The last sample of the 15 we analyzed was a red rock, most likely the Moenkopi sandstone, with lichens growing on the outside - the grayish layer in the picture.
Although the title of the plot is not correct (this was not a soil sample), the data are. The plot below shows a compilation of some of the masses we are interested in (please note which trace goes with which y-axis).
The large green peak between 400 and 550 °C is CO2 - the majority of this peak (>80%) is CO2 evolved from the carbonates in this sample (either calcite: CaCO3, or dolomite: (MgCa)(CO3)2). These minerals decompose at a relatively low temperature under vacuum.
The yellow and very wobbly brownish plots (27, 78) are representative fragments from decomposition of organic material. These compounds are most likely from the lichen decomposition.
The blue line is water that is part of hydrated minerals. Adsorbed water would evolve at temperatures around 100°C, hydrated water at 300-600°C, depending on the mineral.
These are the results from a first quick look, next step, explaining all the other traces we find.
After the cleanly collected samples from the crew reach us, we have to prepare it for analysis. The cartoon below shows how:
First we chip off a fragment with a vice. Technically the vice should be cleaned in between samples, but by brushing it we hope to get at least the mineral cross contamination down.
The fragments are collected in aluminum foil, to prevent exposure to any organic containing surface.
Then the sample is transfered to a mortar to be crushed into fine powder. Both the pestle and mortar were ashed (heated to 500°C for 3 hours) to remove organic contaminants, before they were brought out to the field. The reason to powder the sample is to increase the exposed surface, which makes it easier for volatiles to escape.
The Terra instrument (a portable XRF, brought into the field by Jack Farmer/ASU), a terrestrial version of the CheMin instrument of MSL, requires powder with a grain size of <150 micron (um, micrometer) and we try to analyze one sample with both VAPoR and the Terra. Therefore we sieve the sample to the <150 um fraction, keep half or it ourselves and give the other halve to Terra.
VAPoR can't handle large sample sizes, because the RGA (residual gas analyzer, the mass spec) breaks at pressures higher than 5e-4 mbar. The larger the sample the larger the amount of gases that evolves, so we weigh out the sample to about 10 mg.
This 10 mg sample is then loaded in a quartz tube, which is on one side plugged with quartz wool. Quartz withstands temperatures up to at least 1600 °C, and we reach a sample temperature of ~1300 °C, so we won't melt the tubes.
This sample is loaded into the oven.
Check the video of day 10 to learn how VAPoR operates.
Jake Bleacher is doubling as crew and VAPoR team member. As part of the crew he is involved in all steps of the simulation, from collecting samples to processing them in the GeoLab to living in the DSH, simulating a planetary habitat. Here he describes his adventures during the sampling collection (also on the official NASA blog).
Jake Bleacher: One of the great advantages to sending humans to explore other Solar System bodies is the chance to document, collect, and analyze scientific samples. Here at Desert RATS we primarily focus on the collection of geologic samples, or rocks and soils. Although these samples can be studied in the Deep Space Habitat (DSH) Geolab, or back on Earth, it is extremely critical to document the context in which the samples are collected so that the science team can use those samples to piece together a geologic history for the area. The hammer, shovel, and tongs enable us to break off a piece of local rock or scoop up a sample of soil. However, prior to doing so we use cameras that are mounted on our backpacks to show the intended sample in its undisturbed location, preferably with the hammer or shovel in the picture to provide a sense of scale, or the size of the rocks.
Jake sampling (credit NASA/DRATS)
The SEV (credit NASA/DRATS
Crew member Jose Hurtado taking notes for the science team (credit NASA/DRATS)
Once we pick up the rock or soil sample we describe its color, texture, size, and general makeup as well as any other important observations. This information helps the science backroom determine what type of sample it is. After collecting the sample we take a picture showing the sample along with its sample bag, with the number clearly visible. This enables us to keep track of what samples go in what bags. We also acquire an image showing the sample’s location once the sample has been collected to provide further context of the environment in which the sample was located. After an EVA is complete and we have returned to our Space Exploration Vehicle (SEV) we place all the samples on the aft deck (back end) of the rover and take one last photo. This helps the science team keep track of which samples were collected on which EVAs, because with so many samples being collected it just takes one computer error or malfunction to lose track of your samples. This picture provides another piece of data to help us keep track of that information. We weigh all of the samples in their storage locker and then place them into what we call the sample mailbox on the aft deck.
sample mailbox on the aft deck
This is our standard way of collecting geologic samples during Desert RATS. However, just like during the Apollo Missions, we also have what we call “special samples” that are collected in a slightly different way. This year we have two science instrument teams involved in the test. I am involved with one of these instruments, called Volatile Analysis by Pyrolysis of Regolith (VAPoR). This instrument has the potential to “sniff” out water or other volatiles that we might use to help survive on another planet. It can also help identify bio-signatures, or signs of past or present life. However, one problem with collecting our samples is that we ourselves create a bio-signature and are composed of water. So our standard sample collection protocols can potentially contaminate a sample to the point that the instrument cannot identify minor traces of what it is looking for. As such, this year we have incorporated a new “special” sample collection protocol for VAPoR samples. Once a crewmember or the backroom identifies a possible VAPoR sample we are careful to not touch it with our gloves. We also never let the sample touch the bags. So we basically encase the sample in aluminum foil to isolate it from interactions with the gloves or bags. This is a first step for Desert RATS to incorporate new science instruments that are in development at different NASA Centers, and to begin thinking about the steps necessary to collect samples in a non-traditional way.
Addition by Inge: The VAPoR team went out to collect a few samples of their own. This short movie shows Jim chipping of a rock and Inge collecting it in a clean way.
This year the VAPoR team has brought its own geologist, Jim Rice. Jim is here only for a few days and amongst his duties was observing the crew in their efforts of clean sampling (more about that in a next post) and organically clean collecting some more samples for VAPoR.
After we ran our second sample of the day he took us out for a field trip first to SP Crater and then to Sunset Crater (for more information about volcanoes, check out this site).
What we learned:
1) the oldest (visible) layer in this region is the Kaibab Limestone - Early Permian, or 299-270 million years old:
Kaibab Limestone with Jim for scale
2) the layer on top of that is the Moenkopi Sandstone - Early (and possibly Middle) Triassic, 240 million years old:
Moenkopi Sandstone with Inge's foot (size 37/6.5) for size. The ripples are leftovers from a shallow sea that was present at the deposition of this formation. (240 million year old flow ripples!!)
3) Black Point Lava Flow (our test site) is about 2 million years old.
4) SP crater is a text book example of a cinder cone volcano and is estimated to be ~71,000 year old. SP is short for Shit Pot, what is what this volcano looked like according to one of the earlier owners of land that included the volcano (C.J. Babbit, 1880s). Obviously, in the geology textbooks only the abbreviation is used.
5) Sunset Crater is the youngest cinder cone volcano around here, about 1000 years old:
Sunset Crater, Jim and Inge for scale
Around Sunset Crater there are some interesting volcanic features, such as squeeze ups - cooling lava being squeezed through a thickening, solidifying lava crust - and hornitos (little ovens) - hot, still liquid lava spattering up through a thickening, solidifying lava crust!