The uncertainties about the Marsis radar on Mars Express have not gone away. As I mentioned back here, doubts were raised this spring about the safety of deploying the radar's antennae, because it seemed possible that they would snap back and hit the spacecraft itself, which would probably be bad and possibly catastrophic. According to the ESA website, analysis of the problem has yet to provide an all clear, and so deployment is being further delayed, on the basis that it's better to do without Marsis data -- which might conceivably provide evidence of liquid water in deep aquifers -- than to endanger the whole mission. The system won't now be deployed until October, if then. There's a little more discussion of the ESA statement in a report at BBC Online.
If the risks of deployment look too great to face this year, though, that may change with time. There must surely come a point at which the trade-off between preserving the spacecraft's remaining life at all costs and getting data from the radar starts to tip in the radar's favour. Once the Omega spectrometer and the HRSC camera have covered most of the planet's surface, and when the atmospheric instruments have been able to capture a full Mars year of readings, I suspect the case for risking the remainder of the mission in the hope of getting some qualitatively new data will seem a good bit stronger. That would be some time in early 2006. If by that time there's a consensus on a specific source region for the methane, the case for deployment would, I suspect, be seen as stronger still.
Another issue that might conceivably factor into the decision would be the risk of getting scooped. In March 2006 the Sharad radar will arrive on board the Mars Reconnaissance Orbiter; its antenna will be deployed about six months later, after aerobraking. Sharad is designed to make a different sort of measurement; it confines itself to the shallow sub-surface and has much higher resolution. It's not in a position to discover big deep aquifers. But it's conceivable that Sharad might pick up evidence of shallow aquifers in some places, if there are any such aquifers there. And a discovery of liquid water by NASA would overshadow any further such discovery by ESA.
So a sense of competition might provide a marginal extra incentive for deploying Marsis before MRO gets into its science orbit in late 2006. But there might also be a case for waiting a little longer. The antenna deployment mechanisms for the two spacecraft are similar and designed by the same company -- it was work on the Sharad deployment that raised the possibility that there could be problems with Marsis. Data from a successful Sharad deployment might conceivably change the analysis-based picture of the risks of deploying Marsis. If Sharad's deployment can be seen as a test run for Marsis, it might be a good idea to let Sharad go first.
If deployment doesn't go ahead this year, the decision about what to do in a few years' time will be a very tricky one. Some Mars Express scientists will want to preserve the integrity of the spacecraft -- and of their own data streams -- come what may. Others will want to push for exploring the subsurface, even if that involves risks. And it's possible the risks aren't evenly distributed -- what if analysis shows deployment as being unlikely to hurt the spacecraft as a whole, but quite likely to poke out the eye of one of the other instruments...
Let's hope there'll be a good, open debate about this. But since we're dealing with ESA, let's not hold our breaths.
PS: for those interested, I've added some links to good obits to the end of the Tommy Gold past