Mars Express Status Report - November 2004
29 Nov 2004 16:46Mission Status
Following a successful period of science data taking in July and early August, end-August and most of September were dominated by a solar conjunction. In such a situation Mars is located diagonally across the Sun, as seen from Earth. Such a constellation blocks efficient radio communications and the spacecraft was prepared to survive extended periods of no contact. In this period almost no science data could be taken. On the egress from conjunction all spacecraft systems were nominal.
Studies on the safe deployment of the radar antenna for the MARSIS experiment are approaching completion, and expected to lead to clear conclusions in the last quarter of 2004. In parallel it has been decided that the earliest deployment window, based on both technical and scientific grounds, starts around mid-March 2005.
Operations and archiving
Operations planning up to the end of the year is progressing steadily. With the Mars-Earth distance still being high, and consequently a low-bit rate on the telecommunications link, there is only a limited data volume which can be downlinked. Together with the other mission constraints this sometimes leads to difficult trade-offs in the distribution of observations over the instruments.
The independent Mars Express Science Archive Review was held on 12-13 July at ESTEC. Although a number of actions to be taken were identified, the review was judged to have been extremely valuable by all involved.
A dedicated Mars Express Science Conference will take place at ESTEC on the week of 21-25 February 2005.
A very successful international Mars conference was held in Ischia, Italy from 19-23 September 2004. A significant number of recent results from Mars-Express were presented, as summarized hereafter.
It is generally believed, and indicated by results from the High Resolution Stereo Camera (HRSC), there once were abundant fluvial activities active on Mars. However, even though recent OMEGA observations confirm that today water still exists as vast fields of perennial water ice, stretching out from its South pole, an efficient mechanism for removing water from the planet must have been at work. Recent results from the ASPERA instrument on board Mars Express confirm that such a process is at work in the Martian atmosphere, explaining the loss of water over time. It is believed the solar wind erodes the atmosphere of Mars, and strips away large amounts of water that were present on the planet about 3.8 billion years ago. The ASPERA instrument on board Mars Express has measured a process called 'solar wind scavenging', or the slow 'invisible' escape of volatile gases and liquid compounds which make up the atmosphere and hydrosphere of a planet. These measurements have established that the solar wind penetrates through the ionosphere and very deeply into the Martian atmosphere down to an altitude of 270 kilometres. This seems to be the reason for the acceleration processes that could explain the loss of atmosphere on Mars.
Measurements by the Planetary Fourier Spectrometer (PFS) reveal that, at 10-15 kilometres above the surface, water vapour is well mixed and uniform in the atmosphere. However, it found that, close to the surface, water vapour is more concentrated in three broad equatorial regions. Here, the concentration is two to three times higher than in other regions observed. New in-depth analysis of PFS data shows that methane is not uniform in the atmosphere, but concentrated in some areas. The PFS team observed that the areas of highest concentration of methane overlap with areas where water vapour and underground water ice are also concentrated. This spatial correlation between water vapour and methane seems to point to a common underground source. Further investigations are needed to fully understand the correlation between (i) presence and distribution of water vapour and methane in the atmosphere and (ii) the presence of a subsurface ice layer.