University Lowbrow Astronomers

Phoenix Selected for 2007 Launch Opportunity.

by Roger Tanner
Printed in Reflections: August, 2003.

In case you haven’t heard, the Phoenix project proposed by Peter Smith (my boss) was selected for the 2007 Mars launch window.  This mission will fly the revised 2001 lander which was canceled after the Mars Polar Lander (MPL) crash on Mars in 1999.  The lander was about 80% done, they were about 1 month away from installing the science instruments.  The lander will have some of the instruments from the MPL mission and the 2001 mission.  The object is to land at about 70 deg north latitude and dig down and find and analyze the ice they think is only a few tens of centimeters below the surface.  The lander has a Robotic Arm (RA) that will do the digging.  This mission is different than most in that it is a PI lead mission, meaning Peter (the Prime Investigator) is responsible for everything, launch, lander, science instruments, everything.  The whole contract comes to 318 million, and of that, almost forty-five million will be spent in Tucson.  Also the science operations center will be in Tucson, with all the instrument teams here.  Lander ops will be from Lockheed Martin in Denver.  The University has acquired a building for this.  As you might expect this has gotten a lot of attention from the U. The last time I was at the club, I gave a talk on the Pascal microlander camera I built.  This proposal as well as the other six I worked on didn’t make the first cut from twenty-two to four proposals.  Phoenix made the final four and then won.

At the time the 2001 mission was canceled, we had just delivered a Robotic Arm Camera (RAC) and a Optical Microscope (OM) to JPL.  Both of these instruments will be on the new Phoenix lander.  In addition the Surface Stereo Imager (SSI) that was on the MPL will be flown in a revised form.  I will be the camera manager for these three cameras.  The revisions to the SSI are to use larger CCD’s from the MER rover flight spares to give each eye 4X the resolution, about one-quarter mrad/pixel.  So for something on the ground, about two meters away, the camera will see about one-half mm/pixel, where as the Mars Pathfinder would see two mm/pixel.  The RAC camera can focus from eleven mm in front of its window to infinity.  At infinity it is about two mrad/pixel, about eight times lower resolution than the SSI.  But at close focus, it can image particles on the tip of the scoop at twenty-three microns/pixel.  On Earth this would be good, particles of dirt are typically several hundred microns across.  But on Mars, the typical dust particle is about one to two microns.  We won’t resolve them, just the clumps.  The OM is inside the MECA instrument.  For a sample put into the MECA instrument, we can look at it with the OM at a resolution of 4 microns/pixel.  Still will just see clumps of dust.

There will be two other cameras on this space craft, a descent camera built by Michael Malin Space Science Systems.  So we will have images all the way down to the surface.  The other camera is a Atomic Force Microscope that will operate on a corner of the optical microscope field.  The field of view of the AFM is very small but the resolution is around ten nm/pixel.  This will clearly resolve the dust and even smaller stuff on the dust.  So this mission will have imaging from km during descent, down to ten’s of nm for the MECA samples.

The other instruments are the Thermal Evolved Gas Analyzer (TEGA) from the MPL and the Robotic Arm from the 2001 lander.  The TEGA will get a mass spectrometer to replace its diode laser gas unit to be able to detect many more molecules.  The TEGA is designed and built at LPL/UofA as well.  The arm will be revised with longer segments to allow it to dig 1 meter below the surface.  The arm is designed and built at JPL.  Another instrument is the Mars Environmental Compatibility Assessment, MECA.  It has a sample wheel that will have samples dropped on to it and then the wheel turns 180 degrees and the samples will be vertical, where we will look at them with the OM an AFM.  Also in the MECA are four water-analysis cells.  Each cell has a drawer that opens, a sample drops in and then it closes.  After that water is added to the sample and the many chemical potentials for various ions are measured.  Also the ph and oxidation/reduction potential will be measured.  The MECA is designed and built at JPL.  The last instrument is a weather station and LIDAR unit to detect dust in the atmosphere.  One observation we hope to make is have the LIDAR range for dust devils and then image them with the SSI.

So now I have to do all the things in the proposal I said I could, on time and under budget.  There is a saying the only thing worse than not getting the proposal is getting the proposal.  Anyway, I will be hiring some engineers and students.  The major task is the modification to the SSI and its electronics to accommodate the new CCD’s.  The other two cameras will fly as is, we will just recalibrate to make sure they are still working as they should.  We will deliver our flight camera and software by Feb of 2006.  Integration on the lander and lander testing will take a year, with a 2007 launch.  Landing is early 2008 and the mission will last for ninety days, with an extended mission that will last another sixty days with just the cameras and weather station operating.  Data analysis and archiving will last another year so I will be busy until 2009 if things go well.  After the extended mission, we will be unable to gather enough power to keep the electronics warm at night and we will loose the lander, similar to Pathfinder.

As if this wasn’t exciting enough, there is a very real possibility that we may discover more than just permafrost under the soil there.  We are landing where the top meter of soil is more than 50% water by weight according to the GRS, that means more than 70% by volume.  They know the surface layers are very dry, so that means the most of the water must be in the bottom 3/4 meter.  This is more like dirty ice rather than icy dirt.  So they expect to only dig twenty cm or so and then they will hit ice.  Scraping up samples of ice for the TEGA and MECA will allow analysis of the composition.  Two recent papers have added some more information about that ice.  A paper about soil grains in ice has found that the soil grains can have a thin layer of liquid water at a temperature of -20C, twenty degrees below the freezing point.  Also another paper has done a dynamics analysis of Mars orbit eccentricity and polar axis tilt.  Both of these things vary on time scales of one hundred thousand years.  The result is for some combination of polar tilt and eccentricity, the solar irradiance at the landing site may have been three to four times what it is now.  Also, liquid water is stable for short periods at the low elevations where we are landing because of the higher atmospheric pressure.  So a picture emerges where this ice will periodically melt for ten thousand years at a time and then refreeze.  They have found bacterial colonies in Antarctica that have thrived in these very conditions.

So if you believe life is a natural occurrence of planet formation, and that the life on Mars could adapt from a warm wet climate to the present permafrost one, as some life forms on Earth have done, then we might possibly find some bacteria or something frozen in the ice.  We could see small stuff with the OM or AFM.  We can see color with the OM.  Even if don’t find something we will have the soil chemistry to figure out why.  The mass spectrometer on the TEGA will be able to detect organic molecules easily.

So we are following the water, a major NASA Mars Exploration Theme.  And at the end we might find more than just an answer to where has all of Mars’s water gone.  We will find a tremendous resource for future exploration, particularly manned exploration.  And if we find life, this will certainly galvanize the whole Mars exploration to go look at it in more detail.  And figure out if it is different or the same as the stuff like it on Earth.  It would also make a dent in question of is there other life in the Universe, or even in just in our solar system.  And having two data points for some of the bacterial life forms instead of one, would probably be a real thought starter for the biologists.

So these are really interesting times.  I’m glad I am living in them.


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