In the images that I showed you in the last lecture.
Some of the most intriguing things that you could see,
were things that were noticed in the very earliest images were these small spherical
things that were immediately called blue berries.
They were called blue berries because they look blue in the false color that's used,
they are not really blue.
But let's take a look at some of those pictures again.
Here they are as you'll remember in the upper parts,
this is where those wavy forms were that look like they were forming damp regions.
Damp stuffing through here, and blueberries, blueberries,
blueberries, blueberries everywhere.
What are these things?
Well there are a couple of experiments on these rovers that were designed to be able
to measure the compositions of small scale things.
One of them was a miniature version of the thermal emission spectrometer,
Mini-TES, in fact it was called.
And the problem is that Mini-TES,
when it looked at a field it looked at a pretty big swaf.
And so if you really wanted to know what the blueberries were and
you looked like this.
You'd be getting some of the spectrum of the blueberries, but
some of it of this stuff.
If you could look here, it's very difficult to isolate the blueberries.
Except that there was this one nice location where the blueberries did a good
job of isolating themselves.
This region came to be known if not surprisingly as the berry bowl.
And what happened was that a spectrum, a thermal emission spectrum was taken
right here and another thermal emission spectrum was taken right here.
And the two were compared and it's great because you have the same background rock
in both locations and the only difference is blueberries.
And what are the blueberries?
Hematite, these are the main source of all that hematite that was seen from space.
These funny looking nodules that are strewn all around the crater.
In the images that you see here, they're in that upper unit of this stratigraphy.
But if you look back at least at the stratigraphic column that we looked at
last time, you see that they're everywhere.
They are the hematitic concretions something, something, something.
Those little black dots, the little black dots are down here in the lower unit.
They're in the middle unit and they're in the upper unit too.
They are infusing this entire region in through here.
What are they?
Well it's hard to know when you just see these little blueberries.
Little blueberries could be things that came in from above,
maybe an impact happens.
These things get strewn all over the place.
They land all over the place.
They could have been formed there.
How do you know?
One of the nice ways in which this was figured out was by looking in
detail with a microscopic imager.
A little, almost like a little handheld lens, and
looking at some of the blueberries in place.
And there are many examples of this sort of image, where you can see this.
But this is one that what I want to show you where you can see that this is
a region that's limited.
It has layers going across here in the small scale picture.
You can't see them as much and here is a layer going across here like that.
And if you look very carefully the layers continue thrpugh the blueberry itself,
parallel to the layers on the outside.
This happens over and over again, and this would not happen unless
this blueberry will form inside of these layers.
These blueberries and their hematite.
These blueberries are now thought to be what are called concretion.
Concretions are things that form when water is flowing through this unit.
And a small bit of hematite will precipitate out and
it will grow rings of hematite around it.
And in fact, there are some blueberries that have been broken open.
And you can see inside almost like tree rings on the inside as these
concretions have grown.
So they're everywhere, they're not just up in this upper layer that was thought to
form in a damp environment.
They are in a very dry environment down here of the dunes.
They're in the semi moist environments up here of the sand sheet.
They're everywhere through there.
Why are there blueberries throughout?
It's because they were formed not at the time that these layers were put down.
But they were formed after the fact as the water level rises up through here,
precipitates out these blueberries throughout the entire column.
So these are much later than these initial dunes.
If you would come back when they had dunes on the surfaces,
you'd have found no blueberries.
But again, an indication of this water table rising and
lowering through this region.
What else do we know about the chemistry and the minerology of this region?
There was yet another instrument onboard the rover called,
the mossbauer spectrograph.
The way a Mossbauer spectrograph works as it puts, there's a rock right here.
It puts the unit right up next to the rock, so
this is on the robotic arm of the rover.
It puts the unit right up next to the rock and it sends gamma rays into the rock.
Gamma rays, once again very useful things, and
those gamma rays interact with the nuclei that are there inside.
Every type of nucleus will absorb and re-emit the different types of gamma rays.
And this particular Mössbauer spectrograph was tuned to send
out gamma rays that are absorbed and emitted by iron.
And taking that iron and putting it in different minerals
slightly changes the energies of the gamma rays that are absorbed and emitted.
So the way the Mössbauer spectrograph works is the energy level of
the gamma rays being emitted is scanned over a range.
And the gamma rays coming back are examined to see which gamma rays come
back.
Because they were absorbed and remitted versus just passing on through the rock.
From this you can tell, not just that there's iron there, but you can tell every
little flavor of iron that there might be, what kind of mineral that iron is in.
The way you do that of course is, you take your Mössbauer spectrograph on the Earth.
And you do the same thing on known minerals on the Earth and
you can identify them.
So what does it look like when you do this?
Here's some of the first data back from the Mössbauer spectrograph.
And let's look to how it works, on this axis is velocity.
It seems a strange thing to have.
But this is the equivalent velocity that the gamma ray has been doppler
shifted by millimeters per second.
Very small change in energy, but the energy states that the nucleus are very
sensitive to the state of the iron as a whole.
And you can see when you send out the gamma rays at zero velocity,
some of them are emitted and reabsorbed.
There's a big peak when you send them out at slightly negative velocity.
Slightly less peak over here and then a series of peaks out through here.
What are these peaks due to?
Well every single mineral with iron in it will have peaks in
different locations, and these peaks here, here,
here, and here are due to a mineral called jarosite.
