Mars Exploration Rovers (MER)

C M Edwards · 2005-06-28 08:08:07

Those are not pebbles, IMO, they closely resemble the blueberries....

I suspect any sort of small pebbles would fill the same role under these conditions. So I'll just concede that this gravel is almost certainly hematite blueberries (the ubiquitous pebbles of Meridiani), and redirect your attention to the small cracks in the imager photos.

I said they're drying cracks, but they could just as easily be due to some sort of thermal weathering or mechanical shock. Please set that aside for a minute. The important thing to realize about these cracks and depressions is that they are not filled in.

These photos were taken at the base of a dune of windblown dust. Dust blows everywhere on Mars. Nearby is Purgatory, a concentration of dust (supposedly) so fine that a six-wheeled RC car can barely dig itself out, and that no doubt blows everywhere just like all the other dust, only faster.

So why aren't these cracks filled with dust like every other half-way level soil surface? And why would there be any depression near those pebbles/blueberries?

Obviously there hasn't been time to fill them. Either they're very young, or there isn't as much loose dust in this area as our terrestrial models would have us believe. Or a little of both.

I'm also very interested by the expanse of apparently similar terrain south of the rover.

I smell water, and I think the odor is wafting from the south! Opportunity needs to finish up here and head that way. I also think MOC pictures of that area should be re-examined for evidence of recent water vapor outgassing. Does anyone know if Mars Express has examined that area with its spectrometer yet?

Rxke · 2005-06-28 11:28:25

Good point!

It's dust-devil season out there.
There's clearly an active cycle on-going there.

What kind of cycle? As a total amateur I'd say very probably water re-lated, it's too hot for CO2 to change states. You only have CO2 gas. So it must be water.
These depressions could be little 'cave-ins':

I mean: suppsose there's subsurface moisture, slowly seeping upwards (capillarity) but once it comes up close enough to the surface, it either evaporates or sublimtes, during the day, leaving a 'rotten' structure, a matrix of solids and holes. Eventually the 'roof' caves in at some places.
Could explain the caking too: salt getting dissolved during the moments there's a possibility of liquids at/close to the surface, when it dries (day) you get a crust.

aldo12xu · 2005-06-28 23:06:46

The process that Rxke is describing is similar to what has been proposed for the formation of duricrust, except that the fluid moving up through the soil contains salts/sulfates in solution. When fluid sublimates, the sulfates act as a cement and create a hard upper surface. Perhaps at Pergatory the soil below the duricrust was very much uncosolidated and so when Opportunity broke through the duricrust, it got jammed in the looser material.

There's a more detail discussion of duricrust on my site below.

I've also just summarized press releases and abstracts discussing Burns Cliff and the evidence for flowing water from cross-bedding features.

The links to all articles on my homepage.

Cheers,
Aldo.

Rxke · 2005-06-29 05:35:54

Um. Somehow I omitted the word 'salts' but in my mind it was the salts acting as 'glue' for the upper-layer, crystallizing out only at the surface, because of the heat, etc.

Palomar · 2005-06-29 15:13:39

http://www.space.com/missionlaunches/05 … tml]Update on Spirit and Oppy

*Oppy's still carefully checking out "Purgatory Dune."

Spirit is perched on the south side of Husband Hill. It's accomplished several drives in excess of 65 feet recently. One driving spurt resulted in the addition of 10 feet of elevation during the climb.

There's also a link in the article to another dust devil captured by Spirit.

One of the major questions facing Spirit is whether they'll have it go for the summit of Husband Hill.

Our MERs are still doing so well.

--Cindy

reddragon · 2005-06-29 17:54:54

I may be wrong, but it looks to me like the pebbles in CM's last two photos have broken through some sort of crust. It is possible that the rover precipitated a small rock slide (pebble slide) during it's maneuvering and thus these holes were formed only very recently and have not had time to fill in. This is hard to judge since from the microscopic imager photos I can't tell if the area is at the bottom of any sort of slope.

As for what the light material is, it could be ice, but I'm going back to a theory of CM's (top of page 9 of this thread, from May 12)

I have a wild guess as to the composition of Opportunity's potential new home: Freeze Dried Salt
A patch of salt, previously saturated with water, will create a crushable matrix of fine particles when freeze dried. The salt patch will hold its original volume until disturbed, but readily grind down to a fine dust when a wheel is rolled over the top of it. That would explain the rover team's inability to find a soil simulant that will settle properly - a freeze dried formation would never have settled at all. It's possible that this is what Opportunity is now stuck in.

This would be a light material that would have a somewhat crusty texture, but that a falling pebble could punch a hole in. This may simply be due to pixelation, but I notice that the pebbles appear to possibly have little specks of something on them. This could be explained if they rolled down through salt deposits. I would also draw attentioin to CM's first picture which shows objects that appear to be not pebbles, but rather clumps. These could be clumped salt.

Of course, ice is also a possibility. However, I do not think that water has frozen around the pebbles. If this were the case, it would likely come right up to them in all places and cover them in some and the crack marks would not be explained. The pebbles could have fallen and broken through the ice, but this would assume that the ice was fairly weak and thin, and thus at relatively high temperatures, and that there was liquid water underneath, not very likely. Also we are talking about a rock slide on a scale of inches probably, thus it will not have much force.

Another possibility is a mixture of salt and ice, or even of salt and liquid water (which would be especially clumpy), although this last seems unlikely.

C M Edwards · 2005-06-30 14:20:07

For comparison, here are microimager shots of soil disturbed by the rover.

http://marsrovers.jpl.nasa.gov/gallery/ … .HTML]This one was taken inside the earlier rover tracks.

http://marsrovers.jpl.nasa.gov/gallery/ … .HTML]This one is immediately adjacent to the earlier rover tracks.

There's an imprint where the imager packed the soil in both photos. Only the second shows a section of "undisturbed" soil, though it's apparently covered with a petina of dust kicked up by the rover as it passed and the original soil surface is not visible.

The cracking is just as clearly visible in the soil packed and ground up by the rover wheels as it is in patches of undisturbed soil, only the edges are cleaner.

Hmm... That's odd. Would a salt crust do that?

[oops]Uh-oh. These images are adjacent photos taken near the same impression. One shows the top half of the circular imprint, the other shows the bottom. The undisturbed soil patch is clearly in some other frame. [/oops]

Palomar · 2005-07-01 06:02:49

http://www.spacedaily.com/news/mars-mer … tml]Update

*Oppy will soon be heading south. Squyres says this past week has been smooth sailing, everything going as they'd hoped. Two months after the initial incident with Purgatory Dune, they're ready to get Oppy really rolling again.

No, we haven't decided to turn tail and run away from Erebus Crater. But after a careful study of all the images we have, we've concluded that the best way to map a path to the south is to start by going north a little bit, and taking some pictures off toward both the east and the west.

As for Spirit on Husband Hill, the ground there is so hard Spirit is barely leaving tracks. Spirit will next study "Independence Rock" -- which is a piece of layered bedrock. That'll be this weekend, apparently.

--Cindy

C M Edwards · 2005-07-01 11:12:25

That's good news.

I'm starting to suspect they'll find recent water activity in the terrain to the south. Purgatory's fascinating, sure, but without further data it's just a unique pile of dirt.

C M Edwards · 2005-07-01 11:38:43

http://marsrovers.jpl.nasa.gov/gallery/ … HTML]Check out the salt crust.

C M Edwards · 2005-07-02 12:22:37

I'm going to retract another statement: Purgatory is slightly more than a pile of dirt, though we'll probably never see it.

Those gaps around the pebbles in those soil target images are almost certainly recent formations. Opportunity's examination of old rover tracks, "Berrybowl" and other formations has revealed that tiny holes in a dune face like those around these pebbles should have a short lifetime, even in a patch of duricrust. Those gaps are certainly less than a few decade old, and probably were formed in the past year. Otherwise, they would be filled in. Some of them already are partially filled.

Now, for my next wild guess...

The most likely cause was gas under pressure. Volcanic vents and geysers clear similar gaps around rocks here on Earth, and create similar deposits of salts. There probably never was enough water percolating through Purgatory to call it a geyser, but I think it's a vent and those little high albedo patches with holes in them are the beginnings of calcera. Further, I think it's technically still active.

I've been over photos of the area, including the various panoramas. Preliminary blink comparisons of Purgatory images (i.e., switching between images of the same location that were made at different times, looking for changes over time) reveals no obvious vent activity at this time. Opportunity could sit at this location for a year and see nothing except some slowly filling holes. But it could see venting start again tomorrow. If it were worth sacrificing the rest of the rover mission just to find an active vent on Mars, I'd seriously recommend driving it right back into Purgatory and parking it there until it dies, just to continue observations.

However, that course isn't worth the risk, especially when we're equally likely to find an active vent just by moving south a few hundred meters.

As the rover's trip south continues, we should continue looking for formations like this, and should keep an eye out for fully developed calcera. We should also begin looking for active vent activity in this area.

If we find one, we'll have just found our first water well on Mars. As long as water vapor is coming out of the vent, it can be condensed and collected even if the water table is a kilometer down.

I am becoming more confindent that Opportunity has a chance to find a well on Mars.

Palomar · 2005-07-05 21:04:46

*I found the following interesting (to Americans anyway) tidbit of info earlier today. It concerns Spirit:

Last weekend, the robot stopped to look at an outcrop on the west side of "Husband Hill". All the target names under study were themed to "4th of July", said Larry Cumpler at the New Mexico Museum of Natural History and Science in Albuquerque. He is on the Mars rover science team.
Spirit's instrumented robot arm surveyed an outcrop named "Independence", while a specific target for science study was dubbed "Franklin". Other targets include some of the other signers of the Declaration of Independence…and other spots were named after various types of fireworks, Crumpler told SPACE.com.

http://www.space.com/missionlaunches/05 … tml]Source

--Cindy

aldo12xu · 2005-07-06 06:32:54

New route maps posted, updated to sol 530 for Spirit and Opportunity to sol 480. Summit 2 on Husband Hill is "only" 125 metres away!!

http://marsrovers.jpl.nasa.gov/mission/ … _maps.html

rgcarnes · 2005-07-06 09:29:00

For those of you who don't haunt the image pages of the Lyle site pertaining to the rovers, I think you might find the following image from the microscopic imager interesting. It's the strongest indication of sizable crystals I've seen. They seem to have a cubic growth habit of some type.

Lyles]http://www.lyle.org/mars/imagery/2M173592641EFFACAQP2977MM2M1.JPG.html]Lyle's Mars image page

This is from the Spirit rover.

Yang Liwei Rocket · 2005-07-12 08:17:52

National Geographic with the NASA / JPL rover
http://www7.nationalgeographic.com/ngm/ … media.html
Mars rovers 3-D real videos of Spirit and Opportunity

Palomar · 2005-07-12 09:36:11

National Geographic with the NASA / JPL rover
http://www7.nationalgeographic.com/ngm/ … media.html
Mars rovers 3-D real videos of Spirit and Opportunity

*Cool. I'll check that link out.

Spirit update:

Over the Fourth of July weekend, Spirit completed a robotic-arm campaign which had some surprising results. It turned out that targets at "Independence Rock" seem to have less iron than expected. This result prompted the science team to take a closer look. On sol 536 (July 6), because the grinding teeth on the rock abrasion tool are worn, the rover team decided to remove some of the surface area by scuffing it with the front left wheel.
Sol-by-sol summaries:
Sol 532 to 535 (July 2 to July 5, 2005): Over this period, Spirit took data with the alpha particle X-ray spectrometer and the Mössbauer spectrometer and made observations with the microscopic imager and remote-sensing instruments. The results motivated a decision to do more work with the robotic arm.
Sol 536: The scuff today worked nicely, except that it did not seem to remove a whole lot of material from the place Spirit scuffed. Overall, the rover only scuffed 9 radians on the rock surface, which is less than 1.5 wheel revolutions. Engineers received no errors during the drive, and it looked like all drive-related telemetry was within acceptable parameters.
After the scuff and before Spirit moved back to its original position, the rover took a picture with the hazard avoidance camera in order to see the effect the scuff had on the wheel treads.
The rover team favored the forward wheel rotation because this creates a torque that needs to work against gravity in order to rotate the rover body.
Sol 537 (July 7, 2005): Spirit started an "Independence" 360-degree color panorama. This mosaic will be run all weekend.

So Independence Rock doesn't seem to have as much iron as expected. I noticed their mention of the grind teeth on the rock abrasion tool is getting worn...no surprise, I suppose.

Am looking forward to that Independence panorama; haven't seen it yet (not sure if that last sentence means it's been run or will be run...).

--Cindy

Palomar · 2005-07-13 14:43:08

http://www.spacedaily.com/news/mars-mer … tml]Update
*Oppy will soon be heading south. Squyres says this past week has been smooth sailing, everything going as they'd hoped. Two months after the initial incident with Purgatory Dune, they're ready to get Oppy really rolling again.

*Seems I've read a handful of articles insisting Oppy is going away from Purgatory Dune (aka "Purgatory Ripple" apparently), yet there's a http://www.spacedaily.com/news/mars-mers-05zzx.html]new article which says Oppy's still been hanging around the area. ??? This has been going on for nearly half a month already. Did I miss something? I figured Oppy would be a few feet distant and moving permanently away already. :hm: But I'm keeping track of so much stuff (happily)...maybe I overlooked something. Just seems like there's this continual "Oppy's going, moving away from Purgatory Dune, we're rolling again"...and there it still is.

?

--Cindy

C M Edwards · 2005-07-14 13:24:22

As of Sol 516, they were poised to start driving away but had not yet done so. That was several days ago, though - no updates since.

Yang Liwei Rocket · 2005-07-16 16:35:26

Mars mission and blog

http://athena.cornell.edu/news/mubss/]h … ews/mubss/

Steve Squyres some updates on the plan for the Martian rovers

Palomar · 2005-07-18 09:15:58

Mars mission and blog
http://athena.cornell.edu/news/mubss/]h … ews/mubss/
Steve Squyres some updates on the plan for the Martian rovers

*Yep. I just now saw the same info in a different article. Oppy is now aprox 90 meters south of Purgatory Dune. Thank goodness. :up:

Driving in this stuff is an interesting challenge. We are literally in a maze. The easiest going is to stay within the troughs between the ripple crests, which run roughly north-south. So the best way to make southward progress is to follow a trough until it peters out, make a "lane change" to a nearby trough, and continue onward.

But there's a catch. The entrance to the Erebus Highway is not straight south of us, along the troughs... it's a bit off to the east, on a heading closer to 160 degrees or so. That means that in order to get to it, we'd have to head off cross-country, going up and over quite a few ripple crests. That's do-able, but it's also a lot slower than just bombing straight south down a nice trough.

Please, please don't get stuck again. :-\ {{knock wood}}

Let's keep Oppy looking for that love getaway. :;):

--Cindy

Palomar · 2005-07-19 13:30:43

http://www.space.com/missionlaunches/05 … html]Those plucky MERs...

*...are each heading for new science objectives. The info about Oppy is a repeat of what YL Rocket posted.

Spirit doing great. Mentions "very strange stuff" in connection with "Independence Rock" (layered bedrock). Apparently one of the oddest things yet seen at Gusev.

MER energy levels are up. Skies above clearing; experiencing more dust cleaning.

--Cindy

Shaun Barrett · 2005-07-19 17:42:51

Can't wait to hear Dr. Squyres' interpretation of the low-iron bedrock Spirit's been investigating. I love a good mystery.

Palomar · 2005-07-21 06:22:03

*Hi Shaun: Yep.

Update on Oppy. I'm concerned about this MER and the potential for it getting stuck again -- what with all that talk about it being in a maze of sorts. It's making progress toward Erebus Crater (what is the correlation to the Erebus Highway?); 187 feet traveled as of July 15, over 4 days' time. Sounds like Oppy's going full steam ahead (relief). Is driving down ripple troughs and they've got plenty of safety checks. Check out especially Sol 523:

OPPORTUNITY UPDATE: Edging Toward 'Erebus' - sol 518-524, July 15, 2005:

Opportunity made impressive progress toward "Erebus Crater" during the week. Four sols of driving totaled 57 meters (187 feet), while slipping less than 10 percent on each drive. A longer drive was plotted for the fifth day.
The rover has continued to drive down ripple troughs. We have a series of checks in place to prevent excessive bogging down, including, tilt, roll, pitch limit checks, current checks and slip checks (set at 40 percent slip).
We look forward to more progress south over the coming week.
Sol-by-sol summaries:
Sol 518 and 519 (July 9 and July 10, 2005): In light of extensive driving and data collection the previous week, these sols were designed to conduct light remote sensing, recharge batteries, and downlink data to free up memory space on the rover.
Sol 520: The uplink team designed a 16-meter (52-foot) drive. Opportunity completed 10.34 meters (33.92 feet) of the drive before tripping a mobility-goal error. There was a bad position estimate given to the onboard slip-checking software, so it incorrectly thought the rover was 0.5 to 1 meters (1.6 to 3.3 feet) back from its actual position, thus making insufficient progress because it thought it was slipping excessively. However, analysis by the mobility team on the ground determined the true slip, and we were "go" to drive the following sol.
Sol 521: Opportunity completed a successful drive of 15.2 meters (about 50 feet) without any faults.
Sol 522: The rover completed another successful drive of 15 meters (49 feet), with only 6.4 percent reported slip.
Sol 523: We drove 16.2 meters (53 feet) of a planned 20-meter (66-foot) drive. The drive stopped short because onboard slip-checking software was having difficulty tracking the rover's rear wheel tracks, which are used as a reference point to monitor the slip. Opportunity does not want to keep trying to drive if it is unsure of how much it is slipping, so the team sets a limit to this failure count. This prevents bogging down in the terrain.
Sol 524 (July 15): The uplink team planned a drive of 27 meters (89 feet). The drive plan is the first in Opportunity's current terrain using a combination of short segments of blind driving followed by shorter segments (40 centimeters, or 16 inches) of slip-check driving. This drive strategy is designed to allow us to drive farther by using a less time-consuming drive option while still verifying every 5 meters that we are not bogging down.
Odometry total after sol 523 drive: 5464.09 meters (3.39 miles).

--Cindy

P.S.: Most recent report on Spirit is lots of gusting winds (and dust devils) at Gusev.

C M Edwards · 2005-07-21 13:31:44

Update on Oppy. I'm concerned about this MER and the potential for it getting stuck again -- what with all that talk about it being in a maze of sorts.

Yeah, me too.

Of course, it has driven for kilometers over similar terrain and encountered only one dune like Purgatory, so in theory it could drive for kilometers more before the team has to worry about another one. Crossing a dune every now and then shouldn't be a nail biter.

And then there's the fact that every time it gets stuck like that is an opportunity to test my theory (no pun intended ) about the veriegated terrain to the south. I should feel guilty about the little twinge of anticipation that gives me, but the anticipation drowns the guilt out. :?

Palomar · 2005-07-25 07:32:33

http://www.spacedaily.com/news/mars-mers-05zzzc.html

*Spirit scampering up Husband Hill. Spirit covering 30 meters per Sol via new driving techniques.

Did someone mention Voltaire??

As always, we've been having fun lately naming things. In our big Independence Day panorama, all the rocks were named after different kinds of fireworks. Since then, starting around July 14th, we've been using mostly French names, in honor of Bastille Day. As always, we've been having fun lately naming things. In our big Independence Day panorama, all the rocks were named after different kinds of fireworks. Since then, starting around July 14th, we've been using mostly French names, in honor of Bastille Day. So the outcrop we've just arrived at has been named Voltaire. After we're done with Voltaire, we'll resume the push to the summit.

--Cindy

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