Tuesday, December 21, 2010

Compelling Planetary Science Missions: Mars Background, Part 3 (Mars Polar Climate Mission)

This continues a series of posts inspired by a similar set of posts at Future Planetary Exploration blog selecting the 5 most compelling missions from the Planetary Science Decadal Survey list.  This is the 3rd of 3 reviews of potential Mars missions, building up to a selection from that list (and I've already revealed that Mars will not be skipped in my overall selection of 5 compelling missions).

The Mars Polar Climate Mission Concepts report doesn't focus on a single mission, but instead gives a broad overview of the types of missions that could study the Martian polar deposits to reveal information about the planet's climate.  Six potential missions, covering Discovery and New Frontiers classes, are investigated: 3 orbiters roughly similar to Mars Odyssey or Mars Reconnaissance Orbiter, 2 landers roughly similar to Mars Phoenix, and 1 MER-class rover.

Clearly the MAX-C rover is a more well-developed plan than these conceptual missions, but that may be balanced somewhat by the argument that these missions are simpler and use a great deal of heritage hardware.

These missions would all study the Martian climate through its polar layers, but they would do that in quite different ways.  Science questions include the age, energy budget, and mass of the polar deposits, volatile movement between the polar layers and other regions, historical Mars climate change as reflected in the polar layer records, and how the layers might be affected by influences like erosion, dust and carbon dioxide cycles, and liquid run-off.  Orbiters tend to be better at measuring large-scale processes like water and dust transport in and out of the polar regions.  Landers would be better at measuring composition of the layers, isotope ratios, and other characteristics that require sample handling or close observation.  Quite a few measurements could be made by either orbiters or landers.

Two Discovery class orbiter missions are described.  One mission selects instruments that emphasize current weather, climate, and polar change over the course of a season.  The other mission emphasizes current movement of water and dust into and out of the polar layers, comparing this information to polar layers that record the history of similar movements.  The single New Frontiers class orbiter addresses both of these areas.  The estimated FY15 costs with reserves for the orbiter missions are $613M, $629M, and $866M, respectively.

The body of 2 static landers described in the report would be similar to the Phoenix lander.  One Discovery class static lander is described.  This would land next to a polar layer region and observe the layers from below using a high resolution multispectral imager.  It would also include a meteorology instrument suite.  The New Frontiers class static lander would land on one of the polar layered deposits and sample the deposit using melting or drilling, laser, camera, microscopic imager, meteorological suite, and spectrometer.  Rough FY15 mission cost estimates with reserves are $751M and $860M, respectively.  Based on the power and mass capabilities of the Phoenix landing platform and the limits placed on the instrument suites by the expected Discovery and New Frontiers cost limits, considerable additional capabilities (drills, robotic arms, sensors, etc) could be added to the landers if funded by external sources.  For example, the mass of the strawman instrument suite for the Discovery mission is 11.3 kg, and the mass of the instrument suite for the New Frontiers mission is 31.2 kg, but the Phoenix platform allowed 65.0 kg.

The New Frontiers class rover, costed at $1,049M, would bring a rock corer like the one planned for the MAX-C rover, a mass spectrometer, imagers, and a meteorological package, all with heritage from other Mars rover missions.  The rover itself would be based closely on the MER rovers.  The mission would be expected to last at most 90 sols if based on solar power because of the encroachment of the polar cap and lack of sunlight near the pole as winter approaches.  The value of the rover is that it would be able to directly access multiple polar deposit layers.

The next post in this series will include my selection of the most compelling mission from among the MAX-C rover, Mars Geophysical Network, and Mar Polar Climate missions.

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