Thursday, July 26, 2012

Updating While Waiting: The Dilemma

Those of us who follow the plans for future planetary exploration are waiting for two breaking events.  The first, expected in July based on NASA’s previously announced schedule but subject to delay, is the announcement of which mission it has selected for the Discovery mission.  Either the interior of Mars, the heterogeneity of a comet, or the surface of a Titan lake will be the focus of a great mission.  (It may say something about what kind of person that I am, but whatever is announced, I will feel that two great opportunities have been passed over.)

The second event, with a firm schedule down to the minute, will be the success or failure of the Curiosity rover’s landing on Mars.  While this may seem like current rather than future planetary exploration, a success will encourage more funding for planetary missions while a failure will do the opposite. quotes the head of NASA’s planetary science program on the importance of this landing in a speech given to lunar scientists, “’It’s absolutely essential for everybody in this room to recognize that, whether you’ve been following this or not, this is going to have an enormous effect on you, personally,” he [Jim Green] told a room filled primarily with lunar scientists. “Whether it’s successful or not successful, it will have an enormous effect on the planetary budget, and therefore, all of our careers… The landing of MSL will be absolutely critical, and we really need to take note of what’s going to happen here.”  

So while we wait, I thought I’d provide updates in this post and following ones on a number of items that don’t quite deserve a post of their own.

First up, published today, is a long article in the journal Science on the options for exploring Mars.  (Unfortunately, it’s subscription only or can be purchased for $15.  You can read the first paragraph and follow the link to purchase.)  Richard Kerr reports on the quandary that the Mars program finds itself in.  With the exception of sample return and the exploration of Mars’ interior (the focus of one of the Discovery missions in competition), all the major firsts for Mars have been done (assuming the Curiosity mission is a success).  So while future orbiters could carry better versions of instruments and rovers could land in new places, the feeling is that the results wouldn’t be revolutionary enough to compete with missions to other worlds.  Kerr quotes the head of the Decadal Survey’s Mars panel on the value of future incremental missions: “[Phillip] Christensen [ Arizona State University, Tempe] says he would love to fly a souped-up version of the instrument [a better multispectral imager] on a future [orbiter] mission. “But is that essential to our understanding of Mars? I think not,” he says. “It wouldn't be revolutionizing. You can do only so much from orbit, no matter how good your spectrometer. We're pretty darn close to doing what you can from orbit.” 

Kerr points out that other scientists disagree with Christensen’s (and many others) view on the value of incremental missions.  John Grotzinger, the Curiosity rover’s project scientist, for example, is promoting the idea of a series of smaller rovers in the class of the Opportunity rover currently at Mars but with significantly more advanced instruments (see below). 

Kerr ends his article by pointing out that NASA’s Mars program is becoming entangled with NASA’s human spaceflight program, which has a long term goal of reaching Mars.  He finishes the article with an assessment of the risks of this strategy: “In other words, planetary science would be riding human exploration's coattails to Mars in the FY 2014 budget request. ‘That is fraught with danger,’ Christensen says. ‘If you attach yourselves to human exploration,’ [Frances] Bagenal [University of Colorado, Boulder] says, ‘you end up tailoring your science to address the needs of human exploration. Then they change their mind. The lunar people have been down that road several times.’”

Another article out this week from the journal Nature, explores the idea behind what an incremental rover mission might do.  (Nature made this article freely available here.)  In a previous post, I described ideas for reusing the basic design of the Mars Exploration Rovers Spirit and Opportunity and outfitting them with modern instrument suites (a lot of instrument development has occurred since Spirit and Opportunity were designed).  One idea would be outfit one or more rovers with a new generation of instruments that can date Martian rocks to within a few tens of millions of years.  The article explains how important these measurements would be, “If chronology on the Moon is still uncertain, then Mars is a mess. The crater-count method does not work as well there, mainly because the wind, water and frost that sculpt the surface also erase craters… With a portable system, researchers could decipher how long volcanism lasted on Mars and when it stopped. They could find out when the planet's warm, wet and possibly habitable environment gave way to the cold desert it has been for several billion years. ‘If any evidence is found for life, we sure as heck will want to know when it was there,” says [Hap] McSween [University of Tennessee in Knoxville].’”  

The article provides a fascinating insight into the process and challenges of developing cutting edge capabilities for new planetary missions.  I highly recommend it.

Editorial Thoughts: These two articles together highlight a tension in how science is done.  The easiest way to make big discoveries is to simply be the first to go somewhere (or at least be the first to bring a new type of instrument such as the first high resolution imaging spectrometers in Mars orbit).  The naturalists who explored the world during the European age of discovery had a field day.  Everywhere they went, there was a new discovery waiting for them.  (To get an idea of what the opportunity was like, look up how many species the Scottish naturalist David Douglas named for himself or had named for him in the Pacific coast states of the U.S.  However, it has taken decades of intensive science to follow up on these discoveries and to start to really understand the geology, biology, and ecology of these areas.  In the Pacific Northwest, where Douglas was an early European explorer, we didn’t even understand the ecological importance of old-growth forests until the last two to three decades, and my colleagues are still trying to understand many key facts how the develop and function.

Planetary science has been in the lucky position of those European naturalists in being able to make many astounding discoveries simply by delivering a spacecraft or an instrument to a new place.  The opportunity for those relatively cheap and frequent missions becomes fewer with each new mission.  As a result, the planetary community is left to decide whether to recommend less expensive missions that do the yeomen’s work of filling in the details or propose the often expensive bigger missions that do the new and extraordinary.  I believe that the fear is that the politicians may balk at paying hundreds of millions of dollars per mission for the former and equally may balk at paying billions of dollars for the latter.

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