Is it possible that the multiple parallel trails are the traces of objects formerly lying on the moon’s surface, that have all been disturbed simultaneously by the moon colliding with something? Then BigBob’s theory looks a goodun’, and explains why thre are so many trails. The chance of them all being the result of oblique collisions is close to nil, given that all other objects seeem to have hit smack on.

I’m sorry for the delay davem and you probably won’t read this but it’s just occurred to me that there’s a factor you may be unaware of.
Phobos (and as it happens Deimos too) is tidally locked with Mars, that is to say it always shows the same ‘side’ to Mars just as our Moon always shows the same ‘side’ to the Earth. So tidally locked moons rotate once on their axis for each orbit around their planet. That means Phobos has a leading face and a trailing face as it orbits Mars. So if the current theory about the grooves being caused by debris thrown up from massive impacts on Mars is correct, that explains why the many grooves are in parallel. The rocks that drew the lines would not have had to arrive all at the same time. Even if Phobos encountered a rock in its path today, it would still roll the rock along its flank and the groove that it made would be in parallel with hundreds of existing grooves. The fact that there are other ‘families’ of grooves on Phobos suggests that it used to be oriented differently, when its leading ‘face’ was not that part of the surface that leads today.
Bob(Big)

Are most of the wounds on moons from a time long ago, before Earth even began to be hospitable to life?

Too many questions, not enough space probes.

Good luck to Russia (and the Chinese) on their mission. They really could use a break from stream of bad luck with Mars. Any successful mission is all the better for all of us.

Even a Russo-Chinese mission to put a giant death ray laden battle-station into orbit above America?

There’s speculation that the orbits of both Phobos and Deimos are decaying and they will eventually skid on to Mars, creating gouges like the Valles Marineris. If Earth, Venus or Mercury had similar tiny moons that crashed long ago, the gouges they made should still be easily visible. So why Mars?

It almost looks like a huge chunk of sand stone with craters!

Fabulous picture!

What amazes me about Phobos, (and indeed many smaller bodies like this) is just how relatively smooth the surface area is. Yes, there are groves and craters… but overall, the surface seems like it started out as being fairly uniform. You would think that a small object like this, without the gravity to pull itself into a sphere, would look more like a rough collection of crags, and lumps held together by common gravity…

Lay it on top and, let’s see, Dupont Circle would be about here… and oh, there’s the Tidal Basin… and there’s Anacostia… and the Pentagon…

Not that I’m advocating anybody should try laying Phobos on DC…. though if Russia is going to send a probe there… Hey, just kidding, it’s my home town! (DC, that is, not Phobos! Nothing against Phobosians, Leather Goddesses or otherwise…)

The fainter and highly parallel banding could be a feature of the original rock mass rather than from meteor impacts. On Earth this would be a sign of differential weathering, where one layer of rock is slightly more resistant erosion/weather than the layer immediately below it and so one layer “stands out” in higher relief.

Assuming Phobos is made of igneous rock, one thing that could cause banding like this is magmatic segregation, where the original rock is molten and cools slowly enough to allow the various minerals to separate into layers. This would suggest that Phobos was originally part of a much larger object, which would be required for the molten rock to cool slowly enough to chemically separate. If Phobos was, as some suggest, a big pile of loosely aggregated material fused together by impact without any further evolution, it would be hard to explain the origin of this banding and layering, since there should not be any order or arrangement to the aggregation.