On Monday March 7th, NASA and NSF received the results of the Planetary Science Decadal Survey, which recommended planetary exploration priorities to NASA and the NSF for the 2013-2022 decade. The highlights of the recommendations are, in order of priority, to (1) collect rocks on Mars; (2) study Europa from Orbit; and (3) orbit Uranus and drop an atmospheric entry probe. I was a member of the Giant Planets Panel, and had an inside view of the Survey's creation; what follows is both an overview of the results, and a look at the process that created them.

The survey's final results were announced by Cornell University's Steve Squyres, who chaired the study. They come in the form of a 400+ page document that reviews the state of planetary science today and spells out what should come next. The final report is still undergoing editorial corrections, but a copy is already available for free on the National Academies Press website.

Squyres' description of the final report revolved around NASA's three classes of planetary missions. Flagship missions are the biggest projects and usually take multiple decades from start to finish. New Frontiers are the "medium" class missions, and each costs about one billion dollars and takes less than a decade to complete. Discovery program supports "small" missions that scientists directly manage at their home institution. The goal of the decadal survey is to set recommendations on all of these research activities, along with ground-based observations.

The recommendations for the Flagship missions are a big deal because their impacts will be felt for decades in the future. For example, the current Cassini mission received a green light in 1988, and it took 16 years from there to arrive at its destination—Cassini has been in operation at Saturn since late 2004. These recommendations are also a big deal because progresses in planetary science is spearheaded by these large missions, so carefully crafting a coherent, long-term strategic plan is crucial to staying on track.

The survey's single most important goal was to examine the progresses in planetary science over the last decade, and to come up with a consensus plan that will lead to new breakthroughs. The survey looked at the scientific and technological state of planetary science today; as scientists, the message we are delivering with the survey is simple: we are ready to do these missions.

However, the recommendations come at a tough economic time, and their implementation will depend on whether NASA receives a budget that allows it to afford those plans. Squyres, who is known for his energetic, engaging presentation style, did not hide the uncertain future facing planetary science. Congress has not passed the Fiscal Year 2011 budget, and, if the FY2012 budget proposal just announced is representative of what NASA will actually receive for the subsequent years, there is a strong possibility that we will not be able to fly even one of the priority missions.

Community consensus



The recommendations reflect the consensus view of planetary scientists about where we want to go next. The survey is conducted by a team of scientists and engineers selected by the National Research Council, which is one of the four divisions of the National Academies (the other three are the National Academy of Science, National Academy of Engineering, and Institute of Medicine).

The survey was divided into five sub-disciplines. The Inner Planets Panel dealt with Mercury, Venus, and Earth's Moon; Mars had a panel of its own. The Giant Planets Panel covered the four outer planets: Jupiter, Saturn, Uranus and Neptune, while the Satellites Panel looked at the numerous moons of the outer planets. All the other smaller bodies that orbit around the Sun, such as the asteroids, comets, and Kuiper belt objects were covered by the Primitive Bodies Panel.

We started working on the survey in the summer of 2009, and the first step was to gather input from the entire planetary science community, which came in the form of white papers. In the end, we received 199 papers with a total of 1,669 authors. As of October 2010, Planetary Science Division of the American Astronomy Society had about 1,415 members, so the survey gathered voices from a majority of planetary scientists in the US and abroad. It was an extremely active process and many of us participated in multiple white papers—I was an author on six of them. The white papers spelled out the scientific priorities, requisite technological developments, and mission plans to be considered by the survey.

Each of these five disciplines had equal weight in crafting the final recommendations, and contributed a chapter for the final report, which underwent rigorous peer review. The chapters were compiled into a single document with a unified introduction and final recommendations by the Steering Committee, which oversaw the entire survey process.

In writing the report, we were handed common Crosscutting Themes to maintain coherence across the five panels, and were asked to focus on scientific questions that address the origin and formation of the Solar System, the processes presently acting to maintain it in its current state, and conditions that support life.

Big missions, more rovers



For the Flagship class, the top priority identified by the survey is the Mars Astrobiology Explorer-Cacher, or MAX-C. MAX-C is the first of the three missions that will eventually bring rock samples from Mars back to Earth. The plan is for MAX-C to collect samples and store them in a special long-term cache box. The second step in the proposal sample return campaign is called the Mars Sample Return-Lander, which will lift the samples collected by MAX-C into orbit around Mars. Then, the third mission, Mars Sample Return Orbiter, will finally bring the rocks back to Earth. The recommendation for the next decade is to execute MAX-C only, with the rest of the sample-return campaign to be carried out in the subsequent decades.

This mission to Mars is a continuation of NASA's Mars exploration strategy that got kickstarted by the last decadal survey. That recommended, among other things, the Mars Science Laboratory and MAVEN as lead-off missions that will open the way for a Mars Sample Return campaign—MSL is on schedule to be launched later this year, and MAVEN, which will study the Martian atmosphere, in 2013.

In the current design, MAX-C is a six-wheeled rover with about the same size as Spirit and Opportunity. The plan considered by the survey will launch MAX-C with another rover provided by the ESA called the ExoMars Rover in 2018, and land them together in one shot using the Sky-Crane landing system originally developed for the MSL.

As the name suggests, MAX-C is a mission to search for signs of life on Mars. Past missions' objectives focused on the environmental conditions and whether they were friendly to life, but we now have a lot of evidence that Mars could have harbored life in the past, if it does not today. So, the MAX-C mission will now search for direct evidence of living organisms. The ESA's ExoMars has a similar mission, but it is designed to analyze the samples on board without bringing them back to Earth.

Waiting for a new start



The second priority, the Jupiter Europa Orbiter, also has an astrobiology emphasis—it will employ ice-penetrating radar to peer through the moon's surface ice and measure its thickness. There is now a strong evidence that the moon has a deep saline ocean underneath the surface ice, which may harbor living organisms.

This mission concept has a long history, which has already been covered in depth. It was recommended as the single highest Flagship priority by the last decadal survey, and NASA and ESA made an agreement two years ago to work together to develop a joint mission. The plan calls for NASA and ESA to separately send their respective orbiters to Europa and Ganymede, two of the four Galilean satellites, (planet-sized moons of Jupiter). The joint mission is now called the Europa Jupiter System Mission. Since then, the mission plans have been made more specific, and meetings and workshops have been held to help scientists develop instruments to be carried onboard for both the NASA and ESA orbiters.

However, the mission has not been started to date—past large missions to the outer planets including the Cassini mission to Saturn were funded through a special line of budget specifically passed by Congress. The creation of a new budget line is called a new start—but a new start for JEO has not happened to date, so the mission concept, which is basically ready to be implemented, has come back before the decadal survey again. The survey's recommendation confirms that a mission to Europa remains one of the top priorities in planetary science, and makes it clear that the mission is waiting for a new start to be passed by Congress.

Listing image by Ted Stryk/NASA