Phobos - a moon of Mars. Courtesy NASA
A new study has calculated how the Martian moon, Phobos, may be peppered with material from Mars itself.
Therefore, a planned Russian mission to return a sample from the Martian moon Phobos will likely be a twofer.
Work by James Head, professor of geological sciences at Brown University, an author on the study, helps to confirm the idea that the surface of Phobos contains tons of dust, soil, and rock blown off the Martian surface by large projectile impacts.
That means a sample return mission planned by the Russian space agency could sample two celestial bodies for the price of one.
Ejecta from Mars
“The mission is scheduled to be flown early in the next decade, so the question is not academic,” said Head in a press statement. “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.”
Head and Ken Ramsley, a visiting researcher in Brown’s planetary geosciences group, focused on just how much Mars material might be on Phobos and where it could be found.
“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,” Ramsley said. “So we can crunch those numbers and find out what proportion of material on the surface of Phobos comes from Mars.”
According to calculations, the regolith on Phobos should contain Martian material at a rate of about 250 parts per million. The Martian bits should be distributed fairly evenly across the surface, mostly in the upper layers of regolith, the researchers showed.
Moon mystery
Phobos itself is a mystery.
Scientists are still not sure where it came from. Is it a chunk of Mars that was knocked off by an impact early in Martian history, or is it an asteroid snared in Mars’s orbit? There are also questions about whether its interior might hold significant amounts of water.
If all goes well, the upcoming Russian mission will help solve some of those mysteries about Phobos. And we might learn a good deal about Mars in the process.
The research appears in the latest issue of Planetary and Space Science
Volume 87, October 2013, Pages 115–129
Go to: http://www.sciencedirect.com/science/article/pii/S0032063313002328
By Leonard David