The demise of Phobos and development of a Martian ring system

Benjamin A. Black, Tushar Mittal

Research output: Contribution to journalReview articlepeer-review

20 Scopus citations


All of the gas giants in our Solar System host ring systems, in contrast to the inner planets. One proposed mechanism of planetary ring formation is disruption or mass shedding of moons. The orbit of Phobos, the larger of Mars's two moonlets, is gradually spiralling inwards towards Mars and the moon is experiencing increasing tidal stresses. Eventually, Phobos will either break apart to form a ring or it will crash into Mars. We evaluate these outcomes based on geologic, spectral and theoretical constraints, in conjunction with a geotechnical model that helps us determine the strength of Phobos. Our analysis suggests that much of Phobos is composed of weak, heavily damaged materials. We suggest that-with continued inward migration of the moon-the weakest material will disperse tidally in 20 to 40 million years to form a Martian ring. We predict that this ring will persist for 106 to 108 years and will initially have a comparable mass density to that of Saturn's rings. Any large fragment of Phobos that is strong enough to escape tidal breakup will eventually collide with Mars in an oblique, low-velocity impact. Our analysis of the evolution of Phobos underscores the potential orbital and topographic consequences of the growth and self-destruction of other inwardly migrating moons, including those that met their demise early in our Solar System's history.

Original languageEnglish (US)
Pages (from-to)913-917
Number of pages5
JournalNature Geoscience
Issue number12
StatePublished - Dec 1 2015

All Science Journal Classification (ASJC) codes

  • General Earth and Planetary Sciences


Dive into the research topics of 'The demise of Phobos and development of a Martian ring system'. Together they form a unique fingerprint.

Cite this