Japan Mission to Grab Sample from Mars Moon Phobos

In just days, a spacecraft will blast off from Japan on a mission that could rewrite what we know about Mars and its mysterious moons.

The Mars Moons Exploration mission launches Monday with an ambitious goal: land on the tiny moon Phobos, grab a sample, and bring it back to Earth by 2031. If successful, it will mark the first time anyone has returned material from Mars or its moons for scientists to study in their labs.

"I think this is an incredibly ambitious and fun mission," says Prof Sara Russell from the Natural History Museum, who serves as the mission's deputy for sample analysis. She's not exaggerating about the challenge ahead.

The spacecraft faces a journey of nearly three years, arriving at Mars in August 2027. It will first study the smaller moon Deimos before setting its sights on Phobos, a potato-shaped rock just 20 kilometers across.

Landing a rover on something so small presents a unique puzzle. Phobos has almost no gravity of its own, but sits right next to Mars, which has enormous gravitational pull. No one has ever successfully landed a rover on such a tiny moon so close to a massive planet.

Once the rover scouts a safe landing spot, the main spacecraft will touch down and deploy a robotic arm to collect moon dust. The entire sample coming back to Earth weighs just 10 grams, about two teaspoons.

Dr Chrysa Avdellidou from Leicester University says that's plenty. "You don't need to have kilos back from a surface in order to do science. So it's worth every gram."

Why This Inspires

This tiny handful of moon dust could answer one of planetary science's biggest questions: where did Mars' two moons come from?

Scientists have two competing theories. Either a massive space rock crashed into Mars billions of years ago and the moons formed from the debris, or Phobos and Deimos are captured asteroids from the outer Solar System that Mars' gravity snagged.

The sample's chemistry and mineral composition will reveal the answer almost immediately when it reaches Earth in 2031.

There's an exciting bonus possibility too. Phobos orbits so close to Mars that debris from asteroid impacts on the Red Planet's surface may be embedded in the moon itself. That means the sample could contain actual grains of Mars, giving scientists direct information about the composition and history of the planet.

This comes as other Mars sample return missions face setbacks. NASA's ambitious Mars Sample Return mission lost its funding from the US Congress, though China plans to launch its own mission in 2028.

We do have some Martian meteorites on Earth, pieces blasted off Mars by asteroid strikes that eventually fell here. But those samples become contaminated the moment they arrive, mixing with our air, dust, soil and water.

The Phobos sample will be pristine, untouched, exactly as it's existed for billions of years. That's why scientists around the world are counting down to Monday's launch with such excitement.

For a mission grabbing just 10 grams of moon dust, the potential to transform our understanding of Mars is absolutely massive.