Sunday, May 8, 2011

Geophysical Monitoring Station (GEMS)

Over the last few days, since the announcement of the Discovery mission candidates, I've done some sleuthing on the internet to find out more about the mission candidates.  (Thank you for tips in the comments and on the Unmanned Spaceflight Forum.)  I've found some abstracts and presentations on the candidate missions.

Before I present what I found, I want to say that I am delighted by the complexity of the missions that made the final list.  A Mars lander, a sophisticated comet orbiter and multiple lander, and a Titan lake probe.  It appears that effectively increasing the Discovery mission budget by no longer counting the launch vehicle against the Principal Investigator's budget allows sophisticated missions within the Discovery program.  Imagine four to five of these missions flying within a decade (plus two New Frontiers missions and with any luck, the Mars 2016 Trace Gas Orbiter and a joint ESA-NASA Mars rover mission).  I still hope for an outer planets small flagship mission, but even without it, this is an exciting program.

With this post, I'll present the Mars GEMS mission and move on to the other Discovery candidates with the following posts.

An artist's concept portrays the proposed Geophysical Monitoring Station mission for studying the deep interior of Mars. Image Credit: NASA/JPL-Caltech

Geophysical Monitoring Station (GEMS): A Discovery-Class Mission to Explore the Interior of Mars

American Geophysical Union, Fall Meeting 2010, abstract #DI43A-1938

Banerdt, B.; Cox, Z. N.; Seybold, C.; Warwick, R.; Barry, S.; Hudson, T. L.; Hurst, K. J.;Kobie, B.; Sklyanskiy, E.

"The GEophysical Monitoring Station (GEMS) is a proposed Discovery-class mission designed to fill a longstanding gap in the scientific exploration of the solar system by performing, for the first time, an in-situ investigation of the interior ofMars. This mission would provide unique and critical information about the fundamental processes governing the initial accretion of the planet, the formation and differentiation of its core and crust, and the subsequent evolution of the interior. The scientific goals of GEMS are to understand the formation and evolution of terrestrial planets through investigation of the interior structure and processes of Mars and to determine its present level of tectonic activity and impact flux. A straightforward set of scientific objectives address these goals: 1) Determine the size, composition and physical state of the core; 2) Determine the thickness and structure of the crust; 3) Determine the composition and structure of the mantle; 4) Determine the thermal state of the interior; 5) Measure the rate and distribution of internal seismic activity; and 6) Measure the rate of impacts on the surface. To accomplish these objectives, GEMS carries a tightly-focused payload consisting of 3 investigations: 1) SEIS, a 6-component, very-broad-band seismometer, with careful thermal compensation/control and a sensitivity comparable to the best terrestrial instruments across a frequency range of 1 mHz to 50 Hz; 2) HP3 (Heat Flow and Physical Properties Package), an instrumented self-penetrating mole system that trails a string of temperature sensors to measure the planetary heat flux; and 3) RISE (Rotation and Interior Structure Experiment), which uses the spacecraft X-band communication system to provide precision tracking for planetary dynamical studies. The two instruments are moved from the lander deck to the martian surface by an Instrument Deployment Arm, with an appropriate location identified using an Instrument Deployment Camera. In order to ensure low risk within the tight Discovery cost limits, GEMS reuses the successful Lockheed Martin Phoenix spacecraft design, with a cruise and EDL system that has demonstrated capability for safe landing on Mars with well-understood costs. To take full advantage of this approach, all science requirements (such as instrument mass and power, landing site, and downlinked data volume) strictly conform to existing, demonstrated capabilities of the spacecraft and mission system. It is widely believed that multiple landers making simultaneous measurements (a network) are required to address the objectives for understanding terrestrial planet interiors. Nonetheless, comprehensive measurements from a single geophysical station are extremely valuable, because observations constraining the structure and processes of the deep interior of Mars are virtually nonexistent. GEMS will utilize sophisticated analysis techniques specific to single-stationmeasurements to determine crustal thickness, mantle structure, core state and size, and heat flow, providing our first real look deep beneath the surface of Mars."

A reader asked in a comment to the previous post whether a single station severely compromised the return of a geophysical mission to Mars compared to a network of several missions.  This question was addressed in a presentation to the Mars Panel of the Decadal Survey (  The short answer is that a single station would be a major step forward, even though multiple stations would be ideal.  Since a three to four station network would likely be a small Flaghsip mission, a single station would begin the surface geophysical study of Mars.

MSR would be a completed Mars Sample Return; MAX-C was the proposed NASA rover to collect samples for MSR, and if it flies, it will be a joint rover mission with ESA.


  1. Any word on whether GEMS would include meteorological instruments? The larger geophysical network mission concepts have (almost) always included meteo instruments as well. Not surprised that they're given the boot to fit into the cost cap of the Discovery mission.

  2. There are apparently no scientific meteorological instruments. I understand that temperature change, air pressure, and wind can impact seismic readings, so there may be engineering instruments for these measurements to remove them as noise factors from the seismic measurements.

  3. Wind, as well as temperature and pressure measurements are foreseen in the GEMS science baseline.

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