French National Center for Scientific Research (CNRS) | 2016 July 04
The aura of mystery surrounding Mars has long been intensified by its curious pair of moons: Phobos and Deimos, whose origins have remained clouded until now.
[c][youtube]https://www.youtube.com/watch?v=iAgdkMPuCWc[/youtube]The Formation of Mars' Moons - Credit: LabEx UnivEarthS[/c]No planet stirs human imagination quite like Mars. As non-stop land-based missions continue to probe its past and search for possible traces of life, another intrigue—this time high above its skyline—had long baffled scientists: how did Mars end up with its two small moons, Phobos and Deimos, first spotted in 1877? This riddle may have just been solved by a multidisciplinary study combining French, Belgian and Japanese expertise.
Scientists have long hesitated between two hypotheses. The first suggests that the moons are asteroids like those found in the belt between Jupiter and Mars; but why they should have been trapped around Mars remains unclear. An alternative theory posits that the moons formed from the debris of a collision between Mars and a protoplanet—a planet in the making; here though, uncertainty has hovered over the mechanism producing two small satellites. “A major difficulty has been to explain why a giant impact on Mars would have left two moons so different from our own Moon, a huge single mass, that also formed from Earth undergoing such an impact,” explains planetary scientist Sébastien Charnoz of the IPG, who contributed to the new study.
According to the simulations, Mars suffered a colossal impact with a body three times smaller some 4 to 4.5 billion years ago. Debris from the collision initially accumulated into a long disk around Mars, resembling one of Saturn’s rings. Within this disk, an enormous moon a thousand times the mass of Phobos gradually formed—similar to the way in which our Moon amassed from debris created by Earth’s impact. ...
A Giant Impact: Solving the Mystery of How Mars’ Moons Formed
LabEx UnivEarthS | 2016 July 04
A Reappraisal of the Origin of Mars’ Moons
Royal Observatory of Belgium | 2016 July 04
Accretion of Phobos and Deimos in an extended debris disc stirred by transient moons - Pascal Rosenblatt et al
- Nature Geoscience (online 04 July 2016) DOI: 10.1038/ngeo2742
- Astrophysical Journal (forthcoming)