Here is a key point to add to your coverage of the new U.S. decadal survey for planetary science planning, including “NASA Money Woes Batter Planetary Flagship Budget” [March 21, page 14] and “Discovery Deferred — Indefinitely” [editorial, March 21, page 18]. As reported, Mars sample return is the highest-priority flagship mission, but the latest budget expectations may prevent it from happening.

To summarize the two-year decadal survey process, opinions were widely invited from the planetary science community, then numerous scientific committee discussions led to the 400-page public document that recommends priorities. Over 200 “white paper” suggestions from scientists are also online at

In stark contrast, there has been no open process that invites aerospace engineers to suggest and discuss alternative technologies for implementing planetary missions. Considering the importance of squeezing science from tight budgets, it seems counterproductive that mission cost estimates for the decadal survey relied on restricted input.

One very significant example is that the cost of Mars sample return hinges on the size of the miniature launch vehicle that needs to be delivered to Mars in order to lift geology samples off that planet. It is widely appreciated that a smaller Mars ascent vehicle would render Mars sample return more affordable.

Only a sketchy concept for a large and heavy Mars ascent vehicle is shown by the mission design study that was done in support of the decadal survey (also on the website). The heavy Mars ascent vehicle concept is in turn supported by only a single cited publication from 2002, which itself was just a program manager’s summary of brief industry studies done so long ago. The decadal survey has effectively ignored all the published engineering literature pertaining to possibilities for a smaller Mars ascent vehicle. In contrast, the Mars chapter alone has roughly 50 references to peer-reviewed Mars science papers, e.g., geology and astrobiology.

The decadal survey document does have a dedicated technology chapter, to emphasize the overall importance of engineering advances for planetary missions. The Mars chapter even states that the Mars ascent vehicle is the greatest technological challenge for the upcoming decade. What is missing? There is no open process to discuss solutions. While engineering details can’t all be public, that doesn’t explain a lack of interest in results already published. It might be very productive for planetary science leaders to organize open discussions to better understand technology challenges and possible solutions.


John Whitehead

Davis, Calif.