What’s Missing from NASA’s Toolbox?

Last week, we reported on new isotopic data from Mars, which revealed that ancient carbonates found in Gale Crater formed under extreme environmental conditions, providing insight into how the planet's once water-rich climate became the inhospitable desert it is today. The findings, made using NASA’s Curiosity rover, suggest a shift between wet–dry cycles and frigid, cryogenic environments.

We reached out to David Burtt, lead author of the study from NASA’s Goddard Space Flight Center, to find out more about the analytical challenges his team faces, as well as what’s on his instrumentation wishlist. 

Were there any significant analytical challenges you faced in this study?
 

It might not be a huge surprise, but it’s really difficult to operate instrumentation once it has put a healthy 140 million miles between you (it’s difficult enough when it’s in the lab next door). I’m fortunate to benefit from a team of brilliant engineers and scientists who designed instruments and procedures that simplified the process of analyzing samples. One example of this is the carbonates we analyzed in this study. On Earth, we would digest those carbonates in phosphoric acid, distill the resulting CO₂, and then analyze that gas. But how do you safely shoot phosphoric acid into space? The simple answer is that you don’t. Instead of using acid digestion, we use a technique called evolved gas analysis, where samples are heated up to 900 degrees Celsius in an oven to produce gasses (including CO₂), which are then measured using a mass spec. Without these simplified procedures, these analyses would be significantly more difficult and the Curiosity rover likely would not have lasted nearly as long.

Are there any analytical techniques or technologies on your wishlist for the next generation Rovers?
 

I’m an isotope geochemist by trade so I might be a bit biased, but I see value in developing techniques to make more advanced measurements such as position-specific isotope analysis and clumped isotopes. These position-specific measurements could be incredibly useful for identifying organic molecules formed by abiogenic processes and understanding planetary-scale resource cycling (e.g., carbon, nitrogen, water) among other applications.

Please could you explain, in a nutshell, why your findings are significant?
 

There is a lot to this paper, but I think one of the major contributions of this paper relates to the ancient martian climate. As a community, we have spent decades refining our understanding of how the climate evolved on Mars with the help of almost a dozen rovers and 18 orbiters. We have searched for signs of liquid water, investigated how the atmosphere has changed, and explored the rock record for evidence of different climate regimes. What our findings do is place a marker in martian climate history. The carbonate minerals we analyzed likely formed in one of two settings: 1) a climate defined by wet-dry cycling and extreme amounts of evaporation, or 2) a cold, salt-rich environment. These settings are not mutually exclusive, but both point towards environments that would be less conducive towards life. This means that the uninhabitable conditions that define the modern surface of Mars may have extended further back than previously thought.

Any future plans for this work?
 

In terms of future plans, I’m very interested in seeing what kinds of other carbonates we find on Mars, both with the two active rovers (Curiosity and Perseverance) and any future missions like the European Space Agency’s Rosalind Franklin rover. Admittedly, our study only includes a few data points and we’re very curious how these select carbonates compare to others that we will encounter. It’s possible that we find more carbonates that were subject to the same evaporative wet-dry cycling or we might find something entirely different like hydrothermal carbonates. Either way, these discoveries will help paint a more complete picture of how the martian climate evolved.