Mars Express Results Options

[remcook]

http://physicsweb.org/articles/news/9/2/10/1

he latest results from Mars Express reveal that the surface of the red planet is much more diverse than previously thought, with evidence for the presence of hydrated sulphates, silicates and various rock-forming minerals. Space scientists working on the European Space Agency mission have just analysed the first nine months of data from the OMEGA instrument and published six papers that give the first detailed inventory of the entire Martian surface. Last year Mars Express identified frozen water at both the north and south poles of the planet.

[imran]

Jon Clarke's summary of Mars Express findings from the Vienna Conference.

Hi all

I have just got back from an amazing European Geoscience Union conference in Vienna. There must have been 10,000 people there. The titles alone of the talks require some 440 pages. Subjects included hydrology, atmospheric sciences, geophysics, sedimentology, petrology, oceanography, and planetary science. The pressures of time precluded me from seeing all I wanted to, plus I was there for work, so could not go to as many planetary science sessions as I wanted. Those I did attend were mainly on Mars, but I got to a few on the moon, Iapetus and Titan as well. I will post a few threads on these in the next day or so, but will start with current Mars missions. Make of them what you will

Jon

There were many papers on the results of Mars Express. Some highlights.

OMEGA (first V-NIR spectrometer sent to Mars, 300 m resolution) sulphate mapping presented by Gendrin et al. Extensive hydrated sulphates identified at various location and Valles Marinaris, in the north polar dune sea, and of course Terra Meridiani. There is very strong correlation between sulphates and layered terrain, down to single pixels. However not all pale layered units are sulphates. Strong correlation exists regionally between sulphates and iron oxides, locally they occur in different but juxtaposed beds. Opportunity landed some 400 km away from the thickest sulphate deposits in terra Meridiani, which include at least 100 m of very pure epsomite. The locally high abundance of epsomite in the polar erg was unexpected, suggests that some of the dunes are cemented by sulphate, supported in a poster by Schatz et al.. At low latitudes there is a good correlation between high levels of hydrogen reported in neutron spectroscopy and sulphates. It is possible to explain all the hydrogen as being near surface hydrated sulphates, although this does not preclude the presence of ices at depth, consistent with other evidence. The presenter also reminded the audience that not all hydrated sulphates are sedimentary – they can form via weathering and hydrothermal processes.

HRSC mapping of Gusev crater were presented by Pinet et al. HRSC reveals much greater variation in surface properties than identified by MOC and THEMIS, largely because of better resolution. Overall the properties resemble those of Apollinaris Patera to the north, this is consistent with the predominantly basaltic nature of the surface seen by Spirit. At 100 m resolution imaging of the Spirit site, three types of surface were identified – basalt, dunes, and the hills, confirming what was identified by the rover and allowing extrapolation to other areas beyond the rover’s reach.

HRSC and OMEGA investigations of Cerberus Fossae were presented by Voucher et al. MOLA data shows this area as having a very low (less than 0.1 degree) eastward slope, defining a very low relief shield volcano. The most recent basalt flows in the area arise from a series of tectonic fissures but not the most recent ones, giving the region its name. Water flows are, however from these recent troughs, giving rise to Athabasca Vallis. The shield volcano is probably 2 Ga, the most recent lava flows 10 Ma, as are the fluvial features.

Preuschmann et al. compared the morphology of parts of Valles Marinaris as revealed by HRSC with terrestrial subadjacent karst, where dissolution of soluble rocks underneath insoluble cap rocks causes collapse. A number of basalt plateaus overlying limestones in the Middle East show morphologies similar to those seen on Mars.

Van Gasselt et al. presented a very interesting poster on polygons in the South Polar Trough using MOLA and MOC data. The authors noted significant changes over a three-year period, clearly pointing to active permafrost.

A summary of the status of Mars methane was even by Encrenaz et al. She reviewed previous work to date, resent observations using the M-E PFS and future prospects. She considered the Formisano detection as marginal because of the poor spectral resolution and the Kransnopolsky study as marginal because of poor detection limits. The Mumma study (unfortunately the only one not yet fully published) was the best because of good spectral and spatial resolution. However, her attempts to duplicate this using the ME PFS observations were unsuccessful, although getting indicates of 10 ppb methane. However a few runs gave 20 ppb methane, suggesting that high methane production might be not only localized but also episodic. The best hope for Mars methane work in the short term appears to be in better ground based observations because of their better spectral and spatial resolution.

[tty]

Extensive hydrated sulphates identified at various location and Valles Marinaris, in the north polar dune sea, and of course Terra Meridiani. There is very strong correlation between sulphates and layered terrain, down to single pixels. However not all pale layered units are sulphates. Strong correlation exists regionally between sulphates and iron oxides, locally they occur in different but juxtaposed beds. Opportunity landed some 400 km away from the thickest sulphate deposits in terra Meridiani, which include at least 100 m of very pure epsomite. The locally high abundance of epsomite in the polar erg was unexpected, suggests that some of the dunes are cemented by sulphate, supported in a poster by Schatz et al.. At low latitudes there is a good correlation between high levels of hydrogen reported in neutron spectroscopy and sulphates. It is possible to explain all the hydrogen as being near surface hydrated sulphates, although this does not preclude the presence of ices at depth, consistent with other evidence. The presenter also reminded the audience that not all hydrated sulphates are sedimentary – they can form via weathering and hydrothermal processes.

Now that is interesting since we know that the Meridiani sulphates are waterlaid evaporites. Such a thick evaporite layer means either a very deep brine pool (very unlikely considering the lack of topographic relief), or (more likely) a long period of evaporite deposition, or (most likely) a large number of shallow water evaporation episodes.
Were there any hints what the other pale layered deposits are? They could of course be eolian, but also non-sulphatic evaporites.

Also if the total depth of evaporites is <100 m thick near Opportunity it means that Victoria crater may have punched right through the evaporite layer and the underlying deposits might occur in the ejecta and be visible in situ in the crater.

tty