts). CTX images provide many examples in which a younger, harder substrate (e.g., a lava flow) is more heavily cratered (with < 1 km diameter craters) than subjacent, older rock units. One example occurs in the form of lava flows located immediately west of Meridiani Planum; similar flows underlie the hematite-bearing, plains- forming rock in nearby Miyamoto Crater. Northern Meridiani also exhibits exhumed, low-order streams (of the scale of hillslope rills and creeks); these were filled, buried, lithified, and later returned to the surface by erosion—some of them in inverted form. Terrain immediately west of Juventae Chasma exhibits similar inverted streams and rills that were first documented by MOC and provide key evidence for rainfall and hillslope runoff. CTX data show that there are many hundreds of inverted fluvial channels, of a variety of sizes, all over the planet, especially in Arabia Terra, Solis Planum, and Thaumasia. We also used CTX to map a small, unnamed outflow channel system west of Bond Crater, and we have been documenting all of the small Martian volcanoes, typically < 30 km across, including those occurring in the Labyrinthus Noctis. CTX data are widely available, as they are archived with the NASA Planetary Data System on a rolling basis every 6 months.
P31D-05 INVITED
CRISM Findings after One Mars Year in Orbit
CRISM has operated for one Mars year in orbit, and has returned over 8000 high-resolution (20-40 m/pixel)
targeted observations, mapped nearly 60% of the planet at reduced spatial resolution (200 m/pixel), and
monitored spatial and temporal variations in atmospheric trace gases and aerosols. The major discoveries
regarding surface composition are that aqueous alteration was more widespread and diverse than previously
thought. (1) Phyllosilicates occur as thousands of outcrops distributed throughout Noachian crustal units.
There are different classes of phyllosilicate-containing deposits: massive exposures in crater walls and
central peaks and the walls of Valles Marineris, compositionally stratified deposits in Nili Fossae and Mawrth
Vallis, and intracrater fans. A wide variety of mineralogies is observed, suggesting a variety of environments
and intensities of alteration of the early crust by liquid water. (2) Sulfate-containing layered materials in Valles
Marineris exhibit unexpectedly fine compositional stratification. Interbedded sulfates in differing hydration
states occur as layers as thin as tens of meters, sometimes in a repeating sequence. In some locations the
sulfate-rich beds exhibit enhanced signatures of crystalline ferric minerals, and ferric minerals are
concentrated by mass wasting processes to form the hematite concentrations observed by TES. These
observations suggest variations in the depositional environment on geologically short time scales, and
significant effects of subsequent erosion and redeposition. (3) A third major type of aqueous mineralogy,
hydrated silica, has been found in widespread thin, light-toned, Hesperian-age layers on the plateau
surrounding Valles Marineris. Some layers exhibit hydrated sulfates suggesting formation of the silica in an
acidic environment. (4) Restricted thin layers of carbonate have been located in and around the Nili Fossae
region, stratigraphically above the phyllosilicates and in close spatial association. The deposits are too
limited to hold a massive ancient atmosphere, but their preservation indicates that subsequent sulfate-
forming acidic aqueous environments were not sufficiently widespread to destroy all pre-existing carbonates.
(5) Most recently a number of closed basins in the highlands, in both craters and intercrater plains, have
been found to contain phyllosilicates or silica interbedded with or in close association with evaporites
including sulfates and material interpreted from THEMIS data as chlorides. These may represent a variety of
alluvial or lacustrine deposits.
http://crism.jhuapl.edu
P31D-06 INVITED
Recent Results From MRO/HiRISE
The High Resolution Imaging Science Experiment (HiRISE) on Mars Reconnaissance Orbiter (MRO) has
acquired more than 7.8 Terapixels of Mars imaging since October 2006, covering less than 0.8% of the
surface. Images are 5-6 km wide with 3-color coverage over the central 20%, and their scales usually range
from 25-60 cm/pixel. More than 800 stereo pairs have been acquired and ~20 digital terrain models (DTMs)
completed; these data have led to some of the most significant science results. New methods to measure
and correct distortions due to pointing jitter facilitate topographic and change-detection studies at sub-meter
scales. There are recent results concerning Noachian bedrock stratigraphy and megabreccia, fluvially-
deposited fans in craters and in or near Valles Marineris, groundwater flow in fractures and porous media,
quasi-periodic layering in polar and non-polar deposits, tectonic history of west Candor Chasm, geometry of
clay-rich deposits near and within Mawrth Vallis, dynamics of flood lavas in the Cerberus Palus region, new
evidence for pyroclastic deposits, columnar jointing in rapidly-cooled lava flows, recent collapse pits,
evidence for water in well-preserved impact craters, newly-discovered large rayed craters, and glacial and
periglacial processes. We are particularly interested in ongoing processes such as those driven by the wind,
impact cratering, dust avalanches, icy avalanches on north polar scarps, relatively bright deposits on steep
gullied slopes, and the especially dynamic seasonal processes over polar regions in the spring and summer.
For landing sites (past, present, and future) HiRISE has acquired hundreds of large images and contributed
to scientific and engineering studies.
http://hirise.lpl.arizona.edu
P31D-07
Mars Volatile Mass Motions: Results from Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Global Surveyor
Since February 1999, one and at times multiple spacecraft have been operating in Mars orbit, continuously tracked by the NASA Deep Space Network. This nearly decade-long time series of tracking observations has afforded the opportunity to monitor the Martian gravity field and its miniscule changes due to the seasonal cycling of the primary atmospheric constituent, CO2, between the planet's atmosphere and surface. Beginning with Mars Global Surveyor (MGS), followed by Mars Odyssey (Odyssey), and finally Mars Reconnaissance Orbiter (MRO) we have recovered changes in the masses of the seasonal icecaps and the atmosphere through analyses of small perturbations of the orbits of the spacecraft. Using models of the two seasonal icecaps derived from temporal spectral and altimetric observations and a general circulation model (GCM) of the atmosphere as a priori constraints, we have obtained estimates of the masses of the CO2 on each of the icecaps and the mean global atmospheric pressure at 5-day intervals for over 4 Mars years (approx. 8 Earth years). MGS and Odyssey provide the strongest solutions because the altitude (approx. 400 km) of both spacecraft dictates that their orbits are less affected by atmospheric drag than spacecraft in lower-altitude orbits. MRO, with a periapse at 255 km, is more sensitive to Mars' gravity but also more affected by atmospheric drag and its variability, making the identification of the very small seasonal changes in the gravity field more difficult to extract. Clear but small inter-annual departures from the predictions of GCMs are evident and some are consistent across years, suggesting that other processes could be involved in the seasonal cycling of volatiles. Gravity is the only measurement able to detect these changes.
P31D-08 INVITED
Response of the Mars Thermosphere to Dynamical Effects
The 2006 Mars Reconnaissance Orbiter (MRO) Accelerometer Experiment measurements above 100km give neutral densities and inferred temperatures over the entire Southern Hemisphere of Mars due to the precession of periapsis. When combined with our previous accelerometers on Mars Global Surveyor (MGS) and Mars Odyssey (MO), measurements are obtained showing global dynamical effects. We have discovered high amplitude (+-30 percent) planetary scale waves from all 3 spacecraft. These waves were observed from near sun-synchronous orbits and thus the observed wave 2 was apparently actually a wave 1 (non-migrating) diurnal Kelvin wave moving to the east around the planet in one Martian day (non-migrating tides) while the sun was moving (migrating) to the west around the planet in one Martian day. Thus, the wave 2 was actually a wave 1. This phenomenon occurred from the equator to near the pole. The observed phase of the wave changes from day to night by about 90 deg in longitude in accord with predictions of Forbes et al., 2002. The diurnal Kelvin wave apparently propagates upwards linking together the upper and lower atmosphere. Near the North Winter pole at 100km we discovered temperatures sharply increased with latitude from 75 deg N to 87 deg N by 85 K contrary to an atmosphere in radiative equilibrium. Apparently dynamical effects cause the phenomenon (Keating et al., 2002; Keating et al., 2002a). We proposed that perhaps there is meridional flow from the summer to winter hemisphere and then subsidence near the winter pole resulting in strong adiabatic heating near 100km (Keating et al., 2002). The Mars Thermosphere General Circulation Model (MTGCM) (Bougher et al., 2006) is consistent with our explanation. We find the winter polar warming is stronger near perihelion than near aphelion. This may be related to the stronger solar heating near perihelion. To confirm the various dynamical effects, observations are compared with the MTGCM and other GCMs. These temperature changes result in changes in density which, in turn, could produce strong aerodynamic heating endangering spacecraft. Knowledge of the nature of the thermospheric variations should reduce the risk on spacecraft from aerobraking and aerocapture.