We met Mark Sephton, Professor of organic geochemistry at Imperial College London (UK). He is a university geochemist, planetary scientist and astrobiologist. He has been also Principal Investigator for over 40 funded research projects and has been involved with a number of space missions. Mark has been selected as one of the few European scientists participating in NASA’s Mars 2020 science team.
The Mars 2020 rover landed near the Jezero Crater on 18 February 2021. After eight months hurtling through space, the Mars Perseverance rover has successfully landed and begun its mission. The most important objective of Perseverance rover is the collection of Mars samples from ancient river delta, where 3 billion years ago water flowed. The next mission NASA/ESA Mars Sample Return will have the task of fetching those samples collected by the Perseverance rover and, through a very complex mission, will bring them to Earth by 2032. Geochemist Mark Sephton will be one of the few European scientists to study those Mars samples.
In space missions the Geochemist is a Space detective. What are your survey methods? How do you manage to discover the secrets of the planets?
I am a geochemist, so I use the signals in rocks to tell me about what existed when the rocks were formed. My particular specialty is organic geochemistry, so I look for carbon-based structures that represent fingerprints of past life or the chemistry that led to it.
What do you love most about your job? What is the discovery that surprised you the most?
I love the uncertainty. Each day could be the day when a discovery is made and science changes forever. The discoveries that surprise me the most are the best, but the most difficult to deal with. Evidence can appear that was unexpected and needs some imaginative thought to interpret. Then, when a solution appears, science has made a big leap forward. Evidence of a hydrocarbon generation event on asteroids in the early solar system and markers of massive soil erosion in rocks that record the end Permian mass extinction are two examples of unexpected results.
You are part of the team of scientists of the Mars Sample Return mission, which will bring some Martian samples to Earth. What will be the various steps to analyze the Martian rock?
We will use the planet’s best and most sensitive equipment to interrogate the samples for their evidence of Martian history. From cutting edge mass spectrometers to synchrotrons, we are intensively preparing for the return of these valuable samples.
What will be the planetary protection techniques that you will use when the Martian samples arrive on Earth? Can microbial life survive during space travel and, more importantly, can it survive on the planet Mars?
We are more likely to find evidence of fossil life than active life on Mars. The red planet was much more habitable billions of years ago before it lost its atmosphere. But the rocks will still be studied carefully for planetary protection purposes. We will look at the three-dimensional structure of the samples to guide our testing and then analyze any gases, minerals and organic molecules present. We will look for evidence of life as we know it but also life as we do not know it. Statistics will help us understand the certainty of our conclusions.
You are also part of the team of scientists of the Europa Clipper mission, which will search for traces of microbial life in Europa’s ocean. How will you manage to search for traces of life with a space probe?
Europa Clipper will fly past Jupiter’s icy moon and we hope to sample materials ejected from the subsurface by plumes. Any organic molecules hitting the space craft will be detected by a mass spectrometer. Biological molecules have quite specific architectures and can act as fingerprints of life.