Phobos, one of Mars' natural satellites, is seen in this image provided by NASA.

TOKYO -- The Japan Aerospace Exploration Agency (JAXA) has decided that the next target for its galactic sample collection projects will be Phobos, one of Mars' two small natural satellites.

The project, which will follow on from the Hayabusa2 probe currently returning to Earth with samples from the asteroid Ryugu, is hoped to become the first ever successful trip to and from Mars by a probe. JAXA intends to launch it in 2024, and have it return in 2029.

It's being called the Martian Moons eXploration (MMX) project, and is a "sample return" mission in which material from the celestial body will be collected and brought to Earth. Following on from the Hayabusa and Hayabusa2 missions, it will inherit the technology refined over the agency's previous endeavors.

Mars is orbited by two small natural satellites: Phobos, which measures around 23 kilometers in diameter, and Deimos, which is some 12 kilometers. The plan was originally to land on either of the celestial objects, but until now it hadn't been decided precisely which of them the probe would aim for.

Now, the target is for the probe to land on Phobos for a few hours, and collect 10 grams or more of the sand believed to be covering its surface.

Yasuhiro Kawakatsu, the project manager for MMX and a professor at JAXA, is seen at the JAXA Sagamihara Campus in Sagamihara, Kanagawa Prefecture, on Aug. 8, 2019. (Mainichi/Tomohiro Ikeda)

Phobos is closer to the surface of Mars than Deimos, and because the planet's gravitational pull has a greater influence on it, more fuel will be required to land the probe. But it's expected that Phobos will have a wealth of materials that have landed on it from Mars, and it's hoped that obtaining some of it will further our understanding of the planet.

There are two theories as to why objects like Phobos came to orbit planets: one is the capture theory positing that wandering asteroids have been pulled by the gravitational force of Mars. The other is the impact hypothesis, which suggests that Mars collided with another celestial object, thereby creating separate bodies.

One of MMX's major goals is to find scientific evidence supporting one of the two theories by analyzing the material brought back, and through up-close observation of Phobos.

Additionally, the mission intends to use a high-resolution camera to photograph Deimos, as well as using other means to observe the natural satellite from above.

Development of the three-stage probe is underway at a total cost of 46.4 billion yen ($421.6 million). In 2011, Russia launched a probe to go to Phobos, but the mission ended in failure.

(Japanese original by Tomohiro Ikeda, Science & Environment News Department)