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May 28, 2005
Nothing really new at Meridiani. We're seeing slow, steady progress, at a
remarkably constant rate. For every meter of wheel turns that we
command, we get half a centimeter of actual motion.
It's been like this since the start of the extraction process.
We're typically doing 12 meters of wheel turns a day, and
typically seeing about six centimeters of motion. We'll get out
of here eventually, but it's a slow, laborious process.
At Gusev, though, the progress has been rather more satisfying.
We're starting to understand this place. What we've
got is a thick sequence of layered rocks, dipping gently
to the northwest. As you go up and down the sequence, there is
a remarkable diversity of textures. Some rocks, like
Watchtower, which we saw at Larry's Lookout quite awhile
ago, are massive. Others, like Keystone at Methuselah, are
finely laminated. Still others, like Keel at Jibsheet and
like a new one called Ahab that we've just found on the
eastern side of Larry's Lookout, have an unusual bulbous or
globular texture. So texturally, the rocks in this sequence
are all over
Despite the huge diversity in texture, though, all of these rocks have the
same chemical composition. Every single rock we've looked at
in this region shows a distinctive chemical "fingerprint" of
high titanium, high phosphorous, and low chromium. They're all
fundamentally made of the same stuff.
But then, despite the constant chemistry, the rocks show an
enormous range in how severely they have been altered. Alteration
is something we can assess with our Moessbauer spectrometer, and
the Moessbauer spectra of these rocks are incredibly diverse.
Keystone, for example, is only lightly altered, with plenty
of the mineral pyroxene in it. Paros, on the other hand (which,
like Ahab, is on the eastern side of Larry's Lookout) is one
of the most heavily altered rocks we've ever seen at Gusev.
And some of the most-altered rocks contain the mineral goethite,
which is a clear sign that their alteration involved water.
So what are we dealing with here? Our best bet is that this is
a stack of "volcaniclastic" rocks... granular rocks of volcanic
origin. Some of the rocks may have formed by violent eruptions,
followed by ashfall from the sky or hot, ground-hugging flows.
Others may have formed when volcanic deposits were
"reworked" by other processes, stirred up and redeposited.
The very constant chemistry suggests that all the layers in
the stack came from a common volcanic source.
We're still working out some of the implications of the
alteration. Is the alteration greatest at the bottom of the
stack and least at the top, indicating a decrease in
alteration processes with time? Or does the alteration
also vary laterally, with rocks of the same age that are
only tens of meters apart showing very different amounts
of alteration? This is the piece of the puzzle that we're
still struggling with, taking lots of Moessbauer measurements
and trying to work out stratigraphic relationships between
rocks in different outcrops. It's an important
it's related to what the water was doing.
And I wouldn't say that we're 100% convinced yet that these
are volcaniclastic rocks. While it seems like the best
explanation, we haven't ruled out the possibility that they
could have been formed by impacts. Impacts are violent
explosions too, and impacts certainly were happening on Mars
billions of years ago when these rocks formed. These don't
look anything like impact deposits on the Moon, but Mars
has an atmosphere, and back when these rocks formed it may
have had a more substantial one. So it's possible that
martian impact deposits could look like this too. We're
keeping our minds open to the possibility, and looking for
clues that might
settle it definitively.
Finally, an interesting side note. If some of the rocks
are highly altered and some lightly altered, but they all
have the same amount of phosporous in them, that suggests that the
phosphorous was primary. In other words, the phosphorous
was in the rock
before any alteration took place, not put there by the
alteration. When we first saw this high phosphorous
signature, all the way back at Wishstone five or six
months ago, our initial suspicion was that it was in
phosphate salts that had been deposited by water. But
it's looking now like this stuff was phosphorous-rich
from the git-go.
May 18, 2005
Gradual progress. To extract Opportunity from her little predicament,
we've commanded a total of 12 meters of wheel turns so
far... 2 meters, then 2 meters, then 4 meters, then 4 meters. We've
seen slow, steady progress each time. We're going to kick her into
a slightly higher gear today, commanding 8 meters of wheel turns,
and we'll see what we see. Optimism continues to run high.
At Gusev, Spirit has arrived at a safe standoff position for observing
the eastern side of Larry's Lookout. We're going to sit here and do
some serious Pancamming for a sol or two, and then we're going
to have to decide what comes next. There are a bunch of possibilities,
and we're going to have a very interesting time choosing among them.
May 16, 2005
Sorry I haven't done an update in awhile! I was on the West Coast
most of last week and my laptop died while I was out there, cutting
me off from the world for a little bit.
We have begun the extraction process at Meridiani. So far we've
executed three sols worth of activity. On the first one we simply straightened the
wheels, which worked fine.
The next two sols were executed over the weekend, and each commanded two
meters worth of wheel turns. We were pleased with the outcome of
those, too. The rover moved more than a centimeter in the
expected direction during each maneuver,
which was just the kind of behavior we were hoping for. (In fact, the
motion was actually more than I was personally expecting to
see this early in the game.) We clearly moved some soil in the
process, and there was an encouraging amount of clearing of
caked-up debris from between cleats on some of the wheels.
We'll be continuing to work at this over the coming week. Each
day, for the next few days at least, we'll command some number
of meters worth of wheel turns, based on the results we got
from the prior sol. Today we chose 4 meters, based on the good
progress that each of the 2-meter sols gave us over the weekend.
After that we may
keep it at 4 meters for awhile, drop it back to 2, or bump it up to something
even higher, depending on what we see.
Anyway, we're real pleased with the results so far, and we'll
keep chugging away, bit by bit, until we're out.
Over at Gusev, life is good. We've finished our work on Jibsheet,
the composition and texture of which both fit nicely into an
evolving story that we have on all the rocks here
on Cumberland Ridge. With Jibsheet done, we're now planning a
drive back toward Larry's Lookout. This will be a long one,
at least by Columbia Hills standards,
since it's mostly downhill we expect it to go pretty quickly.
The plan is to drive to a point that's on safe ground a few
meters shy of the east side of the Lookout. There are some
rocks there that lie stratigraphically older than anything we
have seen yet... in fact, they may be the oldest rocks that we
have yet seen at Gusev. We'll look at them from a safe distance
first, and see what we see. After that, we've got some
decisions to make. Back when we had lots of dust on the solar
arrays, we had to get around to the south side of Husband
Hill quickly or the rover would die. With clean arrays now,
though, it's a different world, and we've got a lot of options.
We're going to be making some very
interesting strategic decisions with Spirit over the next
couple of weeks.
May 7, 2005
Okay, we're going to be ready soon to start making our move at Meridiani.
This has been a long, hard week of testing. We tested with one mix of
materials, decided it wasn't quite nasty enough, and then made the mix
nastier and tested again. We tested getting the rover stuck and
then unstuck in a bunch of different configurations, some of which
we think were worse than the one we've gotten ourselves into
on Mars. The goal
of this kind of testing is to be "conservative"... to test under
conditions that are at least as bad as -- and preferably worse
than -- what you're dealing with in reality. You can see
of one of the test setups on the JPL MER web site, though the
pictures don't really do justice to all the work that was done,
or to all the different kinds of tests that were run.
Then, once we'd done the
testing, we brought in a panel of experts from outside
the project to give us an independent review of whether
we'd done things right or not. Like conservative testing,
outside reviews are standard operating procedure in the space biz.
So soon it'll be time to put what we've learned into
action on Mars. We've learned quite a bit, and one of the things
that we've learned is that it can take a lot of wheel
turns to move the rover from a configuration like the one we're
in. And while it's tempting to go for it all in one shot,
the smart approach is to be cautious about it and do the job in
small steps. So that's what we're going to do.
And here's something to keep in mind: The early steps
in the extraction process don't look like much. The wheels turn
and turn, and even though you're making crucial progress, moving
soil bit by bit beneath the wheels, the rover itself hardly
for quite awhile.
So when we do begin the extraction process and you see lots of
evidence for wheels turning on Mars but not much movement
by Opportunity, don't
worry... that's exactly what we're expecting. Like the testing,
this is going to take awhile.
Over at Gusev, we've finished up our work on Methuselah and
done a nifty, complicated little one-sol drive over to a close
standoff distance from Jibsheet. The purpose of the
standoff is to let us take some good Pancam images over the
weekend to plan our attack, just like we did a couple of
weeks ago with Methuselah. (And, in the meantime, it also lets
us do some
IDD work on soil, which we haven't done in quite awhile.)
After that, we'll see what we see.
Jibsheet is a much tougher target than Methuselah was... tall,
rugged, and with a steep and slippery-looking sand slope
below it. The Monday morning Spirit SOWG meeting will be an
May 4, 2005
We've made some substantial progress over the past week in getting
ready to get Opportunity out of the drift that she's driven into.
All the action so far has been on Earth, doing testing with
the two rovers we have on this planet. It's been nasty work...
shovel-and-wheelbarrow stuff, moving around literally tons of
fine-grained soil. Rob Sullivan from the science team came up with
a "recipe" for a soil mix that rather nicely matches the
properties of what we've gotten ourselves into on Mars. Jeff
Biesadecki has led the charge from the engineering side, pulling
some very long hours in the testbed driving the rovers into and
out of the dirt, working out the best way to do it on Mars. We're still
testing, and it's going to be a few more days, at least,
before we're ready to try anything on Mars. So patience is
still necessary. But there are some very good people out at
JPL working very hard on this problem, and I remain
optimistic that we're going to be out of this stuff and
on our way again before too long.
Over at Gusev crater, wonderful things have been happening.
We took an enormous Microscopic Imager mosaic on Keystone
recently: 4000 by 6000 pixels, the most MI frames we've ever
taken on a single rock. The resulting mosaic is stunning,
and it reveals Keystone to be finely layered and with a
strange porous texture.
The big surprise, for me at least, was the composition. I
was expecting Keystone (and by inference all of Methuselah)
to be rich in sulfates, like the rocks called Peace and
Alligator that we found some time ago. I based this
expectation on the fact that Keystone looked a bit like
Peace and Alligator in the MI images. Instead, Keystone
turns out to have a composition much like Wishstone, a
massive-looking piece of loose rock that we encountered
during our climb to Larry's Lookout. Like Wishstone (and
like Larry's Lookout) Keystone has lots of titanium and lots
of phosphorous in it... a distinctive chemical "fingerprint"
that many of the rocks on this side of Husband Hill seem
The really good news is that we now have emerging the
first true stratigraphy that we've seen in the
Columbia Hills... a suite of stratified rocks that we
can put together into a time-ordered sequence and work
out a history of geologic events. We don't have the whole
story yet, but it's really coming together now. I'm
hoping to be able to report on it at the American
Geophysical Union meeting that's coming up in New
Orleans in a few weeks.
In order to add to our emerging understanding of this
stratigraphy, we've planned out our moves with Spirit for
what'll probably be the next couple of weeks. We're just
now finishing up some arm work on "Pittsburgh", another
target on Methuselah. After that, we're going to leave
Methuselah and head back to an outcrop named Jibsheet that
we passed by on our way up the hill. And after we've
learned what we can there, the plan is to head back
toward Larry's Lookout once more, this time circling
around toward the eastern side of the Lookout. There are
some rocks there, down low on the outcrop, that we have
become very interested in...