JAXA's MMX mission to the Mars moons will carry Idefix, the first wheeled rover built to drive in ultra-low gravity

JAXA

JAXA's Martian Moons eXploration mission is scheduled to launch on October 20 to find out whether Phobos and Deimos are leftover collision debris or captured asteroids. It carries Idefix, a 25-kg wheeled rover built by DLR and CNES that is designed to drive on Phobos for 100 days. Phobos's gravity is about 2,000 times weaker than Earth's, so the rover would weigh roughly 12 grams there.

• Launch is set for 4:41 a.m. JST on October 20 (3:41 p.m. ET on October 19); arrival at the Martian system is planned for late 2027.
• Idefix is released from about 40 meters and lands at about 1 m/s, below Phobos's 10 m/s escape speed, then bounces for about 15 minutes.
• A CNES-developed mechanism can upright the rover if it lands on its side; its solar panels unfold afterwards.
• The rover moves at 1 mm/s, with a hard limit of 5 cm/s; two WheelCams will show how the regolith behaves around the wheels.
• MMX plans to bring back 10 grams of Phobos regolith in 2031, which is a first for the Mars system unless China's Tianwen-3 returns first.