[X] My Assistant

[djellison]

For information - we have discussed the biology issue in the Admin section. The discussion came to a very near unanimous decision that the outright ban on Biology is the right step for UMSF at the moment. Reasons cited include those I've mentioned before, as well as others. In no particular order

- Biology (like Politics or Manned v Unmanned) takes on a religious like status in peoples minds with no grounds for actual debate
- There are no biological instruments flying, or planned for flight.
- Setting a limit for what would or would not be acceptable would be near impossible. There is no fair or valid means to half-open the door on this.
- The administrative workload would increase significantly (high admin workload being the sign of a badly administered forum)
- There are alternate venues that are better suited to these sorts of discussions.

It is by taking difficult decisions like this one, that UMSF has become and continues to be what people admire it for. Such decisions are, to some extent, a judgement call. But the admin team has agreed, that this is the right judgement at this time.

[ngunn]

I'd been chewing this over and come to the same conclusion - there was nothing else you could do, for now, to avoid having to stay up every night containing wildfires. Let's just hope that no banned items are unequivocally discovered in the near future. Fingers crossed, eh?

Once again, Doug, thanks for everything - awkward decisions and all. We don't say it often enough.

[Juramike]

Mars methane map made APOD.

Global map of methane release during martian summer available here: http://apod.nasa.gov/apod/image/0901/marsm...ne_nasa_big.jpg

[MarsIsImportant]

Much of the known plumes seem to originate from the Arabia Terra region. Some of the areas with the least amount of methane include Hellas Planitia and Elysium Mons.

Hellas Planitia is a known area where most dust storms originate on Mars. So if dust storms have anything to do with production of methane, then you would have to explain the huge discrepancy in the amount of methane build up there.

Elysium Mons is a known volcanic region. So if volcanic activity has anything to do with the production, then likely that region is truly dead volcanically speaking. I would like to a map that includes Olympus Mons before forming an opinion on that.

Why over Arabia Terra? I think NASA has this correct. This tends to indicate subsurface sources for the methane that maybe unique to that area. What that is, we cannot be sure of yet.

If the source were photochemical, explain the distribution. I would think there would be a distribution bias horizontally over the equatorial latitudes instead of what we actually see. Perhaps it is because of ice reservoirs or perhaps something else.

The known distribution would be a problem for a lot of possible different explanations for the source. Let's face the fact that we need better methane maps. The need might suggest a dedicated mission of some sort!

Regardless, it is a fascinating mystery. I would think following the methane is now a good strategy; but we need the proper equipment and advanced planning to do the job properly. I would think changing the landing spot for MSL would be risky at this late stage, unless there are instruments that could easily be brought aboard to make it worth it. I have my doubts.

[nprev]

Doug, I support the decision because the rationale is sound, aside from admin workload. Most UMSFers love it here because above all it's a no-drama place where some extremely smart people freely share their ideas with us laymen, and preserving that feature of the forum is certainly a priority.

As Nigel said, we don't thank you & the admin team enough for this place, nor do we express our appreciation as often as we should for consistently keeping the standards high. If it was easy, anybody could do it; you guys aren't "anybodies". Thanks.

[SpaceListener]

The plumes of methane appeared over northern hemisphere regions such as east of Arabia Terra, the Nili Fossae region, and the south-east quadrant of Syrtis Major, an ancient volcano 1,200 kilometers (about 745 miles) across

If you do Mars Google, I found the three regions to be about the same northern latitud. However, Syrtis and Nili Fossae are very close and Arabia Terra is about 3,000 kilometers west of the first ones.

The other thing, I have observed the methane distribution thru the APOD picture and found that the plumes are not uniformily distributed all planet but localized mostly in that zone. Is that methane distribution consistent in spite of the fact its intensity varies with the seasons.

These many questions might be solved with the future orbiters with adequate instruments to detect the methane. MSL will have it but it won't see all Mars. Hence, the Nili Fossae would be considered again as the one of the four potentials landings.

[ArMaP]

Sorry for this question from someone that does not understand these things very well.

When they say "parts per billion", what billions are they talking about, other atmosphere components?

Considering the thinness of Mars atmosphere, how would that translate to Earth's atmosphere?

Thanks in advance.

[Juramike]

That is an EXCELLENT question.

It would imply one gram of stuff (methane) in a billion grams of other stuff (air).

Here is a more detailed article: http://en.wikipedia.org/wiki/Parts_per_notation

My favorite quote:
"it is not formally part of the International System of Units (SI).[2] Consequently, according to IUPAP, 'a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt.'"

[I count myself among the 'annoyed': for most drug-like molecules, ppm is directly proportional to units molar (M). But if you are comparing with especially heavy or light molecules in the mix, this can throw off the relationship.]

-Mike

[aggieastronaut]

it seems someone else answered the question before I posted...

[Juramike]

And I think I know why in this particular case it's easier to use ppb: volume will fluctuate at different pressures and temperatures.

Trying to sort out the volume at the particular temperature (which will vary widely on Mars) and pressure (big difference from Hellas Basin (1.155 kPa) to the top of Olympus Mons (0.03 kPa)) would make trying to calculate concentration of g (or moles) per volume a pain.

But I think the spectroscopic method gives units molar from Beer's law. A = cl: A is absorbance, c= concentration, l = path length.

-Mike

[Fun random trivia fact: the human nose can detect this molecule at 10 ppb on Earth at standard temperature and pressure (STP)]

[Juramike]

(I just had to run this death....)

At standard temperature and pressure on Earth (273 K, 101.3 kPa), 1 mol = 22.4 L

Assuming a pure N2 (m.w. = 28) atmosphere for Earth: 1 mol/22.4 L = 28 grams/22.4 L.

So air 1 ppb on Earth in 22.4 L (STP) = 28E-9 grams/28 grams (=1 part per billion)
28E-9 grams in 22.4 L = 28 nanograms/22.4 L (STP)

For methane (CH4; m.w. 16), 1 ppb corresponds to is 28E-9 g * (1 mol methane/16 g) = 1.75E-9 mol methane

1.75 E-9 mol methane/22.4 L = 0.078 nM concentration.

***

On Mars, what is a typical pressure/temperature at the surface?

Wild guesstimate/generalization: use 233 K (=-40 C), and 0.6 kPa

So pV=nRT:
For pressure: 22.4 L mol -1 x (101.3 kPa/0.6 kPa) = 3782 L mol-1 at Mars pressure
For temperature: 3782 L mol-1 x (233 K/273 K) = 3230 L mol-1 at Mars surface pressure temp.

Assuming pure CO2 (m.w. = 44) atmosphere for Mars: 1 mol/3230 L = 44 grams/3230 L

So 1 ppb at Mars surface in 22.4 L (Mars guesstimate) = 44E-9 grams/44 grams (=1 part per billion)
44E-9 grams in 3230 L (Mars guesstimate).

For methane (CH4, m.w. 16) this corresponds to 44E-9 grams * 1 mol methane/16 g = 2.75E-9 mol methane

2.75 E-9 mol methane/3230 L = 0.8 picomolar concentration. (=0.0008 nM concentration)

Put another way, 1 ppb methane on Earth has 100 times more CH4 molecules per unit volume than on Mars at my guesstimated surface temp and pressure.

(Handy data for all of you thinking about growing beans on Mars…..)

[/nerdgasm]

-Mike

[nprev]

...Mike, thou art an ubersciencegeek amongst geeks...thank you very much!

That truly puts this in perspective; ain't very much methane at all, and that actually makes the whole issue even more puzzling. Are there really only a (literal) handful of vents on the entire planet? I know that the crust is supposed to be very thick, but jeez...

[rlorenz]

(I just had to run this death....)

At standard temperature and pressure on Earth (273 K, 101.3 kPa), 1 mol = 22.4 L

Sloppy, Mike, sloppy ;-)

If one cares enough to worry about ppb or whatever not being kosher units, then one should
really note that the litre is a unit of capacity, rather than volume

1 mole occupies 22.4 dm^3 at STP.

[CosmicRocker]

For information - we have discussed the biology issue in the Admin section. The discussion came to a very near unanimous decision that the outright ban on Biology is the right step for UMSF at the moment. ...

As if my opinion might be important, I would have voted for such a ban, too.

Sorry for this question from someone that does not understand these things very well. ... When they say "parts per billion", what billions are they talking about ...

When you begin to talk about PPBs, PPMs, or even simple percentages, such ratios need further definition to become useful. I normally prefer to think about mass ratios, but volume and weight ratios remind us that there are other perspectives that are useful to consider. 22.4 liters/mole at STP is one of my favorite numbers.

[nprev]

Interesting analysis from Kelly Beatty over on Sky & Telescope. Apparently there was water vapor associated with the emissions, and they were definitely transient. The plot thickens considerably.

Now, what's REALLY strange is why two or more locales separated by hundreds if not thousands of km seemed to pop off at nearly the same time. Not even close to enough information to make an intelligent guess as to what's going on geologically, if anything. Boy, do we need some seismometers on Mars.