Thursday, April 26, 2007

IDD bonanza at Home Plate

This week, I've been working with Spirit as it investigates the eastern side of Home Plate. Home Plate is turning out to be super-cool in a science kind of way. Every outcrop we get close to turns out to be a gem. In these last few weeks, we've deployed the instrument arm (IDD) onto several rocks called Elizabeth_Mahon, Madeleine_English, and Examine_This, plus a light-colored soil near Madeleine_English. The instrument arm holds the RAT, the Microscopic Imager, the APXS, and the Mossbauer spectrometer, and we've put all of them to good use.

I've already explained that Mossbauer spectroscopy determines the kinds of iron-bearing minerals in the rock. The APXS is the Alpha Particle X-Ray Spectrometer. It works by exposing the rock target to a source of alpha particles and X-rays and then measuring the alpha particles and X-rays that come back. Each element interacts with X-rays differently, the X-ray interaction depends on the electron shells of an atom. When an atom is hit with an X-ray, the atom can absorb the energy by having one of its electrons go to an excited state. The excited state is unstable, so the electron will want to come back down and when it does, the atom emits energy. The exact frequency of the emitted energy is specific to the flavor of the atom - that is, the exact element. Therefore, you can look at a specific frequency and count the number of returned X-rays and know how much of that element is in the target. In practice, the MER APXS looks at a whole spectrum of frequencies returned and we pick out the peaks at specific energies to say how much of each element is in the rock. Unlike Mossbauer, which is tuned to iron, APXS detects the amount of every element in the rock. But APXS doesn't tell us anything about how those elements are combined into minerals. So, we like to use the APXS and Mossbauer on the same rock to get both the elemental makeup and the mineralogy.

RAT brushAPXS and Mossbauer spectra aren't much to look at unless you're a geek who likes squiggles on graphs (ok, I admit I like them). But this week we also found a nice flat rock exposure that we could brush with the RAT. The Rock Abrasion Tool grinding bit on Spirit wore out long ago, but it still has fantastic wire bristles that can brush soil away. Check out these before and after hazcam shots of the rock, the RAT brush, and placing the APXS on the brushed spot. The RAT brush spot is the spectacular shining beacon in the middle left. (I made this using

Then we looked at the shining beacon of brushed rock close-up. I mean REALLY close up. Here's the Microscopic Imager mosaic of the brushed spot, which is about 3cm across. Though it's a mostly flat-ish rock, it's got a knobby texture that we're still discussing. Compare this texture with what we saw at Madeleine_English, described below.

Wednesday, April 25, 2007

Sunday, April 15, 2007

Spinning wheels

Spirit is on the east side of Home Plate, which is this raised platform-like structure that we're trying to understand. It could be some kind of volcanic structure, possibly formed by hot lava inteacting with groundwater, and it would be the first volcanic feature either rovers or landers have gotten to investigate. Because the surface of Mars is largely volcanic, it's important for us to understand the processes of volcanism and so we're trying to do a really full-up investigation of Home Plate.

Our next target is called Madeleine_English (the team is informally naming targets after deceased members of the All-American Girls Professional Baseball League, complementing the names from the Negro Leagues on HP's west side last fall) and is a really interesting target for understanding Home Plate. It is pretty obviously a layer of rock, near the bottom of the stack of layers that make up Home Plate. We'd really like to understand what the different layers are made of and how they are put together. We got to take a look at Madeleine_English a couple of days ago in all 13 glorious Pancam filters (you can see the pictures filter by filter, like here, or combined to make the true-color filter combination at left) and the results are intriguing, showing a very interesting texture in the rock.

So all this week, Spirit and her handlers tried valiantly to approach Madeleine_English so we could deploy the arm instruments. Unfortunately, we're really feeling the effects of having a gimpy wheel. During these short drives over rough terrain angling for a precise approach, the rover has to strain against the wheel, because the wheel doesn't rotate freely. But as I've said here before, the rover drivers are amazing at coaxing the rover into places to wring more science out of this planet. Here's their summary of the driving maneuver to get to this target: "The route involves driving backward, turning around, backing up, parking in parallel between two sizable rocks flanking the target, pivoting clockwise on the stuck right front wheel, and finally "crabbing" forward to the target. Spirit performs crabbing by steering the two rear wheels toward the stuck right front wheel, thus opposing resistance from the right front wheel and keeping yawing (swinging from side to side) to a minimum." (You can see weekly summaries of rover activities in the JPL Mission Manager reports)

Whew! Check out where Spirit ended up (through her front hazcam). Sweet! That's the target rock right in front of us! Can't wait to have a closer look!

Friday, April 06, 2007

An APXS / MB observation in every plan, a chicken in every pot

That was my campaign promise when I took on the role of Keeper of the Plan. This is a science team job in the daily planning process that puts together the plan of activities that science wants that day and hands it off to the engineering team. I love it because it's detail-oriented, like me, and because it's another one of those jobs that gets me working with the engineers, which I love. Anyway, I had facetiously said that because I was the one putting activities into the plan, I could slip in my favorite ones - which of course, I can't do - both because obviously we do what the team wants every day but also because of the huge issue that my favorite instruments, APXS and MB, are on the end of the long rover arm and I can't personally command that to move too.

But this week, I had the distinct pleasure of *almost* making my campaign promise come true. This week, both rovers got down and dirty, putting their instruments on the ground. Opportunity is working on a week-long campaign to characterize the "dark streaks" emanating from Victoria Crater. The way we decided to do this was to first go to a spot between two streaks that looked "normal" and then go to the place with the darkest soil. On both spots, we did a whole series of observations, including photometry (photographs at different times of day on the same sopt to see how the soils' spectral characteristics change with sun angle), Microscopic Imager photos (to see what the soils look like on a fine scale, are there blueberries, is the sand different sizes, etc.), and APXS (to get the composition of the soil).

Spirit worked all week on characterizing Elizabeth Mahon, an outcrop of light-toned rock near Home Plate that may be in-place exposures of the lowest stratigraphic unit - exciting for geologists, really! Spirit spent a week on this one outcrop, largely because of the time it takes to conduct Mossbauer observations. We did four days (96 hours!) of Mossbauer on this rock. Mossbauer works by inducing a response from iron in the rock and then detecting its spectrum. To induce the transition in the iron, the Mossbauer carries a little source, and that source is getting old and weak. In the beginning of the mission, we only needed half a day or a day of Mossbauer integration to understand the iron mineralogy of the target. With each new day of the mission, we need to spend longer and longer to get a good spectrum. Because this rock is an important one for understanding the geology of Home Plate, we made the commitment to get a really good Mossbauer analysis here, plus APXS data for elemental composition and Microscopic Imager photos of the rock itself - which show it's an interesting, irregular, windscuplted rock. MI images are pretty cool - here are some of the Elizabeth Mahon shots this one and another one, or go check them all out!

Monday, April 02, 2007

What to do while Doc-ing

Today, I spent the majority of the day as documentarian for Opportunity. One of the team members has described this activity as like watching paint dry. I line it though - it really keeps me in touch with what is going on with the rover activities. Opportunity just finished some in-depth observations of a valley into Victoria Crater called the Valley Without Peril and now the team has to evaluate whether the valley lives up to its optimistic name! The capes and valleys as we circumnavigate Victoria are named after places Magellan visited on his circumnavigation of the globe.

But, being Doc means there's a lot of sort-of-dead time, when the engineering team is hard at work. That's when I catch up on my web surfing. A couple of weeks ago I visited my alma mater, Stony Brook and drove upstate to see my family. I used to love that drive, crossing Long Island, from the New Englandiness of Suffolk to the suburbs of Nassau and then coming up on the spectacular city vista with bridges and buildings all lit up. Then, the tree-lined parkways north to the Thruway and the wide open spaces of the Catsills and Hudson River Valley. Ahhhh, New York. What about you?

What American accent do you have?
Your Result: The Northeast

Judging by how you talk you are probably from north Jersey, New York City, Connecticut or Rhode Island. Chances are, if you are from New York City (and not those other places) people would probably be able to tell if they actually heard you speak.

The Inland North
North Central
The South
The West
The Midland
What American accent do you have?
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You rate 89% New Yorker!

For scores between 85% and 100%: Superb job! Outstanding! A true-blue New Yorker! Maybe you should consider running for governor. Excelsior, dude!

Are You a New Yorker?
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You are 92% native to New York State.

Not only are you native to the state of New York, you probably have been to Albany more often than to NYC. You must have aced your Regents exam or used GOOGLE. You have probably tried a Speidie, and Dinosaur BBQ. You know that there is way more to New York than the "city".

Are you A New Yorker?... not city.
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