Monday, June 11, 2012

Next Generation MERs for Mars?

Example of proposed upgrades to the basic Mars Exploration Rover design for missions to Mars in 2018 and beyond.  This particular upgrade would enhance the rover with next generation instruments and add capabilities to collect and cache samples for eventual return to Earth.  The full abstract is available here.

This week NASA will hold its conference on Concepts and Approaches forMars Exploration.   The space agency will use this meeting to hear new ideas for exploring the Red Planet.   The planetary science community responded with a wide range of ideas for both future robotic and manned missions.   The best ideas presumably will be incorporated into NASA’s new Mars exploration plan for 2018 through 2033 to be released this summer.

Extended two page abstracts for most of the talks have been posted at the website, and I use them for the information in this and probably the next several posts.

A wide range of robotic missions will be proposed from orbiters to explore the subsurface with ground penetrating radars to rovers that would be blown like tumbleweeds by the winds across the surface. 

A number of the talks will propose new rover missions that would reuse the basic design of the Mars Exploration Rovers (MER) (see, for example, this abstract).  This is the design used by the highly successful Spirit and Opportunity rovers currently on Mars.  By reusing a proven design for entry, descent, mobility, and science operations, costs of future missions would be substantially reduced.  One talk will propose that five to ten rovers be delivered in the 2020s to both explore different regions of Mars as well as to possibly carry different instrument compliments. 

In terms of size, the MER design is much smaller than the Curiosity rover en route to Mars for a landing this August or the planned ExoMars rover.  The MER design is roughly the size of golf cart while the Curiosity rover is the size of sports utility vehicle.  In terms of capabilities, size matters.  Future rovers based on the MER design cannot replicate the full range of measurements the Curiosity and ExoMars rovers will.

Examples of a mineralogical map of a rock sample create from a prototype next generation multispectral microscopic imager proposed for future rovers (see this abstract).  Other instruments could measure the composition of each mineral assemblage in this sample (see this abstract).

In reading over the abstracts for the talks, however, I was surprised at the range of possibilities for upgrading the basic MER design to carry out sophisticated new investigations.  For example, a major upgrade discussed in two talks would be to the contact instruments that are placed against rocks by the robotic arm.  Where the current rovers carry a panchromatic (black and white) microscopic imager, future rovers could carry multispectral microscopic imagers that would take spectra of individual grains for composition analysis.  Where the current MER instruments record average composition across each measurement location (a few centimeters across if I remember correctly), the next generation of instruments would measure the composition of individual grains within rocks.  (In techno-speak, the instrument would use a microscopic laser to enable Raman spectroscopy, Laser Induced Breakdown Spectroscopy (LIBS) and fluorescence spectroscopy with measurements at the scale of 1-5 microns. The combination will provide both elemental and mineralogic composition.  While the abstract doesn’t mention one way or another about detecting organic molecules, other Raman spectrometers I’ve seen discussed would.  See this abstract for details.)  To use a crude analogy, these instruments compared to those on Spirit and Opportunity would be like going from black and white analog television to full color, 3D, 1080p high definition television.

The big upgrades to the MER design, though, would come from attaching new packages to the exterior of the rover.   The Curiosity rover in route to Mars for a landing this August also has cameras and contact instruments, but its major instrument advancements comes from sophisticated chemistry laboratories within the rover.  The MER design lacks room for instruments inside its body, but two talks will discuss packages attached to the exterior. 

One talk will propose a mission (see this abstract) that would carry an advanced laboratory that would conduct sophisticated compositional analysis and organic characterization using a combined a high-resolution mass spectrometer (HRMS) to analyze biotic and abiotic chemistry as well as Raman spectroscopy and Laser Induced Breakdown Spectroscopy for mineralogical and elemental composition measurements.  These capabilities would be similar to some of those that will be done by the Curiosity and ExoMars rovers (although sometimes with different combinations of instruments than these). 

A completely new capability in this instrument package not found in the Curiosity or ExoMars instruments suites would date samples to ~±50 million years (specifically by measuring ratios of the elements rubidium-strontium and potassium-argon.)  A major goal for returning samples to Earth is to establish firm dates (plus or minus a few tens of millions of years) for key events in Martian history.  If this could be done with a future rover, this would be a huge advance for the scientific understanding of Mars at a tiny fraction of the cost of returning samples to Earth

Sample return isn’t forgotten for the proposed MER class rovers.  Two talks will focus on bolting a sample return caching system to the exterior of the rover.  A coring drill would collect around 35 sample cores that would be deposited in a canister ready for collection by a subsequent mission for return to Earth.  The rover would also carry multispectral cameras, a remote sensing spectrometer, and sophisticated contact composition instruments to aid in sample selection.

While these talks will propose reusing the basic MER design, at least one key upgrade will be done.  The Spirit and Opportunity rovers used ballistic, unguided entry and descent that resulted in large landing ellipses.  As a result, many interesting sites, such as Curiosity’s Gale Crater site, had to be ruled out because the large ellipses contained rough terrain.  Curiosity will use guided entry and descent to substantially reduce the size of the landing ellipse.  Future MER-class missions would be upgraded to also use guided entry and descent allowing them to land at many more geologically interesting sites than were available for Spirit and Opportunity.

Beyond this upgrade, the rover design could also be upgraded in many small ways.  One talk mentions options for upgrades including advanced electronics to increase computational capabilities, higher efficiency solar cells, and upgraded telecommunications components.

While the instrument, entry and descent, and other upgrades promise exciting new capabilities, it’s important to remember that these would still be small, solar powered rovers that use airbags for landing.  They will lack the range of capabilities and driving distance of the Curiosity rover.  There are no free lunches in planetary exploration.  MER-class missions with price tags around $700M will not replace Curiosity with its price tag around $2.5B.  What is exciting is that so much could be done with upgrades to the basic design of a proven small rover   Imagine even two to three upgraded MER missions in the 2020s.


DJF said...

Could they add something to clean off the dust from the solar panels? This would greatly increase both the distance traveled and the length of mission if they could have full power from the solar panels.

Van Kane said...

DJF - I've read of experiments with self cleaning solar panels (can't remember what technique was used) that sounded promising. No idea if they would be technically ready by 2018-2020.