- Why go to Mars?
- Seeking signs of habitability
- Where to look?
- Destination: Gale crater
- Rover vision
- Surface and atmospheric studies
- Curiosity's arm
- Curiosity's hand
- Chemistry and mineralogy
- SAM Instruments
- Preparing for landing
- Entry, descent & landing
- MSL Brief
- Curiosity landing simulation
A sensitive nose
About the size of a microwave oven, SAM can be thought of as a sensitive robotic nose that can sniff out air and soil samples in order to identify composition. Its job is to look for the presence of organics present billions of years ago that are preserved in the rock record.
Notice the inlet tubes at the top. They can either “inhale” the atmosphere or accept solid samples delivered with the arm.
In order to “sniff” the solids it heats up samples in a oven to release gasses. Here is a short video on the sample heating and delivery process:
After a sample is baked to release its gases, SAM's can “taste” it using three instruments: a gas chromatograph, a quadupole mass spectrometer and a tunable laser spectrometer. This diagram shows the flow from sample processing through analysis using the instruments.
Let's summarize what happens after the sample is collected. It is a three step process.
Separate the molecules (gas chromatography)
The gas chromatograph (GC) can sort out all the different molecules in the sample, and tell how much of each kind there is. It accomplishes this by using a stream of helium gas to push the sample down a long, narrow tube (which is wound into a coil to save space).
Gas from the sample first travels to the Gas Chromatograph (GC) instrument. The purpose of Helium is used because it is inert, meaning it won't react with and change any of the sample molecules. The inside of the tube is coated with a thin film. As molecules travel through the tube, they stick for a bit on the film, and the heavier the molecule, the longer it sticks. Thus, the lighter molecules emerge from the tube first, followed by the middleweight molecules, with the heaviest molecules last.
Identify the molecules (quadrupole mass spectrometer)
This is the Quadrupole Mass Spectrometer (QMS) fires high-speed electrons at the molecules, breaking them up into fragments and giving the molecules and their fragments an electric charge. Molecules and fragments of different mass are counted by a detector at different times to generate a mass spectrum, which is a pattern that uniquely identifies molecules. This short video covers the basics:
Fine tuning (tunable laser spectrometer)
The tunable laser spectrometer will measure the abundance of various isotopes of carbon, hydrogen, and oxygen in atmospheric gases such as methane, water vapor, and carbon dioxide. The TLS will help determine the origin of any Methane that is detected. Tunable semiconductor lasers produce a very specific wavelength of light tuned to a fundamental frequency of the target gas molecule in the near infrared band.
The light causes the molecule to vibrate and therefore, absorb energy. The absorption lines allow us to measure concentrations and isotope ratios of specific chemicals important to life: methane, carbon dioxide, and water vapor.
Watch full press conference on SAM:
Want to join the conversation?
- Why again is NASA trying to find methane on Mars? Is it proof for something?(10 votes)
- Why is the cup made of quartz? full press conference on SAM @4:56(6 votes)
- quartz can be heated to very high temperatures, I would guess that it is a material that does not contaminate the samples when heated very high.(7 votes)
- What exactly would happen if mars was sustainable for people to live on Mars?(3 votes)
- Do you think there is any life or water in Mars? I think there are no life in Mars and since there is ice there might be water.(3 votes)
- how do the rocks turn into air?(1 vote)
- How much does curiosity weigh(0 votes)
- how did mars dried and ran out of water, and its there really a sign of life if they find the right molecules?(0 votes)