JAXA Targets 2031 Phobos Samples to Resolve Moon's Origin

1 articles · Updated · Universe Today · Jun 20

Late-2026 launch plans for JAXA’s MMX mission call for orbiting Phobos, collecting surface material with two samplers, and returning the samples to Earth by mid-2031.
22.2-km-wide Phobos could settle a long-running debate over whether Mars’s inner moon is a captured asteroid or debris from a giant impact, with researchers saying its poorly known gravity field and interior are the key.
9-km Stickney Crater is central to that effort: new modeling suggests the impact could date to about 4.2 billion years ago under the giant-impact scenario, versus roughly 2.6 billion years ago if Phobos was captured later.
No stable orbit exists around Phobos because Mars’s gravity dominates nearby, complicating MMX operations but also making detailed gravitational mapping especially valuable for testing whether the moon has a porous, possibly ice-bearing interior and a densified zone beneath Stickney.