MSL Meteorology Results |
MSL Meteorology Results |
Nov 16 2012, 01:59 AM
Post
#1
|
|
Member Group: Members Posts: 611 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
Evidence of the diurnal pressure cycle in the radiation detector data, and the suggestion of dust devil encounters in the meteorology package (REMS) data.
http://www.jpl.nasa.gov/news/news.php?rele...elease_2012-361 Suggests 'over 20' events with one or more in-situ signatures of dust devil encounters (e.g. pressure drop, wind direction change etc.) In 12 weeks that means only ~0.25 events per day, which is pretty low compared with Phoenix and Pathfinder (more like 1-3 / day, depending on event threshold e.g. see http://www.lpl.arizona.edu/~rlorenz/dustde...ssuredrops.pdf) but we'll need to wait and see this published properly to understand what thresholds were used and what correction factors for observation duty cycle need to be applied. |
|
|
Nov 16 2012, 10:49 AM
Post
#2
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
Can we infer anything about the diameter/size of these dust devils ? The press conference slide showed only the wind direction and pressure changes over time but nothing about horizontal wind speed. The DD diameters at Pathfinder, Phoenix(and Gusev ?)varied by over an order of magnitude but that covered an entire DD season( 3 seasons at Gusev, 80 days for PF). Have we reached the peak DD season at Gale yet ?
|
|
|
Nov 16 2012, 11:11 AM
Post
#3
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
In the press conference it was stated that the RAD levels at the surface were about 50% of cruise values. Is it the dust in the atmosphere that is responsible ? If so the RAD levels should be more sensitive to atmospheric opacity than to surface pressure. Is tau being measure ? If so, from the rover or from orbit? It will be interesting to see what happens to the RAD levels during major dust storms.
|
|
|
Nov 16 2012, 11:17 AM
Post
#4
|
|
Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
At the surface 50% of the nominal cruise radiation is being blocked by Mars. It doesn't sound like the atmosphere and/or dust is doing much at all.
Andy |
|
|
Nov 16 2012, 11:27 AM
Post
#5
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
|
|
|
Nov 16 2012, 12:26 PM
Post
#6
|
|
Member Group: Members Posts: 293 Joined: 29-August 06 From: Columbia, MD Member No.: 1083 |
Also interesting that the semidiurnal tide seems to be significantly weaker than the diurnal (just from eyeballing), in contrast to some of the other landers. I haven't looked closely enough yet to see if this is a seasonal effect, but this should be the time that both tides have higher amplitude as Mars is approaching equinox.
|
|
|
Nov 16 2012, 01:41 PM
Post
#7
|
|
Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
Not simply, Eyesonmars - the RAD "telescope" points upwards. I can't find out how directional it is. But the higher energy cosmic rays will be Mars-shielded.
Andy |
|
|
Nov 16 2012, 03:17 PM
Post
#8
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
Andy, the detector has a 65 degree cone of view normal to the rover body ( upward hopefully( i'm kidding))
Here is a quote from the Nov 15 press conference that is the core of my confusion. "We see a definite pattern related to the daily thermal tides of the atmosphere," said RAD Principal Investigator Don Hassler of the Southwest Research Institute's Boulder, Colo., branch. "The atmosphere provides a level of shielding, and so charged-particle radiation is less when the atmosphere is thicker. Overall, Mars' atmosphere reduces the radiation dose compared to what we saw during the flight to Mars." Hence my original question. What is it about the atmosphere that provides the shielding ? The gas or the dust? It should be easy to answer once we get RAD data over a wider range of tau and pressure values |
|
|
Nov 16 2012, 03:46 PM
Post
#9
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
http://marsmobile.jpl.nasa.gov/msl/multime...s/?ImageID=4874
In the above image, from the press conference, it looks like the lowest areas are dominated by dark basaltic dunes. I would think that this would work against typical slope winds. From personal experience living on a mountain slope the diurnal mountain valley breeze is completely suppressed after the mountain slopes get a fresh snow cover when the valley does not. In other words the albedo induced thermal wind and daytime slope winds cancel each other out. Loosely speaking |
|
|
Nov 16 2012, 03:57 PM
Post
#10
|
|
Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
What is it about the atmosphere that provides the shielding ? The gas or the dust? I think you'll find that the mass of the dust is negligible from a shielding perspective. From http://citeseerx.ist.psu.edu/viewdoc/downl...p1&type=pdf if you precipitated all the dust in the middle of a severe dust storm it would only form a layer 18 microns thick. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
|
|
|
Nov 16 2012, 04:10 PM
Post
#11
|
|
Member Group: Members Posts: 507 Joined: 10-September 08 Member No.: 4338 |
Still nothing on humidity?
|
|
|
Nov 16 2012, 04:26 PM
Post
#12
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
It is amazing that only 18 microns of dust can completely obscure the surface. I guess the extremely small particle size is the key. So then we should not see the RAD values affected by major dust storms. Still, it will be interesting to watch.
I suppose they rigourously modeled and tested how dust settling on the detector affects results. So i guess that it doesnt matter too much if that 18 um is in the atmosphere or on the detector |
|
|
Nov 16 2012, 09:05 PM
Post
#13
|
|
Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
Dust storms will do other things - not just put more dust in the atmosphere. That atmosphere will get warmer, and taller. It's a complex interplay. There will be an effect, I'm sure.
|
|
|
Nov 16 2012, 09:49 PM
Post
#14
|
|
Senior Member Group: Members Posts: 1045 Joined: 17-February 09 Member No.: 4605 |
Since the comparison is cruise to surface intensity, does anyone know if there is any residual magnetic field loop in the vicinity of Gale that would provide a localised magnetosphere effect? If so then would atmospheric pressure changes affect the level of local ionization and hence deflection?
|
|
|
Nov 16 2012, 09:59 PM
Post
#15
|
|
Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
Still nothing on humidity? A tongue in cheek answer is that the relative humidity is always 100% at sunrise and 0% at midday. But I'm sure you mean absolute humidity. If/When we do get numbers they will be only a few precipitable microns. Typical earth values are a few precipitable centimeters by comparison. |
|
|
Lo-Fi Version | Time is now: 3rd June 2024 - 10:53 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |