Mars Pulls Phobos Inward 1.8 Centimeters a Year as Models Predict Ring in 20-40 Million Years
Updated
Updated · spacedaily.com · Aug 11
Mars Pulls Phobos Inward 1.8 Centimeters a Year as Models Predict Ring in 20-40 Million Years
1 articles · Updated · spacedaily.com · Aug 11
Summary
Phobos is drifting toward Mars by about 1.8 centimeters a year, and one leading model says the moon’s weakest material could be torn apart in 20 million to 40 million years.
That inward spiral happens because Phobos orbits Mars every 7 hours 39 minutes—faster than Mars rotates—so tidal forces drain the moon’s orbital energy and accelerate its descent.
At roughly 6,000 kilometers above Mars, Phobos is already inside the critical orbit where a moon would match the planet’s rotation, making a simple straight-line estimate from today’s drift misleading.
The ring outcome depends on Phobos’s internal strength: a 2015 Nature Geoscience analysis argued its battered, weak interior could disperse first, while stronger fragments would keep falling toward Mars.
NASA puts Phobos’s breakup or impact at about 50 million years, ESA says within 100 million years, and any ring that forms could still last 1 million to 100 million years before fading.