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ToSeek
2004-Jun-08, 05:59 PM
Only six days after the last one (which was about a month after the one before). Is there a reason? When will Opportunity enter Endurance Crater? When will Spirit reach the Columbia Hills? And are there any more science babes at JPL? These and other important questions will be answered shortly!

ToSeek
2004-Jun-08, 06:05 PM
Dramatis personae:

Firouz Naderi - Manager of Mars Exploration Program at JPL
Steve Squyres - PI
Johannes Brueckner - scientist
Jim Erickson - Opportunity deputy program manager
Randel Lindemann - rover mobility engineer

All guys, but some big guns. :(

Both rovers have mostly been in transit, now approaching next "port of call."

Spirit approaching 1-year anniversary of launch (Thursday), has gone over 3 kilometers, now at foot of "unreachable" hills. Some intriguing discoveries.... Plans for extensive science campaign at base of hills.

Opportunity to look at layers beneath ones seen at Eagle, rover will go into Endurance crater to look at them. Some possibility of not being able to get out.

ToSeek
2004-Jun-08, 06:12 PM
Squyres: unprecedented events about to happen to rovers, most significant science discovery yet from Spirit.

Hints of salts in Gusev crater, coatings of salts on rocks, veins running through rocks. Trench dug a couple hundred meters ago, did analysis with APXS, evidence of salts = past water.

Brueckner: Graph showing magnesium/sulfur ratio for soil, two trenches. Top layer of sol 140 trench much like surface soil. Side of trench shows high concentration of sulfur, way out from average previously seen. Straight line in sol 140 measurements, consistent ratio. "Enrichments" in trenches.

Squyres: Correlation suggests magnesium sulfates = epsom salts. Side of trench is 15% epsom salts - "That's a lot!" May be talking about a situation where water percolated through the surface, dissolved stuff out of rocks, gets to surface, evaporates away, leaves salt deposits. Doesn't have to be large amounts of water, can be small amounts.

ToSeek
2004-Jun-08, 06:14 PM
Squyres talking about Columbia Hills: Just about completed an unprecedented traverse, only about 100 meters away. Still grappling with how to approach science investigation. First: what is this stuff made of? "Don't have a clue what these hills are composed of." Approach hills, look for outcrop or piece of rock that's fallen down, then use instrument arm to investigate.

ToSeek
2004-Jun-08, 06:18 PM
Squyres talking about Endurance Crater: top layer looks like same stuff as Eagle, sulfates, final layer of water activity. Lower layers will show the earlier part of the story.

Layering is extensive horizontallly over a broad area - previous image a cliff, rover can't handle. Much shallower band being shown now. Here we have the ability to drive down into the crater and get arm onto stuff. Rock looks different from rock above it, indicates different environmental conditions. By looking at boundary can see what caused environment to change.

Could potentially drive long distances out into countryside to find where layers come to surface. But Meridiani is very flat. Looking down slope where will try to enter crater. Jumbled up newer sulfate rocks, will go in and down these rocks to go to older layers.

ToSeek
2004-Jun-08, 06:23 PM
Erickson: Rovers in good shape but winter taking toll on power.

Opportunity will crest hill, go down into crater, take measurements, and then back out. Will look at what rover wheels do to crater. Very cautious, straight in, straight out approach. Arrive at target around Tuesday of next week. Examine interactions between wheels and soil/rock.

Randy: Talking about testing. Rovers not just robots but "interplanetary all-terrain vehicles." Job has been to assess risk of driving into Endurance, only concern is ability to drive back out again.

Showing video of rover testing: running test rover over 25-degree platform. Unlike pre-launch testing, picked out some flat stones that they think are like the ones at Meridiani and drove rover over them to see how well rover would go. Added sand and simulated blueberries. Found that rover is much more capable over this terrain than in pure-sand terrain that gave trouble getting out of Eagle crater.

ToSeek
2004-Jun-08, 06:39 PM
Question time:

Aviation Week: Tested at 30 degrees? Characterized slopes accurately?

Slopes at entry are about 20 degrees, will avoid steeper ones. Confident that angle is what they think it is. 25 degrees steeper than tested pre-launch, were talking about 30 degrees because some slopes initially looked that way. Figure out rover margin by holding rover back ("fish-scale test"), decided rover could just barely go past 30 degree mark. Could go past 25 degree mark, but with caution.

(My question: are they compensating for Mars gravity? Guess if the test rover is lighter, that would do it.)

Squyres very impressed with how rover handled slick-looking rocks. Aluminum wheels did well on "flagstone" surface.

Leonard David, space.com: Figure out more about water in Gusev?

Squyres: think there was lake in Gusev, but since then a lot has happened: impacts, volcanoes, etc. Puzzling over distribution of stuff. More and more salt as get closer to hills. Could be correlation, might just be chance (not enough trenches to be sure). Need to dig trenches once up in hills.

Contrast water history Spirit vs. Opportunity.

Salts at Gusev are starting to connect together stories at two landing sites. Speculation: evaporation at both places, just on a much larger scale at Meridiani, lots of water, liquid water at surface, lake of brine, actual flowing water and currents. Just a little crust at Gusev, many layers at Meridiani. Water may be very acidic, sulfuric acid. Very different appearances but may have underlying similarities.

Florida Today: What intrigues you most about hills, see evidence of water?

Squyres: May see bedrock, bedrock very good at preserving evidence (rock came from that same place). Got some hopes that hills will show evidence of lake, no actual evidence yet.

Aviation Week: What's lost if rover gets stuck?

Biggest risk is that we're "Gonna get stuck in the candy store for the rest of the mission." Would lose chance to go kilometers to south to find more of the same stuff that we know is in the crater. Other things to look at: wind ripples, pebbles. But an awful lot of interesting stuff in the crater.

Expect to go in crater, come back out, head out across plains. But if not, plenty of wind ripples in bottom of crater.

Kilometers to south: etched terrain. Speculating that that's where the rocks have been eroded enough to possibly expose the layers they want to look at, but again the layers are right in the crater.

01101001
2004-Jun-08, 07:00 PM
(My question: are they compensating for Mars gravity? Guess if the test rover is lighter, that would do it.)
Story about Earth tests here (http://marsrovers.jpl.nasa.gov/spotlight/opportunity/b20_20040309.html).

The test rover on Earth is the same size and mass as those on Mars. Hmm, wait... the article says "same weight". The Earth model is called "Lite" because it doesn't have the IDD, but I wonder if they are same weight, under the two different gravities, or the same mass. Does "Lite" to them mean less capability or less mass? Hmm...

Well, one thing they have going for them is experience. They made predictions for getting out of Eagle crater based on Earth tests, and then did the job, observed the results, measured the actual slippage, to compare them back to the test predictions.

The biggest unknown seems to be the precise characteristics of the soil, but builders sand surprisingly echoed the actual performance of the Meridiani soil.

And, now, the tests for Endurance involve a 80-90% flagstone base, with sand filling between and upon, and simulated spherules lightly glued on, so they are really trying to duplicate the soil conditions. It sounded like they have enough margin to have very high confidence of climbing back out the 25-degree slope.

Swift
2004-Jun-08, 07:29 PM
ToSeek, once again, thanks for updates. The mag sulfate is really exciting. It sounds a lot like evaporated lakes on earth.

ToSeek
2004-Jun-08, 11:19 PM
Accompanying press release, as usual:


Dwayne Brown (202) 358-1726
NASA Headquarters,Washington, D.C

Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Release: 2004-144 June 8, 2004

NASA Rovers Continue Unique Exploration of Mars

NASA's Mars Opportunity rover began its latest adventure
today inside the martian crater informally called Endurance.
Opportunity will roll in with all six wheels, then back out
to the rim to check traction by looking at its own track
marks.

"We're going in, but we're doing it cautiously," said Jim
Erickson, deputy project manager for the Mars Exploration
Rovers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Barring any surprises, Opportunity will enter the stadium-
sized crater Wednesday for two to three weeks of scientific
studies.

"NASA has made a careful decision. The potential science
benefits of sending Opportunity into the crater are well
worth the calculated risk the rover might not be able to
climb back out," said JPL's Dr. Firouz Naderi, manager of
NASA's Mars Exploration Program. "Inside the Endurance
crater waits the possibility for the most compelling science
investigations Opportunity could add to what it has already
accomplished. We have done the ground testing necessary to
evaluate the likelihood of exiting the crater afterwards."

"Spirit and Opportunity are well into their bonus periods
after successfully completing their three-month primary
missions in April," Naderi said. "Both rovers are starting
new chapters. Spirit is within a stone's throw of Columbia
Hills, and Opportunity is entering the crater."

Dr. Steve Squyres of Cornell University, Ithaca, N.Y., the
rovers' principal investigator, said, "We expect the science
return of going a short way into Endurance to be very high."
The target for inspection within the crater is an exposure
of rock layers beneath a layer that corresponds to rocks
Opportunity previously examined in the shallower Eagle
crater, where the rover landed in January.

The sulfur-rich layer seen in Eagle yielded evidence that a
body of gently flowing water once covered the area. The
underlying rock layers come from an earlier period.
Opportunity's observations from the rim of Endurance already
have shown their composition differs from the Eagle crater's
layers.

"If there was a change in rock type, there was a change in
environment," Squyres said. "This unit will tell us what
came before the salty water environment the Eagle crater
unit told us about. We want to get to the contact between
the two units to see how the environment changed. Is it
gradual? Is it abrupt?" Even if the lower layers formed
under dry conditions, they may have been exposed to water
later. The water's effect on them could have left telltale
evidence of that interaction."

One section of the target outcrop is only five to seven
meters (16 to 23 feet) from the crater rim in an area dubbed
Karatepe. The rover team's plan is to get there, examine the
rocks for several days, and then exit the crater. Reaching
lower-priority targets, like at the bottom of the crater,
would entail driving on sand, with a higher risk of not
getting out again.

The strategy for driving on the crater's inner slope is to
keep wheels on rock surfaces instead of sand, said JPL rover-
mobility engineer Randy Lindemann. The team ran trials with
a test rover on a surface specifically built to simulate
Karatepe's surface conditions. "The tests indicate we have a
substantial margin of safety for going up a rocky slope of
25 degrees," Lindemann said. Opportunity's observations from
the rim at the top of the planned entry route show a slope
of less than 20 degrees.

Spirit, launched one year ago Thursday, has driven more than
3.2 kilometers (2 miles) inside the Gusev Crater. A trench
it dug in May exposed soil with relatively high levels of
sulfur and magnesium, reported Dr. Johannes Brueckner, of
Max-Planck-Institut fuer Chemie, Mainz, Germany. Spirit's
alpha particle X-ray spectrometer showed concentrations of
these two elements varied in parallel at different locations
in the trench, suggesting they may be paired as a magnesium sulfate
salt.

Squyres said, "The most likely explanation is water
percolated through the subsurface and dissolved out
minerals. As the water evaporated near the surface, it left
concentrated salts behind. I'm not talking about a standing
body of water like we saw signs of at Eagle crater, but we
also have an emerging story of subsurface water at Gusev,"
he said.

JPL, a division of the California Institute of Technology in
Pasadena, manages the Mars Exploration Rover project for
NASA's Office of Space Science, Washington, D.C.

For images and information about the Mars project on the
Internet, visit http://marsrovers.jpl.nasa.gov and
http://athena.cornell.edu .

harlequin
2004-Jun-09, 12:39 AM
(My question: are they compensating for Mars gravity? Guess if the test rover is lighter, that would do it.)

And for the amount of light falling on the solar array....

Irishman
2004-Jun-09, 06:06 PM
The test rover on Earth is the same size and mass as those on Mars. Hmm, wait... the article says "same weight". The Earth model is called "Lite" because it doesn't have the IDD, but I wonder if they are same weight, under the two different gravities, or the same mass. Does "Lite" to them mean less capability or less mass? Hmm...

Mars Team Description:

While Opportunity was cruising through deep space on the way to Mars, engineers on Earth tested the rover’s mobility using an engineering model of the rover of the same weight and size with identical wheels. Engineers affectionately named it the “SSTB-lite rover.” SSTB-lite stands for Surface System TestBed, and the lite means that this rover doesn’t have any of the appendages, such as the robotic arm, high-gain antenna, or panoramic camera mast assembly.

My interpretation of their description is the test rover has the same mass as the Martian rovers, but the appendages are replaced by dummy masses. "Lite" refers to less capability, not weight. Looking at the sample chart (http://marsrovers.jpl.nasa.gov/spotlight/opportunity/images/b20_Slip-Up-Slope_040302045337_br2.jpg) shown, the heading is "MER Rover Driving directly Up Slope on Dry, Loose Sand : Mars Wt". The "Mars Wt" bit at the end leads me to be that is an adjusted value for the difference in Earth to Mars weight.

Some concerns include the weight difference and how scaling the weight affects traction versus power. However, they used data collected from Eagle crater (and all data collected since) to refine the response model, so at least they are getting good feedback.


On February 18, the wake up song for Opportunity was ‘Body Movin’ by the Beastie Boys in honor of the 15-meter (49-foot) drive, which was Opportunity’s farthest distance to date. “We were off by less than 0.5 meters (1.6 feet) from our desired final destination, which is an error of about 3%. In contrast, Opportunity actually slipped between 10% and 17%, so without this slippage planning, we would have been off by as much as 2.6 meters (8.5 feet).

3% is pretty good, and that was pretty early on compared to now.

RGClark
2004-Jun-10, 09:03 AM
Only six days after the last one (which was about a month after the one before). Is there a reason? When will Opportunity enter Endurance Crater? When will Spirit reach the Columbia Hills? And are there any more science babes at JPL? These and other important questions will be answered shortly!

Is this archived anywhere?

Bob C.

Kullat Nunu
2004-Jun-10, 09:36 AM
Is this archived anywhere?

Bob C.

It's archived in Space.tv (http://www.space.tv/).