The flawless landing of the Curiosity rover on Mars has re-energized discussion about exploration of the red planet — and what is planned next. It is well known that the planetary science budget and Mars in particular suffered massive cuts in the current budget proposal — diminishing any thoughts for the next-decade program.

Speculation about the reason for the cut has been widespread. Based on public statements by representatives of President Barack Obama’s administration, it would appear that the decision was largely motivated by fear that the next-decade program — a campaign to understand the possibility of past life by returning samples from Mars — will balloon in cost and threaten NASA’s other missions.

It is my strong conviction that such fears are quite unwarranted. My opinion recently has been further bolstered by the Mars Program Planning Group report.

The scientific exploration of Mars has been a line item in the U.S. budget since fiscal year 1994. After the twin losses of the Mars Climate Orbiter and Mars Polar Lander in 1999, I got the extraordinary opportunity to completely redesign a decade’s worth of Mars missions including the Mars Science Laboratory/Curiosity.

This last decade was no haphazard collection of missions. Rather, the program was designed as an interrelated set of projects aimed at understanding Mars as a system and particularly the potential for past life on Mars. The summary organizing principle was “Follow the Water.” And, as was planned, the missions were also intentionally crafted to prepare for a Mars sample return in the following decade.

As explained by the National Academy of Sciences in painstaking detail, the next step in understanding and verifying Mars’ habitability is to bring back samples from places identified by Curiosity and other past missions.

So why is sample return so important to the quest for life? Bringing samples back to Earth is critical for three reasons that have stood the test of time: utilizing instruments that cannot be shrunk to spacecraft size; engaging hundreds of scientists across dozens of laboratories; and most importantly, being able to follow the pathways of discovery as new experiments are conducted. As capable as Curiosity is, the instrument suite is fixed.

But, it is argued, isn’t bringing back samples a daunting task with enormous risk? I agreed with that statement 12 years ago as the first “Mars czar” and as a consequence canceled the Mars sample return project then being studied. But built into the decade we restructured (2000 to present) was a stepwise attack on the scientific, technical and cost risk.

There was one huge scientific risk in 2000: No consensus existed in the science community, especially the astrobiology (life in the universe) field, about where to go and how to select compelling samples that were worth the cost and effort.

There were also four major technical challenges in 2000: No validated “Earth entry return vehicle”; no demonstration of on-orbit autonomous rendezvous needed to get the samples to a return vehicle; no “Mars ascent vehicle,” a rocket to launch the samples from the surface of the red planet; and finally, no demonstrated end-to-end sample handling capability to ensure the protection of Earth until samples are proved harmless.

Today the scientific and sample acquisition risk has been largely set aside. The science community has concluded that we can identify and carefully select samples that will provide compelling evidence of past habitability. The last decade of Mars orbiters and landers have provided the knowledge to find the areas of most interest. The deliberate stepwise improvement in landing accuracy and capability of missions from Pathfinder to Curiosity has provided us with the tools to go where we want and the capability to select the samples.

Two NASA missions, Stardust and Genesis, have proved the existence of a robust Earth entry vehicle. A Department of Defense program called Orbital Express has demonstrated autonomous on-orbit rendezvous. The Mars Phoenix mission has shown how to develop a “bioshield” for planetary protection. The Mars ascent vehicle does still need work, but there are promising new technologies that can be tested here on Earth.

Finally, the skeptics say, what about cost? Couldn’t a sample return mission get out of hand and create a budget spike that torpedoes the rest of NASA science?

During the work 12 years ago, sample return was already a constant driver, so in our studies we separated a notional single mission into a campaign of three projects. This approach allowed for an essentially flat funding profile and spread out the risk of any new elements into more tractable pieces. Very recently the Mars Program Planning Group led by my colleague Orlando Figueroa endorsed Mars sample return as the best path forward for both robotic science and human exploration. Its report presented an independently validated cost estimate of $1.4 billion to $1.7 billion for the first element in the sample return campaign — a caching rover. This realistic estimate is less than half of the $3.5 billion flagship mission studied earlier.

In my opinion, Mars exploration is ready to plan for the next steps in understanding Mars as a possible abode of life. We should restore the program to its 2011 budget of roughly $550 million per year and begin to plan for the reasonably priced rover mission in 2018 or 2020 that would use all the information from Curiosity and its predecessors to travel to the best possible spot on Mars to get samples we will bring back in the future. International collaboration can lower the U.S. cost even further.

Let us continue to be bold in our endeavors, acting as practical visionaries where we have confronted and minimized unnecessary risk.


Scott Hubbard is a professor in the Department of Aeronautics and Astronautics at Stanford University, former director of NASA’s Ames Research Center in Silicon Valley and the first NASA “Mars czar” (Mars program director). His new book, “Exploring Mars: Chronicles from a Decade of Discovery,” details the effort described above.

G. Scott Hubbard has held key roles at NASA, including director of Ames Research Center, first Mars Program director, founder of NASA's Astrobiology Institute, and the agency’s sole member of the Columbia Accident Investigation Board. Hubbard, now retired,...