Brian, Seattle asked:
One of the instruments aboard the Mars Lander has been described as sniffing chemicals after heating samples of soil up. How are the effects of the Martian atmosphere taken into account. Is the container set to a vacuum or is the background reading from the atmosphere subtracted out?
We spoke to William Boynton on the show back in May about the mission so we decided to get back in touch with him to answer this question...
"We put the sample into a very small oven about the size of two drops of water and seal it to isolate it from the atmosphere. We then flush out the atmosphere that was sealed in the oven with the sample with a flow of pure nitrogen gas. The nitrogen gas is called a carrier gas and besides removing the atmosphere it is used to carry the evolved vapours generated during the heating over to the evolved gas analyser known as the sniffer. This sniffer is a mass spectrometer – a machine that you can find in any chemistry lab back here on Earth. This can accurately tell what molecules and atoms are in the sample."
Brian M. Stephanik asked the Naked Scientists: One of the instruments aboard the Mars Phoenix lander has been described as 'sniffing' chemicals after heating samples of soil up. How are the effects of the Martian atmosphere taken into account? Is the container set to vacuum or is the 'background' reading from the atmosphere subtracted out, or other? Brian Seattle, USA What do you think? Brian M. Stephanik , Tue, 5th Aug 2008
This website (http://phoenix.lpl.arizona.edu/) has an abundance of information on the Phoenix lander. Personally, I think it is much more informative than the NASA site. This page (http://phoenix.lpl.arizona.edu/science05.php/) specifically talks about the instruments on the lander. I didn't read anywhere where it talked about the interaction of the atmosphere with the samples, but the site is extensive and you may be able to find something. Failing that, you can send an email to firstname.lastname@example.org and ask them your question. Then you can get the answer straight from the experts!