Station On Phobos

[redliox]

Assuming a Phobos station is established, how useful of a communication relay could it be for Mars surface missions, be they telerobotic or crewed missions?  I presume one issue would be the need for the Phobos station to be Mars-facing, and the second issue being how much of Phobos itself would obscure Earth.  Even if the Phobos station is only used once for a one-off precursor mission, it does represent a substantial orbiting asset more robust than any probe or com satellite will ever be; it ought to have a long-term use even if effectively abandoned.  Considering Phobos is in a ~8 hour orbit near the equator, a Martian base, up to the mid-latitudes, would have 3 decent daily passes with the Phobos station on this note, which is better than what a low-orbiting probe could offer and on a more regular basis.

[Bob Shaw]

A Molniya-like constellation of orbiters, combined with a manned base, would do the trick. Phobos is invisible from even moderately high Mars latitudes - as Tennyson didn't put it, 'The moonless poles of snowy Mars' don't see either moon.

Remember, though, that the speed of light begins to be an issue as you bounce your signal around. This doesn't have to be a problem - human consciousness copes well with the physical reality of our fleshy bodies, where our perceptions often don't match up with our intended movements (and vice versa). In other words, the humans would guide, rather than control, with the 'arms and legs' on Mars doing their stuff at a lower operating level.

[redliox]

A Molniya-like constellation of orbiters, combined with a manned base, would do the trick. Phobos is invisible from even moderately high Mars latitudes - as Tennyson didn't put it, 'The moonless poles of snowy Mars' don't see either moon.

That's useful, and I would presume at least 1 satellite or probe would be utilized, but I was referring to the station itself as a relay.  As I said, it is a large asset and, even if abandoned after the Phobos mission, could still be of use.

[gospacex]

Mars moons are probably bone-dry. This is a significant downside.

[alexterrell]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.   

[Dalhousie]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.

I think we should avoid the term "kerogen" in asteroids and satellites, as it has clear implications of biogenesis. Even "kerogen-like" is misleading.

[redliox]

Even if a station is put on Phobos, how often will it be occupied, especially after a Mars landing?

[Blackstar]

Even if a station is put on Phobos, how often will it be occupied, especially after a Mars landing?

The answer is four. Which, coincidentally, is the same number of angels that can fit on the head of a pin.

Really, this is all speculating on top of speculating.

[Bynaus]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.

The question whether they are dry or volatile-rich is a function of their mode of formation. If they are captured asteroids with a composition similar of carbonaceous chondrites, they might have a significant volatile content. If, on the other hand, they were formed from a debris disk after a Giant Impact on Mars, they will likely be dry. So if they are dry, they are dry all the way through (same if they are rich in volatiles).

But then, nature has that tendency to be different from what we imagine. Lets go and see.

[Lar]

if we built an outpost on either, or both, I'd expect it was there to stay. I think that's just how Musk rolls.

[guckyfan]

if we built an outpost on either, or both, I'd expect it was there to stay. I think that's just how Musk rolls.

I don't see such a station by Elon Musk any time soon. NASA may want to go there. That would likely be temporary. For SpaceX something would have to be in it. Like water and CO2 to produce fuel for earth return, which would mean permanent presence. With people or remote controlled robotic.

Assuming that MCT can do more than one launch and landing before earth return, a visit with MCT on phobos could be a mission with a lot of ressources and not that expensive.

[Bob Shaw]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.

The question whether they are dry or volatile-rich is a function of their mode of formation. If they are captured asteroids with a composition similar of carbonaceous chondrites, they might have a significant volatile content. If, on the other hand, they were formed from a debris disk after a Giant Impact on Mars, they will likely be dry. So if they are dry, they are dry all the way through (same if they are rich in volatiles).

But then, nature has that tendency to be different from what we imagine. Lets go and see.

The biggest value of the Martian moons might be - literally - nothing at all. There is real reason to believe that they may be rock piles, with significant voids. Such voids (if stable) would be perfect places to put habitats and storage areas. Leave the dusty surface for visitors, and PV farms, burrow in, and Port Phobos is in business!

[alexterrell]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.

The question whether they are dry or volatile-rich is a function of their mode of formation. If they are captured asteroids with a composition similar of carbonaceous chondrites, they might have a significant volatile content. If, on the other hand, they were formed from a debris disk after a Giant Impact on Mars, they will likely be dry. So if they are dry, they are dry all the way through (same if they are rich in volatiles).

But then, nature has that tendency to be different from what we imagine. Lets go and see.

Surely if formed from a giant impact, they would have been unstable over the course of billions of years. Phobos has a short life ahead of it.

This probably means they are captured asteroids. Whether originally dry asteroids, or whether they've had moisture baked out of them, we don't know.

[alexterrell]

The biggest value of the Martian moons might be - literally - nothing at all. There is real reason to believe that they may be rock piles, with significant voids. Such voids (if stable) would be perfect places to put habitats and storage areas. Leave the dusty surface for visitors, and PV farms, burrow in, and Port Phobos is in business!

If the moon is soft - e.g. a rubble pile, voids won't be stable.

However, stable voids can be made with a balloon and a supply of compressed air.  Somewhere between 0.4 and 1.0 bar Oxygen / Nitrogen mix would do the job.

[Bob Shaw]

The biggest value of the Martian moons might be - literally - nothing at all. There is real reason to believe that they may be rock piles, with significant voids. Such voids (if stable) would be perfect places to put habitats and storage areas. Leave the dusty surface for visitors, and PV farms, burrow in, and Port Phobos is in business!

If the moon is soft - e.g. a rubble pile, voids won't be stable.

However, stable voids can be made with a balloon and a supply of compressed air.  Somewhere between 0.4 and 1.0 bar Oxygen / Nitrogen mix would do the job.

I was thinking of cutting down to voids and backfilling a la Camp Century. A lot will depend on tides - I believe the jury is still out on the origin of the grooves, but if they indicate tidal effects then the interior might not be very trustworthy.

Has the density of Phobos been nailed down yet? Mathilde is certainly blessed with a lot of empty space.

Good article on Wikipedia: https://en.wikipedia.org/wiki/Rubble_pile

[alexterrell]

I'd rather expect a rubble pile to be like a shingle beach with a few boulders thrown in - except under microgravity. The voids won't be much use, but you can always make your own big voids.

Any digging will be difficult and limited to fairly shallow slope angles.

[Bynaus]

Mars moons are probably bone-dry. This is a significant downside.

We don't know that. It could be they're dry to a few metres.

Kerogen would also be a nice material to find - as well as water.

The question whether they are dry or volatile-rich is a function of their mode of formation. If they are captured asteroids with a composition similar of carbonaceous chondrites, they might have a significant volatile content. If, on the other hand, they were formed from a debris disk after a Giant Impact on Mars, they will likely be dry. So if they are dry, they are dry all the way through (same if they are rich in volatiles).

But then, nature has that tendency to be different from what we imagine. Lets go and see.

Surely if formed from a giant impact, they would have been unstable over the course of billions of years. Phobos has a short life ahead of it.

This probably means they are captured asteroids. Whether originally dry asteroids, or whether they've had moisture baked out of them, we don't know.

If you mean "unstable" in the sense of having tidally migrating orbits (like the Moon has), then yes, they are "unstable". Their orbits have been migrating over the last billions of years. Deimos is beyond the co-rotation orbit, so it has been migrating slowly outward (like our Moon). Phobos is below the co-rotation orbit and must have been so since its formation (because that orbit cannot be crossed by tidal migration).

There was an interesting talk at this year's LPSC about a Giant Impact formation scenario where Mars once had a larger, interior satellite which has since crashed back onto the planet: http://www.hou.usra.edu/meetings/lpsc2016/pdf/1943.pdf (PDF). After this happened (billions of years ago), the two remaining satellites were left to migrate away from the co-rotation radius. We just happen to live at a time just before Phobos' demise.

The idea of them being captured asteroids is problematic because their orbits are circular and co-planar. No easy way to explain this if they are captured. But perhaps we are just not clever enough (yet) how to figure that one out.

[JasonAW3]

The biggest value of the Martian moons might be - literally - nothing at all. There is real reason to believe that they may be rock piles, with significant voids. Such voids (if stable) would be perfect places to put habitats and storage areas. Leave the dusty surface for visitors, and PV farms, burrow in, and Port Phobos is in business!

If the moon is soft - e.g. a rubble pile, voids won't be stable.

However, stable voids can be made with a balloon and a supply of compressed air.  Somewhere between 0.4 and 1.0 bar Oxygen / Nitrogen mix would do the job.

Or you could use a spray on epoxy resin.  Might actually be a good idea, to reinforce the void space prior to inflating a balloon in the void.  Kind of like shotcrete is used to reinforce many tunnels and cliff faces that stand a good chance of collapse.

[TakeOff]

It wouldn't need permanent crew, but Phobos and Deimos (both at the first trip) is a pretty obvious first target. The expedition there could leave a habitat in the well shielded Stickney crater as a survivable emergency backup, or an outpost for further exploration, for the next expedition which goes to Mars's surface.

Teleoperation of rovers on Mars from orbit is nonsense. It is very much cheaper and safer to teleoperate them from Earth. The time delay is only 10 to 40 minutes. Curiosity is given a set of commands only once every 25 hours, and some days not at all. Spending $100B on a risky human mission to teleoperate a $3B slow moving rover is not rational. For a few minutes per orbit when it is in line of sight. By a tiny 4 or 6 man crew who should be busy with other things, like escavations on Deimos. This stupid idea out there needs to go away. You either teleoperate rovers from Earth, even if delayed and slow, operating Martian rovers 24/7 using large groups of specialists would massively multiply the productivity, or you send humans to the surface who move themselves quickly. Sending people to Mars' orbit to remotely control rovers on Mars is just wrong. Like launching people to Earth's orbit to teleoperate rovers on Earth. Makes no sense.

[MATTBLAK]

Tele-operating Science rovers might be a marginal activity - but not rovers that might be undertaking future base-building activities. Also, having the manned vehicle collect an array of Sample Return Ascent vehicles from several Martian hemispheres could be good. The whole point of even sending humans to Phobos & Deimos in the first place in a manned craft is to 'shake out' the whole interplanetary transportation infrastructure ahead of a manned landing, if the landing has to be delayed because of low funding levels for the manned lander or if further development of it is deemed necessary.

I'd like to think that the very first manned Mars landing would be an 'all up test' on the very first mission all the way out there - but we have no way of knowing at this point if NASA (or Space X) will be brave enough to dive right into that attempt. Somehow, I don't think so.