[X] My Assistant

[Bill Thompson]

What is the latest on the origins or the existence of methane on Mars? Have there been any new thoughts or information.

This is my very first post here so I do not know who visits this forum and how current the information is.

[Guest_BruceMoomaw_*]

It wasn't MEPAG that recommended a 2013 orbiter to NASA -- it was the other way around! Because the overspecialized 2009 Mars Telecom Orbiter has been cancelled, and because MRO's design lifetime is only a decade, NASA has decided that they will need to launch more combined science/communications orbiters at the rate of about once/decade to provide their future landers with the communications capability that they need. They therefore ordered MEPAG to recommend the best science payload for the orbiter which they'll be launching in 2013 in any case. And MEPAG, as was made clear at the November COMPLEX meeting, was strongly oriented toward atmospheric investigations for that orbiter from the start.

You're certainly correct that MARVEL would serve functions besides methane-mapping -- it was a mapper of all sorts of trace gases, as well as providing a lot more data on altitude profiles of air density, dust, and (I believe) air temperature. But the instruments that it would have used for that purpose are all now included on MEPAG's recommended payload list for the bigger 2013 orbiter (along with all the instruments recommended by several past groups for a Scout-class Mars Aeronomy Orbiter for upper-atmospheric studies).

There is also another good reason for flying an atmospheric orbiter this early -- it's been made clear both by MEPAG and by other NASA engineers that we very badly need more data on the the fluctuations in Mars' upper air density, and its lower-altitude winds and turbulence, to maximize the safety of future landers. (Oddly, this wasn't listed among the 2013 orbiter's goals in the MEPAG document - maybe because MEPAG was just ordered to provide recommendations as to the purely scientific uses of a 2013 orbiter. But the instruments required for both types of studies are almost identical.)

[mwolff]

[snip]

They therefore ordered MEPAG to recommend the best science payload for the orbiter which they'll be launching in 2013 in any case. And MEPAG, as was made clear at the November COMPLEX meeting, was strongly oriented toward atmospheric investigations for that orbiter from the start.

[snip]
There is also another good reason for flying an atmospheric orbiter this early -- it's been made clear both by MEPAG and by other NASA engineers that we very badly need more data on the the fluctuations in Mars' upper air density, and its lower-altitude winds and turbulence, to maximize the safety of future landers. (Oddly, this wasn't listed among the 2013 orbiter's goals in the MEPAG document - maybe because MEPAG was just ordered to provide recommendations as to the purely scientific uses of a 2013 orbiter. But the instruments required for both types of studies are almost identical.)

That's bad news for Scout PIs proposing an atmospheric mission (of which there are an amazing number)...though I suppose it will make proposal preparation easier if NASA allows complete payload proposals for 2013.

"lower altitude winds" will be very difficult, unless they are only talking about measuring down to 20 km.
Microwave techniques suffer from pressure-broadening (of lines) below 20 km and interferometric techniques typically use an emission line of molecular oxygen which is collisionally quenched below 20-25 km. so
the bottom two scale-heights will be hard to get (one can use absorption lines as long as one looks at the
surface -- as opposed to the limb -- but there are other technical issues.

there are several aeronomy mission concepts, so they will have something to cheer even if they don't win in 2011.

thanks for providing the info about COMPLEX. i have to admit, i am still very skeptical about NASA actually following up on an atmospheric orbiter...but your statements provide insight into the number of aeronomy scout missions concepts.