February 26th, 2016: Phobos and Deimos: What we know, what we don’t know, and why we care

The moons of Mars, Phobos and Deimos, are high priority targets for future exploration by both robotic and human missions. Despite decades of study by ground and Mars-orbiting spacecraft, key questions about the moons’ origin, geologic evolution, and potential to provide in situ resources for future manned missions remain unresolved. Phobos and Deimos either formed in situ around Mars through co-accretion or giant impact, or they are captured asteroids that originated from elsewhere in the solar system. One key to unlocking this mystery will be to determine whether the moons are composed of materials expected to be native to Martian system or if they are made of something more exotic that more likely would have been introduced from another location. Determining Phobos’ and Deimos’ surface compositions remotely has proven to be challenging in part because they lack strong diagnostic absorption features and in part because spectral observations of the moons are acquired at a variety of lighting conditions, which makes it difficult to compare them to laboratory spectra of well-characterized samples collected under controlled lighting conditions. I will present analyses of spectral data that address both of these challenges and demonstrate the moons are likely composed of volatile-rich, carbonaceous-chondrite like material, supporting the idea that they are captured asteroids from the outer solar system. I will also discuss the importance and benefits of future in situ exploration to address some of the many remaining questions about these fascinating solar system bodies.

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