Five Questions with William Boynton
On the NASA Phoenix lander
GS member William Boynton is Professor of Cosmochemistry and Geochemistry at the University of Arizona. He has been involved with space exploration for several decades working closely with NASA to develop instruments for the Mars Polar Lander and Mars Odyssey Orbiter. Most recently, he was the scientific lead for the Phoenix Lander's on-board geochemistry lab TEGA. The Phoenix Lander continues to collect and analyze soil samples into October 2008, far surpassing its originally planned 90-day mission. Prof. Boynton recently answered these questions for GN via email.
1) How did you get involved with designing instruments for space flight?
I have always had an interest in building things with my hands. I began by building my own multichannel analyzer for gamma-ray spectrometry and neutron activation analysis when I came to Arizona in 1977. I wanted
to get involved in the space program and took a sabbatical at Goddard Space Flight Center to learn about using gamma-ray spectrometers (GRS) in space.
I proposed to be the team leader for the GRS on Mars Observer, but the instrument was built for me by NASA. After that mission failed just before arrival at Mars in 1993, I was given the opportunity to fly again on Mars Odyssey, and I proposed that we build it in house at Arizona rather than use an aerospace contractor. I feel that one can get a much better instrument for the money by building it in house.
2) What are some of the main challenges associated with designing instrumentation for operation on Mars?
Wow. There are lots. Mostly it is trying to find the right balance between available resources (schedule and money, mostly) and performance. There is the saying "faster, cheaper, better: chose any two" and achieving the right balance between all three is what is the most challenging. For specifics, building instruments for the harsh conditions on Mars and testing under those conditions are probably the toughest technical challenges.
3) What is TEGA and how does it work?
TEGA is the Thermal and Evolved-Gas Analyzer. It is a combination of a differential scanning calorimeter and a mass spectrometer. A small sample (~0.04 g) is sealed in an oven which is heated on a controlled temperature ramp to 1000 deg C. (typically at 20 deg/min). The energy required is carefully monitored 300 times a second and are used to detect either endothermic or exothermic phase changes. During the heating any minerals that decompose by release of a gas, such as CO2 from a carbonate, are passed on to the mass spectrometer for analysis.
4) What has TEGA revealed about Mars that we didn¹t already know (e.g. the habitability of Mars, possibility of former life on Mars, Martian geology, etc.)?
One thing we have found was a high content of calcium carbonate that was not expected. This mineral is generally thought to require reaction with water and carbon dioxide (though there are other ways to make it). Mars has evidence of flowing water in the lower latitudes, but seeing evidence at least suggestive of liquid water in the polar region was not expected. These data may suggest that the region could have been more habitable in the past, but, of course, that does not say anything about where there was or was not former life on Mars. The mission was designed to collect data on habitability, but not on the presence or absence of life.
5) What are some lingering questions that TEGA has the possibility of answering during Phoenix¹s remaining time on Mars?
At this writing there is not much time left for TEGA and the Phoenix mission, but we are hopeful that we can put constraints on the amount of organic material in the soil. This material, if found, would likely be from meteorite infall rather than some indigenous Mars source, but its presence would go a long way to showing organic molecules can survive in the highly oxidizing environment of Mars.