MSL scientific results Options

[Robotbeat]

According to en.wikipedia.org/wiki/Background_radiation, average exposure in USA is 0.006 Sv/yr. There are several inhabited places on Earth with ~100 times more natural background - making 0.66 Sv/yr not as "ouch" as it looks at the first glance.

Indeed, it's almost exactly in line with other estimates of radiation from GCR in deep space. Lithium hydride, by the way, is quite effective (i.e. good shielding per mass, low secondary production) given the low atomic masses, about even with methane (though LiH is solid and denser, both good) and better than basically everything else except liquid hydrogen. Aluminum is horrible. It may even make things worse in some cases.

I'd like to see what the total levels are at the surface. It should be less than half the deep space level, and it should depend on altitude.

I came here looking for figures on the surface radiation level measured by the RAD instrument. Anyone have them?

[Greenish]

Well, you could just go here & process it yourself: http://ppi.pds.nasa.gov/search/view/?f=yes...PPI/MSLRAD_1002

But so as not to be rude, I did look around and there don't appear to be any peer-reviewed or significant public data on the surface radiation measurements. Best I could find is actually a nice summary, in the most recent PPT file (26MB) on this page: http://mslrad.boulder.swri.edu/educators.html which does have some decent (preliminary) surface info starting at slide 35, with dosimetry info on 45-47.

Bottom line is 1.84 +/-0.30 mSv/day in cruise and 0.7 +/- 0.17 mSv/day on surface. Don't want to go into implications because this is not a human spaceflight forum.

To keep this planetary-science relevant: they also have some neat charts showing the variations of charged particles and neutron dose (oppositely correlated) with pressure each sol, and comparisons with GCR spectra.

[Paolo]

A new MSL pre-print in Science Express today: Low Upper Limit to Methane Abundance on Mars

[Explorer1]

It looks more and more likely that methane emissions are highly localized, dependent on wind, temperature, etc. to spread across a wide area.
We may have to wait for dedicated instruments (on Mangalyaan) and missions (Exomars Trace Gas Orbiter) to show which places it occurs. Then would come a lander, and ground truth would follow.

[marsbug]

Barring instrument faults on either the rover or orbiter in question, three scenarios pop into my head: Either the methane is somehow very well isolated to a higher region of the atmosphere, the lifespan of methane in the martian atmosphere is much shorter than previously believed, or some unrecognised factor in the equation has changed. Could Mars Express re-take the atmospheric methane measurements?

[Phil Stooke]

A fourth scenario occurs to me. The methane doesn't exist.

Phil

[Explorer1]

Yes, that is technically possible as well. It would mean the Mars Express and Earth observations are somehow flawed.

[siravan]

The earth based observations were always somewhat suspect, because they had to account for the methane in earth atmosphere, which was estimated based on some models. The end result was subtracting two large numbers and showing the difference was small, but different from zero.

[djellison]

There are good reasons to doubt both the ground and the MEX PFS based observations - this paper takes them to task thoroughly.
http://faculty.washington.edu/dcatling/Zah..._CH4_Doubts.pdf

[nprev]

Given that methane decomposes rapidly when exposed to UV this finding to me implies that any methane in the atmosphere (if there ever is a significant amount of it) is very transient, and most likely related to occasional geological events.

We need a couple of seismometers on Mars BAD.

[mcaplinger]

Given that methane decomposes rapidly when exposed to UV this finding to me implies that any methane in the atmosphere (if there ever is a significant amount of it) is very transient...

Are you suggesting that there was methane when MEx looked, but there isn't any now? The lifetime of CH4 in the atmosphere is short, but not that short (hundreds of years.)

Occam's Razor suggests something other than transience.

[Explorer1]

Well, Insight's arrival will tell us a great deal more about the geological processes, if any, that continue. Like I said before it would be best to wait for the dedicated trace gas hunters and their results to weigh in conclusively on causal factors.

[ngunn]

It's a long shot, but there is one other way to reconcile detection of a substance from the outside but not at the surface. We are talking about very small quantities. Perhaps it is present in the upper atmosphere but not lower down. How much mixing is there? Maybe it forms at altitude and is quickly desroyed there. Maybe it arrives from comets?

[nprev]

Are you suggesting that there was methane when MEx looked, but there isn't any now? The lifetime of CH4 in the atmosphere is short, but not that short (hundreds of years.)

Occam's Razor suggests something other than transience.

Not implying that, and I agree. I think that any significant amount of methane from ongoing seismic activity would result in a concentration well above what was observed by MSL. However, there may be VERY local and small-scale releases from inorganic sources from time to time.

Biggest bummer here to me is that this finding also presumably constrains the possibility of hot springs; that's been something I'd hoped we'd find somewhere someday. Looks even more unlikely now.

[serpens]

If the ground based / Mars Express methane measurements were correct then we would have the really weird scenario of highly concentrated (for Mars) local releases of methane in limited areas over an exceedingly short timeframe that then just as mysteriously disappeared due to some unknown process unique to Mars. No known process could remove methane with an efficiency so much greater than on Earth where the efficiency of methane loss should be far greater. The interpretation of the data has been the subject of vigorous debate for some years and now Curiosity has again shown the advantages of ground truth.