Mission to Mars Moon, Phobos, May Collect Samples from Two Celestial Bodies

There's some good news when it comes to a mission to one of the moons of Mars. It turns out that due to past impacts, the surface of the moon, Phobos, may have samples from Martian castoffs. The findings mean that the mission could collect samples from two celestial bodies by just visiting one of them.

"The mission is scheduled to be flown early in the next decade, so the question is not academic," said James Head, one of the researchers, in a news release. "This work shows that samples from Mars can indeed be found in the soil of Phobos and how their concentration might change with depth. That will be critical in the design of the drills other equipment."

Scientists have long thought that it was likely that Phobos contained samples from Mars. Until now, though, they hadn't confirmed that fact. In order to get a better look at the Martian moon, the researchers created a model based on our own moon to estimate how much of Phobos' loose rock and dust on the surface would come from projectiles. The scientists then used gravitational and orbital data to determine what proportion of that projectile material came from Mars.

"When an impactor hits Mars, only a certain of proportion of ejecta will have enough velocity to reach the altitude of Phobos, and Phobos' orbital path intersects only a certain proportion of that," said Ken Ramsley, one of the researchers, in a news release.  "So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars."

In the end, the researchers found that Phobos should contain Martian material at a rate of about 250 parts per million. In addition, these pieces from Mars should be distributed fairly evenly across the surface, mostly in the upper layers.

The findings are exciting for scientists. While 250 parts per million may not seem like a lot, the possibility of collecting Martian samples from Phobos provides researchers with an unexpected opportunity. It's essentially a bonus for a mission primarily aimed at learning more about the moon, a rock that has mysterious origins in its own right.

The findings are published in the journal Space and Planetary Science.