Paris, March 5 (ANI): Reports indicate that Mars Express has smoothly skimmed past Phobos at just 67 km, the closest any manmade object has ever approached Mars' enigmatic moon.
The data collected could help unlock the origin of not just Phobos but other 'second generation' moons.
Phobos looks like a solid object but previous flybys have shown that it is not dense enough to be solid all the way through.
Instead, it must be 25-35 percent porous.
This has led planetary scientists to believe that it is little more than a 'rubble pile' circling Mars.
Such a rubble pile would be composed of blocks both large and small resting together, with possibly large spaces between them where they do not fit easily together.
The latest flyby was close enough to give scientists their most exquisite data yet about the gravitational field of Phobos.
Now that the data are all collected, the analysis can begin.
First will be an estimate of the density variation across the moon, which will tell scientists just how much of Phobos' interior is likely to be composed of voids.
"Phobos is probably a second-generation Solar System object," said Martin Patzold, Universitat Koln, Cologne, Germany, and Principal Investigator of the Mars Radio Science (MaRS) experiment.
Second generation means that it coalesced in orbit after Mars formed, rather than forming concurrently out of the same birth cloud as the Red Planet.
There are other moons around other planets where this is thought to have been the case too, such as Amalthea around Jupiter.maging starts at the next flyby.
Whatever the precise origin, Phobos will eventually crumble back into this disrupted state. It is gradually spiralling towards Mars and will eventually be pulled apart.
"It came from debris, it will return to debris," said Patzold. (ANI)