Veteran ESA probe rolls out welcome mat for Japan's Phobos mission

Japan's mission to the Martian moon Phobos launched this week, with a veteran European probe expected to be waiting when it arrives.

JAXA, Japan's space agency, confirmed that the Martian Moons eXploration (MMX) spacecraft launched aboard an H3 rocket on October 19 at 19:41 UTC – October 20 in Japan. On October 21, it said that initial critical operations, including solar array deployment, were complete. Equipment checks will follow as the spacecraft prepares for its outbound cruise.

The probe is due to reach Mars in 2027, deploy the Idefix rover on Phobos, and attempt one or two landings on the moon itself. The rover is named after the dog from the Asterix comics. Scientists plan to collect about 10 g of material from Phobos and send it to Earth, with a return planned for 2031.

The European Space Agency (ESA) is supporting the trip with Mars Express (MEX), which has orbited Mars since 2003. A former team member told The Register that plans include joint observations and imaging of MMX's landing site.

MEX's latest mission extension runs to 2029, covering MMX's expected arrival. The former team member described it as definitely the last – before adding that "the first 'last ever extension' was in about 2007."

Discussions about another "last ever extension" could begin in 2028 or 2029, with support for MMX and the Rosalind Franklin rover among the potential reasons to keep MEX going. Funding and scientific returns would determine the outcome. A software update announced in May 2025 reduced wear on its gyroscopes, potentially allowing them to last until 2034.

Rosalind Franklin is due for launch in 2028 after repeated delays and Russia's ejection from the project. MEX will likely be able to image the rover's landing site on the surface of Mars and take part in data relay operations, though ESA's Trace Gas Orbiter (TGO) will be the main relay asset.

Several years ago, another team member joked that MEX was so tough it would punch straight through Phobos if sent there for disposal. We wouldn't take that as an engineering assessment, but it says something about the team's affection for their spacecraft.

MEX's longevity is a tribute to its builders and operators. With funding through 2029, it could welcome MMX next year. Further extensions might keep it working through the sample-return departure and Rosalind Franklin's arrival.

"We all want our '30 years in flight' T-shirts," the former team member said. ®