The budget slump precipitated NASA’s withdrawal from a joint effort with the European Space Agency, ExoMars, which comprised joint orbiter and lander missions in 2016 and 2018 to set up a multinational sample-return expedition as soon as 2022. NASA new starts for Mars, beyond the late 2013 launch of the Mars Atmosphere and Volatile Evolution Mission, are now uncertain.

What has not changed, however, are two overarching policy factors: the emphasis placed by the National Research Council (NRC) on sample return as part of its decadal survey of planetary mission priorities between 2013 and 2022, and President Obama’s 2010 directive to NASA that it prepare to send astronauts to the Mars environs by the mid-2030s.

“We are trying to satisfy both of these at the same time, and that is the challenge,” McCuistion says, emphasizing the perhaps not-so-apparent significance of the NRC’s assessment. “Without decadals, you just end up with chaos — communities arguing whose science is more important, whose mission is more important.”

Called for by the MPPG in April, the LPI workshop should provide a wealth of competing ideas for reaching and probing Mars with machines and humans to determine its suitability for past or present life. Aside from the budget, the efforts will be paced by the 26-month separation in favorable Mars launch windows and a daunting assortment of technology challenges, including heavy-lift rocket and entry, descent and landing strategies.