Mars Trace Gas Orbiter Instruments Selected

ESA-supplied MTGO orbiter releasing the ExoMars demonstration lander.  Credit ESA.

Earlier this week, ESA and NASA announced the instruments selected to fly on the proposed 2016 Mars Trace Gas Orbiter (MTGO) mission.  This mission has several goals.  It will follow up on discoveries of short-lived trace gases previously discovered in the Martian atmosphere that suggest either active geological processes or life to replenish them.  Another focus will be to continue measurements of the Martian weather and climate to provide context for the trace gas measurements, to aid current landed missions (for example, to predict atmospheric conditions for entry and descent or to monitor dust storms), and to extend similar measurements that currently operating orbiters provide.  A high resolution camera will continue studies of selected spots on the planet in detail.  And finally, the orbiter will carry a communications package to relay data from future landers and rovers to and from Earth.

Previously measured methane concentrations in the Martian atmosphere.  Credit NASA.

The detection of methane in the Martian atmosphere has made trace gas measurements at this world a priority.  The discovery implies that Mars is currently active -- methane has a short lifetime in the Martian atmosphere and must be regularly refreshed.  However, the discovery brought with it two mysteries.  First, is the source of the methane geological or biological activity?  Either would have major implications for our understanding of this planet and the latter would have major implications for our understanding of our place in the universe.  The second mystery is what is removing the methane so quickly, much more quickly than known processes could account for?  The issue of trace gases is not limited to methane.  Other important concentrations to measure include CO2, CO, H2O, H2O2, NO2 N2O, O3, CH4, C2H2, C2H4, C2H6, H2CO, HCN, N2S, OCS, SO2, HCl, and CO.

Two instruments will study the trace gases, with the first focused on measuring trace concentrations (it reportedly could detect the the methane emitted by three cows) and the second on the sources of the trace gases:

• Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS) An infrared spectrometer to detect very low concentrations of molecular constituents of the atmosphere. Principal Investigator: Paul Wennberg, California Institute of Technology, Pasadena, USA. Participating countries: US, CA.
• High-resolution solar occultation and nadir spectrometer (SOIR/NOMAD) An infrared spectrometer to detect trace constituents in the atmosphere and to map their location on the surface. Principal Investigator: Ann Vandaele, Belgian Institute for Space Aeronomy, Brussels, Belgium. Participating countries: BE, IT, ES, GB, US, CA.

Two instruments will make weather and climate measurements:

• ExoMars Climate Sounder (EMCS) An infrared radiometer to provide daily global measurements of dust, water vapour and chemical species in the atmosphere to aid the analysis of the spectrometer data. Principal Investigator: John Schofield, Jet Propulsion Laboratory, Pasadena, USA. Participating countries: US, GB, FR.
• Mars Atmospheric Global Imaging Experiment (MAGIE) A wide-angle multi-spectral camera to provide global images in support of the other instruments. Principal Investigator: Bruce Cantor, Malin Space Science Systems, San Diego, USA. Participating countries: US, BE, FR, RU. 

The final instrument continues high resolution mapping of the Martian surface to study possible sources of trace gases, examine future landing sites, and continue geological studies of the planet:

• High-resolution Stereo Color Imager (HiSCI) A camera to provide 4-colour stereo imaging at 2 m resolution per pixel over an 8.5 km swathe. Principal Investigator: Alfred McEwen, University of Arizona, Tucson, USA. Participating countries: US, CH, GB, IT, DE, FR.

HiSCI will have lower spatial resolution (2 m) than the current HiRISE instrument (0.3 m), but will cover a larger area in each image.  The HiSCI instrument apparently will have color imaging over the entire image area while HiRISE has just three colors over a 1.2 km swathe and a single color, red, over a 6 km swathe.  Where HiRISE could image only a tiny fraction of one percent of Mars a year, HiSCI will be able to image around two percent per year.  HiSCI will also be able to obtain stereo coverage for every image, while HiRISE must acquire images on different orbits that may be months apart.  (It's not clear if HiSCI will have the stereo channel built into the instrument, or takes a second image on a the next orbital pass.  See the University of Arizona press release for what details are available.)

The orbiter will carry a communications package to relay data from future landers and rovers to and from Earth.

Spaceflightnow.com has an article with additional information on some of the instruments.  You can read the original press releases from ESA and NASA.  A presentation on the goals and implementation of the mission can be found at the MEPAG website.

Editorial thoughts: The status of this mission is currently unclear.  If I understand the Decadal Survey process, this mission must be recommended by the Survey for NASA to proceed with development.  However, I personally think it is unlikely that it won't be recommended.  The communications relay is needed for future Mars landers and rovers and the weather monitoring and high resolution camera would be useful to those missions.  The discovery of trace gases also begs for follow up measurements to determine concentrations and sources.  This is also an international mission, and the Survey would have to ask NASA to cancel plans on which ESA depends to fly its ExoMars mission elements.

As currently planned, NASA will provide the launch vehicle and the instrument package.  NASA will pay for the US instrument development; it's not clear whether it will pay for foreign instrument development.  NASA also will provide tracking services.  Together, these investments probably total several hundred million dollars (see this blog entry to get an idea of instrument costs).  ESA will pay for the orbiter and its ExoMars landing demonstration package.  This mission appears to be true partnership with each party contributing major elements.

You can find more information on the goals and measurement techniques of the classes of instruments selected in a report that analyzed possible instruments for the mission to guide the two space agencies in their final selection.

End of the Mars Scout Program

 Phoenix lander self portrait.  Courtesy NASA/JPL-Caltech/University Arizona/Texas A&M University

Spaceflightnow.com has an article on the end of the Mars Scout program.  The article suggests that this was a recent event, while I recall the program having been canceled -- or perhaps more correctly being folded into the Discovery program -- a year or two ago.

Originally conceived of as a series of small missions similar in scope and cost to the Discovery program, the Scout program was envisioned to fly missions to supplement the large missionss.  Each Scout mission would be lead by a principal investigator who would propose the mission and manage it through development and flight.  This was in contrast to the large orbiters and rovers that were defined by committees of scientists and managed by the Jet Propulsion Laboratory.  The Phoenix lander was the first mission in the program and the MAVEN orbiter planned for launch in 2013 will be the second and last mission.

The article states that the reason for cancellation was that the focus for Mars exploration will be landed missions, which don't fit into the Scout budget.  (Phoenix slipped in under the budget cap because it used an already designed and mostly built lander from a canceled mission.)  My understanding is that a changing budget situation ended the program.  When it was initiated, the Mars program was expected to be funded at a higher level than turned out to be be case.  In addition, cost overruns on the Mars Science Laboratory reduced funding for future Mars missions (although the MAVEN mission was protected from cuts). 

NASA has not abandoned small missions to Mars.  Now they must compete with other solar system targets within the Discovery program.  The Spaceflightnow.com article notes that several proposals for Mars missions will be submitted as part of the current Discovery mission selection process.  

The MAVEN orbiter will study the upper atmosphere of Mars.  Courtesy NASA

Editorial Note:  Small Mars missions may lack the inherent attraction of missions to less visit parts of the solar system such as Io, Titan, comets, and asteroids.  However, Mars orbiters may represent excellent science return for the buck while representing low implementation risks.  Our moon has been the most visited destination in the solar system, but the last Discovery competition selected the GRAIL lunar gravity mission, presumably on these criteria.

Mars III workshop and goals for planetary exploration

The Mars III workshop was help at the end of March into early April.  Unlike many conferences, this one didn't focus on the latest findings reported in 15-20 minute presentations.  Instead, this workshop was a synthesis with a goal "to integrate the main results of both the recent Earth-based observations and the missions to Mars (MarsExpress, Mars Reconnaissance Orbiter, Phoenix and Mars Exploration Rovers) into a new global picture of Mars evolution."  As such, the presentations that are posted are fantastic tutorials on a wide range of topics, from the geological history, to the climate, to the interior structure.  Typical presentations (presumably with time for questions) lasted one-and-a-half hours.  A series of hour long presentations on current and recently ended (Phoenix) missions and thirty minute presentations on future missions rounded out the program.

If you are interested in Mars, this is a great place to spend some time.

I found three slides in the introduction presentation by Jack Mustard, particularly interesting.  The two following slides present key questions that dominated the field ten years ago and the key questions that dominate the field today.  Note how little overlap there is.  The past decade of exploration has done a great job of answering what had been the key questions, but of course that just led to new questions for the coming decade.  The exception to this story was studies of the Martian interior which largely will remain on hold until a network of geophysical landers is eventually flown.  (The presentation on network missions gives the long and sad history of attempts to get a network mission flown.  Best current hope is for a mission around 2020, assuming that it once again is not bumped to fund higher priority missions.)

The third slide from Mustard's presentation provides the goals for exploration of the terrestrial worlds (which would in this context include the other half of our double world system, our own moon).  All are key questions to understanding the evolution of our own world.  I am beginning to feel that the goal for the next decade of exploration should be twin focuses on the terrestrial planets (with Mars receiving the bulk of the money and attention, but significant missions to Venus and/or the moon) and on the icy moons of Jupiter and Titan as possible abodes of life.  Perhaps $5B to each set of missions, leaving ~$2B for Discovery class missions to asteroids and comets.  While this would leave many missions I would very much like to see fly such as the Io Volcano Explorer and the Argo Neptune-Triton flyby, the success at Mars in answering a string of high priority questions in the past decade shows the power of focusing exploration.

Link to Mars III workshop presentations: http://sci.esa.int/workshopmars3

Making 1 + 1 > 2

Wags frequently blame designs that appear to be kludges to the deliberations of committees.  Camels and wildebeests have been held up as examples.  When it was first announced that ESA and NASA would deliver two separate rovers to the same location on Mars in 2018, many commentators on message boards would apparently concluded that attributing this to design by committee might be generous.

The basic deal was that NASA and ESA would combine their landing technology demonstration (ESA), Mars Trace Gas Orbiter (NASA), ExoMars rover (ESA), and MAX-C astrobiology and caching rover (NASA) missions.  The first two elements would fly in 2016 in a mission led by ESA, while the latter two elements would be delivered to Mars in a mission led by NASA.  To keep the 2018 mission within fiscal bounds, NASA would do a single launch and a single landing on Mars that would deliver two rovers to the same location.

 The rovers would have different missions.  The ExoMars rover would have a sophisticated analysis lab (a la NASA's 2011 Mars Science Laboratory rover) with sample delivered via drill from as deep as 2 m below the surface.  The MAX-C rover would have a suite of contact instruments to study the surface soils and rocks and would also collect a cache of samples for latter return to Earth.  Still, two rovers to one location seemed like a stretch of credibility.  I suggested that NASA's rover be delayed and the ESA rover could be enhanced with the MAX-C contact instruments.  (This blog entry also had a lot of background on the two rovers.)

ESA and NASA have moved forward to look at how the two missions could be combined.  The first question appears to have been whether or not a modified MSL entry capsule and the skycrane descent and landing system could deliver two rovers to Mars.  A team has looked into this question and concluded it could, although future studies will also look at airbag landings and landers with legs a al Viking and Phoenix.

The next question is how the two rovers could operate synergistically on the surface of Mars.  That apparently is proving to be a harder question.  To understand the tradeoffs, here are some basic facts about the two missions:

ExoMars

• Primary goal: Acquire and analyze samples from up to 2 m beneath the surface
• Be capable of operating for a total traverse path length of at least [3] km.
• Be capable of conducting Mars sample location selection, sub-surface sample collection down to 2m depth, and sample analysis operations at [6] different locations for at least [180] sols.

MAX-C

• Find locations of interest for sampling and characterize composition, mineralogy, and presence of organic materials to allow sampling decision at many locations
• Select, acquire, and cache at least [38] core samples ([2] caches of at least [19] cores each) from surface materials
• Traverse path length capability of at least [20] km.
• Conduct Mars surface sample selection and coring/caching operations for at least [500] sols.

Based on the design goals, MAX-C will rove almost six times further and operate almost three times longer than ExoMars.  It will also be able to use its instruments to investigate many more sites.  If the experience of the MER rovers with their 90 day planned lifetimes is any example, then both of these rovers may operate for many years and travel many tens of kilometers.

A team has been chartered to look at joint mission opportunities.  They used a couple of analogies, apple orchards and marriage to describe the options and issues.  First, the apple analogies were used to describe how two children in an orchard looking for apples might divide the work:

In the first option, “One looking for apples, the other picking them,” MAX-C scouts for locations that ExoMars will sample with its more sophisticated instruments.  This option makes use of MAX-C’s greater mobility, faster analysis capabilities, and larger limit on the number of sites it can analyze.

In the second option, “Have a 2nd opinion on your best apple,” the two rovers would operate independently, but would combine analytic capabilities when one finds an interesting “apple”.

In the third option, “Are the apples better on different trees?,” rovers separately examine the landing area to maximize the changes of stumbling on the best “apples.”

In the fourth option, “Give you best apple to your friend to take to town,” interesting samples collected by ExoMars would be transferred to MAX-C for caching and eventual return to Earth.

In the fifth option, “Scouting to help choose the best trees to pick,” MAX-C would receive additional instruments too allow it to more efficiently search for ExoMars sampling sites.

In the sixth option, “Make sure not to run into the trees,” the landing system would be enhanced so it could land in more geologically diverse and otherwise hazardous regions to better exploit the capabilities of both rovers.

The marriage analogy comes in as the costs of the two missions getting married.  First, operating together would require extra time and complicate mission operations for both rovers.  Second, finding a landing site that would meet the two rovers engineering constraints and science objectives becomes much harder.

The team did not make any final recommendations, but suggested that the most compelling advantages for using the rovers as a team would be for MAX-C to scout for locations to study, use their different instruments suites (MAX-C surface, ExoMars subsurface) to study interesting sites, and to allow ExoMars to pass samples to MAX-C for caching.

The recommended hardware changes to the missions to enable their cooperative exploration (and most of these would be considered major changes except as noted) would be:

• Improve landing hazard avoidance to allow landing at a site that better addresses both rovers’ goals
• Modify ExoMars and MAX-C sampling handling to allow transfer and caching of samples
• Extend ExoMars roving distance to ~ 10 km and double its planned lifetime (this might be a major change; not noted in the team’s report)
• Allow two telecommunications sessions per sol with each rover to reduce conflicts for available communications bandwidth (this might be a minor change; not noted in the team’s report)

 From 2 Rover International SAG presentation to MEPAG, March 2010

Editorial Thoughts: If all of this makes you worry that this is a mission designed by a committee and possibly a kludge, remember that camels and wildebeests are highly successful species.  I suspect that the combined efforts of these two rovers will be greater than the sum of their separate contributions.  And without this marriage, the Mars Trace Gas Orbiter would be a minimalistic endeavor instead of the highly capable mission now planned and ExoMars might not fly at all.   That's a "committee" decision I have grown to like.

Resources: The following presentations form the basis of this report and were presented at the March 2010 MEPAG meeting

2018 mission update

2 Rover International Science Advisory Group

The Promise of MSL

I had planned to post this blog entry a couple of weeks ago, but then budget news intervened.  One piece of news that came out of the Decadal Survey meeting last week was that the Mars Science Laboratory (MSL) rover Curiosity is on track for its 2011 launch.  About a week before that meeting JPL released information on one of the possible landing sites for MSL, Gale Crater.  Currently there are four finalists for the landing site with two additional sites under consideration for the short list.  (Final selection of the landing site is planned for early 2011.)  The goal of the mission is to use the new precision landing system to place MSL within a terrain that shows obvious evidence of a watery past.  Ideally the location will have access to ancient clay and sulfate minerals that formed in the presence of water.

I don't know whether Gale Crater will be ultimate choice for the landing site.  Similar studies to the one reported below are underway for all the candiates sites.  However, this early look at one of the candiates suggests what a stunning scientific bonnanza awaits MSL.

When you finish reading the portion of the press release below on Gale Crater, you might want to check out the recent BBC article on MSL and its development travails, read this  write up on the current four candidate landing sites, read a mission summary on Wikipedia, or go to the candidate landing site website for more details on Gale Crater and the other candidate sites.

The complete press release can be found at http://www.jpl.nasa.gov/news/news.cfm?release=2010-044

PASADENA, Calif. -- Near the center of a Martian crater about the size of Connecticut, hundreds of exposed rock layers form a mound as tall as the Rockies and reveal a record of major environmental changes on Mars billions of years ago.

The history told by this tall parfait of layers inside Gale Crater matches what has been proposed in recent years as the dominant planet-wide pattern for early Mars, according to a new report by geologists using instruments on NASA's Mars Reconnaissance Orbiter.

"Looking at the layers from the bottom to the top, from the oldest to the youngest, you see a sequence of changing rocks that resulted from changes in environmental conditions through time," said Ralph Milliken of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This thick sequence of rocks appears to be showing different steps in the drying-out of Mars."

Using geological layers to understand stages in the evolution of a planet's climate has a precedent on Earth. A change about 1.8 billion years ago in the types of rock layers formed on Earth became a key to understanding a dramatic change in Earth's ancient atmosphere.

Milliken and two co-authors report in Geophysical Research Letters that clay minerals, which form under very wet conditions, are concentrated in layers near the bottom of the Gale stack. Above that, sulfate minerals are intermixed with the clays. Sulfates form in wet conditions and can be deposited when the water in which they are dissolved evaporates. Higher still are sulfate-containing layers without detectable clays. And at the top is a thick formation of regularly spaced layers bearing no detectable water-related minerals.

Rock exposures with compositions like various layers of the Gale stack have been mapped elsewhere on Mars, and researchers, including Jean-Pierre Bibring of the University of Paris, have proposed a Martian planetary chronology of clay-producing conditions followed by sulfate-producing conditions followed by dry conditions. However, Gale is the first location where a single series of layers has been found to contain these clues in a clearly defined sequence from older rocks to younger rocks.

"If you could stand there, you would see this beautiful formation of Martian sediments laid down in the past, a stratigraphic section that's more than twice the height of the Grand Canyon, though not as steep," said Bradley Thomson of the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. He and John Grotzinger of the California Institute of Technology in Pasadena are Milliken's co-authors.

NASA selected Gale Crater in 2008 as one of four finalist sites for the Mars Science Laboratory rover, Curiosity, which has a planned launch in 2011. The finalist sites all have exposures of water-related minerals, and each has attributes that distinguish it from the others. This new report is an example of how observations made for evaluating the landing-site candidates are providing valuable science results even before the rover mission launches.

Two Strategies for Mars Rover Instruments

ESA and NASA are both planning small Flagship ($1-2B each) rover missions to explore Mars in 2018. The agencies have recently decided to merge their efforts to pool costs. As plans stand now, NASA will provide the launch vehicle and a skycrane entry-descent-and landing system. Each agency will provide its own rover, which will be simultaneously delivered to the same location by the skycrane system.

They idea of sending two rovers to the same location has caused a lot of raised eyebrows (to put it mildly) at Unmanned Spaceflight. In this blog entry, I want to explain why this isn't necessarily as stupid as it sounds and to discuss what I think may eventually happen.

In any mission, there's are fundamental tradeoffs that drive the mission design made to keep costs reasonable. For ExoMars, that key tradeoff was to acquire samples using a deep drill (up to 2 m) that would get beneath the level of organic sample degregation. Samples would then be processed by a very sophisticated set of instruments housed inside the rover. A fundamental tradeoff to this approach is that ExoMars will not have a robotic arm to acquire samples or place instruments in contact with rocks or soil. (The Mars Science Laboratory Curiosity will use a sample arm with a drill to deliver samples to its own internal suite of instruments as well as place instruments in contact with the surface.)
NASA's 2018 MAX-C rover has a primary task of selecting, acquiring, and caching samples for a potential future Mars sample return mission. The system to acquire, handle, and store the samples is quite complex and heavy (tens of kilograms). As a result, there is insufficient mass and space for a suite of internal instruments. Instead, the mission proposes to have a set of highly advanced contact instruments on a robotic arm. Unlike MER and MSL, these instruments will be able to study micro-variations in composition across the contact point much as might be done in a terrestrial laboratory with a sample. The instruments can examine the contact area in multiple spectra, measure elemental and minerological composition, and measure organics (if present). The instruments are potentially light, perhaps 15 kg (probably not including the robotic arm, although the presentations are not clear on that point). Currently, many of these contact instruments are in a low state of technology readiness, but with nine years to flight, there's time to address that issue.
ExoMars also will carry a ground penetrating radar and a power wide- and narrow-angle camera system. MAX-C presumably would also carry a capable imaging system and tentative plans have it carrying a spectrometer on the mast for remote identification of surface composition.

No single rover can do it all. If you want to sample deep beneath the surface, have a sophisticated laboratory of instruments inside the rover, have sophisticated contact instruments, and acquire and cache samples, you need multiple rovers. Flying ExoMars and MAX-C to the same location would provide complimentary, not redundant, measurements.

Editorial Thoughts: In a world with unlimited budgets, flying two rovers to the same location would be wonderful. In a world of constrained budgets, it seems unlikely to me to happen (but please, ESA and NASA, prove me wrong). So, if we are reduced to one rover, what should it look like? That depends on priorities, and your's, mine, and the scientific community's may be quite different. But here are mine. I think the idea of a deep drill with an internal laboratory is compelling, but the number of samples is likely to be limited either by drill life or the number of experiment chambers. (An ExoMars presentation states that there would be six sample acquisitions.) I also think that the idea of an infinitely reusable suite of contact instruments on an arm is powerful. (An arm also allows measuring locations on the sides of rocks, hillslopes, and rock/soil faces that would be challenging or impossible for a deep drill.)

Caching samples is less compelling to me. Before the flight of ExoMars, we won't know, for example, how important it is to acquire samples from deep beneath the surface. What happens if the site you dedicated a rover to sample turns out not to be the one you want to return samples from? And will Europe and the U.S. actually fund a $5-6B return mission? For me, the more compelling sequence of missions is to study several locations with science oriented rovers such as ExoMars and MSL. Then, if funding for a sample return comes through, fly a rover dedicated to acquiring samples followed by the return vehicle. (Note: The Mars scientific community would disagree with this and is willing to forgo a much more sophisticated suite of instruments on MAX-C to kick start the move towards a sample return.)

If budgets or landed weight limits restrict the 2018 to a single rover, what I think would be compelling would be to add an arm with micro-scale contact instruments to an ExoMars rover. The arm and its instruments would be relatively light (20 - 25 kg?) become a complete subsystem that can be developed and supplied by NASA, simplifying the development interfaces.

In the best of all worlds, I would advocate enhancing ExoMars with the MAX-C arm and instruments for 2018. Then I'd fly MAX-C in 2020 with its arm and instruments and caching to either the same site (if ExoMars finds compelling reasons to make it the site for a sample return) or to a new site (or possibly the Mars Science Laboratory site if it is the compelling site). All it takes is money.

As the following two slides highlight, the question of how to merge the two missions is one the two space agencies are wrestling with.

Resources:

All images and slides are from the following presentations:

ExoMars: ESA’s Mission to Search for Signs of Life

Proposed 2018 Mars Astrobiology Explorer-Cacher (MAX-C) Mission